Deprecate register and add plugin use (#12607)

# Description

Adds a new keyword, `plugin use`. Unlike `register`, this merely loads
the signatures from the plugin cache file. The file is configurable with
the `--plugin-config` option either to `nu` or to `plugin use` itself,
just like the other `plugin` family of commands. At the REPL, one might
do this to replace `register`:

```nushell
> plugin add ~/.cargo/bin/nu_plugin_foo
> plugin use foo
```

This will not work in a script, because `plugin use` is a keyword and
`plugin add` does not evaluate at parse time (intentionally). This means
we no longer run random binaries during parse.

The `--plugins` option has been added to allow running `nu` with certain
plugins in one step. This is used especially for the `nu_with_plugins!`
test macro, but I'd imagine is generally useful. The only weird quirk is
that it has to be a list, and we don't really do this for any of our
other CLI args at the moment.

`register` now prints a deprecation parse warning.

This should fix #11923, as we now have a complete alternative to
`register`.

# User-Facing Changes

- Add `plugin use` command
- Deprecate `register`
- Add `--plugins` option to `nu` to replace a common use of `register`

# Tests + Formatting

I think I've tested it thoroughly enough and every existing test passes.
Testing nu CLI options and alternate config files is a little hairy and
I wish there were some more generic helpers for this, so this will go on
my TODO list for refactoring.

- 🟢 `toolkit fmt`
- 🟢 `toolkit clippy`
- 🟢 `toolkit test`
- 🟢 `toolkit test stdlib`

# After Submitting

- [ ] Update plugins sections of book
- [ ] Release notes

crates/nu-cmd-plugin/src/commands/plugin/add.rs

@@ -54,7 +54,7 @@ apparent the next time `nu` is next launched with that plugin cache file.
     }
 
     fn search_terms(&self) -> Vec<&str> {
-        vec!["plugin", "add", "register", "load", "signature"]
+        vec!["load", "register", "signature"]
     }
 
     fn examples(&self) -> Vec<Example> {

crates/nu-cmd-plugin/src/commands/plugin/list.rs

@@ -29,6 +29,10 @@ impl Command for PluginList {
         "List installed plugins."
     }
 
+    fn search_terms(&self) -> Vec<&str> {
+        vec!["scope"]
+    }
+
     fn examples(&self) -> Vec<nu_protocol::Example> {
         vec![
             Example {

crates/nu-cmd-plugin/src/commands/plugin/mod.rs

@@ -4,11 +4,13 @@ mod add;
 mod list;
 mod rm;
 mod stop;
+mod use_;
 
 pub use add::PluginAdd;
 pub use list::PluginList;
 pub use rm::PluginRm;
 pub use stop::PluginStop;
+pub use use_::PluginUse;
 
 #[derive(Clone)]
 pub struct PluginCommand;
@@ -28,10 +30,6 @@ impl Command for PluginCommand {
         "Commands for managing plugins."
     }
 
-    fn extra_usage(&self) -> &str {
-        "To load a plugin, see `register`."
-    }
-
     fn run(
         &self,
         engine_state: &EngineState,
@@ -54,6 +52,20 @@ impl Command for PluginCommand {
 
     fn examples(&self) -> Vec<Example> {
         vec![
+            Example {
+                example: "plugin add nu_plugin_inc",
+                description: "Run the `nu_plugin_inc` plugin from the current directory and install its signatures.",
+                result: None,
+            },
+            Example {
+                example: "plugin use inc",
+                description: "
+Load (or reload) the `inc` plugin from the plugin cache file and put its commands in scope.
+The plugin must already be in the cache file at parse time.
+"
+                .trim(),
+                result: None,
+            },
             Example {
                 example: "plugin list",
                 description: "List installed plugins",
@@ -64,11 +76,6 @@ impl Command for PluginCommand {
                 description: "Stop the plugin named `inc`.",
                 result: None,
             },
-            Example {
-                example: "plugin add nu_plugin_inc",
-                description: "Run the `nu_plugin_inc` plugin from the current directory and install its signatures.",
-                result: None,
-            },
             Example {
                 example: "plugin rm inc",
                 description: "Remove the installed signatures for the `inc` plugin.",

crates/nu-cmd-plugin/src/commands/plugin/rm.rs

@@ -51,7 +51,7 @@ fixed with `plugin add`.
     }
 
     fn search_terms(&self) -> Vec<&str> {
-        vec!["plugin", "rm", "remove", "delete", "signature"]
+        vec!["remove", "delete", "signature"]
     }
 
     fn examples(&self) -> Vec<Example> {

crates/nu-cmd-plugin/src/commands/plugin/use_.rs

@@ -0,0 +1,81 @@
+use nu_engine::command_prelude::*;
+
+#[derive(Clone)]
+pub struct PluginUse;
+
+impl Command for PluginUse {
+    fn name(&self) -> &str {
+        "plugin use"
+    }
+
+    fn usage(&self) -> &str {
+        "Load a plugin from the plugin cache file into scope."
+    }
+
+    fn signature(&self) -> nu_protocol::Signature {
+        Signature::build(self.name())
+            .input_output_types(vec![(Type::Nothing, Type::Nothing)])
+            .named(
+                "plugin-config",
+                SyntaxShape::Filepath,
+                "Use a plugin cache file other than the one set in `$nu.plugin-path`",
+                None,
+            )
+            .required(
+                "name",
+                SyntaxShape::String,
+                "The name of the plugin to load (not the filename)",
+            )
+            .category(Category::Plugin)
+    }
+
+    fn extra_usage(&self) -> &str {
+        r#"
+This command is a parser keyword. For details, check:
+  https://www.nushell.sh/book/thinking_in_nu.html
+
+The plugin definition must be available in the plugin cache file at parse time.
+Run `plugin add` first in the REPL to do this, or from a script consider
+preparing a plugin cache file and passing `--plugin-config`, or using the
+`--plugin` option to `nu` instead.
+
+If the plugin was already loaded, this will reload the latest definition from
+the cache file into scope.
+"#
+        .trim()
+    }
+
+    fn search_terms(&self) -> Vec<&str> {
+        vec!["add", "register", "scope"]
+    }
+
+    fn is_parser_keyword(&self) -> bool {
+        true
+    }
+
+    fn run(
+        &self,
+        _engine_state: &EngineState,
+        _stack: &mut Stack,
+        _call: &Call,
+        _input: PipelineData,
+    ) -> Result<PipelineData, ShellError> {
+        Ok(PipelineData::empty())
+    }
+
+    fn examples(&self) -> Vec<Example> {
+        vec![
+            Example {
+                description: "Load the commands for the `query` plugin from $nu.plugin-path",
+                example: r#"plugin use query"#,
+                result: None,
+            },
+            Example {
+                description:
+                    "Load the commands for the `query` plugin from a custom plugin cache file",
+                example: r#"plugin use --plugin-config local-plugins.msgpackz query"#,
+                result: None,
+            },
+        ]
+    }
+}

crates/nu-cmd-plugin/src/commands/register.rs

@@ -35,12 +35,17 @@ impl Command for Register {
     }
 
     fn extra_usage(&self) -> &str {
-        r#"This command is a parser keyword. For details, check:
+        r#"
-  https://www.nushell.sh/book/thinking_in_nu.html"#
+Deprecated in favor of `plugin add` and `plugin use`.
+
+This command is a parser keyword. For details, check:
+  https://www.nushell.sh/book/thinking_in_nu.html
+"#
+        .trim()
     }
 
