Support redirect stderr and stdout+stderr with a pipe (#11708)

# Description
Close: #9673
Close: #8277
Close: #10944

This pr introduces the following syntax:
1. `e>|`, pipe stderr to next command. Example: `$env.FOO=bar nu
--testbin echo_env_stderr FOO e>| str length`
2. `o+e>|` and `e+o>|`, pipe both stdout and stderr to next command,
example: `$env.FOO=bar nu --testbin echo_env_mixed out-err FOO FOO e+o>|
str length`

Note: it only works for external commands. ~There is no different for
internal commands, that is, the following three commands do the same
things:~ Edit: it raises errors if we want to pipes for internal
commands
``` 
❯ ls e>| str length
Error:   × `e>|` only works with external streams
   ╭─[entry #1:1:1]
 1 │ ls e>| str length
   ·    ─┬─
   ·     ╰── `e>|` only works on external streams
   ╰────

❯ ls e+o>| str length
Error:   × `o+e>|` only works with external streams
   ╭─[entry #2:1:1]
 1 │ ls e+o>| str length
   ·    ──┬──
   ·      ╰── `o+e>|` only works on external streams
   ╰────
```

This can help us to avoid some strange issues like the following:

`$env.FOO=bar (nu --testbin echo_env_stderr FOO) e>| str length`

Which is hard to understand and hard to explain to users.

# User-Facing Changes
Nan

# Tests + Formatting
To be done

# After Submitting
Maybe update documentation about these syntax.

crates/nu-cli/src/completions/completer.rs

@@ -129,6 +129,8 @@ impl NuCompleter {
             for pipeline_element in pipeline.elements {
                 match pipeline_element {
                     PipelineElement::Expression(_, expr)
+                    | PipelineElement::ErrPipedExpression(_, expr)
+                    | PipelineElement::OutErrPipedExpression(_, expr)
                     | PipelineElement::Redirection(_, _, expr, _)
                     | PipelineElement::And(_, expr)
                     | PipelineElement::Or(_, expr)

crates/nu-cli/src/syntax_highlight.rs

@@ -264,6 +264,8 @@ fn find_matching_block_end_in_block(
         for e in &p.elements {
             match e {
                 PipelineElement::Expression(_, e)
+                | PipelineElement::ErrPipedExpression(_, e)
+                | PipelineElement::OutErrPipedExpression(_, e)
                 | PipelineElement::Redirection(_, _, e, _)
                 | PipelineElement::And(_, e)
                 | PipelineElement::Or(_, e)

crates/nu-command/src/formats/from/nuon.rs

@@ -124,6 +124,8 @@ impl Command for FromNuon {
             } else {
                 match pipeline.elements.remove(0) {
                     PipelineElement::Expression(_, expression)
+                    | PipelineElement::ErrPipedExpression(_, expression)
+                    | PipelineElement::OutErrPipedExpression(_, expression)
                     | PipelineElement::Redirection(_, _, expression, _)
                     | PipelineElement::And(_, expression)
                     | PipelineElement::Or(_, expression)

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

@@ -60,6 +60,26 @@ fn let_pipeline_redirects_externals() {
     assert_eq!(actual.out, "3");
 }
 
+#[test]
+fn let_err_pipeline_redirects_externals() {
+    let actual = nu!(
+        r#"let x = with-env [FOO "foo"] {nu --testbin echo_env_stderr FOO e>| str length}; $x"#
+    );
+
+    // have an extra \n, so length is 4.
+    assert_eq!(actual.out, "4");
+}
+
+#[test]
+fn let_outerr_pipeline_redirects_externals() {
+    let actual = nu!(
+        r#"let x = with-env [FOO "foo"] {nu --testbin echo_env_stderr FOO o+e>| str length}; $x"#
+    );
+
+    // have an extra \n, so length is 4.
+    assert_eq!(actual.out, "4");
+}
+
 #[ignore]
 #[test]
 fn let_with_external_failed() {

