Benchmark each pipeline element (#7854)

# Description

Adds a `profile` command that profiles each pipeline element of a block
and can also recursively step into child blocks.

# Limitations
* It is implemented using pipeline metadata which currently get lost in
some circumstances (e.g.,
https://github.com/nushell/nushell/issues/4501). This means that the
profiler will lose data coming from subexpressions. This issue will
hopefully be solved in the future.
* It also does not step into individual loop iteration which I'm not
sure why but maybe that's a good thing.

# User-Facing Changes

Shouldn't change any existing behavior.

# Tests + Formatting

Don't forget to add tests that cover your changes.

Make sure you've run and fixed any issues with these commands:

- `cargo fmt --all -- --check` to check standard code formatting (`cargo
fmt --all` applies these changes)
- `cargo clippy --workspace -- -D warnings -D clippy::unwrap_used -A
clippy::needless_collect` to check that you're using the standard code
style
- `cargo test --workspace` to check that all tests pass

# After Submitting

If your PR had any user-facing changes, update [the
documentation](https://github.com/nushell/nushell.github.io) after the
PR is merged, if necessary. This will help us keep the docs up to date.

---------

Co-authored-by: Darren Schroeder <343840+fdncred@users.noreply.github.com>

crates/nu-command/src/core_commands/metadata.rs

@@ -75,7 +75,7 @@ impl Command for Metadata {
             None => {
                 let mut cols = vec![];
                 let mut vals = vec![];
-                if let Some(x) = &input.metadata() {
+                if let Some(x) = input.metadata().as_deref() {
                     match x {
                         PipelineMetadata {
                             data_source: DataSource::Ls,
@@ -89,6 +89,12 @@ impl Command for Metadata {
                             cols.push("source".into());
                             vals.push(Value::string("into html --list", head))
                         }
+                        PipelineMetadata {
+                            data_source: DataSource::Profiling(values),
+                        } => {
+                            cols.push("profiling".into());
+                            vals.push(Value::list(values.clone(), head))
+                        }
                     }
                 }
 
@@ -118,7 +124,11 @@ impl Command for Metadata {
     }
 }
 
-fn build_metadata_record(arg: &Value, metadata: &Option<PipelineMetadata>, head: Span) -> Value {
+fn build_metadata_record(
+    arg: &Value,
+    metadata: &Option<Box<PipelineMetadata>>,
+    head: Span,
+) -> Value {
     let mut cols = vec![];
     let mut vals = vec![];
 
@@ -140,7 +150,7 @@ fn build_metadata_record(arg: &Value, metadata: &Option<PipelineMetadata>, head:
         });
     }
 
-    if let Some(x) = &metadata {
+    if let Some(x) = metadata.as_deref() {
         match x {
             PipelineMetadata {
                 data_source: DataSource::Ls,
@@ -154,6 +164,12 @@ fn build_metadata_record(arg: &Value, metadata: &Option<PipelineMetadata>, head:
                 cols.push("source".into());
                 vals.push(Value::string("into html --list", head))
             }
+            PipelineMetadata {
+                data_source: DataSource::Profiling(values),
+            } => {
+                cols.push("profiling".into());
+                vals.push(Value::list(values.clone(), head))
+            }
         }
     }
 

crates/nu-command/src/default_context.rs

@@ -475,6 +475,7 @@ pub fn create_default_context() -> EngineState {
         // Experimental
         bind_command! {
             IsAdmin,
+            Profile,
             View,
             ViewFiles,
             ViewSource,

crates/nu-command/src/experimental/mod.rs

@@ -1,10 +1,12 @@
 mod is_admin;
+mod profile;
 mod view;
 mod view_files;
 mod view_source;
 mod view_span;
 
 pub use is_admin::IsAdmin;
+pub use profile::Profile;
 pub use view::View;
 pub use view_files::ViewFiles;
 pub use view_source::ViewSource;