     fn search_terms(&self) -> Vec<&str> {
-        vec!["plugin", "add", "register"]
+        vec!["add"]
     }
 
     fn is_parser_keyword(&self) -> bool {

crates/nu-cmd-plugin/src/default_context.rs

@@ -12,11 +12,12 @@ pub fn add_plugin_command_context(mut engine_state: EngineState) -> EngineState
         }
 
         bind_command!(
-            PluginCommand,
             PluginAdd,
+            PluginCommand,
             PluginList,
             PluginRm,
             PluginStop,
+            PluginUse,
             Register,
         );
 

crates/nu-command/tests/format_conversions/nuon.rs

@@ -479,5 +479,5 @@ fn read_code_should_fail_rather_than_panic() {
     let actual = nu!(cwd: "tests/fixtures/formats", pipeline(
         r#"open code.nu | from nuon"#
     ));
-    assert!(actual.err.contains("error when parsing"))
+    assert!(actual.err.contains("Error when loading"))
 }

crates/nu-parser/src/parse_keywords.rs

@@ -71,6 +71,7 @@ pub const UNALIASABLE_PARSER_KEYWORDS: &[&[u8]] = &[
     b"source",
     b"where",
     b"register",
+    b"plugin use",
 ];
 
 /// Check whether spans start with a parser keyword that can be aliased
@@ -93,11 +94,14 @@ pub fn is_unaliasable_parser_keyword(working_set: &StateWorkingSet, spans: &[Spa
 /// This is a new more compact method of calling parse_xxx() functions without repeating the
 /// parse_call() in each function. Remaining keywords can be moved here.
 pub fn parse_keyword(working_set: &mut StateWorkingSet, lite_command: &LiteCommand) -> Pipeline {
+    let orig_parse_errors_len = working_set.parse_errors.len();
+
     let call_expr = parse_call(working_set, &lite_command.parts, lite_command.parts[0]);
 
-    // if err.is_some() {
+    // If an error occurred, don't invoke the keyword-specific functionality
-    //     return (Pipeline::from_vec(vec![call_expr]), err);
+    if working_set.parse_errors.len() > orig_parse_errors_len {
-    // }
+        return Pipeline::from_vec(vec![call_expr]);
+    }
 
     if let Expression {
         expr: Expr::Call(call),
@@ -121,6 +125,8 @@ pub fn parse_keyword(working_set: &mut StateWorkingSet, lite_command: &LiteComma
             "overlay hide" => parse_overlay_hide(working_set, call),
             "overlay new" => parse_overlay_new(working_set, call),
             "overlay use" => parse_overlay_use(working_set, call),
+            #[cfg(feature = "plugin")]
+            "plugin use" => parse_plugin_use(working_set, call),
             _ => Pipeline::from_vec(vec![call_expr]),
         }
     } else {
@@ -1946,7 +1952,7 @@ pub fn parse_module_file_or_dir(
     let cwd = working_set.get_cwd();
 
     let module_path =
-        if let Some(path) = find_in_dirs(&module_path_str, working_set, &cwd, LIB_DIRS_VAR) {
+        if let Some(path) = find_in_dirs(&module_path_str, working_set, &cwd, Some(LIB_DIRS_VAR)) {
             path
         } else {
             working_set.error(ParseError::ModuleNotFound(path_span, module_path_str));
@@ -3402,7 +3408,7 @@ pub fn parse_source(working_set: &mut StateWorkingSet, lite_command: &LiteComman
                     }
                 };
 
-                if let Some(path) = find_in_dirs(&filename, working_set, &cwd, LIB_DIRS_VAR) {
+                if let Some(path) = find_in_dirs(&filename, working_set, &cwd, Some(LIB_DIRS_VAR)) {
                     if let Some(contents) = path.read(working_set) {
                         // Add the file to the stack of files being processed.
                         if let Err(e) = working_set.files.push(path.clone().path_buf(), spans[1]) {
@@ -3546,11 +3552,13 @@ pub fn parse_where(working_set: &mut StateWorkingSet, lite_command: &LiteCommand
     }
 }
 
+/// `register` is deprecated and will be removed in 0.94. Use `plugin add` and `plugin use` instead.
 #[cfg(feature = "plugin")]
 pub fn parse_register(working_set: &mut StateWorkingSet, lite_command: &LiteCommand) -> Pipeline {
-    use nu_plugin::{get_signature, PersistentPlugin, PluginDeclaration};
+    use nu_plugin::{get_signature, PluginDeclaration};
     use nu_protocol::{
-        engine::Stack, ErrSpan, PluginCacheItem, PluginIdentity, PluginSignature, RegisteredPlugin,
+        engine::Stack, ErrSpan, ParseWarning, PluginCacheItem, PluginIdentity, PluginSignature,
+        RegisteredPlugin,
     };
 
     let spans = &lite_command.parts;
@@ -3561,7 +3569,7 @@ pub fn parse_register(working_set: &mut StateWorkingSet, lite_command: &LiteComm
     // Maybe this is not necessary but it is a sanity check
     if working_set.get_span_contents(spans[0]) != b"register" {
         working_set.error(ParseError::UnknownState(
-            "internal error: Wrong call name for parse plugin function".into(),
+            "internal error: Wrong call name for 'register' function".into(),
             span(spans),
         ));
         return garbage_pipeline(spans);
@@ -3609,6 +3617,16 @@ pub fn parse_register(working_set: &mut StateWorkingSet, lite_command: &LiteComm
         }
     };
 
+    // Now that the call is parsed, add the deprecation warning
+    working_set
+        .parse_warnings
+        .push(ParseWarning::DeprecatedWarning {
+            old_command: "register".into(),
+            new_suggestion: "use `plugin add` and `plugin use`".into(),
+            span: call.head,
+            url: "https://www.nushell.sh/book/plugins.html".into(),
+        });
+
     // Extracting the required arguments from the call and keeping them together in a tuple
     let arguments = call
         .positional_nth(0)
@@ -3619,7 +3637,8 @@ pub fn parse_register(working_set: &mut StateWorkingSet, lite_command: &LiteComm
                 .coerce_into_string()
                 .map_err(|err| err.wrap(working_set, call.head))?;
 
-            let Some(path) = find_in_dirs(&filename, working_set, &cwd, PLUGIN_DIRS_VAR) else {
+            let Some(path) = find_in_dirs(&filename, working_set, &cwd, Some(PLUGIN_DIRS_VAR))
+            else {
                 return Err(ParseError::RegisteredFileNotFound(filename, expr.span));
             };
 
@@ -3695,27 +3714,8 @@ pub fn parse_register(working_set: &mut StateWorkingSet, lite_command: &LiteComm
         // Create the plugin identity. This validates that the plugin name starts with `nu_plugin_`
         let identity = PluginIdentity::new(path, shell).err_span(path_span)?;
 
