Rollup merge of rust-lang#129096 - Kobzol:bootstrap-cmd-verbosity, r=onur-ozkan

Print more verbose error for commands that capture output

rust-lang#128874 made bootstrap command errors less verbose without `-v`. However, in some cases it's too extreme. If a command fails, it now outputs just `Command has failed. Rerun with -v to see more details.`, without providing any context.

I think that I found a reasonable heuristic to figure out when we should print a more verbose error. When the command doesn't capture output, its stdout/stderr is printed, therefore the user sees context about the error. However, when the command captures its output, the user won't see any error message in the output, which is not great. So only in that case, bootstrap now prints a slightly more verbose output (and also prints the captured output).

r? `@onur-ozkan`

Author: matthiaskrgr

src/bootstrap/src/lib.rs

@@ -1056,11 +1056,29 @@ Executed at: {executed_at}"#,
             }
         };
 
-        let fail = |message: &str| {
+        let fail = |message: &str, output: CommandOutput| -> ! {
             if self.is_verbose() {
                 println!("{message}");
             } else {
-                println!("Command has failed. Rerun with -v to see more details.");
+                let (stdout, stderr) = (output.stdout_if_present(), output.stderr_if_present());
+                // If the command captures output, the user would not see any indication that
+                // it has failed. In this case, print a more verbose error, since to provide more
+                // context.
+                if stdout.is_some() || stderr.is_some() {
+                    if let Some(stdout) =
+                        output.stdout_if_present().take_if(|s| !s.trim().is_empty())
+                    {
+                        println!("STDOUT:\n{stdout}\n");
+                    }
+                    if let Some(stderr) =
+                        output.stderr_if_present().take_if(|s| !s.trim().is_empty())
+                    {
+                        println!("STDERR:\n{stderr}\n");
+                    }
+                    println!("Command {command:?} has failed. Rerun with -v to see more details.");
+                } else {
+                    println!("Command has failed. Rerun with -v to see more details.");
+                }
             }
             exit!(1);
         };
@@ -1069,14 +1087,14 @@ Executed at: {executed_at}"#,
             match command.failure_behavior {
                 BehaviorOnFailure::DelayFail => {
                     if self.fail_fast {
-                        fail(&message);
+                        fail(&message, output);
                     }
 
                     let mut failures = self.delayed_failures.borrow_mut();
                     failures.push(message);
                 }
                 BehaviorOnFailure::Exit => {
-                    fail(&message);
+                    fail(&message, output);
                 }
                 BehaviorOnFailure::Ignore => {
                     // If failures are allowed, either the error has been printed already

src/bootstrap/src/utils/exec.rs

@@ -291,6 +291,11 @@ impl CommandOutput {
         .expect("Cannot parse process stdout as UTF-8")
     }
 
+    #[must_use]
+    pub fn stdout_if_present(&self) -> Option<String> {
+        self.stdout.as_ref().and_then(|s| String::from_utf8(s.clone()).ok())
+    }
+
     #[must_use]
     pub fn stdout_if_ok(&self) -> Option<String> {
         if self.is_success() { Some(self.stdout()) } else { None }
@@ -303,6 +308,11 @@ impl CommandOutput {
         )
         .expect("Cannot parse process stderr as UTF-8")
     }
+
+    #[must_use]
+    pub fn stderr_if_present(&self) -> Option<String> {
+        self.stderr.as_ref().and_then(|s| String::from_utf8(s.clone()).ok())
+    }
 }
 
 impl Default for CommandOutput {