crates/nu-command/src/experimental/profile.rs

@@ -0,0 +1,113 @@
+use nu_engine::{eval_block, CallExt};
+use nu_protocol::ast::Call;
+use nu_protocol::engine::{Closure, Command, EngineState, ProfilingConfig, Stack};
+use nu_protocol::{
+    Category, DataSource, Example, IntoPipelineData, PipelineData, PipelineMetadata, Signature,
+    Spanned, SyntaxShape, Type, Value,
+};
+
+#[derive(Clone)]
+pub struct Profile;
+
+impl Command for Profile {
+    fn name(&self) -> &str {
+        "profile"
+    }
+
+    fn usage(&self) -> &str {
+        "Profile each pipeline element in a closure."
+    }
+
+    fn extra_usage(&self) -> &str {
+        r#"The command collects run time of every pipeline element, recursively stepping into child closures
+until a maximum depth. Optionally, it also collects the source code and intermediate values.
+
+Current known limitations are:
+* profiling data from subexpressions is not tracked
+* it does not step into loop iterations"#
+    }
+
+    fn signature(&self) -> nu_protocol::Signature {
+        Signature::build("profile")
+            .required(
+                "closure",
+                SyntaxShape::Closure(Some(vec![SyntaxShape::Any])),
+                "the closure to run",
+            )
+            .switch("source", "Collect source code in the report", None)
+            .switch("values", "Collect values in the report", None)
+            .named(
+                "max-depth",
+                SyntaxShape::Int,
+                "How many levels of blocks to step into (default: 1)",
+                Some('d'),
+            )
+            .input_output_types(vec![(Type::Any, Type::Table(vec![]))])
+            .allow_variants_without_examples(true)
+            .category(Category::Debug)
+    }
+
+    fn run(
+        &self,
+        engine_state: &EngineState,
+        stack: &mut Stack,
+        call: &Call,
+        input: PipelineData,
+    ) -> Result<nu_protocol::PipelineData, nu_protocol::ShellError> {
+        let capture_block: Spanned<Closure> = call.req(engine_state, stack, 0)?;
+        let block = engine_state.get_block(capture_block.item.block_id);
+
+        let redirect_stdout = call.redirect_stdout;
+        let redirect_stderr = call.redirect_stderr;
+
+        let mut stack = stack.captures_to_stack(&capture_block.item.captures);
+
+        let input_val = input.into_value(call.head);
+
+        if let Some(var) = block.signature.get_positional(0) {
+            if let Some(var_id) = &var.var_id {
+                stack.add_var(*var_id, input_val.clone());
+            }
+        }
+
+        stack.profiling_config = ProfilingConfig::new(
+            call.get_flag::<i64>(engine_state, &mut stack, "max-depth")?
+                .unwrap_or(1),
+            call.has_flag("source"),
+            call.has_flag("values"),
+        );
+
+        let profiling_metadata = Box::new(PipelineMetadata {
+            data_source: DataSource::Profiling(vec![]),
+        });
+
+        let result = if let Some(PipelineMetadata {
+            data_source: DataSource::Profiling(values),
+        }) = eval_block(
+            engine_state,
+            &mut stack,
+            block,
+            input_val.into_pipeline_data_with_metadata(profiling_metadata),
+            redirect_stdout,
+            redirect_stderr,
+        )?
+        .metadata()
+        .map(|m| *m)
+        {
+            Value::list(values, call.head)
+        } else {
+            Value::nothing(call.head)
+        };
+
+        Ok(result.into_pipeline_data())
+    }
+
+    fn examples(&self) -> Vec<Example> {
+        vec![Example {
+            description:
+                "Profile some code, stepping into the `spam` command and collecting source.",
+            example: r#"def spam [] { "spam" }; profile { spam | str length } -d 2 --source"#,
+            result: None,
+        }]
+    }
+}

crates/nu-command/src/filesystem/ls.rs

@@ -264,9 +264,9 @@ impl Command for Ls {
                 _ => Some(Value::Nothing { span: call_span }),
             })
             .into_pipeline_data_with_metadata(
-                PipelineMetadata {
+                Box::new(PipelineMetadata {
                     data_source: DataSource::Ls,
-                },
+                }),
                 engine_state.ctrlc.clone(),
             ))
     }

crates/nu-command/src/filters/uniq.rs

@@ -264,7 +264,7 @@ pub fn uniq(
     call: &Call,
     input: Vec<Value>,
     item_mapper: Box<dyn Fn(ItemMapperState) -> ValueCounter>,
-    metadata: Option<PipelineMetadata>,
+    metadata: Option<Box<PipelineMetadata>>,
 ) -> Result<PipelineData, ShellError> {
     let ctrlc = engine_state.ctrlc.clone();
     let head = call.head;

crates/nu-command/src/formats/to/html.rs

@@ -320,9 +320,9 @@ fn to_html(
             vals: result,
             span: head,
         }
-        .into_pipeline_data_with_metadata(PipelineMetadata {
+        .into_pipeline_data_with_metadata(Box::new(PipelineMetadata {
             data_source: DataSource::HtmlThemes,
-        }));
+        })));
     } else {
         let theme_span = match &theme {
             Some(v) => v.span,