-        // Find garbage collection config
+        let plugin = nu_plugin::add_plugin_to_working_set(working_set, &identity)
-        let gc_config = working_set
+            .map_err(|err| err.wrap(working_set, call.head))?;
-            .get_config()
-            .plugin_gc
-            .get(identity.name())
-            .clone();
-
-        // Add it to the working set
-        let plugin = working_set.find_or_create_plugin(&identity, || {
-            Arc::new(PersistentPlugin::new(identity.clone(), gc_config.clone()))
-        });
-
-        // Downcast the plugin to `PersistentPlugin` - we generally expect this to succeed. The
-        // trait object only exists so that nu-protocol can contain plugins without knowing anything
-        // about their implementation, but we only use `PersistentPlugin` in practice.
-        let plugin: Arc<PersistentPlugin> = plugin.as_any().downcast().map_err(|_| {
-            ParseError::InternalError(
-                "encountered unexpected RegisteredPlugin type".into(),
-                spans[0],
-            )
-        })?;
 
         let signatures = signature.map_or_else(
             || {
@@ -3731,8 +3731,6 @@ pub fn parse_register(working_set: &mut StateWorkingSet, lite_command: &LiteComm
                     )
                 })?;
 
-                plugin.set_gc_config(&gc_config);
-
                 let signatures = get_signature(plugin.clone(), get_envs).map_err(|err| {
                     log::warn!("Error getting signatures: {err:?}");
                     ParseError::LabeledError(
@@ -3776,6 +3774,100 @@ pub fn parse_register(working_set: &mut StateWorkingSet, lite_command: &LiteComm
     }])
 }
 
+#[cfg(feature = "plugin")]
+pub fn parse_plugin_use(working_set: &mut StateWorkingSet, call: Box<Call>) -> Pipeline {
+    use nu_protocol::{FromValue, PluginCacheFile};
+
+    let cwd = working_set.get_cwd();
+
+    if let Err(err) = (|| {
+        let name = call
+            .positional_nth(0)
+            .map(|expr| {
+                eval_constant(working_set, expr)
+                    .and_then(Spanned::<String>::from_value)
+                    .map_err(|err| err.wrap(working_set, call.head))
+            })
+            .expect("required positional should have been checked")?;
+
+        let plugin_config = call
+            .named_iter()
+            .find(|(arg_name, _, _)| arg_name.item == "plugin-config")
+            .map(|(_, _, expr)| {
+                let expr = expr
+                    .as_ref()
+                    .expect("--plugin-config arg should have been checked already");
+                eval_constant(working_set, expr)
+                    .and_then(Spanned::<String>::from_value)
+                    .map_err(|err| err.wrap(working_set, call.head))
+            })
+            .transpose()?;
+
+        // Find the actual plugin config path location. We don't have a const/env variable for this,
+        // it either lives in the current working directory or in the script's directory
+        let plugin_config_path = if let Some(custom_path) = &plugin_config {
+            find_in_dirs(&custom_path.item, working_set, &cwd, None).ok_or_else(|| {
+                ParseError::FileNotFound(custom_path.item.clone(), custom_path.span)
+            })?
+        } else {
+            ParserPath::RealPath(
+                working_set
+                    .permanent_state
+                    .plugin_path
+                    .as_ref()
+                    .ok_or_else(|| ParseError::LabeledErrorWithHelp {
+                        error: "Plugin cache file not set".into(),
+                        label: "can't load plugin without cache file".into(),
+                        span: call.head,
+                        help:
+                            "pass --plugin-config to `plugin use` when $nu.plugin-path is not set"
+                                .into(),
+                    })?
+                    .to_owned(),
+            )
+        };
+
+        let file = plugin_config_path.open(working_set).map_err(|err| {
+            ParseError::LabeledError(
+                "Plugin cache file can't be opened".into(),
+                err.to_string(),
+                plugin_config.as_ref().map(|p| p.span).unwrap_or(call.head),
+            )
+        })?;
+
+        // The file is now open, so we just have to parse the contents and find the plugin
+        let contents = PluginCacheFile::read_from(file, Some(call.head))
+            .map_err(|err| err.wrap(working_set, call.head))?;
+
+        let plugin_item = contents
+            .plugins
+            .iter()
+            .find(|plugin| plugin.name == name.item)
+            .ok_or_else(|| ParseError::PluginNotFound {
+                name: name.item.clone(),
+                name_span: name.span,
+                plugin_config_span: plugin_config.as_ref().map(|p| p.span),
+            })?;
+
+        // Now add the signatures to the working set
+        nu_plugin::load_plugin_cache_item(working_set, plugin_item, Some(call.head))
+            .map_err(|err| err.wrap(working_set, call.head))?;
+
+        Ok(())
+    })() {
+        working_set.error(err);
+    }
+
+    let call_span = call.span();
+
+    Pipeline::from_vec(vec![Expression {
+        expr: Expr::Call(call),
+        span: call_span,
+        ty: Type::Nothing,
+        custom_completion: None,
+    }])
+}
+
 pub fn find_dirs_var(working_set: &StateWorkingSet, var_name: &str) -> Option<VarId> {
     working_set
         .find_variable(format!("${}", var_name).as_bytes())
@@ -3799,13 +3891,13 @@ pub fn find_in_dirs(
     filename: &str,
     working_set: &StateWorkingSet,
     cwd: &str,
-    dirs_var_name: &str,
+    dirs_var_name: Option<&str>,
 ) -> Option<ParserPath> {
     pub fn find_in_dirs_with_id(
         filename: &str,
         working_set: &StateWorkingSet,
         cwd: &str,
-        dirs_var_name: &str,
+        dirs_var_name: Option<&str>,
     ) -> Option<ParserPath> {
         // Choose whether to use file-relative or PWD-relative path
         let actual_cwd = working_set
@@ -3845,8 +3937,10 @@ pub fn find_in_dirs(
         }
 
         // Look up relative path from NU_LIB_DIRS
-        working_set
+        dirs_var_name
-            .get_variable(find_dirs_var(working_set, dirs_var_name)?)
+            .as_ref()
+            .and_then(|dirs_var_name| find_dirs_var(working_set, dirs_var_name))
+            .map(|var_id| working_set.get_variable(var_id))?
             .const_val
             .as_ref()?
             .as_list()
@@ -3868,7 +3962,7 @@ pub fn find_in_dirs(
         filename: &str,
         working_set: &StateWorkingSet,
         cwd: &str,
-        dirs_env: &str,
+        dirs_env: Option<&str>,
     ) -> Option<PathBuf> {
         // Choose whether to use file-relative or PWD-relative path
         let actual_cwd = working_set
@@ -3882,7 +3976,9 @@ pub fn find_in_dirs(
             let path = Path::new(filename);
 
             if path.is_relative() {
-                if let Some(lib_dirs) = working_set.get_env_var(dirs_env) {
+                if let Some(lib_dirs) =
+                    dirs_env.and_then(|dirs_env| working_set.get_env_var(dirs_env))
+                {
                     if let Ok(dirs) = lib_dirs.as_list() {
                         for lib_dir in dirs {
                             if let Ok(dir) = lib_dir.to_path() {

crates/nu-parser/src/parser.rs

@@ -5149,12 +5149,24 @@ pub fn parse_expression(working_set: &mut StateWorkingSet, spans: &[Span]) -> Ex
             #[cfg(feature = "plugin")]
             b"register" => {
                 working_set.error(ParseError::BuiltinCommandInPipeline(
-                    "plugin".into(),
+                    "register".into(),
                     spans[0],
                 ));
 
                 parse_call(working_set, &spans[pos..], spans[0])
             }
+            #[cfg(feature = "plugin")]
+            b"plugin" => {
+                if spans.len() > 1 && working_set.get_span_contents(spans[1]) == b"use" {
+                    // only 'plugin use' is banned
+                    working_set.error(ParseError::BuiltinCommandInPipeline(
+                        "plugin use".into(),
+                        spans[0],
+                    ));
+                }
+
+                parse_call(working_set, &spans[pos..], spans[0])
+            }
 
