feat: Allow process_wrapper to capture exit codes instead of forwarding them

rust/private/clippy.bzl

@@ -101,7 +101,7 @@ def get_clippy_ready_crate_info(target, aspect_ctx = None):
     else:
         return None
 
-def rust_clippy_action(ctx, clippy_executable, process_wrapper, crate_info, config, output = None, success_marker = None, cap_at_warnings = False, extra_clippy_flags = [], error_format = None, clippy_diagnostics_file = None):
+def rust_clippy_action(ctx, clippy_executable, process_wrapper, crate_info, config, output = None, success_marker = None, exit_code_file = None, forward_clippy_exit_code = True, cap_at_warnings = False, extra_clippy_flags = [], error_format = None, clippy_diagnostics_file = None):
     """Run clippy with the specified parameters.
 
     Args:
@@ -112,6 +112,8 @@ def rust_clippy_action(ctx, clippy_executable, process_wrapper, crate_info, conf
         config (File): The clippy configuration file. Reference: https://doc.rust-lang.org/clippy/configuration.html#configuring-clippy
         output (File): The output file for clippy stdout/stderr. If None, no output will be captured
         success_marker (File): A file that will be written if clippy succeeds
+        exit_code_file (File): A file that will contain clippy's exit code
+        forward_clippy_exit_code (bool): If set, let the action exit with the same exit code as clippy
         cap_at_warnings (bool): If set, it will cap all reports as warnings, allowing the build to continue even with clippy failures
         extra_clippy_flags (List[str]): A list of extra options to pass to clippy. If not set, every warnings will be turned into errors
         error_format (str): Which error format to use. Must be acceptable by rustc: https://doc.rust-lang.org/beta/rustc/command-line-arguments.html#--error-format-control-how-errors-are-produced
@@ -200,6 +202,13 @@ def rust_clippy_action(ctx, clippy_executable, process_wrapper, crate_info, conf
         args.process_wrapper_flags.add("--touch-file", success_marker)
         outputs.append(success_marker)
 
+    if forward_clippy_exit_code == False:
+        args.process_wrapper_flags.add("--swallow-subprocess-exit-code", "true")
+
+    if exit_code_file != None:
+        args.process_wrapper_flags.add("--exit-code-file", exit_code_file)
+        outputs.append(exit_code_file)
+
     if clippy_flags or lint_files:
         args.rustc_flags.add_all(clippy_flags)
     else:

util/process_wrapper/main.rs

@@ -22,6 +22,7 @@ use std::collections::HashMap;
 use std::fmt;
 use std::fs::{copy, OpenOptions};
 use std::io;
+use std::io::Write;
 use std::process::{exit, Command, ExitStatus, Stdio};
 
 use tinyjson::JsonValue;
@@ -228,7 +229,24 @@ fn main() -> Result<(), ProcessWrapperError> {
         }
     }
 
-    exit(code)
+    if let Some(ecf) = opts.exit_code_file {
+        let exit_code_file = OpenOptions::new()
+            .create(true)
+            .truncate(true)
+            .write(true)
+            .open(ecf)
+            .map_err(|e| ProcessWrapperError(format!("failed to create exit code file: {}", e)))?;
+        let mut writer = io::LineWriter::new(exit_code_file);
+        writeln!(writer, "{}", code).map_err(|e| {
+            ProcessWrapperError(format!("failed to write exit code to file: {}", e))
+        })?;
+    }
+
+    if opts.forward_exit_code {
+        exit(code)
+    } else {
+        exit(0)
+    }
 }
 
 #[cfg(test)]

util/process_wrapper/options.rs

@@ -44,6 +44,10 @@ pub(crate) struct Options {
     // If set, also logs all unprocessed output from the rustc output to this file.
     // Meant to be used to get json output out of rustc for tooling usage.
     pub(crate) output_file: Option<String>,
+    // If set, exit with the same exit code as the child process if there are no internal errors.
+    pub(crate) forward_exit_code: bool,
+    // If set, writes the exit code of the process into this file.
+    pub(crate) exit_code_file: Option<String>,
     // If set, it configures rustc to emit an rmeta file and then
     // quit.
     pub(crate) rustc_quit_on_rmeta: bool,
@@ -64,6 +68,8 @@ pub(crate) fn options() -> Result<Options, OptionError> {
     let mut stdout_file = None;
     let mut stderr_file = None;
     let mut output_file = None;
+    let mut swallow_exit_code_raw = None;
+    let mut exit_code_file = None;
     let mut rustc_quit_on_rmeta_raw = None;
     let mut rustc_output_format_raw = None;
     let mut flags = Flags::new();
@@ -102,6 +108,16 @@ pub(crate) fn options() -> Result<Options, OptionError> {
         "Log all unprocessed subprocess stderr in this file.",
         &mut output_file,
     );
+    flags.define_flag(
+        "--swallow-subprocess-exit-code",
+        "If set, the process_wrapper will not forward the exit code for the subprocess, and instead only fail if there are internal errors.",
+        &mut swallow_exit_code_raw,
+    );
+    flags.define_flag(
+        "--exit-code-file",
+        "Log the exit code of the process to this file.",
+        &mut exit_code_file,
+    );
     flags.define_flag(
         "--rustc-quit-on-rmeta",
         "If enabled, this wrapper will terminate rustc after rmeta has been emitted.",
@@ -179,6 +195,7 @@ pub(crate) fn options() -> Result<Options, OptionError> {
         })
         .transpose()?;
 
+    let swallow_exit_code = swallow_exit_code_raw.is_some_and(|s| s != "true");
     let rustc_quit_on_rmeta = rustc_quit_on_rmeta_raw.is_some_and(|s| s == "true");
     let rustc_output_format = rustc_output_format_raw
         .map(|v| match v.as_str() {
@@ -227,6 +244,8 @@ pub(crate) fn options() -> Result<Options, OptionError> {
         stdout_file,
         stderr_file,
         output_file,
+        forward_exit_code: !swallow_exit_code,
+        exit_code_file,
         rustc_quit_on_rmeta,
         rustc_output_format,
     })