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

@@ -333,31 +333,71 @@ fn redirection_should_have_a_target() {
 }
 
 #[test]
-fn redirection_with_pipe() {
+fn redirection_with_out_pipe() {
     use nu_test_support::playground::Playground;
-    Playground::setup(
+    Playground::setup("redirection with out pipes", |dirs, _| {
-        "external with many stdout and stderr messages",
+        // check for stdout
-        |dirs, _| {
+        let actual = nu!(
-            // check for stdout
+            cwd: dirs.test(),
+            r#"$env.BAZ = "message"; nu --testbin echo_env_mixed out-err BAZ BAZ err> tmp_file | str length"#,
+        );
+
+        assert_eq!(actual.out, "8");
+        // check for stderr redirection file.
+        let expected_out_file = dirs.test().join("tmp_file");
+        let actual_len = file_contents(expected_out_file).len();
+        assert_eq!(actual_len, 8);
+    })
+}
+
+#[test]
+fn redirection_with_err_pipe() {
+    use nu_test_support::playground::Playground;
+    Playground::setup("redirection with err pipe", |dirs, _| {
+        // check for stdout
+        let actual = nu!(
+            cwd: dirs.test(),
+            r#"$env.BAZ = "message"; nu --testbin echo_env_mixed out-err BAZ BAZ out> tmp_file e>| str length"#,
+        );
+
+        assert_eq!(actual.out, "8");
+        // check for stdout redirection file.
+        let expected_out_file = dirs.test().join("tmp_file");
+        let actual_len = file_contents(expected_out_file).len();
+        assert_eq!(actual_len, 8);
+    })
+}
+
+#[test]
+fn no_redirection_with_outerr_pipe() {
+    Playground::setup("redirection does not accept outerr pipe", |dirs, _| {
+        for redirect_type in ["o>", "e>", "o+e>"] {
             let actual = nu!(
                 cwd: dirs.test(),
-                r#"$env.BAZ = "message"; nu --testbin echo_env_mixed out-err BAZ BAZ err> tmp_file | str length"#,
+                &format!("echo 3 {redirect_type} a.txt o+e>| str length")
             );
-
+            assert!(actual.err.contains("not allowed to use with redirection"));
-            assert_eq!(actual.out, "8");
+            assert!(
-            // check for stderr redirection file.
+                !dirs.test().join("a.txt").exists(),
-            let expected_out_file = dirs.test().join("tmp_file");
+                "No file should be created on error"
-            let actual_len = file_contents(expected_out_file).len();
-            assert_eq!(actual_len, 8);
-
-            // check it inside a function
-            let actual = nu!(
-                cwd: dirs.test(),
-                r#"$env.BAZ = "message"; nu --testbin echo_env_mixed out-err BAZ BAZ err> tmp_file; print aa"#,
             );
-            assert!(actual.out.contains("messageaa"));
+        }
-        },
+
-    )
+        // test for separate redirection
+        let actual = nu!(
+            cwd: dirs.test(),
+            "echo 3 o> a.txt e> b.txt o+e>| str length"
+        );
+        assert!(actual.err.contains("not allowed to use with redirection"));
+        assert!(
+            !dirs.test().join("a.txt").exists(),
+            "No file should be created on error"
+        );
+        assert!(
+            !dirs.test().join("b.txt").exists(),
+            "No file should be created on error"
+        );
+    });
 }
 
 #[test]

crates/nu-engine/src/eval.rs

@@ -7,8 +7,8 @@ use nu_protocol::{
     },
     engine::{Closure, EngineState, Stack},
     eval_base::Eval,
-    Config, DeclId, IntoPipelineData, PipelineData, ShellError, Span, Spanned, Type, Value, VarId,
+    Config, DeclId, IntoPipelineData, PipelineData, RawStream, ShellError, Span, Spanned, Type,
-    ENV_VARIABLE_ID,
+    Value, VarId, ENV_VARIABLE_ID,
 };
 use std::thread::{self, JoinHandle};
 use std::{borrow::Cow, collections::HashMap};
@@ -391,6 +391,7 @@ fn might_consume_external_result(input: PipelineData) -> (PipelineData, bool) {
     input.is_external_failed()
 }
 