             _ => parse_call(working_set, &spans[pos..], spans[0]),
         }
@@ -5286,6 +5298,20 @@ pub fn parse_builtin_commands(
         b"where" => parse_where(working_set, lite_command),
         #[cfg(feature = "plugin")]
         b"register" => parse_register(working_set, lite_command),
+        // Only "plugin use" is a keyword
+        #[cfg(feature = "plugin")]
+        b"plugin"
+            if lite_command
+                .parts
+                .get(1)
+                .is_some_and(|span| working_set.get_span_contents(*span) == b"use") =>
+        {
+            if let Some(redirection) = lite_command.redirection.as_ref() {
+                working_set.error(redirecting_builtin_error("plugin use", redirection));
+                return garbage_pipeline(&lite_command.parts);
+            }
+            parse_keyword(working_set, lite_command)
+        }
         _ => {
             let element = parse_pipeline_element(working_set, lite_command);
 

crates/nu-parser/src/parser_path.rs

@@ -103,17 +103,33 @@ impl ParserPath {
         }
     }
 
-    pub fn read<'a>(&'a self, working_set: &'a StateWorkingSet) -> Option<Vec<u8>> {
+    pub fn open<'a>(
+        &'a self,
+        working_set: &'a StateWorkingSet,
+    ) -> std::io::Result<Box<dyn std::io::Read + 'a>> {
         match self {
-            ParserPath::RealPath(p) => std::fs::read(p).ok(),
+            ParserPath::RealPath(p) => {
+                std::fs::File::open(p).map(|f| Box::new(f) as Box<dyn std::io::Read>)
+            }
             ParserPath::VirtualFile(_, file_id) => working_set
                 .get_contents_of_file(*file_id)
-                .map(|bytes| bytes.to_vec()),
+                .map(|bytes| Box::new(bytes) as Box<dyn std::io::Read>)
+                .ok_or(std::io::ErrorKind::NotFound.into()),
 
-            ParserPath::VirtualDir(..) => None,
+            ParserPath::VirtualDir(..) => Err(std::io::ErrorKind::NotFound.into()),
         }
     }
 
+    pub fn read<'a>(&'a self, working_set: &'a StateWorkingSet) -> Option<Vec<u8>> {
+        self.open(working_set)
+            .and_then(|mut reader| {
+                let mut vec = vec![];
+                reader.read_to_end(&mut vec)?;
+                Ok(vec)
+            })
+            .ok()
+    }
+
     pub fn from_virtual_path(
         working_set: &StateWorkingSet,
         name: &str,

crates/nu-plugin/src/lib.rs

@@ -78,10 +78,11 @@ pub use serializers::{json::JsonSerializer, msgpack::MsgPackSerializer};
 // Used by other nu crates.
 #[doc(hidden)]
 pub use plugin::{
-    create_plugin_signature, get_signature, load_plugin_cache_item, load_plugin_file,
+    add_plugin_to_working_set, create_plugin_signature, get_signature, load_plugin_cache_item,
-    serve_plugin_io, EngineInterfaceManager, GetPlugin, Interface, InterfaceManager,
+    load_plugin_file, serve_plugin_io, EngineInterfaceManager, GetPlugin, Interface,
-    PersistentPlugin, PluginDeclaration, PluginExecutionCommandContext, PluginExecutionContext,
+    InterfaceManager, PersistentPlugin, PluginDeclaration, PluginExecutionCommandContext,
-    PluginInterface, PluginInterfaceManager, PluginSource, ServePluginError,
+    PluginExecutionContext, PluginInterface, PluginInterfaceManager, PluginSource,
+    ServePluginError,
 };
 #[doc(hidden)]
 pub use protocol::{PluginCustomValue, PluginInput, PluginOutput};

crates/nu-plugin/src/plugin/interface/plugin.rs

@@ -748,9 +748,9 @@ impl PluginInterface {
                     PluginCall::CustomValueOp(val, _) => Some(val.span),
                 },
                 help: Some(format!(
-                    "the plugin may have experienced an error. Try registering the plugin again \
+                    "the plugin may have experienced an error. Try loading the plugin again \
                         with `{}`",
-                    self.state.source.identity.register_command(),
+                    self.state.source.identity.use_command(),
                 )),
                 inner: vec![],
             })?;

crates/nu-plugin/src/plugin/mod.rs

@@ -25,7 +25,7 @@ use nu_engine::documentation::get_flags_section;
 use nu_protocol::{
     ast::Operator, engine::StateWorkingSet, report_error_new, CustomValue, IntoSpanned,
     LabeledError, PipelineData, PluginCacheFile, PluginCacheItem, PluginCacheItemData,
-    PluginIdentity, PluginSignature, ShellError, Span, Spanned, Value,
+    PluginIdentity, PluginSignature, RegisteredPlugin, ShellError, Span, Spanned, Value,
 };
 use thiserror::Error;
 
@@ -942,7 +942,7 @@ pub fn load_plugin_cache_item(
     working_set: &mut StateWorkingSet,
     plugin: &PluginCacheItem,
     span: Option<Span>,
-) -> Result<(), ShellError> {
+) -> Result<Arc<PersistentPlugin>, ShellError> {
     let identity =
         PluginIdentity::new(plugin.filename.clone(), plugin.shell.clone()).map_err(|_| {
             ShellError::GenericError {
@@ -960,6 +960,33 @@ pub fn load_plugin_cache_item(
 
     match &plugin.data {
         PluginCacheItemData::Valid { commands } => {
+            let plugin = add_plugin_to_working_set(working_set, &identity)?;
+
+            // Ensure that the plugin is reset. We're going to load new signatures, so we want to
+            // make sure the running plugin reflects those new signatures, and it's possible that it
+            // doesn't.
+            plugin.reset()?;
+
+            // Create the declarations from the commands
+            for signature in commands {
+                let decl = PluginDeclaration::new(plugin.clone(), signature.clone());
+                working_set.add_decl(Box::new(decl));
+            }
+            Ok(plugin)
+        }
+        PluginCacheItemData::Invalid => Err(ShellError::PluginCacheDataInvalid {
+            plugin_name: identity.name().to_owned(),
+            span,
+            add_command: identity.add_command(),
+        }),
+    }
+}
+
+#[doc(hidden)]
+pub fn add_plugin_to_working_set(
+    working_set: &mut StateWorkingSet,
+    identity: &PluginIdentity,
+) -> Result<Arc<PersistentPlugin>, ShellError> {
     // Find garbage collection config for the plugin
     let gc_config = working_set
         .get_config()
@@ -968,31 +995,19 @@ pub fn load_plugin_cache_item(
         .clone();
 
     // Add it to / get it from the working set
-            let plugin = working_set.find_or_create_plugin(&identity, || {
+    let plugin = working_set.find_or_create_plugin(identity, || {
         Arc::new(PersistentPlugin::new(identity.clone(), gc_config.clone()))
     });
 
