Loops return external stream when external command failed. (#8646)

crates/nu-cmd-lang/src/core_commands/for_.rs

@@ -122,7 +122,9 @@ impl Command for For {
                         Ok(pipeline) => {
                             let exit_code = pipeline.print(&engine_state, stack, false, false)?;
                             if exit_code != 0 {
-                                break;
+                                return Ok(PipelineData::new_external_stream_with_only_exit_code(
+                                    exit_code,
+                                ));
                             }
                         }
                     }
@@ -164,7 +166,9 @@ impl Command for For {
                         Ok(pipeline) => {
                             let exit_code = pipeline.drain_with_exit_code()?;
                             if exit_code != 0 {
-                                break;
+                                return Ok(PipelineData::new_external_stream_with_only_exit_code(
+                                    exit_code,
+                                ));
                             }
                         }
                     }

crates/nu-cmd-lang/src/core_commands/loop_.rs

@@ -69,7 +69,9 @@ impl Command for Loop {
                 Ok(pipeline) => {
                     let exit_code = pipeline.drain_with_exit_code()?;
                     if exit_code != 0 {
-                        break;
+                        return Ok(PipelineData::new_external_stream_with_only_exit_code(
+                            exit_code,
+                        ));
                     }
                 }
             }

crates/nu-cmd-lang/src/core_commands/while_.rs

@@ -79,7 +79,11 @@ impl Command for While {
                             Ok(pipeline) => {
                                 let exit_code = pipeline.drain_with_exit_code()?;
                                 if exit_code != 0 {
-                                    break;
+                                    return Ok(
+                                        PipelineData::new_external_stream_with_only_exit_code(
+                                            exit_code,
+                                        ),
+                                    );
                                 }
                             }
                         }

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

@@ -28,3 +28,27 @@ fn for_break_on_external_failed() {
     // so our output will be `1`
     assert_eq!(actual.out, "1");
 }
+
+#[test]
+fn failed_for_should_break_running() {
+    let actual = nu!(
+        cwd: ".",
+        r#"
+        for i in 1..2 {
+            nu --testbin fail
+        }
+        print 3"#
+    );
+    assert!(!actual.out.contains('3'));
+
+    let actual = nu!(
+        cwd: ".",
+        r#"
+        let x = [1 2]
+        for i in $x {
+            nu --testbin fail
+        }
+        print 3"#
+    );
+    assert!(!actual.out.contains('3'));
+}

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

@@ -40,3 +40,22 @@ fn loop_break_on_external_failed() {
     // so our output will be `1`.
     assert_eq!(actual.out, "1");
 }
+
+#[test]
+fn failed_loop_should_break_running() {
+    let actual = nu!(
+        cwd: ".",
+        r#"
+        mut total = 0;
+        loop {
+            if $total == 3 {
+                break;
+            } else {
+                $total += 1;
+            }
+            nu --testbin fail;
+        }
+        print 3"#
+    );
+    assert!(!actual.out.contains('3'));
+}

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

@@ -31,3 +31,12 @@ fn while_break_on_external_failed() {
     // so our output will be `1`
     assert_eq!(actual.out, "1");
 }
+
+#[test]
+fn failed_while_should_break_running() {
+    let actual = nu!(
+        cwd: ".",
+        "mut total = 0; while $total < 2 { $total = $total + 1; nu --testbin fail }; print 3"
+    );
+    assert!(!actual.out.contains('3'));
+}

crates/nu-protocol/src/pipeline_data.rs

@@ -72,6 +72,23 @@ impl PipelineData {
         PipelineData::Value(Value::Nothing { span }, metadata)
     }
 
+    /// create a `PipelineData::ExternalStream` with proper exit_code
+    ///
+    /// It's useful to break running without raising error at user level.
+    pub fn new_external_stream_with_only_exit_code(exit_code: i64) -> PipelineData {
+        PipelineData::ExternalStream {
+            stdout: None,
+            stderr: None,
+            exit_code: Some(ListStream::from_stream(
+                [Value::int(exit_code, Span::unknown())].into_iter(),
+                None,
+            )),
+            span: Span::unknown(),
+            metadata: None,
+            trim_end_newline: false,
+        }
+    }
+
     pub fn empty() -> PipelineData {
         PipelineData::Empty
     }