Fix a bug where stdout was copying stderr

CHANGELOG.md

@@ -1,5 +1,7 @@
 ## Unreleased
 
+- Fix stderr copying to stdout bug (https://github.com/schneems/fun_run/pull/3)
+
 ## 0.1.0
 
 - First release

Cargo.toml

@@ -15,3 +15,6 @@ regex = "1"
 
 [features]
 which_problem = ["dep:which_problem"]
+
+[dev-dependencies]
+pretty_assertions = "1"

src/command.rs

@@ -23,7 +23,7 @@ pub(crate) fn output_and_write_streams<OW: Write + Send, EW: Write + Send>(
         let stdout_thread = mem::take(&mut child.stdout).map(|mut child_stdout| {
             scope.spawn(move || std::io::copy(&mut child_stdout, &mut stdout))
         });
-        let stderr_thread = mem::take(&mut child.stdout).map(|mut child_stderr| {
+        let stderr_thread = mem::take(&mut child.stderr).map(|mut child_stderr| {
             scope.spawn(move || std::io::copy(&mut child_stderr, &mut stderr))
         });
 
@@ -53,14 +53,43 @@ pub(crate) fn output_and_write_streams<OW: Write + Send, EW: Write + Send>(
     })
 }
 
+/// Constructs a writer that writes to two other writers. Similar to the UNIX `tee` command.
+pub(crate) fn tee<A: io::Write, B: io::Write>(a: A, b: B) -> TeeWrite<A, B> {
+    TeeWrite {
+        inner_a: a,
+        inner_b: b,
+    }
+}
+
+/// A tee writer that was created with the [`tee`] function.
+#[derive(Debug, Clone)]
+pub(crate) struct TeeWrite<A: io::Write, B: io::Write> {
+    inner_a: A,
+    inner_b: B,
+}
+
+impl<A: io::Write, B: io::Write> io::Write for TeeWrite<A, B> {
+    fn write(&mut self, buf: &[u8]) -> io::Result<usize> {
+        self.inner_a.write_all(buf)?;
+        self.inner_b.write_all(buf)?;
+        Ok(buf.len())
+    }
+
+    fn flush(&mut self) -> io::Result<()> {
+        self.inner_a.flush()?;
+        self.inner_b.flush()
+    }
+}
+
 #[cfg(test)]
 mod test {
     use super::*;
+    use pretty_assertions::assert_str_eq;
     use std::process::Command;
 
     #[test]
     #[cfg(unix)]
-    fn test_output_and_write_streams() {
+    fn test_output_and_write_streams_stdout() {
         let mut stdout_buf = Vec::new();
         let mut stderr_buf = Vec::new();
 
@@ -76,32 +105,18 @@ mod test {
         assert_eq!(output.stdout, "Hello World!".as_bytes());
         assert_eq!(output.stderr, Vec::<u8>::new());
     }
-}
 
-/// Constructs a writer that writes to two other writers. Similar to the UNIX `tee` command.
-pub(crate) fn tee<A: io::Write, B: io::Write>(a: A, b: B) -> TeeWrite<A, B> {
-    TeeWrite {
-        inner_a: a,
-        inner_b: b,
-    }
-}
+    #[test]
+    #[cfg(unix)]
+    fn test_output_and_write_streams_stderr() {
+        let mut stdout_buf = Vec::new();
+        let mut stderr_buf = Vec::new();
 
-/// A tee writer that was created with the [`tee`] function.
-#[derive(Debug, Clone)]
-pub(crate) struct TeeWrite<A: io::Write, B: io::Write> {
-    inner_a: A,
-    inner_b: B,
-}
+        let mut cmd = Command::new("bash");
+        cmd.args(["-c", "echo -n Hello World! >&2"]);
 
-impl<A: io::Write, B: io::Write> io::Write for TeeWrite<A, B> {
-    fn write(&mut self, buf: &[u8]) -> io::Result<usize> {
-        self.inner_a.write_all(buf)?;
-        self.inner_b.write_all(buf)?;
-        Ok(buf.len())
-    }
+        let _ = output_and_write_streams(&mut cmd, &mut stdout_buf, &mut stderr_buf).unwrap();
 
-    fn flush(&mut self) -> io::Result<()> {
-        self.inner_a.flush()?;
-        self.inner_b.flush()
+        assert_str_eq!(&String::from_utf8_lossy(&stderr_buf), "Hello World!");
     }
 }