+#[allow(clippy::too_many_arguments)]
 fn eval_element_with_input(
     engine_state: &EngineState,
     stack: &mut Stack,
@@ -398,17 +399,85 @@ fn eval_element_with_input(
     mut input: PipelineData,
     redirect_stdout: bool,
     redirect_stderr: bool,
+    redirect_combine: bool,
     stderr_writer_jobs: &mut Vec<DataSaveJob>,
 ) -> Result<(PipelineData, bool), ShellError> {
     match element {
-        PipelineElement::Expression(_, expr) => eval_expression_with_input(
+        PipelineElement::Expression(pipe_span, expr)
-            engine_state,
+        | PipelineElement::OutErrPipedExpression(pipe_span, expr) => {
-            stack,
+            if matches!(element, PipelineElement::OutErrPipedExpression(..))
-            expr,
+                && !matches!(input, PipelineData::ExternalStream { .. })
-            input,
+            {
-            redirect_stdout,
+                return Err(ShellError::GenericError {
-            redirect_stderr,
+                    error: "`o+e>|` only works with external streams".into(),
-        ),
+                    msg: "`o+e>|` only works on external streams".into(),
+                    span: *pipe_span,
+                    help: None,
+                    inner: vec![],
+                });
+            }
+            match expr {
+                Expression {
+                    expr: Expr::ExternalCall(head, args, is_subexpression),
+                    ..
+                } if redirect_combine => {
+                    let result = eval_external(
+                        engine_state,
+                        stack,
+                        head,
+                        args,
+                        input,
+                        RedirectTarget::CombinedPipe,
+                        *is_subexpression,
+                    )?;
+                    Ok(might_consume_external_result(result))
+                }
+                _ => eval_expression_with_input(
+                    engine_state,
+                    stack,
+                    expr,
+                    input,
+                    redirect_stdout,
+                    redirect_stderr,
+                ),
+            }
+        }
+        PipelineElement::ErrPipedExpression(pipe_span, expr) => {
+            let input = match input {
+                PipelineData::ExternalStream {
+                    stdout,
+                    stderr,
+                    exit_code,
+                    span,
+                    metadata,
+                    trim_end_newline,
+                } => PipelineData::ExternalStream {
+                    stdout: stderr, // swap stderr and stdout to get stderr piped feature.
+                    stderr: stdout,
+                    exit_code,
+                    span,
+                    metadata,
+                    trim_end_newline,
+                },
+                _ => {
+                    return Err(ShellError::GenericError {
+                        error: "`e>|` only works with external streams".into(),
+                        msg: "`e>|` only works on external streams".into(),
+                        span: *pipe_span,
+                        help: None,
+                        inner: vec![],
+                    })
+                }
+            };
+            eval_expression_with_input(
+                engine_state,
+                stack,
+                expr,
+                input,
+                redirect_stdout,
+                redirect_stderr,
+            )
+        }
         PipelineElement::Redirection(span, redirection, expr, is_append_mode) => {
             match &expr.expr {
                 Expr::String(_)
@@ -420,32 +489,8 @@ fn eval_element_with_input(
                         _ => None,
                     };
 
-                    // when nushell get Stderr Redirection, we want to take `stdout` part of `input`
+                    let (input, result_out_stream, result_is_out) =
-                    // so this stdout stream can be handled by next command.
+                        adjust_stream_for_input_and_output(input, redirection);
-                    let (input, out_stream) = match (redirection, input) {
-                        (
-                            Redirection::Stderr,
-                            PipelineData::ExternalStream {
-                                stdout,
-                                stderr,
-                                exit_code,
-                                span,
-                                metadata,
-                                trim_end_newline,
-                            },
-                        ) => (
-                            PipelineData::ExternalStream {
-                                stdout: stderr,
-                                stderr: None,
-                                exit_code,
-                                span,
-                                metadata,
-                                trim_end_newline,
-                            },
-                            Some(stdout),
-                        ),
-                        (_, input) => (input, None),
-                    };
 
                     if let Some(save_command) = engine_state.find_decl(b"save", &[]) {
                         let save_call = gen_save_call(
@@ -453,7 +498,7 @@ fn eval_element_with_input(
                             (*span, expr.clone(), *is_append_mode),
                             None,
                         );
-                        match out_stream {
+                        match result_out_stream {
                             None => {
                                 eval_call(engine_state, stack, &save_call, input).map(|_| {
                                     // save is internal command, normally it exists with non-ExternalStream
@@ -472,7 +517,7 @@ fn eval_element_with_input(
                                     })
                                 })
                             }
-                            Some(out_stream) => {
+                            Some(result_out_stream) => {
                                 // delegate to a different thread
                                 // so nushell won't hang if external command generates both too much
                                 // stderr and stdout message
@@ -484,11 +529,25 @@ fn eval_element_with_input(
                                     save_call,
                                     input,
                                 ));
-
+                                let (result_out_stream, result_err_stream) = if result_is_out {
+                                    (result_out_stream, None)
+                                } else {
+                                    // we need `stdout` to be an empty RawStream
+                                    // so nushell knows this result is not the last part of a command.
+                                    (
+                                        Some(RawStream::new(
+                                            Box::new(vec![].into_iter()),
+                                            None,
+                                            *span,
+                                            Some(0),
+                                        )),
+                                        result_out_stream,
+                                    )
+                                };
                                 Ok(might_consume_external_result(
                                     PipelineData::ExternalStream {
-                                        stdout: out_stream,
+                                        stdout: result_out_stream,
-                                        stderr: None,
+                                        stderr: result_err_stream,
                                         exit_code,
                                         span: *span,
                                         metadata: None,
@@ -582,6 +641,7 @@ fn eval_element_with_input(
                         input,
                         true,
                         redirect_stderr,
+                        redirect_combine,
                         stderr_writer_jobs,
                     )
                     .map(|x| x.0)?
@@ -599,6 +659,7 @@ fn eval_element_with_input(
                 input,
                 redirect_stdout,
                 redirect_stderr,
+                redirect_combine,
                 stderr_writer_jobs,
             )
         }
@@ -621,6 +682,146 @@ fn eval_element_with_input(
     }
 }
 
