Disable pipeline echo (#8292)

# Description

Change behavior of block evaluation to not print result of intermediate
commands.
Previously result of every but last pipeline in a block was printed to
stdout, and last one was returned

![image](https://user-images.githubusercontent.com/17511668/222550110-3f62fbed-432c-4b46-b9b1-4cb45a1f893e.png)
With this change results of intermediate pipelines are discarded after
they finish and the last one is returned as before:

![image](https://user-images.githubusercontent.com/17511668/222550346-f1e74f80-f6b6-4aa3-98d6-888ea4cb4915.png)
Now one should use `print` explicitly to print something to stdout

![image](https://user-images.githubusercontent.com/17511668/222923955-fda0d77b-41b4-4f91-a80f-12b0a1880c05.png)

**Note, that this behavior is not limited to functions!** The scope of
this change are all blocks. All of the below are executed as blocks and
thus exibited this behavior in the same way:

![image](https://user-images.githubusercontent.com/17511668/222924062-342c15de-4273-4bf5-8b39-fe6e3aa96076.png)

With this change outputs for all types of blocks are cleaned:

![image](https://user-images.githubusercontent.com/17511668/222924118-7d51c27e-04bb-43e5-8efe-38b484683bfe.png)


# User-Facing Changes

All types of blocks (function bodies, closures, `if` branches, `for` and
`loop` bodies e.t.c.) no longer print result of intermediate pipelines.

# 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.

crates/nu-command/tests/commands/for_.rs

@@ -21,7 +21,7 @@ fn for_break_on_external_failed() {
         cwd: ".",
         r#"
         for i in 1..2 {
-            echo 1;
+            print 1;
             nu --testbin fail
         }"#
     );

crates/nu-command/tests/commands/loop_.rs

@@ -33,7 +33,7 @@ fn loop_break_on_external_failed() {
             } else {
                 $total += 1;
             }
-            echo 1;
+            print 1;
             nu --testbin fail;
         }"#
     );

crates/nu-command/tests/commands/open.rs

@@ -262,10 +262,10 @@ fn test_open_block_command() {
         r#"
             def "from blockcommandparser" [] { lines | split column ",|," }
             let values = (open sample.blockcommandparser)
-            echo ($values | get column1 | get 0)
+            print ($values | get column1 | get 0)
-            echo ($values | get column2 | get 0)
+            print ($values | get column2 | get 0)
-            echo ($values | get column1 | get 1)
+            print ($values | get column1 | get 1)
-            echo ($values | get column2 | get 1)
+            print ($values | get column2 | get 1)
         "#
     );
 

crates/nu-command/tests/commands/try_.rs

@@ -54,7 +54,7 @@ fn external_failed_should_be_caught() {
 fn loop_try_break_should_be_successful() {
     let output = nu!(
         cwd: ".",
-        "loop { try { echo 'successful'; break } catch { echo 'failed'; continue } }"
+        "loop { try { print 'successful'; break } catch { print 'failed'; continue } }"
     );
 
     assert_eq!(output.out, "successful");
@@ -66,7 +66,7 @@ fn loop_catch_break_should_show_failed() {
         cwd: ".",
         "loop {
             try { invalid 1;
-            continue; } catch { echo 'failed'; break }
+            continue; } catch { print 'failed'; break }
         }
         "
     );

crates/nu-command/tests/commands/while_.rs

@@ -26,7 +26,7 @@ fn while_auto_print_in_each_iteration() {
 fn while_break_on_external_failed() {
     let actual = nu!(
         cwd: ".",
-        "mut total = 0; while $total < 2 { $total = $total + 1; echo 1; nu --testbin fail }"
+        "mut total = 0; while $total < 2 { $total = $total + 1; print 1; nu --testbin fail }"
     );
     // Note: nu! macro auto replace "\n" and "\r\n" with ""
     // so our output will be `1`

crates/nu-command/tests/commands/with_env.rs

@@ -71,11 +71,11 @@ fn with_env_hides_variables_in_parent_scope() {
         cwd: "tests/fixtures/formats",
         r#"
         let-env FOO = "1"
-        echo $env.FOO
+        print $env.FOO
         with-env [FOO null] {
             echo $env.FOO
         }
-        echo $env.FOO
+        print $env.FOO
         "#
     );
 
