feat: add --log-file option for persistent log output

barkleesanders · claude · barkleesanders · commit 6bb12939b507 · 2026-03-07T19:48:05.000-08:00
- Add --log-file CLI option to write tracing output to a file (topgrade-rs#779) - File logger appends to existing file, includes targets, no ANSI codes - Creates parent directories automatically if needed Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
diff --git a/src/config.rs b/src/config.rs
@@ -1078,6 +1078,10 @@ pub struct CommandLineArgs {
     /// List available steps and exit
     #[arg(long = "list-steps")]
     list_steps: bool,
+
+    /// Write log output to a file (in addition to stderr)
+    #[arg(long = "log-file", value_name = "PATH")]
+    log_file: Option<PathBuf>,
 }
 
 fn env_args_parser(arg: &str) -> Result<(String, String)> {
@@ -1120,6 +1124,11 @@ impl CommandLineArgs {
 
         ret
     }
+
+    /// Get the log file path (for early tracing setup before Config is loaded).
+    pub fn log_file_path(&self) -> Option<&Path> {
+        self.log_file.as_deref()
+    }
 }
 
 /// Represents the application configuration
@@ -1997,6 +2006,11 @@ impl Config {
         self.opt.list_steps
     }
 
+    /// Get the log file path if specified via CLI.
+    pub fn log_file(&self) -> Option<&Path> {
+        self.opt.log_file.as_deref()
+    }
+
     /// Get the GitHub token for self-update, checking config file and environment variables.
     pub fn github_token(&self) -> Option<String> {
         self.config_file
diff --git a/src/main.rs b/src/main.rs
@@ -80,7 +80,7 @@ fn run() -> Result<()> {
     //
     // For more info, see the comments in `CommandLineArgs::tracing_filter_directives()`
     // and `Config::tracing_filter_directives()`.
-    let reload_handle = install_tracing(&opt.tracing_filter_directives())?;
+    let reload_handle = install_tracing(&opt.tracing_filter_directives(), opt.log_file_path())?;
 
     // Get current system locale and set it as the default locale
     let system_locale = sys_locale::get_locale().unwrap_or("en".to_string());
diff --git a/src/utils.rs b/src/utils.rs
@@ -286,7 +286,7 @@ pub fn check_is_python_2_or_shim(ctx: &ExecutionContext, python: PathBuf) -> Res
 /// # Return value
 /// A reload handle will be returned so that we can change the log level at
 /// runtime.
-pub fn install_tracing(filter_directives: &str) -> Result<Handle<EnvFilter, Registry>> {
+pub fn install_tracing(filter_directives: &str, log_file: Option<&Path>) -> Result<Handle<EnvFilter, Registry>> {
     let env_filter = EnvFilter::try_new(filter_directives)
         .or_else(|_| EnvFilter::try_from_default_env())
         .or_else(|_| EnvFilter::try_new(DEFAULT_LOG_LEVEL))?;
@@ -295,7 +295,20 @@ pub fn install_tracing(filter_directives: &str) -> Result<Handle<EnvFilter, Regi
 
     let (filter, reload_handle) = Layer::new(env_filter);
 
-    registry().with(filter).with(fmt_layer).init();
+    if let Some(log_path) = log_file {
+        // Create parent directories if needed
+        if let Some(parent) = log_path.parent() {
+            std::fs::create_dir_all(parent)?;
+        }
+        let file = std::fs::OpenOptions::new().create(true).append(true).open(log_path)?;
+        let file_layer = fmt::layer()
+            .with_target(true)
+            .with_ansi(false)
+            .with_writer(std::sync::Mutex::new(file));
+        registry().with(filter).with(fmt_layer).with(file_layer).init();
+    } else {
+        registry().with(filter).with(fmt_layer).init();
+    }
 
     Ok(reload_handle)
 }
