Fix non-zero exit code errors in middle of pipeline (#13899)

# Description
Fixes #13868. Should come after #13885.

# User-Facing Changes
Bug fix.

# Tests + Formatting
Added a test.

crates/nu-cli/src/print.rs

@@ -1,4 +1,5 @@
 use nu_engine::command_prelude::*;
+use nu_protocol::ByteStreamSource;
 
 #[derive(Clone)]
 pub struct Print;
@@ -50,7 +51,7 @@ Since this command has no output, there is no point in piping it with other comm
         engine_state: &EngineState,
         stack: &mut Stack,
         call: &Call,
-        input: PipelineData,
+        mut input: PipelineData,
     ) -> Result<PipelineData, ShellError> {
         let args: Vec<Value> = call.rest(engine_state, stack, 0)?;
         let no_newline = call.has_flag(engine_state, stack, "no-newline")?;
@@ -69,6 +70,11 @@ Since this command has no output, there is no point in piping it with other comm
                 }
             }
         } else if !input.is_nothing() {
+            if let PipelineData::ByteStream(stream, _) = &mut input {
+                if let ByteStreamSource::Child(child) = stream.source_mut() {
+                    child.ignore_error(true);
+                }
+            }
             if raw {
                 input.print_raw(engine_state, no_newline, to_stderr)?;
             } else {

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

@@ -147,6 +147,7 @@ impl Command for Do {
                             None
                         };
 
+                        child.ignore_error(false);
                         child.wait()?;
 
                         let mut child = ChildProcess::from_raw(None, None, None, span);
@@ -172,7 +173,7 @@ impl Command for Do {
                     ) =>
             {
                 if let ByteStreamSource::Child(child) = stream.source_mut() {
-                    child.ignore_error();
+                    child.ignore_error(true);
                 }
                 Ok(PipelineData::ByteStream(stream, metadata))
             }

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

@@ -1,5 +1,5 @@
 use nu_engine::command_prelude::*;
-use nu_protocol::{engine::StateWorkingSet, OutDest};
+use nu_protocol::{engine::StateWorkingSet, ByteStreamSource, OutDest};
 
 #[derive(Clone)]
 pub struct Ignore;
@@ -32,8 +32,13 @@ impl Command for Ignore {
         _engine_state: &EngineState,
         _stack: &mut Stack,
         _call: &Call,
-        input: PipelineData,
+        mut input: PipelineData,
     ) -> Result<PipelineData, ShellError> {
+        if let PipelineData::ByteStream(stream, _) = &mut input {
+            if let ByteStreamSource::Child(child) = stream.source_mut() {
+                child.ignore_error(true);
+            }
+        }
         input.drain()?;
         Ok(PipelineData::empty())
     }

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

@@ -182,6 +182,8 @@ impl Command for Save {
                             }
                             (None, None) => {}
                         };
+
+                        child.wait()?;
                     }
                 }
 

crates/nu-command/src/system/run_external.rs

@@ -180,12 +180,19 @@ impl Command for External {
         }
 
         // Wrap the output into a `PipelineData::ByteStream`.
-        let child = ChildProcess::new(
+        let mut child = ChildProcess::new(
             child,
             merged_stream,
             matches!(stderr, OutDest::Pipe),
             call.head,
         )?;
+
+        if matches!(stdout, OutDest::Pipe | OutDest::PipeSeparate)
+            || matches!(stderr, OutDest::Pipe | OutDest::PipeSeparate)
+        {
+            child.ignore_error(true);
+        }
+
         Ok(PipelineData::ByteStream(
             ByteStream::child(child, call.head),
             None,

crates/nu-protocol/src/process/child.rs

@@ -202,8 +202,8 @@ impl ChildProcess {
         }
     }
 
-    pub fn ignore_error(&mut self) -> &mut Self {
-        self.ignore_error = true;
+    pub fn ignore_error(&mut self, ignore: bool) -> &mut Self {
+        self.ignore_error = ignore;
         self
     }
 

tests/shell/pipeline/mod.rs

@@ -6,6 +6,14 @@ use pretty_assertions::assert_eq;
 #[test]
 fn doesnt_break_on_utf8() {
     let actual = nu!("echo ö");
-
     assert_eq!(actual.out, "ö", "'{}' should contain ö", actual.out);
 }
+
+#[test]
+fn non_zero_exit_code_in_middle_of_pipeline_ignored() {
+    let actual = nu!("nu -c 'print a b; exit 42' | collect");
+    assert_eq!(actual.out, "ab");
+
+    let actual = nu!("nu -c 'print a b; exit 42' | nu --stdin -c 'collect'");
+    assert_eq!(actual.out, "ab");
+}