From c3cc40d2ac6f93b5e16177c274861b8f9c860e98 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Jes=C3=BAs=20Lapastora?= <cyber.gsuscode@gmail.com>
Date: Sun, 6 Feb 2022 23:04:28 +0100
Subject: [PATCH] feat(cli): Print arguments if argument parsing fails (#3560)

* fix(#3554): Print the command line argv on clap error

This is a very bare implementation that just prints the error
and then a note with the arguments passed, it does this manually
and doesn't use clap. I've also chosen to use `Vec`'s `Debug`
implementation instead of rolling my own one because I thought it was
good enough, but there might be a better way of doing all this.

Altogether, I think this will be very useful to help in the diagnostic
of other bugs :)

* fix(#3554): Print the command line argv on clap error

This is a very bare implementation that just prints the error
and then a note with the arguments passed, it does this manually
and doesn't use clap. I've also chosen to use `Vec`'s `Debug`
implementation instead of rolling my own one because I thought it was
good enough, but there might be a better way of doing all this.

Altogether, I think this will be very useful to help in the diagnostic
of other bugs :)

EDIT: removed `dbg!`, set it to exit always.

* correctness(exit): don't print argv / exit with error on help and
version error kinds

* fix: Avoid panicking when stdout/stderr closing unexpectedly

* refactor(cli): use `use_stderr` instead of manual match for error kinds

`clap` uses `use_stderr` to reliably check whether the error given is
actually an error coming from user input or rather a hint to display
other info (version, help, etc.)

Also reworded/moved a couple of comments so that they explain better
what is the thought process behind the code
---
 src/main.rs | 33 ++++++++++++++++++++++++++++++++-
 1 file changed, 32 insertions(+), 1 deletion(-)

diff --git a/src/main.rs b/src/main.rs
index c41926d4..a2dfad57 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -108,7 +108,38 @@ fn main() {
     let _ = ansi_term::enable_ansi_support();
     logger::init();
 
-    let args = Cli::parse();
+    let args = match Cli::try_parse() {
+        Ok(args) => args,
+        Err(e) => {
+            // if the error is not printed to stderr, this means it was not really
+            // an error but rather some information is going to be listed, therefore
+            // we won't print the arguments passed
+            let is_info_only = !e.use_stderr();
+            // print the error and void panicking in case of stdout/stderr closing unexpectedly
+            let _ = e.print();
+            // if there was no mistake by the user and we're only going to display information,
+            // we won't put arguments or exit with non-zero code
+            let exit_code = if is_info_only {
+                0
+            } else {
+                // print the arguments
+                // avoid panicking in case of stderr closing
+                let mut stderr = io::stderr();
+                use io::Write;
+                let _ = writeln!(
+                    stderr,
+                    "\nNOTE:\n    passed arguments: {:?}",
+                    // collect into a vec to format args as a slice
+                    std::env::args().skip(1).collect::<Vec<_>>()
+                );
+                // clap exits with status 2 on error:
+                //  https://docs.rs/clap/latest/clap/struct.Error.html#method.exit
+                2
+            };
+
+            std::process::exit(exit_code);
+        }
+    };
     log::trace!("Parsed arguments: {:#?}", args);
 
     match args.command {