+    plugin.set_gc_config(&gc_config);
+
     // Downcast the plugin to `PersistentPlugin` - we generally expect this to succeed.
     // The trait object only exists so that nu-protocol can contain plugins without knowing
     // anything about their implementation, but we only use `PersistentPlugin` in practice.
-            let plugin: Arc<PersistentPlugin> =
     plugin
         .as_any()
         .downcast()
         .map_err(|_| ShellError::NushellFailed {
             msg: "encountered unexpected RegisteredPlugin type".into(),
-                    })?;
+        })
-
-            // Create the declarations from the commands
-            for signature in commands {
-                let decl = PluginDeclaration::new(plugin.clone(), signature.clone());
-                working_set.add_decl(Box::new(decl));
-            }
-            Ok(())
-        }
-        PluginCacheItemData::Invalid => Err(ShellError::PluginCacheDataInvalid {
-            plugin_name: identity.name().to_owned(),
-            register_command: identity.register_command(),
-        }),
-    }
 }

crates/nu-protocol/src/ast/expression.rs

@@ -108,6 +108,13 @@ impl Expression {
         }
     }
 
+    pub fn as_filepath(&self) -> Option<(String, bool)> {
+        match &self.expr {
+            Expr::Filepath(string, quoted) => Some((string.clone(), *quoted)),
+            _ => None,
+        }
+    }
+
     pub fn as_import_pattern(&self) -> Option<ImportPattern> {
         match &self.expr {
             Expr::ImportPattern(pattern) => Some(*pattern.clone()),

crates/nu-protocol/src/errors/parse_error.rs

@@ -439,6 +439,19 @@ pub enum ParseError {
     #[diagnostic(code(nu::parser::file_not_found))]
     FileNotFound(String, #[label("File not found: {0}")] Span),
 
+    #[error("Plugin not found")]
+    #[diagnostic(
+        code(nu::parser::plugin_not_found),
+        help("plugins need to be added to the plugin cache file before your script is run (see `plugin add`)"),
+    )]
+    PluginNotFound {
+        name: String,
+        #[label("Plugin not found: {name}")]
+        name_span: Span,
+        #[label("in this cache file")]
+        plugin_config_span: Option<Span>,
+    },
+
     #[error("Invalid literal")] // <problem> in <entity>.
     #[diagnostic()]
     InvalidLiteral(String, String, #[label("{0} in {1}")] Span),
@@ -544,6 +557,7 @@ impl ParseError {
             ParseError::SourcedFileNotFound(_, s) => *s,
             ParseError::RegisteredFileNotFound(_, s) => *s,
             ParseError::FileNotFound(_, s) => *s,
+            ParseError::PluginNotFound { name_span, .. } => *name_span,
             ParseError::LabeledError(_, _, s) => *s,
             ParseError::ShellAndAnd(s) => *s,
             ParseError::ShellOrOr(s) => *s,

crates/nu-protocol/src/errors/parse_warning.rs

@@ -5,19 +5,21 @@ use thiserror::Error;
 
 #[derive(Clone, Debug, Error, Diagnostic, Serialize, Deserialize)]
 pub enum ParseWarning {
-    #[error("Deprecated: {0}")]
+    #[error("Deprecated: {old_command}")]
-    DeprecatedWarning(
+    #[diagnostic(help("for more info: {url}"))]
-        String,
+    DeprecatedWarning {
-        String,
+        old_command: String,
-        #[label = "`{0}` is deprecated and will be removed in 0.90. Please use `{1}` instead, more info: https://www.nushell.sh/book/custom_commands.html"]
+        new_suggestion: String,
-        Span,
+        #[label("`{old_command}` is deprecated and will be removed in 0.94. Please {new_suggestion} instead")]
-    ),
+        span: Span,
+        url: String,
+    },
 }
 
 impl ParseWarning {
     pub fn span(&self) -> Span {
         match self {
-            ParseWarning::DeprecatedWarning(_, _, s) => *s,
+            ParseWarning::DeprecatedWarning { span, .. } => *span,
         }
     }
 }

crates/nu-protocol/src/errors/shell_error.rs

@@ -750,17 +750,19 @@ pub enum ShellError {
         span: Span,
     },
 
-    /// The cached plugin data (in `$nu.plugin-path`) for a plugin is invalid.
+    /// The cached plugin data for a plugin is invalid.
     ///
     /// ## Resolution
     ///
-    /// `register` the plugin again to update the data, or remove it.
+    /// `plugin add` the plugin again to update the data, or remove it with `plugin rm`.
     #[error("The cached plugin data for `{plugin_name}` is invalid")]
     #[diagnostic(code(nu::shell::plugin_cache_data_invalid))]
     PluginCacheDataInvalid {
         plugin_name: String,
-        #[help("try registering the plugin again with `{}`")]
+        #[label("plugin `{plugin_name}` loaded here")]
-        register_command: String,
+        span: Option<Span>,
+        #[help("the format in the plugin cache file is not compatible with this version of Nushell.\n\nTry adding the plugin again with `{}`")]
+        add_command: String,
     },
 
     /// A plugin failed to load.

crates/nu-protocol/src/plugin/identity.rs

@@ -1,11 +1,10 @@
 use std::path::{Path, PathBuf};
 
-use crate::{ParseError, Spanned};
+use crate::{ParseError, ShellError, Spanned};
 
-/// Error when an invalid plugin filename was encountered. This can be converted to [`ParseError`]
+/// Error when an invalid plugin filename was encountered.
-/// if a span is added.
 #[derive(Debug, Clone)]
-pub struct InvalidPluginFilename;
+pub struct InvalidPluginFilename(PathBuf);
 
 impl std::fmt::Display for InvalidPluginFilename {
     fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
@@ -23,6 +22,18 @@ impl From<Spanned<InvalidPluginFilename>> for ParseError {
     }
 }
 
+impl From<Spanned<InvalidPluginFilename>> for ShellError {
+    fn from(error: Spanned<InvalidPluginFilename>) -> ShellError {
+        ShellError::GenericError {
+            error: format!("Invalid plugin filename: {}", error.item.0.display()),
+            msg: "not a valid plugin filename".into(),
+            span: Some(error.span),
+            help: Some("valid Nushell plugin filenames must start with `nu_plugin_`".into()),
+            inner: vec![],
+        }
+    }
+}
+
 #[derive(Debug, Clone, PartialEq, Eq, PartialOrd, Ord, Hash)]
 pub struct PluginIdentity {
     /// The filename used to start the plugin
@@ -35,17 +46,25 @@ pub struct PluginIdentity {
 
 impl PluginIdentity {
     /// Create a new plugin identity from a path to plugin executable and shell option.
+    ///
+    /// The `filename` must be an absolute path. Canonicalize before trying to construct the
+    /// [`PluginIdentity`].
     pub fn new(
         filename: impl Into<PathBuf>,
         shell: Option<PathBuf>,
     ) -> Result<PluginIdentity, InvalidPluginFilename> {
-        let filename = filename.into();
+        let filename: PathBuf = filename.into();
+
+        // Must pass absolute path.
+        if filename.is_relative() {
+            return Err(InvalidPluginFilename(filename));
+        }
 
         let name = filename
             .file_stem()
             .map(|stem| stem.to_string_lossy().into_owned())
             .and_then(|stem| stem.strip_prefix("nu_plugin_").map(|s| s.to_owned()))
-            .ok_or(InvalidPluginFilename)?;
+            .ok_or_else(|| InvalidPluginFilename(filename.clone()))?;
 
         Ok(PluginIdentity {
             filename,
@@ -89,30 +108,42 @@ impl PluginIdentity {
             .expect("fake plugin identity path is invalid")
     }
 