+// In redirection context, if nushell gets an ExternalStream
+// it might want to take a stream from `input`(if `input` is `PipelineData::ExternalStream`)
+// so this stream can be handled by next command.
+//
+//
+// 1. get a stderr redirection, we need to take `stdout` out of `input`.
+//    e.g:  nu --testbin echo_env FOO e> /dev/null | str length
+// 2. get a stdout redirection, we need to take `stderr` out of `input`.
+//    e.g:  nu --testbin echo_env FOO o> /dev/null e>| str length
+//
+// Returns 3 values:
+// 1. adjusted pipeline data
+// 2. a result stream which is taken from `input`, it can be handled in next command
+// 3. a boolean value indicates if result stream should be a stdout stream.
+fn adjust_stream_for_input_and_output(
+    input: PipelineData,
+    redirection: &Redirection,
+) -> (PipelineData, Option<Option<RawStream>>, bool) {
+    match (redirection, input) {
+        (
+            Redirection::Stderr,
+            PipelineData::ExternalStream {
+                stdout,
+                stderr,
+                exit_code,
+                span,
+                metadata,
+                trim_end_newline,
+            },
+        ) => (
+            PipelineData::ExternalStream {
+                stdout: stderr,
+                stderr: None,
+                exit_code,
+                span,
+                metadata,
+                trim_end_newline,
+            },
+            Some(stdout),
+            true,
+        ),
+        (
+            Redirection::Stdout,
+            PipelineData::ExternalStream {
+                stdout,
+                stderr,
+                exit_code,
+                span,
+                metadata,
+                trim_end_newline,
+            },
+        ) => (
+            PipelineData::ExternalStream {
+                stdout,
+                stderr: None,
+                exit_code,
+                span,
+                metadata,
+                trim_end_newline,
+            },
+            Some(stderr),
+            false,
+        ),
+        (_, input) => (input, None, true),
+    }
+}
+
+fn is_redirect_stderr_required(elements: &[PipelineElement], idx: usize) -> bool {
+    let elements_length = elements.len();
+    if idx < elements_length - 1 {
+        let next_element = &elements[idx + 1];
+        match next_element {
+            PipelineElement::Redirection(_, Redirection::Stderr, _, _)
+            | PipelineElement::Redirection(_, Redirection::StdoutAndStderr, _, _)
+            | PipelineElement::SeparateRedirection { .. }
+            | PipelineElement::ErrPipedExpression(..)
+            | PipelineElement::OutErrPipedExpression(..) => return true,
+            PipelineElement::Redirection(_, Redirection::Stdout, _, _) => {
+                // a stderr redirection, but we still need to check for the next 2nd
+                // element, to handle for the following case:
+                // cat a.txt out> /dev/null e>| lines
+                //
+                // we only need to check the next 2nd element because we already make sure
+                // that we don't have duplicate err> like this:
+                // cat a.txt out> /dev/null err> /tmp/a
+                if idx < elements_length - 2 {
+                    let next_2nd_element = &elements[idx + 2];
+                    if matches!(next_2nd_element, PipelineElement::ErrPipedExpression(..)) {
+                        return true;
+                    }
+                }
+            }
+            _ => {}
+        }
+    }
+    false
+}
+
+fn is_redirect_stdout_required(elements: &[PipelineElement], idx: usize) -> bool {
+    let elements_length = elements.len();
+    if idx < elements_length - 1 {
+        let next_element = &elements[idx + 1];
+        match next_element {
+            // is next element a stdout relative redirection?
+            PipelineElement::Redirection(_, Redirection::Stdout, _, _)
+            | PipelineElement::Redirection(_, Redirection::StdoutAndStderr, _, _)
+            | PipelineElement::SeparateRedirection { .. }
+            | PipelineElement::Expression(..)
+            | PipelineElement::OutErrPipedExpression(..) => return true,
+
+            PipelineElement::Redirection(_, Redirection::Stderr, _, _) => {
+                // a stderr redirection, but we still need to check for the next 2nd
+                // element, to handle for the following case:
+                // cat a.txt err> /dev/null | lines
+                //
+                // we only need to check the next 2nd element because we already make sure
+                // that we don't have duplicate err> like this:
+                // cat a.txt err> /dev/null err> /tmp/a
+                if idx < elements_length - 2 {
+                    let next_2nd_element = &elements[idx + 2];
+                    if matches!(next_2nd_element, PipelineElement::Expression(..)) {
+                        return true;
+                    }
+                }
+            }
+            _ => {}
+        }
+    }
+    false
+}
+
+fn is_redirect_combine_required(elements: &[PipelineElement], idx: usize) -> bool {
+    let elements_length = elements.len();
+    idx < elements_length - 1
+        && matches!(
+            &elements[idx + 1],
+            PipelineElement::OutErrPipedExpression(..)
+        )
+}
+
 pub fn eval_block_with_early_return(
     engine_state: &EngineState,
     stack: &mut Stack,
@@ -655,50 +856,26 @@ pub fn eval_block(
     for (pipeline_idx, pipeline) in block.pipelines.iter().enumerate() {
         let mut stderr_writer_jobs = vec![];
         let elements = &pipeline.elements;
-        let elements_length = elements.len();
+        let elements_length = pipeline.elements.len();
         for (idx, element) in elements.iter().enumerate() {
             let mut redirect_stdout = redirect_stdout;
             let mut redirect_stderr = redirect_stderr;
-            if !redirect_stderr && idx < elements_length - 1 {
+            if !redirect_stderr && is_redirect_stderr_required(elements, idx) {
-                let next_element = &elements[idx + 1];
+                redirect_stderr = true;
-                if matches!(
-                    next_element,
-                    PipelineElement::Redirection(_, Redirection::Stderr, _, _)
-                        | PipelineElement::Redirection(_, Redirection::StdoutAndStderr, _, _)
-                        | PipelineElement::SeparateRedirection { .. }
-                ) {
-                    redirect_stderr = true;
-                }
             }
 