crates/nu-command/src/viewers/table.rs

@@ -612,9 +612,9 @@ fn handle_row_stream(
     call: &Call,
     row_offset: usize,
     ctrlc: Option<Arc<AtomicBool>>,
-    metadata: Option<PipelineMetadata>,
+    metadata: Option<Box<PipelineMetadata>>,
 ) -> Result<PipelineData, ShellError> {
-    let stream = match metadata {
+    let stream = match metadata.as_deref() {
         // First, `ls` sources:
         Some(PipelineMetadata {
             data_source: DataSource::Ls,

crates/nu-engine/src/eval.rs

@@ -6,11 +6,12 @@ use nu_protocol::{
         Operator, PathMember, PipelineElement, Redirection,
     },
     engine::{EngineState, Stack},
-    Config, IntoInterruptiblePipelineData, IntoPipelineData, PipelineData, Range, ShellError, Span,
-    Spanned, Unit, Value, VarId, ENV_VARIABLE_ID,
+    Config, DataSource, IntoInterruptiblePipelineData, IntoPipelineData, PipelineData,
+    PipelineMetadata, Range, ShellError, Span, Spanned, Unit, Value, VarId, ENV_VARIABLE_ID,
 };
 use nu_utils::stdout_write_all_and_flush;
 use std::collections::HashMap;
+use std::time::Instant;
 
 pub fn eval_operator(op: &Expression) -> Result<Operator, ShellError> {
     match op {
@@ -989,7 +990,16 @@ pub fn eval_block(
             *stack.recursion_count += 1;
         }
     }
+
     let num_pipelines = block.len();
+
+    let mut input_metadata = if stack.profiling_config.should_debug() {
+        stack.profiling_config.enter_block();
+        input.metadata()
+    } else {
+        None
+    };
+
     for (pipeline_idx, pipeline) in block.pipelines.iter().enumerate() {
         let mut i = 0;
 
@@ -1003,6 +1013,12 @@ pub fn eval_block(
                             | PipelineElement::SeparateRedirection { .. }
                     )));
 
+            let start_time = if stack.profiling_config.should_debug() {
+                Some(Instant::now())
+            } else {
+                None
+            };
+
             // if eval internal command failed, it can just make early return with `Err(ShellError)`.
             let eval_result = eval_element_with_input(
                 engine_state,
@@ -1021,6 +1037,106 @@ pub fn eval_block(
                 redirect_stderr,
             );
 
+            let end_time = if stack.profiling_config.should_debug() {
+                Some(Instant::now())
+            } else {
+                None
+            };
+
+            if let (Some(start_time), Some(end_time), Some(input_metadata)) =
+                (start_time, end_time, input_metadata.as_deref_mut())
+            {
+                let span = pipeline.elements[i].span();
+                let element_str = Value::string(
+                    String::from_utf8_lossy(
+                        engine_state.get_span_contents(&pipeline.elements[i].span()),
+                    ),
+                    span,
+                );
+                let time_ns = (end_time - start_time).as_nanos() as i64;
+
+                let mut cols = vec![
+                    "pipeline_idx".to_string(),
+                    "element_idx".to_string(),
+                    "depth".to_string(),
+                    "span".to_string(),
+                ];
+
+                let mut vals = vec![
+                    Value::int(pipeline_idx as i64, span),
+                    Value::int(i as i64, span),
+                    Value::int(stack.profiling_config.depth, span),
+                    Value::record(
+                        vec!["start".to_string(), "end".to_string()],
+                        vec![
+                            Value::int(span.start as i64, span),
+                            Value::int(span.end as i64, span),
+                        ],
+                        span,
+                    ),
+                ];
+
+                if stack.profiling_config.collect_source {
+                    cols.push("source".to_string());
+                    vals.push(element_str.clone());
+                }
+
+                if stack.profiling_config.collect_values {
+                    let value = match &eval_result {
+                        Ok((PipelineData::Value(val, ..), ..)) => val.clone(),
+                        Ok((PipelineData::ListStream(..), ..)) => {
+                            Value::string("list stream", span)
+                        }
+                        Ok((PipelineData::ExternalStream { .. }, ..)) => {
+                            Value::string("raw stream", span)
+                        }
+                        Ok((PipelineData::Empty, ..)) => Value::Nothing { span },
+                        Err(err) => Value::Error { error: err.clone() },
+                    };
+
+                    cols.push("value".to_string());
+                    vals.push(value);
+                }
+
+                cols.push("time".to_string());
+                vals.push(Value::Duration { val: time_ns, span });
+
+                let record = Value::Record { cols, vals, span };
+
+                let element_metadata = if let Ok((pipeline_data, ..)) = &eval_result {
+                    pipeline_data.metadata()
+                } else {
+                    None
+                };
+
+                if let PipelineMetadata {
+                    data_source: DataSource::Profiling(tgt_vals),
+                } = input_metadata
+                {
+                    tgt_vals.push(record);
+                } else {
+                    *input_metadata = PipelineMetadata {
+                        data_source: DataSource::Profiling(vec![record]),
+                    };
+                }
+
+                if let Some(PipelineMetadata {
+                    data_source: DataSource::Profiling(element_vals),
+                }) = element_metadata.map(|m| *m)
+                {
+                    if let PipelineMetadata {
+                        data_source: DataSource::Profiling(tgt_vals),
+                    } = input_metadata
+                    {
+                        tgt_vals.extend(element_vals);
+                    } else {
+                        *input_metadata = PipelineMetadata {
+                            data_source: DataSource::Profiling(element_vals),
+                        };
+                    }
+                }
+            }
+
             match (eval_result, redirect_stderr) {
                 (Ok((pipeline_data, _)), true) => {
                     input = pipeline_data;
@@ -1037,6 +1153,9 @@ pub fn eval_block(
                     // make early return so remaining commands will not be executed.
                     // don't return `Err(ShellError)`, so nushell wouldn't show extra error message.
                     if output.1 {
+                        if stack.profiling_config.should_debug() {
+                            stack.profiling_config.leave_block();
+                        }
                         return Ok(input);
                     }
                 }
@@ -1120,8 +1239,13 @@ pub fn eval_block(
         }
     }
 