-    /// A command that could be used to register the plugin, for suggesting in errors.
+    /// A command that could be used to add the plugin, for suggesting in errors.
-    pub fn register_command(&self) -> String {
+    pub fn add_command(&self) -> String {
         if let Some(shell) = self.shell() {
             format!(
-                "register --shell '{}' '{}'",
+                "plugin add --shell '{}' '{}'",
                 shell.display(),
                 self.filename().display(),
             )
         } else {
-            format!("register '{}'", self.filename().display())
+            format!("plugin add '{}'", self.filename().display())
         }
     }
+
+    /// A command that could be used to reload the plugin, for suggesting in errors.
+    pub fn use_command(&self) -> String {
+        format!("plugin use '{}'", self.name())
+    }
 }
 
 #[test]
 fn parses_name_from_path() {
     assert_eq!("test", PluginIdentity::new_fake("test").name());
     assert_eq!("test_2", PluginIdentity::new_fake("test_2").name());
+    let absolute_path = if cfg!(windows) {
+        r"C:\path\to\nu_plugin_foo.sh"
+    } else {
+        "/path/to/nu_plugin_foo.sh"
+    };
     assert_eq!(
         "foo",
-        PluginIdentity::new("nu_plugin_foo.sh", Some("sh".into()))
+        PluginIdentity::new(absolute_path, Some("sh".into()))
             .expect("should be valid")
             .name()
     );
+    // Relative paths should be invalid
+    PluginIdentity::new("nu_plugin_foo.sh", Some("sh".into())).expect_err("should be invalid");
     PluginIdentity::new("other", None).expect_err("should be invalid");
     PluginIdentity::new("", None).expect_err("should be invalid");
 }

crates/nu-test-support/src/macros.rs

@@ -235,7 +235,6 @@ macro_rules! nu_with_plugins {
 
 use crate::{Outcome, NATIVE_PATH_ENV_VAR};
 use std::ffi::OsStr;
-use std::fmt::Write;
 use std::{
     path::Path,
     process::{Command, Stdio},
@@ -340,17 +339,17 @@ where
 
     crate::commands::ensure_plugins_built();
 
-    let registrations: String = plugins
+    let plugin_paths_quoted: Vec<String> = plugins
         .iter()
-        .fold(String::new(), |mut output, plugin_name| {
+        .map(|plugin_name| {
             let plugin = with_exe(plugin_name);
             let plugin_path = nu_path::canonicalize_with(&plugin, &test_bins)
                 .unwrap_or_else(|_| panic!("failed to canonicalize plugin {} path", &plugin));
             let plugin_path = plugin_path.to_string_lossy();
-            let _ = write!(output, "register {plugin_path};");
+            escape_quote_string(plugin_path.into_owned())
-            output
+        })
-        });
+        .collect();
-    let commands = format!("{registrations}{command}");
+    let plugins_arg = format!("[{}]", plugin_paths_quoted.join(","));
 
     let target_cwd = crate::fs::in_directory(&cwd);
     // In plugin testing, we need to use installed nushell to drive
@@ -362,13 +361,15 @@ where
     let process = match setup_command(&executable_path, &target_cwd)
         .envs(envs)
         .arg("--commands")
-        .arg(commands)
+        .arg(command)
         .arg("--config")
         .arg(temp_config_file)
         .arg("--env-config")
         .arg(temp_env_config_file)
         .arg("--plugin-config")
         .arg(temp_plugin_file)
+        .arg("--plugins")
+        .arg(plugins_arg)
         .stdout(Stdio::piped())
         .stderr(Stdio::piped())
         .spawn()

src/command.rs

@@ -36,6 +36,8 @@ pub(crate) fn gather_commandline_args() -> (Vec<String>, String, Vec<String>) {
             "--log-level" | "--log-target" | "--testbin" | "--threads" | "-t"
             | "--include-path" | "--lsp" | "--ide-goto-def" | "--ide-hover" | "--ide-complete"
             | "--ide-check" => args.next(),
+            #[cfg(feature = "plugin")]
+            "--plugins" => args.next(),
             _ => None,
         };
 
@@ -87,6 +89,8 @@ pub(crate) fn parse_commandline_args(
             let testbin = call.get_flag_expr("testbin");
             #[cfg(feature = "plugin")]
             let plugin_file = call.get_flag_expr("plugin-config");
+            #[cfg(feature = "plugin")]
+            let plugins = call.get_flag_expr("plugins");
             let no_config_file = call.get_named_arg("no-config-file");
             let no_history = call.get_named_arg("no-history");
             let no_std_lib = call.get_named_arg("no-std-lib");
@@ -131,17 +135,60 @@ pub(crate) fn parse_commandline_args(
                 }
             }
 
+            fn extract_path(
+                expression: Option<&Expression>,
+            ) -> Result<Option<Spanned<String>>, ShellError> {
+                if let Some(expr) = expression {
+                    let tuple = expr.as_filepath();
+                    if let Some((str, _)) = tuple {
+                        Ok(Some(Spanned {
+                            item: str,
+                            span: expr.span,
+                        }))
+                    } else {
+                        Err(ShellError::TypeMismatch {
+                            err_message: "path".into(),
+                            span: expr.span,
+                        })
+                    }
+                } else {
+                    Ok(None)
+                }
+            }
+
             let commands = extract_contents(commands)?;
             let testbin = extract_contents(testbin)?;
             #[cfg(feature = "plugin")]
-            let plugin_file = extract_contents(plugin_file)?;
+            let plugin_file = extract_path(plugin_file)?;
-            let config_file = extract_contents(config_file)?;
+            let config_file = extract_path(config_file)?;
-            let env_file = extract_contents(env_file)?;
+            let env_file = extract_path(env_file)?;
             let log_level = extract_contents(log_level)?;
             let log_target = extract_contents(log_target)?;
             let execute = extract_contents(execute)?;
             let include_path = extract_contents(include_path)?;
 
+            #[cfg(feature = "plugin")]
+            let plugins = plugins
+                .map(|expr| match &expr.expr {
+                    Expr::List(list) => list
+                        .iter()
+                        .map(|item| {
+                            item.expr()
+                                .as_filepath()
+                                .map(|(s, _)| s.into_spanned(item.expr().span))
+                                .ok_or_else(|| ShellError::TypeMismatch {
+                                    err_message: "path".into(),
+                                    span: item.expr().span,
+                                })
+                        })
+                        .collect::<Result<Vec<Spanned<String>>, _>>(),
+                    _ => Err(ShellError::TypeMismatch {
+                        err_message: "list<path>".into(),
+                        span: expr.span,
+                    }),
+                })
+                .transpose()?;
+
             let help = call.has_flag(engine_state, &mut stack, "help")?;
 
             if help {
@@ -175,6 +222,8 @@ pub(crate) fn parse_commandline_args(
                 testbin,
                 #[cfg(feature = "plugin")]
                 plugin_file,
+                #[cfg(feature = "plugin")]
+                plugins,
                 no_config_file,
                 no_history,
                 no_std_lib,
@@ -217,6 +266,8 @@ pub(crate) struct NushellCliArgs {
     pub(crate) testbin: Option<Spanned<String>>,
     #[cfg(feature = "plugin")]
     pub(crate) plugin_file: Option<Spanned<String>>,
+    #[cfg(feature = "plugin")]
+    pub(crate) plugins: Option<Vec<Spanned<String>>>,
     pub(crate) no_config_file: Option<Spanned<String>>,
     pub(crate) no_history: Option<Spanned<String>>,
     pub(crate) no_std_lib: Option<Spanned<String>>,
@@ -294,13 +345,13 @@ impl Command for Nu {
             .switch("version", "print the version", Some('v'))
             .named(
                 "config",
-                SyntaxShape::String,
+                SyntaxShape::Filepath,
                 "start with an alternate config file",
                 None,
             )
             .named(
                 "env-config",
-                SyntaxShape::String,
+                SyntaxShape::Filepath,
                 "start with an alternate environment config file",
                 None,
             )
@@ -337,12 +388,19 @@ impl Command for Nu {
 