-            if !redirect_stdout && idx < elements_length - 1 {
+            if !redirect_stdout {
-                let next_element = &elements[idx + 1];
+                if is_redirect_stdout_required(elements, idx) {
-                match next_element {
+                    redirect_stdout = true;
-                    // is next element a stdout relative redirection?
-                    PipelineElement::Redirection(_, Redirection::Stdout, _, _)
-                    | PipelineElement::Redirection(_, Redirection::StdoutAndStderr, _, _)
-                    | PipelineElement::SeparateRedirection { .. }
-                    | PipelineElement::Expression(..) => redirect_stdout = true,
-
-                    PipelineElement::Redirection(_, Redirection::Stderr, _, _) => {
-                        // a stderr redirection, but we still need to check for the next 2nd
-                        // element, to handle for the following case:
-                        // cat a.txt err> /dev/null | lines
-                        //
-                        // we only need to check the next 2nd element because we already make sure
-                        // that we don't have duplicate err> like this:
-                        // cat a.txt err> /dev/null err> /tmp/a
-                        if idx < elements_length - 2 {
-                            let next_2nd_element = &elements[idx + 2];
-                            if matches!(next_2nd_element, PipelineElement::Expression(..)) {
-                                redirect_stdout = true
-                            }
-                        }
-                    }
-                    _ => {}
                 }
+            } else if idx < elements_length - 1
+                && matches!(elements[idx + 1], PipelineElement::ErrPipedExpression(..))
+            {
+                redirect_stdout = false;
             }
 
+            let redirect_combine = is_redirect_combine_required(elements, idx);
+
             // if eval internal command failed, it can just make early return with `Err(ShellError)`.
             let eval_result = eval_element_with_input(
                 engine_state,
@@ -707,6 +884,7 @@ pub fn eval_block(
                 input,
                 redirect_stdout,
                 redirect_stderr,
+                redirect_combine,
                 &mut stderr_writer_jobs,
             );
 

crates/nu-parser/src/flatten.rs

@@ -560,7 +560,9 @@ pub fn flatten_pipeline_element(
     pipeline_element: &PipelineElement,
 ) -> Vec<(Span, FlatShape)> {
     match pipeline_element {
-        PipelineElement::Expression(span, expr) => {
+        PipelineElement::Expression(span, expr)
+        | PipelineElement::ErrPipedExpression(span, expr)
+        | PipelineElement::OutErrPipedExpression(span, expr) => {
             if let Some(span) = span {
                 let mut output = vec![(*span, FlatShape::Pipe)];
                 output.append(&mut flatten_expression(working_set, expr));

crates/nu-parser/src/lex.rs

@@ -6,6 +6,8 @@ pub enum TokenContents {
     Comment,
     Pipe,
     PipePipe,
+    ErrGreaterPipe,
+    OutErrGreaterPipe,
     Semicolon,
     OutGreaterThan,
     OutGreaterGreaterThan,
@@ -485,8 +487,14 @@ fn lex_internal(
             // If the next character is non-newline whitespace, skip it.
             curr_offset += 1;
         } else {
-            // Otherwise, try to consume an unclassified token.
+            let token = try_lex_special_piped_item(input, &mut curr_offset, span_offset);
+            if let Some(token) = token {
+                output.push(token);
+                is_complete = false;
+                continue;
+            }
 
