Print more verbose error for commands that capture output

Author: Kobzol

Diff for: 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

Diff for: 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 {