         #[cfg(feature = "plugin")]
         {
-            signature = signature.named(
+            signature = signature
+                .named(
                     "plugin-config",
-                SyntaxShape::String,
+                    SyntaxShape::Filepath,
                     "start with an alternate plugin cache file",
                     None,
-            );
+                )
+                .named(
+                    "plugins",
+                    SyntaxShape::List(Box::new(SyntaxShape::Filepath)),
+                    "list of plugin executable files to load, separately from the cache file",
+                    None,
+                )
         }
 
         signature = signature

src/main.rs

@@ -389,6 +389,46 @@ fn main() -> Result<()> {
         use_color,
     );
 
+    #[cfg(feature = "plugin")]
+    if let Some(plugins) = &parsed_nu_cli_args.plugins {
+        use nu_plugin::{GetPlugin, PluginDeclaration};
+        use nu_protocol::{engine::StateWorkingSet, ErrSpan, PluginIdentity};
+
+        // Load any plugins specified with --plugins
+        start_time = std::time::Instant::now();
+
+        let mut working_set = StateWorkingSet::new(&engine_state);
+        for plugin_filename in plugins {
+            // Make sure the plugin filenames are canonicalized
+            let filename = canonicalize_with(&plugin_filename.item, &init_cwd)
+                .err_span(plugin_filename.span)
+                .map_err(ShellError::from)?;
+
+            let identity = PluginIdentity::new(&filename, None)
+                .err_span(plugin_filename.span)
+                .map_err(ShellError::from)?;
+
+            // Create the plugin and add it to the working set
+            let plugin = nu_plugin::add_plugin_to_working_set(&mut working_set, &identity)?;
+
+            // Spawn the plugin to get its signatures, and then add the commands to the working set
+            for signature in plugin.clone().get_plugin(None)?.get_signature()? {
+                let decl = PluginDeclaration::new(plugin.clone(), signature);
+                working_set.add_decl(Box::new(decl));
+            }
+        }
+        engine_state.merge_delta(working_set.render())?;
+
+        perf(
+            "load plugins specified in --plugins",
+            start_time,
+            file!(),
+            line!(),
+            column!(),
+            use_color,
+        )
+    }
+
     start_time = std::time::Instant::now();
     if parsed_nu_cli_args.lsp {
         perf(

src/tests.rs

@@ -39,6 +39,7 @@ pub fn run_test_with_env(input: &str, expected: &str, env: &HashMap<&str, &str>)
     let name = file.path();
 
     let mut cmd = Command::cargo_bin("nu")?;
+    cmd.arg("--no-config-file");
     cmd.arg(name).envs(env);
 
     writeln!(file, "{input}")?;
@@ -53,6 +54,7 @@ pub fn run_test(input: &str, expected: &str) -> TestResult {
 
     let mut cmd = Command::cargo_bin("nu")?;
     cmd.arg("--no-std-lib");
+    cmd.arg("--no-config-file");
     cmd.arg(name);
     cmd.env(
         "PWD",
@@ -70,6 +72,7 @@ pub fn run_test_std(input: &str, expected: &str) -> TestResult {
     let name = file.path();
 
     let mut cmd = Command::cargo_bin("nu")?;
+    cmd.arg("--no-config-file");
     cmd.arg(name);
     cmd.env(
         "PWD",
@@ -105,6 +108,7 @@ pub fn run_test_contains(input: &str, expected: &str) -> TestResult {
 
     let mut cmd = Command::cargo_bin("nu")?;
     cmd.arg("--no-std-lib");
+    cmd.arg("--no-config-file");
     cmd.arg(name);
 
     writeln!(file, "{input}")?;
@@ -132,6 +136,7 @@ pub fn test_ide_contains(input: &str, ide_commands: &[&str], expected: &str) ->
 
     let mut cmd = Command::cargo_bin("nu")?;
     cmd.arg("--no-std-lib");
+    cmd.arg("--no-config-file");
     for ide_command in ide_commands {
         cmd.arg(ide_command);
     }
@@ -162,6 +167,7 @@ pub fn fail_test(input: &str, expected: &str) -> TestResult {
 
     let mut cmd = Command::cargo_bin("nu")?;
     cmd.arg("--no-std-lib");
+    cmd.arg("--no-config-file");
     cmd.arg(name);
     cmd.env(
         "PWD",

src/tests/test_parser.rs

@@ -594,6 +594,42 @@ register $file
     fail_test(input, "expected string, found int")
 }
 
+#[test]
+fn plugin_use_with_string_literal() -> TestResult {
+    fail_test(
+        r#"plugin use 'nu-plugin-math'"#,
+        "Plugin cache file not set",
+    )
+}
+
+#[test]
+fn plugin_use_with_string_constant() -> TestResult {
+    let input = "\
+const file = 'nu-plugin-math'
+plugin use $file
+";
+    // should not fail with `not a constant`
+    fail_test(input, "Plugin cache file not set")
+}
+
+#[test]
+fn plugin_use_with_string_variable() -> TestResult {
+    let input = "\
+let file = 'nu-plugin-math'
+plugin use $file
+";
+    fail_test(input, "Value is not a parse-time constant")
+}
+
+#[test]
+fn plugin_use_with_non_string_constant() -> TestResult {
+    let input = "\
+const file = 6
+plugin use $file
+";
+    fail_test(input, "expected string, found int")
+}
+
 #[test]
 fn extern_errors_with_no_space_between_params_and_name_1() -> TestResult {
     fail_test("extern cmd[]", "expected space")

tests/fixtures/formats/code.nu

@@ -1 +1 @@
-register
+plugin use

tests/plugins/cache_file.rs

@@ -1,8 +1,4 @@
-use std::{
+use std::{fs::File, path::PathBuf};
-    fs::File,
-    path::PathBuf,
-    process::{Command, Stdio},
-};
 
 use nu_protocol::{PluginCacheFile, PluginCacheItem, PluginCacheItemData};
 use nu_test_support::{fs::Stub, nu, nu_with_plugins, playground::Playground};
@@ -69,16 +65,70 @@ fn plugin_add_to_custom_path() {
 
