More verbose Debug implementation of std::process:Command

based on commit: zackmdavis/rust@ccc019a from https://github.com/zackmdavis

close rust-lang/rust#42200

Add env variables and cwd to the shell-like debug output.

Also use the alternate syntax to display a more verbose display, while not showing internal fields and hiding fields when they have their default value.

std/src/process.rs

@@ -1038,6 +1038,15 @@ impl fmt::Debug for Command {
     /// Format the program and arguments of a Command for display. Any
     /// non-utf8 data is lossily converted using the utf8 replacement
     /// character.
+    ///
+    /// The default format approximates a shell invocation of the program along with its
+    /// arguments. It does not include most of the other command properties. The output is not guaranteed to work
+    /// (e.g. due to lack of shell-escaping or differences in path resolution)
+    /// On some platforms you can use [the alternate syntax] to show more fields.
+    ///
+    /// Note that the debug implementation is platform-specific.
+    ///
+    /// [the alternate syntax]: fmt#sign0
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         self.inner.fmt(f)
     }

std/src/process/tests.rs

@@ -417,6 +417,100 @@ fn env_empty() {
     assert!(p.is_ok());
 }
 
+#[test]
+#[cfg(not(windows))]
+#[cfg_attr(any(target_os = "emscripten", target_env = "sgx"), ignore)]
+fn main() {
+    const PIDFD: &'static str =
+        if cfg!(target_os = "linux") { "    create_pidfd: false,\n" } else { "" };
+
+    let mut command = Command::new("some-boring-name");
+
+    assert_eq!(format!("{command:?}"), format!(r#""some-boring-name""#));
+
+    assert_eq!(
+        format!("{command:#?}"),
+        format!(
+            r#"Command {{
+    program: "some-boring-name",
+    args: [
+        "some-boring-name",
+    ],
+{PIDFD}}}"#
+        )
+    );
+
+    command.args(&["1", "2", "3"]);
+
+    assert_eq!(format!("{command:?}"), format!(r#""some-boring-name" "1" "2" "3""#));
+
+    assert_eq!(
+        format!("{command:#?}"),
+        format!(
+            r#"Command {{
+    program: "some-boring-name",
+    args: [
+        "some-boring-name",
+        "1",
+        "2",
+        "3",
+    ],
+{PIDFD}}}"#
+        )
+    );
+
+    crate::os::unix::process::CommandExt::arg0(&mut command, "exciting-name");
+
+    assert_eq!(
+        format!("{command:?}"),
+        format!(r#"["some-boring-name"] "exciting-name" "1" "2" "3""#)
+    );
+
+    assert_eq!(
+        format!("{command:#?}"),
+        format!(
+            r#"Command {{
+    program: "some-boring-name",
+    args: [
+        "exciting-name",
+        "1",
+        "2",
+        "3",
+    ],
+{PIDFD}}}"#
+        )
+    );
+
+    let mut command_with_env_and_cwd = Command::new("boring-name");
+    command_with_env_and_cwd.current_dir("/some/path").env("FOO", "bar");
+    assert_eq!(
+        format!("{command_with_env_and_cwd:?}"),
+        r#"cd "/some/path" && FOO="bar" "boring-name""#
+    );
+    assert_eq!(
+        format!("{command_with_env_and_cwd:#?}"),
+        format!(
+            r#"Command {{
+    program: "boring-name",
+    args: [
+        "boring-name",
+    ],
+    env: CommandEnv {{
+        clear: false,
+        vars: {{
+            "FOO": Some(
+                "bar",
+            ),
+        }},
+    }},
+    cwd: Some(
+        "/some/path",
+    ),
+{PIDFD}}}"#
+        )
+    );
+}
+
 // See issue #91991
 #[test]
 #[cfg(windows)]

std/src/sys/unix/process/process_common.rs

@@ -144,6 +144,7 @@ pub enum ChildStdio {
     Null,
 }
 
+#[derive(Debug)]
 pub enum Stdio {
     Inherit,
     Null,
@@ -510,16 +511,68 @@ impl ChildStdio {
 }
 
 impl fmt::Debug for Command {
+    // show all attributes but `self.closures` which does not implement `Debug`
+    // and `self.argv` which is not useful for debugging
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        if self.program != self.args[0] {
-            write!(f, "[{:?}] ", self.program)?;
-        }
-        write!(f, "{:?}", self.args[0])?;
+        if f.alternate() {
+            let mut debug_command = f.debug_struct("Command");
+            debug_command.field("program", &self.program).field("args", &self.args);
+            if !self.env.is_unchanged() {
+                debug_command.field("env", &self.env);
+            }
+
+            if self.cwd.is_some() {
+                debug_command.field("cwd", &self.cwd);
+            }
+            if self.uid.is_some() {
+                debug_command.field("uid", &self.uid);
+            }
+            if self.gid.is_some() {
+                debug_command.field("gid", &self.gid);
+            }
+
+            if self.groups.is_some() {
+                debug_command.field("groups", &self.groups);
+            }
+
+            if self.stdin.is_some() {
+                debug_command.field("stdin", &self.stdin);
+            }
+            if self.stdout.is_some() {
+                debug_command.field("stdout", &self.stdout);
+            }
+            if self.stderr.is_some() {
+                debug_command.field("stderr", &self.stderr);
+            }
+            if self.pgroup.is_some() {
+                debug_command.field("pgroup", &self.pgroup);
+            }
+
+            #[cfg(target_os = "linux")]
+            {
+                debug_command.field("create_pidfd", &self.create_pidfd);
+            }
 
-        for arg in &self.args[1..] {
-            write!(f, " {:?}", arg)?;
+            debug_command.finish()
+        } else {
+            if let Some(ref cwd) = self.cwd {
+                write!(f, "cd {cwd:?} && ")?;
+            }
+            for (key, value_opt) in self.get_envs() {
+                if let Some(value) = value_opt {
+                    write!(f, "{}={value:?} ", key.to_string_lossy())?;
+                }
+            }
+            if self.program != self.args[0] {
+                write!(f, "[{:?}] ", self.program)?;
+            }
+            write!(f, "{:?}", self.args[0])?;
+
+            for arg in &self.args[1..] {
+                write!(f, " {:?}", arg)?;
+            }
+            Ok(())
         }
-        Ok(())
     }
 }
 

std/src/sys_common/process.rs

@@ -4,12 +4,13 @@
 use crate::collections::BTreeMap;
 use crate::env;
 use crate::ffi::{OsStr, OsString};
+use crate::fmt;
 use crate::io;
 use crate::sys::pipe::read2;
 use crate::sys::process::{EnvKey, ExitStatus, Process, StdioPipes};
 
 // Stores a set of changes to an environment
-#[derive(Clone, Debug)]
+#[derive(Clone)]
 pub struct CommandEnv {
     clear: bool,
     saw_path: bool,
@@ -22,6 +23,14 @@ impl Default for CommandEnv {
     }
 }
 
+impl fmt::Debug for CommandEnv {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        let mut debug_command_env = f.debug_struct("CommandEnv");
+        debug_command_env.field("clear", &self.clear).field("vars", &self.vars);
+        debug_command_env.finish()
+    }
+}
+
 impl CommandEnv {
     // Capture the current environment with these changes applied
     pub fn capture(&self) -> BTreeMap<EnvKey, OsString> {