Support log-file (#4)

* Add log file

* Merge stderr into stdout

.github/workflows/ci.yml

@@ -100,7 +100,7 @@ jobs:
         run: |
           cargo nextest run \
             --workspace \
-            --status-level skip --failure-output immediate-final --no-fail-fast -j 8 --final-status-level slow
+            --status-level skip --failure-output immediate --no-fail-fast -j 8 --final-status-level slow
 
   cargo-test-macos:
     timeout-minutes: 10
@@ -128,7 +128,7 @@ jobs:
         run: |
           cargo nextest run \
             --workspace \
-            --status-level skip --failure-output immediate-final --no-fail-fast -j 8 --final-status-level slow
+            --status-level skip --failure-output immediate --no-fail-fast -j 8 --final-status-level slow
 
   cargo-test-windows:
     timeout-minutes: 15
@@ -168,4 +168,4 @@ jobs:
         run: |
           # use only 1 job for now
           # uv concurrently writes to cache, which causes `Access is denied` errors
-          cargo nextest run --workspace --status-level skip --failure-output immediate-final --no-fail-fast -j 1 --final-status-level slow
+          cargo nextest run --workspace --status-level skip --failure-output immediate --no-fail-fast -j 1 --final-status-level slow

src/cli/run.rs

@@ -83,7 +83,7 @@ pub(crate) async fn run(
     }
 
     let skips = get_skips();
-    let non_skipped = hooks
+    let to_install = hooks
         .iter()
         .filter(|h| !skips.contains(&h.id) && !skips.contains(&h.alias))
         .cloned()
@@ -91,16 +91,15 @@ pub(crate) async fn run(
 
     debug!(
         "Hooks going to run: {:?}",
-        non_skipped.iter().map(|h| &h.id).collect::<Vec<_>>()
+        to_install.iter().map(|h| &h.id).collect::<Vec<_>>()
     );
-    install_hooks(&non_skipped, printer).await?;
+    install_hooks(&to_install, printer).await?;
     drop(lock);
 
-    let filenames = all_filenames(hook_stage, from_ref, to_ref, all_files, files)
-        .await?
-        .into_iter()
-        .map(normalize_path)
-        .collect::<Vec<_>>();
+    let mut filenames = all_filenames(hook_stage, from_ref, to_ref, all_files, files).await?;
+    for filename in &mut filenames {
+        normalize_path(filename);
+    }
 
     let filenames = filter_filenames(
         filenames.par_iter(),
@@ -440,10 +439,22 @@ async fn run_hook(
                 "- files were modified by this hook".dimmed()
             )?;
         }
-        if !(output.stdout.is_empty() && output.stderr.is_empty()) {
-            // TODO: write to log file
-            std::io::stdout().write_all(&output.stdout)?;
-            std::io::stdout().write_all(&output.stderr)?;
+
+        // To be consistent with pre-commit, merge stderr into stdout.
+        let stdout = output.stdout.trim_ascii();
+        if !stdout.is_empty() {
+            if let Some(file) = hook.log_file.as_deref() {
+                fs_err::OpenOptions::new()
+                    .create(true)
+                    .append(true)
+                    .open(file)
+                    .and_then(|mut f| {
+                        f.write_all(stdout)?;
+                        Ok(())
+                    })?;
+            } else {
+                writeln!(printer.stdout(), "{}", String::from_utf8_lossy(stdout))?;
+            };
         }
     }
 
@@ -455,7 +466,6 @@ fn filter_filenames<'a>(
     include: Option<&str>,
     exclude: Option<&str>,
 ) -> Result<impl ParallelIterator<Item = &'a String>, regex::Error> {
-    // TODO: normalize path separators
     let include = include.map(Regex::new).transpose()?;
     let exclude = exclude.map(Regex::new).transpose()?;
 

src/fs.rs

@@ -185,25 +185,23 @@ pub fn copy_dir_all(src: impl AsRef<Path>, dst: impl AsRef<Path>) -> std::io::Re
 /// Normalizes a path to use `/` as a separator everywhere, even on platforms
 /// that recognize other characters as separators.
 #[cfg(unix)]
-pub(crate) fn normalize_path(path: String) -> String {
+pub(crate) fn normalize_path(_path: &mut str) {
     // UNIX only uses /, so we're good.
-    path
 }
 
 /// Normalizes a path to use `/` as a separator everywhere, even on platforms
 /// that recognize other characters as separators.
 #[cfg(not(unix))]
-pub(crate) fn normalize_path(path: String) -> String {
+pub(crate) fn normalize_path(path: &mut str) {
     use std::path::is_separator;
 
-    let mut bytes = path.into_bytes();
-    for c in &mut bytes {
+    let bytes = unsafe { path.as_bytes_mut() };
+    for c in bytes {
         if *c == b'/' || !is_separator(char::from(*c)) {
             continue;
         }
         *c = b'/';
     }
-    String::from_utf8(bytes).expect("Path is valid UTF-8")
 }
 
 /// Compute a path describing `path` relative to `base`.

src/languages/python.rs

@@ -85,6 +85,7 @@ impl LanguageImpl for Python {
             .env("VIRTUAL_ENV", &env)
             .env("PATH", new_path)
             .env_remove("PYTHONHOME")
+            .stderr(std::process::Stdio::inherit())
             .output()
             .await?;
 

tests/run.rs

@@ -1,8 +1,8 @@
+use crate::common::{cmd_snapshot, TestContext};
 use anyhow::Result;
 use assert_cmd::Command;
 use assert_fs::prelude::*;
-
-use crate::common::{cmd_snapshot, TestContext};
+use insta::assert_snapshot;
 
 mod common;
 
@@ -475,3 +475,54 @@ fn subdirectory() -> Result<()> {
 
     Ok(())
 }
+
+/// Test hook `log_file` option.
+#[test]
+fn log_file() -> Result<()> {
+    let context = TestContext::new();
+
+    context.init_project();
+
+    let cwd = context.workdir();
+    cwd.child("file.txt").write_str("Hello, world!  ")?;
+
+    // Global files and exclude.
+    context
+        .workdir()
+        .child(".pre-commit-config.yaml")
+        .write_str(indoc::indoc! {r"
+            repos:
+              - repo: https://github.com/pre-commit/pre-commit-hooks
+                rev: v5.0.0
+                hooks:
+                  - id: trailing-whitespace
+                    log_file: log.txt
+            "
+        })?;
+
+    Command::new("git")
+        .arg("add")
+        .arg(".")
+        .current_dir(cwd)
+        .assert()
+        .success();
+
+    cmd_snapshot!(context.filters(), context.run(), @r#"
+    success: true
+    exit_code: 0
+    ----- stdout -----
+    Cloning https://github.com/pre-commit/pre-commit-hooks@v5.0.0
+    Installing environment for https://github.com/pre-commit/pre-commit-hooks@v5.0.0
+    trim trailing whitespace.................................................Failed
+    - hook id: trailing-whitespace
+    - exit code: 1
+    - files were modified by this hook
+
+    ----- stderr -----
+    "#);
+
+    let log = context.read("log.txt");
+    assert_snapshot!(log, @"Fixing file.txt");
+
+    Ok(())
+}