+    if stack.profiling_config.should_debug() {
+        stack.profiling_config.leave_block();
+        Ok(input.set_metadata(input_metadata))
+    } else {
         Ok(input)
     }
+}
 
 fn print_or_return(pipeline_data: PipelineData, config: &Config) -> Result<(), ShellError> {
     for item in pipeline_data {

crates/nu-explore/src/nu_common/value.rs

@@ -17,7 +17,7 @@ pub fn collect_pipeline(input: PipelineData) -> (Vec<String>, Vec<Vec<Value>>) {
             metadata,
             span,
             ..
-        } => collect_external_stream(stdout, stderr, exit_code, metadata, span),
+        } => collect_external_stream(stdout, stderr, exit_code, metadata.map(|m| *m), span),
     }
 }
 

crates/nu-protocol/src/engine/stack.rs

@@ -7,6 +7,44 @@ use crate::{ShellError, Span, Value, VarId};
 /// Environment variables per overlay
 pub type EnvVars = HashMap<String, HashMap<String, Value>>;
 
+#[derive(Debug, Clone)]
+pub struct ProfilingConfig {
+    pub max_depth: i64,
+    pub depth: i64,
+    pub collect_source: bool,
+    pub collect_values: bool,
+}
+
+impl ProfilingConfig {
+    pub fn new(max_depth: i64, collect_source: bool, collect_values: bool) -> Self {
+        ProfilingConfig {
+            max_depth,
+            depth: 0,
+            collect_source,
+            collect_values,
+        }
+    }
+
+    pub fn enter_block(&mut self) {
+        self.depth += 1;
+    }
+
+    pub fn leave_block(&mut self) {
+        self.depth -= 1;
+    }
+
+    pub fn should_debug(&self) -> bool {
+        self.depth <= self.max_depth
+    }
+
+    pub fn reset(&mut self) {
+        self.max_depth = 0;
+        self.depth = 0;
+        self.collect_source = false;
+        self.collect_values = false;
+    }
+}
+
 /// A runtime value stack used during evaluation
 ///
 /// A note on implementation:
@@ -35,6 +73,7 @@ pub struct Stack {
     /// List of active overlays
     pub active_overlays: Vec<String>,
     pub recursion_count: Box<u64>,
+    pub profiling_config: ProfilingConfig,
 }
 
 impl Stack {
@@ -45,6 +84,7 @@ impl Stack {
             env_hidden: HashMap::new(),
             active_overlays: vec![DEFAULT_OVERLAY_NAME.to_string()],
             recursion_count: Box::new(0),
+            profiling_config: ProfilingConfig::new(0, false, false),
         }
     }
 
@@ -126,6 +166,7 @@ impl Stack {
             env_hidden: HashMap::new(),
             active_overlays: self.active_overlays.clone(),
             recursion_count: self.recursion_count.to_owned(),
+            profiling_config: self.profiling_config.clone(),
         }
     }
 