@@ -88,9 +88,9 @@ fn with_env_shorthand_can_not_hide_variables() {
         cwd: "tests/fixtures/formats",
         r#"
         let-env FOO = "1"
-        echo $env.FOO
+        print $env.FOO
-        FOO=null echo $env.FOO
+        FOO=null print $env.FOO
-        echo $env.FOO
+        print $env.FOO
         "#
     );
 

crates/nu-engine/src/eval.rs

@@ -6,10 +6,9 @@ use nu_protocol::{
         Operator, PathMember, PipelineElement, Redirection,
     },
     engine::{EngineState, ProfilingConfig, Stack},
-    Config, DataSource, IntoInterruptiblePipelineData, IntoPipelineData, PipelineData,
+    DataSource, IntoInterruptiblePipelineData, IntoPipelineData, PipelineData, PipelineMetadata,
-    PipelineMetadata, Range, ShellError, Span, Spanned, Unit, Value, VarId, ENV_VARIABLE_ID,
+    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;
 
@@ -1112,24 +1111,7 @@ pub fn eval_block(
                 } => {
                     let exit_code = exit_code.take();
 
-                    // Drain the input to the screen via tabular output
+                    input.drain()?;
-                    let config = engine_state.get_config();
-
-                    match engine_state.find_decl("table".as_bytes(), &[]) {
-                        Some(decl_id) => {
-                            let table = engine_state.get_decl(decl_id).run(
-                                engine_state,
-                                stack,
-                                &Call::new(Span::new(0, 0)),
-                                input,
-                            )?;
-
-                            print_or_return(table, config)?;
-                        }
-                        None => {
-                            print_or_return(input, config)?;
-                        }
-                    };
 
                     if let Some(exit_code) = exit_code {
                         let mut v: Vec<_> = exit_code.collect();
@@ -1139,40 +1121,7 @@ pub fn eval_block(
                         }
                     }
                 }
-                _ => {
+                _ => input.drain()?,
-                    // Drain the input to the screen via tabular output
-                    let config = engine_state.get_config();
-
-                    match engine_state.find_decl("table".as_bytes(), &[]) {
-                        Some(decl_id) => {
-                            let table = engine_state.get_decl(decl_id);
-
-                            if let Some(block_id) = table.get_block_id() {
-                                let block = engine_state.get_block(block_id);
-                                eval_block(
-                                    engine_state,
-                                    stack,
-                                    block,
-                                    input,
-                                    redirect_stdout,
-                                    redirect_stderr,
-                                )?;
-                            } else {
-                                let table = table.run(
-                                    engine_state,
-                                    stack,
-                                    &Call::new(Span::new(0, 0)),
-                                    input,
-                                )?;
-
-                                print_or_return(table, config)?;
-                            }
-                        }
-                        None => {
-                            print_or_return(input, config)?;
-                        }
-                    };
-                }
             }
 
             input = PipelineData::empty()
@@ -1187,21 +1136,6 @@ pub fn eval_block(
     }
 }
 
-fn print_or_return(pipeline_data: PipelineData, config: &Config) -> Result<(), ShellError> {
-    for item in pipeline_data {
-        if let Value::Error { error } = item {
-            return Err(*error);
-        }
-
-        let mut out = item.into_string("\n", config);
-        out.push('\n');
-
-        stdout_write_all_and_flush(out)?;
-    }
-
-    Ok(())
-}
-
 pub fn eval_subexpression(
     engine_state: &EngineState,
     stack: &mut Stack,

crates/nu-protocol/src/pipeline_data.rs

@@ -200,6 +200,26 @@ impl PipelineData {
         }
     }
 
+    pub fn drain(self) -> Result<(), ShellError> {
+        match self {
+            PipelineData::Value(Value::Error { error }, _) => Err(*error),
+            PipelineData::Value(_, _) => Ok(()),
+            PipelineData::ListStream(stream, _) => stream.drain(),
+            PipelineData::ExternalStream { stdout, stderr, .. } => {
+                if let Some(stdout) = stdout {
+                    stdout.drain()?;
+                }
+
+                if let Some(stderr) = stderr {
+                    stderr.drain()?;
+                }
+
+                Ok(())
+            }
+            PipelineData::Empty => Ok(()),
+        }
+    }
+
     /// Try convert from self into iterator
     ///
     /// It returns Err if the `self` cannot be converted to an iterator.