+            // Otherwise, try to consume an unclassified token.
             let (token, err) = lex_item(
                 input,
                 &mut curr_offset,
@@ -504,3 +512,49 @@ fn lex_internal(
     }
     (output, error)
 }
+
+/// trying to lex for the following item:
+/// e>|, e+o>|, o+e>|
+///
+/// It returns Some(token) if we find the item, or else return None.
+fn try_lex_special_piped_item(
+    input: &[u8],
+    curr_offset: &mut usize,
+    span_offset: usize,
+) -> Option<Token> {
+    let c = input[*curr_offset];
+    let e_pipe_len = 3;
+    let eo_pipe_len = 5;
+    let offset = *curr_offset;
+    if c == b'e' {
+        // expect `e>|`
+        if (offset + e_pipe_len <= input.len()) && (&input[offset..offset + e_pipe_len] == b"e>|") {
+            *curr_offset += e_pipe_len;
+            return Some(Token::new(
+                TokenContents::ErrGreaterPipe,
+                Span::new(span_offset + offset, span_offset + offset + e_pipe_len),
+            ));
+        }
+        if (offset + eo_pipe_len <= input.len())
+            && (&input[offset..offset + eo_pipe_len] == b"e+o>|")
+        {
+            *curr_offset += eo_pipe_len;
+            return Some(Token::new(
+                TokenContents::OutErrGreaterPipe,
+                Span::new(span_offset + offset, span_offset + offset + eo_pipe_len),
+            ));
+        }
+    } else if c == b'o' {
+        // it can be the following case: `o+e>|`
+        if (offset + eo_pipe_len <= input.len())
+            && (&input[offset..offset + eo_pipe_len] == b"o+e>|")
+        {
+            *curr_offset += eo_pipe_len;
+            return Some(Token::new(
+                TokenContents::OutErrGreaterPipe,
+                Span::new(span_offset + offset, span_offset + offset + eo_pipe_len),
+            ));
+        }
+    }
+    None
+}

crates/nu-parser/src/lite_parser.rs

@@ -37,6 +37,12 @@ impl LiteCommand {
 #[derive(Debug)]
 pub enum LiteElement {
     Command(Option<Span>, LiteCommand),
+    // Similar to LiteElement::Command, except the previous command's output is stderr piped.
+    // e.g: `e>| cmd`
+    ErrPipedCommand(Option<Span>, LiteCommand),
+    // Similar to LiteElement::Command, except the previous command's output is stderr + stdout piped.
+    // e.g: `o+e>| cmd`
+    OutErrPipedCommand(Option<Span>, LiteCommand),
     // final field indicates if it's in append mode
     Redirection(Span, Redirection, LiteCommand, bool),
     // SeparateRedirection variant can only be generated by two different Redirection variant
@@ -272,7 +278,9 @@ pub fn lite_parse(tokens: &[Token]) -> (LiteBlock, Option<ParseError>) {
                 last_connector = token.contents;
                 last_connector_span = Some(token.span);
             }
-            TokenContents::Pipe => {
+            pipe_token @ (TokenContents::Pipe
+            | TokenContents::ErrGreaterPipe
+            | TokenContents::OutErrGreaterPipe) => {
                 if let Some(err) = push_command_to(
                     &mut curr_pipeline,
                     curr_command,
@@ -283,8 +291,8 @@ pub fn lite_parse(tokens: &[Token]) -> (LiteBlock, Option<ParseError>) {
                 }
 
                 curr_command = LiteCommand::new();
-                last_token = TokenContents::Pipe;
+                last_token = *pipe_token;
-                last_connector = TokenContents::Pipe;
+                last_connector = *pipe_token;
                 last_connector_span = Some(token.span);
             }
             TokenContents::Eol => {
@@ -429,7 +437,35 @@ fn push_command_to(
                     is_append_mode,
                 ))
             }
-            None => pipeline.push(LiteElement::Command(last_connector_span, command)),
+            None => {
+                if last_connector == TokenContents::ErrGreaterPipe {
+                    pipeline.push(LiteElement::ErrPipedCommand(last_connector_span, command))
+                } else if last_connector == TokenContents::OutErrGreaterPipe {
+                    // Don't allow o+e>| along with redirection.
+                    for cmd in &pipeline.commands {
+                        if matches!(
+                            cmd,
+                            LiteElement::Redirection { .. }
+                                | LiteElement::SameTargetRedirection { .. }
+                                | LiteElement::SeparateRedirection { .. }
+                        ) {
+                            return Some(ParseError::LabeledError(
+                                "`o+e>|` pipe is not allowed to use with redirection".into(),
+                                "try to use different type of pipe, or remove redirection".into(),
+                                last_connector_span
+                                    .expect("internal error: outerr pipe missing span information"),
+                            ));
+                        }
+                    }
+
+                    pipeline.push(LiteElement::OutErrPipedCommand(
+                        last_connector_span,
+                        command,
+                    ))
+                } else {
+                    pipeline.push(LiteElement::Command(last_connector_span, command))
+                }
+            }
         }
         None
     } else if get_redirection(last_connector).is_some() {