@@ -151,6 +192,7 @@ impl Stack {
             env_hidden: HashMap::new(),
             active_overlays: self.active_overlays.clone(),
             recursion_count: self.recursion_count.to_owned(),
+            profiling_config: self.profiling_config.clone(),
         }
     }
 

crates/nu-protocol/src/pipeline_data.rs

@@ -40,14 +40,16 @@ const LINE_ENDING_PATTERN: &[char] = &['\r', '\n'];
 /// Nushell.
 #[derive(Debug)]
 pub enum PipelineData {
-    Value(Value, Option<PipelineMetadata>),
-    ListStream(ListStream, Option<PipelineMetadata>),
+    // Note: the PipelineMetadata is boxed everywhere because the DataSource::Profiling caused
+    // stack overflow on Windows CI when testing virtualenv
+    Value(Value, Option<Box<PipelineMetadata>>),
+    ListStream(ListStream, Option<Box<PipelineMetadata>>),
     ExternalStream {
         stdout: Option<RawStream>,
         stderr: Option<RawStream>,
         exit_code: Option<ListStream>,
         span: Span,
-        metadata: Option<PipelineMetadata>,
+        metadata: Option<Box<PipelineMetadata>>,
         trim_end_newline: bool,
     },
     Empty,
@@ -62,10 +64,11 @@ pub struct PipelineMetadata {
 pub enum DataSource {
     Ls,
     HtmlThemes,
+    Profiling(Vec<Value>),
 }
 
 impl PipelineData {
-    pub fn new_with_metadata(metadata: Option<PipelineMetadata>, span: Span) -> PipelineData {
+    pub fn new_with_metadata(metadata: Option<Box<PipelineMetadata>>, span: Span) -> PipelineData {
         PipelineData::Value(Value::Nothing { span }, metadata)
     }
 
@@ -73,7 +76,7 @@ impl PipelineData {
         PipelineData::Empty
     }
 
-    pub fn metadata(&self) -> Option<PipelineMetadata> {
+    pub fn metadata(&self) -> Option<Box<PipelineMetadata>> {
         match self {
             PipelineData::ListStream(_, x) => x.clone(),
             PipelineData::ExternalStream { metadata: x, .. } => x.clone(),
@@ -82,7 +85,7 @@ impl PipelineData {
         }
     }
 
-    pub fn set_metadata(mut self, metadata: Option<PipelineMetadata>) -> Self {
+    pub fn set_metadata(mut self, metadata: Option<Box<PipelineMetadata>>) -> Self {
         match &mut self {
             PipelineData::ListStream(_, x) => *x = metadata,
             PipelineData::ExternalStream { metadata: x, .. } => *x = metadata,
@@ -284,7 +287,7 @@ impl PipelineData {
     pub fn collect_string_strict(
         self,
         span: Span,
-    ) -> Result<(String, Span, Option<PipelineMetadata>), ShellError> {
+    ) -> Result<(String, Span, Option<Box<PipelineMetadata>>), ShellError> {
         match self {
             PipelineData::Empty => Ok((String::new(), span, None)),
             PipelineData::Value(Value::String { val, span }, metadata) => Ok((val, span, metadata)),
@@ -809,9 +812,10 @@ impl Iterator for PipelineIterator {
 
 pub trait IntoPipelineData {
     fn into_pipeline_data(self) -> PipelineData;
+
     fn into_pipeline_data_with_metadata(
         self,
-        metadata: impl Into<Option<PipelineMetadata>>,
+        metadata: impl Into<Option<Box<PipelineMetadata>>>,
     ) -> PipelineData;
 }
 
@@ -822,9 +826,10 @@ where
     fn into_pipeline_data(self) -> PipelineData {
         PipelineData::Value(self.into(), None)
     }
+
     fn into_pipeline_data_with_metadata(
         self,
-        metadata: impl Into<Option<PipelineMetadata>>,
+        metadata: impl Into<Option<Box<PipelineMetadata>>>,
     ) -> PipelineData {
         PipelineData::Value(self.into(), metadata.into())
     }
@@ -834,7 +839,7 @@ pub trait IntoInterruptiblePipelineData {
     fn into_pipeline_data(self, ctrlc: Option<Arc<AtomicBool>>) -> PipelineData;
     fn into_pipeline_data_with_metadata(
         self,
-        metadata: impl Into<Option<PipelineMetadata>>,
+        metadata: impl Into<Option<Box<PipelineMetadata>>>,
         ctrlc: Option<Arc<AtomicBool>>,
     ) -> PipelineData;
 }
@@ -857,7 +862,7 @@ where
 
     fn into_pipeline_data_with_metadata(
         self,
-        metadata: impl Into<Option<PipelineMetadata>>,
+        metadata: impl Into<Option<Box<PipelineMetadata>>>,
         ctrlc: Option<Arc<AtomicBool>>,
     ) -> PipelineData {
         PipelineData::ListStream(