fix(cli): exit diff check appropriately (#87)

Author: maksym-arutyunyan

README.md

@@ -183,11 +183,11 @@ Use `--diff-command <command>` to delegate diff generation to an external progra
 Use `--mode fix` (or `--fix`) to rewrite the file in place.
 
 The command exits with these codes:
-1. `0` — success
-2. `1` — syntax errors in input
-3. `2` — usage errors: invoked incorrectly
-4. `3` — unexpected runtime errors
-5. `4` — check mode failed (reformat is needed)
+- `0` — success
+- `1` — syntax errors in input
+- `2` — usage errors: invoked incorrectly
+- `3` — unexpected runtime errors
+- `4` — check mode failed (reformat is needed)
 
 ```shell
 $ keepsorted --check Cargo.toml

docs/architecture.md

@@ -7,11 +7,11 @@ This document explains how the main pieces of the `keepsorted` crate fit togethe
 `keepsorted` was inspired by [Buildifier](https://github.com/bazelbuild/buildtools/tree/master/buildifier), which sorts items in Bazel `BUILD` files. The command-line flags and exit codes follow a similar design so that tooling can integrate either tool with minimal changes.
 
 The CLI returns these codes:
-1. `0` — success
-2. `1` — syntax errors in input
-3. `2` — incorrect command usage
-4. `3` — unexpected runtime failures
-5. `4` — check mode detected unsorted files
+- `0` — success
+- `1` — syntax errors in input
+- `2` — incorrect command usage
+- `3` — unexpected runtime failures
+- `4` — check mode detected unsorted files
 
 ## Sorting Behaviour
 

src/main.rs

@@ -8,6 +8,8 @@ use std::process::{self, Command};
 ///
 /// clap also exits with this code on usage errors such as conflicting flags.
 const EXIT_USAGE_ERROR: i32 = 2;
+/// Exit code used for syntax errors in the input.
+const EXIT_SYNTAX_ERROR: i32 = 1;
 /// Exit code used for I/O problems or internal bugs.
 const EXIT_RUNTIME_ERROR: i32 = 3;
 /// Exit code used when `--mode check` or `--mode diff` detects unsorted files.
@@ -270,7 +272,11 @@ fn handle_file(path: &Path, features: &[Feature], mode: Mode, diff_command: Opti
                         Ok(out) => {
                             print!("{}", String::from_utf8_lossy(&out.stdout));
                             if !out.status.success() {
-                                process::exit(out.status.code().unwrap_or(EXIT_RUNTIME_ERROR));
+                                let code = out.status.code().unwrap_or(EXIT_RUNTIME_ERROR);
+                                if code == 1 {
+                                    process::exit(EXIT_SYNTAX_ERROR);
+                                }
+                                process::exit(code);
                             }
                         }
                         Err(e) => {