crates/nu-parser/src/parse_keywords.rs

@@ -1702,7 +1702,9 @@ pub fn parse_module_block(
     for pipeline in output.block.iter() {
         if pipeline.commands.len() == 1 {
             match &pipeline.commands[0] {
-                LiteElement::Command(_, command) => {
+                LiteElement::Command(_, command)
+                | LiteElement::ErrPipedCommand(_, command)
+                | LiteElement::OutErrPipedCommand(_, command) => {
                     let name = working_set.get_span_contents(command.parts[0]);
 
                     match name {

crates/nu-parser/src/parser.rs

@@ -1299,7 +1299,9 @@ fn parse_binary_with_base(
                     }
                     TokenContents::Pipe
                     | TokenContents::PipePipe
+                    | TokenContents::ErrGreaterPipe
                     | TokenContents::OutGreaterThan
+                    | TokenContents::OutErrGreaterPipe
                     | TokenContents::OutGreaterGreaterThan
                     | TokenContents::ErrGreaterThan
                     | TokenContents::ErrGreaterGreaterThan
@@ -5479,7 +5481,9 @@ pub fn parse_pipeline(
 
                     for command in &pipeline.commands[1..] {
                         match command {
-                            LiteElement::Command(Some(pipe_span), command) => {
+                            LiteElement::Command(Some(pipe_span), command)
+                            | LiteElement::ErrPipedCommand(Some(pipe_span), command)
+                            | LiteElement::OutErrPipedCommand(Some(pipe_span), command) => {
                                 new_command.parts.push(*pipe_span);
 
                                 new_command.comments.extend_from_slice(&command.comments);
@@ -5584,6 +5588,18 @@ pub fn parse_pipeline(
 
                     PipelineElement::Expression(*span, expr)
                 }
+                LiteElement::ErrPipedCommand(span, command) => {
+                    trace!("parsing: pipeline element: err piped command");
+                    let expr = parse_expression(working_set, &command.parts, is_subexpression);
+
+                    PipelineElement::ErrPipedExpression(*span, expr)
+                }
+                LiteElement::OutErrPipedCommand(span, command) => {
+                    trace!("parsing: pipeline element: err piped command");
+                    let expr = parse_expression(working_set, &command.parts, is_subexpression);
+
+                    PipelineElement::OutErrPipedExpression(*span, expr)
+                }
                 LiteElement::Redirection(span, redirection, command, is_append_mode) => {
                     let expr = parse_value(working_set, command.parts[0], &SyntaxShape::Any);
 
@@ -5639,6 +5655,8 @@ pub fn parse_pipeline(
     } else {
         match &pipeline.commands[0] {
             LiteElement::Command(_, command)
+            | LiteElement::ErrPipedCommand(_, command)
+            | LiteElement::OutErrPipedCommand(_, command)
             | LiteElement::Redirection(_, _, command, _)
             | LiteElement::SeparateRedirection {
                 out: (_, command, _),
@@ -5743,6 +5761,8 @@ pub fn parse_block(
         if pipeline.commands.len() == 1 {
             match &pipeline.commands[0] {
                 LiteElement::Command(_, command)
+                | LiteElement::ErrPipedCommand(_, command)
+                | LiteElement::OutErrPipedCommand(_, command)
                 | LiteElement::Redirection(_, _, command, _)
                 | LiteElement::SeparateRedirection {
                     out: (_, command, _),
@@ -5836,6 +5856,8 @@ pub fn discover_captures_in_pipeline_element(
 ) -> Result<(), ParseError> {
     match element {
         PipelineElement::Expression(_, expression)
+        | PipelineElement::ErrPipedExpression(_, expression)
+        | PipelineElement::OutErrPipedExpression(_, expression)
         | PipelineElement::Redirection(_, _, expression, _)
         | PipelineElement::And(_, expression)
         | PipelineElement::Or(_, expression) => {
@@ -6181,6 +6203,18 @@ fn wrap_element_with_collect(
         PipelineElement::Expression(span, expression) => {
             PipelineElement::Expression(*span, wrap_expr_with_collect(working_set, expression))
         }
+        PipelineElement::ErrPipedExpression(span, expression) => {
+            PipelineElement::ErrPipedExpression(
+                *span,
+                wrap_expr_with_collect(working_set, expression),
+            )
+        }
+        PipelineElement::OutErrPipedExpression(span, expression) => {
+            PipelineElement::OutErrPipedExpression(
+                *span,
+                wrap_expr_with_collect(working_set, expression),
+            )
+        }
         PipelineElement::Redirection(span, redirection, expression, is_append_mode) => {
             PipelineElement::Redirection(
                 *span,