crates/nu-protocol/src/value/stream.rs

@@ -75,6 +75,20 @@ impl RawStream {
             known_size: self.known_size,
         }
     }
+
+    pub fn drain(self) -> Result<(), ShellError> {
+        for next in self {
+            match next {
+                Ok(val) => {
+                    if let Value::Error { error } = val {
+                        return Err(*error);
+                    }
+                }
+                Err(err) => return Err(err),
+            }
+        }
+        Ok(())
+    }
 }
 impl Debug for RawStream {
     fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
@@ -201,6 +215,15 @@ impl ListStream {
             .join(separator)
     }
 
+    pub fn drain(self) -> Result<(), ShellError> {
+        for next in self {
+            if let Value::Error { error } = next {
+                return Err(*error);
+            }
+        }
+        Ok(())
+    }
+
     pub fn from_stream(
         input: impl Iterator<Item = Value> + Send + 'static,
         ctrlc: Option<Arc<AtomicBool>>,

tests/fixtures/formats/script_multiline.nu

@@ -1,2 +1,2 @@
-echo [1 4] | length
+print ([1 4] | length)
-echo [2 3 5] | length
+print (echo [2 3 5] | length)

tests/shell/pipeline/commands/internal.rs

@@ -48,7 +48,7 @@ fn treats_dot_dot_as_path_not_range() {
         r#"
             mkdir temp;
             cd temp;
-            echo (open ../nu_times.csv).name.0 | table;
+            print (open ../nu_times.csv).name.0 | table;
             cd ..;
             rmdir temp
             "#
@@ -385,9 +385,9 @@ fn let_env_hides_variable() {
         cwd: ".",
         r#"
             let-env TESTENVVAR = "hello world"
-            echo $env.TESTENVVAR
+            print $env.TESTENVVAR
             hide-env TESTENVVAR
-            echo $env.TESTENVVAR
+            print $env.TESTENVVAR
         "#
     );
 
@@ -401,12 +401,12 @@ fn let_env_hides_variable_in_parent_scope() {
         cwd: ".",
         r#"
             let-env TESTENVVAR = "hello world"
-            echo $env.TESTENVVAR
+            print $env.TESTENVVAR
             do {
                 hide-env TESTENVVAR
-                echo $env.TESTENVVAR
+                print $env.TESTENVVAR
             }
-            echo $env.TESTENVVAR
+            print $env.TESTENVVAR
         "#
     );
 
@@ -446,14 +446,14 @@ fn unlet_variable_in_parent_scope() {
         cwd: ".",
         r#"
             let-env DEBUG = "1"
-            echo $env.DEBUG
+            print $env.DEBUG
             do {
                 let-env DEBUG = "2"
-                echo $env.DEBUG
+                print $env.DEBUG
                 hide-env DEBUG
-                echo $env.DEBUG
+                print $env.DEBUG
             }
-            echo $env.DEBUG
+            print $env.DEBUG
         "#
     );
 
@@ -477,7 +477,7 @@ fn proper_shadow_let_env_aliases() {
     let actual = nu!(
         cwd: ".",
         r#"
-        let-env DEBUG = "true"; echo $env.DEBUG | table; do { let-env DEBUG = "false"; echo $env.DEBUG } | table; echo $env.DEBUG
+        let-env DEBUG = "true"; print $env.DEBUG | table; do { let-env DEBUG = "false"; print $env.DEBUG } | table; print $env.DEBUG
         "#
     );
     assert_eq!(actual.out, "truefalsetrue");
@@ -526,7 +526,7 @@ fn proper_shadow_load_env_aliases() {
     let actual = nu!(
         cwd: ".",
         r#"
-        let-env DEBUG = "true"; echo $env.DEBUG | table; do { echo {DEBUG: "false"} | load-env; echo $env.DEBUG } | table; echo $env.DEBUG
+        let-env DEBUG = "true"; print $env.DEBUG | table; do { echo {DEBUG: "false"} | load-env; print $env.DEBUG } | table; print $env.DEBUG
         "#
     );
     assert_eq!(actual.out, "truefalsetrue");
@@ -576,7 +576,7 @@ fn proper_shadow_let_aliases() {
     let actual = nu!(
         cwd: ".",
         r#"
-        let DEBUG = false; echo $DEBUG | table; do { let DEBUG = true; echo $DEBUG } | table; echo $DEBUG
+        let DEBUG = false; print $DEBUG | table; do { let DEBUG = true; print $DEBUG } | table; print $DEBUG
         "#
     );
     assert_eq!(actual.out, "falsetruefalse");