 #[test]
 fn plugin_rm_then_restart_nu() {
-    let result = nu_with_plugins!(
+    let example_plugin_path = example_plugin_path();
-        cwd: ".",
+    Playground::setup("plugin rm from custom path", |dirs, playground| {
-        plugin: ("nu_plugin_example"),
+        playground.with_files(vec![
-        r#"
+            Stub::FileWithContent("config.nu", ""),
-            plugin rm example
+            Stub::FileWithContent("env.nu", ""),
-            ^$nu.current-exe --config $nu.config-path --env-config $nu.env-path --plugin-config $nu.plugin-path --commands 'plugin list | get name | to json --raw'
+        ]);
-        "#
+
-    );
+        let file = File::create(dirs.test().join("test-plugin-file.msgpackz"))
-    assert!(result.status.success());
+            .expect("failed to create file");
-    assert_eq!(r#"[]"#, result.out);
+        let mut contents = PluginCacheFile::new();
+
+        contents.upsert_plugin(PluginCacheItem {
+            name: "example".into(),
+            filename: example_plugin_path,
+            shell: None,
+            data: PluginCacheItemData::Valid { commands: vec![] },
+        });
+
+        contents.upsert_plugin(PluginCacheItem {
+            name: "foo".into(),
+            // this doesn't exist, but it should be ok
+            filename: dirs.test().join("nu_plugin_foo"),
+            shell: None,
+            data: PluginCacheItemData::Valid { commands: vec![] },
+        });
+
+        contents
+            .write_to(file, None)
+            .expect("failed to write plugin file");
+
+        assert_cmd::Command::new(nu_test_support::fs::executable_path())
+            .current_dir(dirs.test())
+            .args([
+                "--no-std-lib",
+                "--config",
+                "config.nu",
+                "--env-config",
+                "env.nu",
+                "--plugin-config",
+                "test-plugin-file.msgpackz",
+                "--commands",
+                "plugin rm example",
+            ])
+            .assert()
+            .success()
+            .stderr("");
+
+        assert_cmd::Command::new(nu_test_support::fs::executable_path())
+            .current_dir(dirs.test())
+            .args([
+                "--no-std-lib",
+                "--config",
+                "config.nu",
+                "--env-config",
+                "env.nu",
+                "--plugin-config",
+                "test-plugin-file.msgpackz",
+                "--commands",
+                "plugin list | get name | to json --raw",
+            ])
+            .assert()
+            .success()
+            .stdout("[\"foo\"]\n");
+    })
 }
 
 #[test]
@@ -176,7 +226,7 @@ fn warning_on_invalid_plugin_item() {
             .write_to(file, None)
             .expect("failed to write plugin file");
 
-        let result = Command::new(nu_test_support::fs::executable_path())
+        let result = assert_cmd::Command::new(nu_test_support::fs::executable_path())
             .current_dir(dirs.test())
             .args([
                 "--no-std-lib",
@@ -189,9 +239,6 @@ fn warning_on_invalid_plugin_item() {
                 "--commands",
                 "plugin list | get name | to json --raw",
             ])
-            .stdin(Stdio::null())
-            .stdout(Stdio::piped())
-            .stderr(Stdio::piped())
             .output()
             .expect("failed to run nu");
 
@@ -209,3 +256,78 @@ fn warning_on_invalid_plugin_item() {
         assert!(err.contains("badtest"));
     })
 }
+
+#[test]
+fn plugin_use_error_not_found() {
+    Playground::setup("plugin use error not found", |dirs, playground| {
+        playground.with_files(vec![
+            Stub::FileWithContent("config.nu", ""),
+            Stub::FileWithContent("env.nu", ""),
+        ]);
+
+        // Make an empty msgpackz
+        let file = File::create(dirs.test().join("plugin.msgpackz"))
+            .expect("failed to open plugin.msgpackz");
+        PluginCacheFile::default()
+            .write_to(file, None)
+            .expect("failed to write empty cache file");
+
+        let output = assert_cmd::Command::new(nu_test_support::fs::executable_path())
+            .current_dir(dirs.test())
+            .args(["--config", "config.nu"])
+            .args(["--env-config", "env.nu"])
+            .args(["--plugin-config", "plugin.msgpackz"])
+            .args(["--commands", "plugin use custom_values"])
+            .output()
+            .expect("failed to run nu");
+        let stderr = String::from_utf8_lossy(&output.stderr);
+        assert!(stderr.contains("Plugin not found"));
+    })
+}
+
+#[test]
+fn plugin_add_and_then_use() {
+    let example_plugin_path = example_plugin_path();
+    let result = nu_with_plugins!(
+        cwd: ".",
+        plugins: [],
+        &format!(r#"
+            plugin add '{}'
+            (
+                ^$nu.current-exe
+                    --config $nu.config-path
+                    --env-config $nu.env-path
+                    --plugin-config $nu.plugin-path
+                    --commands 'plugin use example; plugin list | get name | to json --raw'
+            )
+        "#, example_plugin_path.display())
+    );
+    assert!(result.status.success());
+    assert_eq!(r#"["example"]"#, result.out);
+}
+
+#[test]
+fn plugin_add_then_use_with_custom_path() {
+    let example_plugin_path = example_plugin_path();
+    Playground::setup("plugin add to custom path", |dirs, _playground| {
+        let result_add = nu!(
+            cwd: dirs.test(),
+            &format!("
+                plugin add --plugin-config test-plugin-file.msgpackz '{}'
+            ", example_plugin_path.display())
+        );
+
+        assert!(result_add.status.success());
+
+        let result_use = nu!(
+            cwd: dirs.test(),
+            r#"
+                plugin use --plugin-config test-plugin-file.msgpackz example
+                plugin list | get name | to json --raw
+            "#
+        );
+
+        assert!(result_use.status.success());
+        assert_eq!(r#"["example"]"#, result_use.out);
+    })
+}

tests/plugins/nu_plugin_nu_example.rs

@@ -1,26 +1,42 @@
-use nu_test_support::nu;
+use assert_cmd::Command;
-
-#[test]
-fn register() {
-    let out = nu!("register crates/nu_plugin_nu_example/nu_plugin_nu_example.nu");
-    assert!(out.status.success());
-    assert!(out.out.trim().is_empty());
-    assert!(out.err.trim().is_empty());
-}
 
 #[test]
 fn call() {
-    let out = nu!(r#"
+    // Add the `nu` binaries to the path env
-        register crates/nu_plugin_nu_example/nu_plugin_nu_example.nu
+    let path_env = std::env::join_paths(
-        nu_plugin_nu_example 4242 teststring
+        std::iter::once(nu_test_support::fs::binaries()).chain(
-    "#);
+            std::env::var_os(nu_test_support::NATIVE_PATH_ENV_VAR)
-    assert!(out.status.success());
+                .as_deref()
+                .map(std::env::split_paths)
+                .into_iter()
+                .flatten(),
+        ),
+    )
+    .expect("failed to make path var");
 
-    assert!(out.err.contains("name: nu_plugin_nu_example"));
+    let assert = Command::new(nu_test_support::fs::executable_path())
-    assert!(out.err.contains("4242"));
+        .env(nu_test_support::NATIVE_PATH_ENV_VAR, path_env)
-    assert!(out.err.contains("teststring"));
+        .args([
+            "--no-config-file",
+            "--no-std-lib",
+            "--plugins",
+            &format!(
+                "[crates{0}nu_plugin_nu_example{0}nu_plugin_nu_example.nu]",
+                std::path::MAIN_SEPARATOR
+            ),
+            "--commands",
+            "nu_plugin_nu_example 4242 teststring",
+        ])
+        .assert()
+        .success();
 
-    assert!(out.out.contains("one"));
+    let output = assert.get_output();
-    assert!(out.out.contains("two"));
+    let stdout = String::from_utf8_lossy(&output.stdout);
-    assert!(out.out.contains("three"));
+    let stderr = String::from_utf8_lossy(&output.stderr);
+    assert!(stdout.contains("one"));
+    assert!(stdout.contains("two"));
+    assert!(stdout.contains("three"));
+    assert!(stderr.contains("name: nu_plugin_nu_example"));
+    assert!(stderr.contains("4242"));
+    assert!(stderr.contains("teststring"));
 }