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

@@ -68,6 +68,8 @@ impl Block {
             if let Some(last) = last.elements.last() {
                 match last {
                     PipelineElement::Expression(_, expr) => expr.ty.clone(),
+                    PipelineElement::ErrPipedExpression(_, expr) => expr.ty.clone(),
+                    PipelineElement::OutErrPipedExpression(_, expr) => expr.ty.clone(),
                     PipelineElement::Redirection(_, _, _, _) => Type::Any,
                     PipelineElement::SeparateRedirection { .. } => Type::Any,
                     PipelineElement::SameTargetRedirection { .. } => Type::Any,

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

@@ -13,6 +13,8 @@ pub enum Redirection {
 #[derive(Debug, Clone, Serialize, Deserialize)]
 pub enum PipelineElement {
     Expression(Option<Span>, Expression),
+    ErrPipedExpression(Option<Span>, Expression),
+    OutErrPipedExpression(Option<Span>, Expression),
     // final field indicates if it's in append mode
     Redirection(Span, Redirection, Expression, bool),
     // final bool field indicates if it's in append mode
@@ -32,7 +34,9 @@ pub enum PipelineElement {
 impl PipelineElement {
     pub fn expression(&self) -> &Expression {
         match self {
-            PipelineElement::Expression(_, expression) => expression,
+            PipelineElement::Expression(_, expression)
+            | PipelineElement::ErrPipedExpression(_, expression)
+            | PipelineElement::OutErrPipedExpression(_, expression) => expression,
             PipelineElement::Redirection(_, _, expression, _) => expression,
             PipelineElement::SeparateRedirection {
                 out: (_, expression, _),
@@ -50,11 +54,15 @@ impl PipelineElement {
     pub fn span(&self) -> Span {
         match self {
             PipelineElement::Expression(None, expression)
+            | PipelineElement::ErrPipedExpression(None, expression)
+            | PipelineElement::OutErrPipedExpression(None, expression)
             | PipelineElement::SameTargetRedirection {
                 cmd: (None, expression),
                 ..
             } => expression.span,
             PipelineElement::Expression(Some(span), expression)
+            | PipelineElement::ErrPipedExpression(Some(span), expression)
+            | PipelineElement::OutErrPipedExpression(Some(span), expression)
             | PipelineElement::Redirection(span, _, expression, _)
             | PipelineElement::SeparateRedirection {
                 out: (span, expression, _),
@@ -74,6 +82,8 @@ impl PipelineElement {
     pub fn has_in_variable(&self, working_set: &StateWorkingSet) -> bool {
         match self {
             PipelineElement::Expression(_, expression)
+            | PipelineElement::ErrPipedExpression(_, expression)
+            | PipelineElement::OutErrPipedExpression(_, expression)
             | PipelineElement::Redirection(_, _, expression, _)
             | PipelineElement::And(_, expression)
             | PipelineElement::Or(_, expression)
@@ -96,6 +106,8 @@ impl PipelineElement {
     ) {
         match self {
             PipelineElement::Expression(_, expression)
+            | PipelineElement::ErrPipedExpression(_, expression)
+            | PipelineElement::OutErrPipedExpression(_, expression)
             | PipelineElement::Redirection(_, _, expression, _)
             | PipelineElement::And(_, expression)
             | PipelineElement::Or(_, expression)

tests/shell/pipeline/commands/external.rs

@@ -142,6 +142,22 @@ fn command_substitution_wont_output_extra_newline() {
     assert_eq!(actual.out, "bar");
 }
 
+#[test]
+fn basic_err_pipe_works() {
+    let actual = nu!(r#"with-env [FOO "bar"] { nu --testbin echo_env_stderr FOO e>| str length }"#);
+    // there is a `newline` output from nu --testbin
+    assert_eq!(actual.out, "4");
+}
+
+#[test]
+fn basic_outerr_pipe_works() {
+    let actual = nu!(
+        r#"with-env [FOO "bar"] { nu --testbin echo_env_mixed out-err FOO FOO o+e>| str length }"#
+    );
+    // there is a `newline` output from nu --testbin
+    assert_eq!(actual.out, "8");
+}
+
 mod it_evaluation {
     use super::nu;
     use nu_test_support::fs::Stub::{EmptyFile, FileWithContent, FileWithContentToBeTrimmed};

tests/shell/pipeline/commands/internal.rs

@@ -1113,6 +1113,18 @@ fn pipe_input_to_print() {
     assert!(actual.err.is_empty());
 }
 
+#[test]
+fn err_pipe_input_to_print() {
+    let actual = nu!(r#""foo" e>| print"#);
+    assert!(actual.err.contains("only works on external streams"));
+}
+
+#[test]
+fn outerr_pipe_input_to_print() {
+    let actual = nu!(r#""foo" o+e>| print"#);
+    assert!(actual.err.contains("only works on external streams"));
+}
+
 #[test]
 fn command_not_found_error_shows_not_found_2() {
     let actual = nu!(r#"