Implement --fix with stdin (#405)

src/autofix/fixer.rs

@@ -1,7 +1,3 @@
-use std::fs;
-use std::path::Path;
-
-use anyhow::Result;
 use itertools::Itertools;
 use rustpython_parser::ast::Location;
 
@@ -24,17 +20,15 @@ impl From<bool> for Mode {
 }
 
 /// Auto-fix errors in a file, and write the fixed source code to disk.
-pub fn fix_file(checks: &mut [Check], contents: &str, path: &Path) -> Result<()> {
+pub fn fix_file(checks: &mut [Check], contents: &str) -> Option<String> {
     if checks.iter().all(|check| check.fix.is_none()) {
-        return Ok(());
+        return None;
     }
 
-    let output = apply_fixes(
+    Some(apply_fixes(
         checks.iter_mut().filter_map(|check| check.fix.as_mut()),
         contents,
-    );
-
-    fs::write(path, output).map_err(|e| e.into())
+    ))
 }
 
 /// Apply a series of fixes.

src/linter.rs

@@ -1,4 +1,6 @@
 use std::fs::write;
+use std::io;
+use std::io::Write;
 use std::path::Path;
 
 use anyhow::Result;
@@ -83,7 +85,12 @@ pub(crate) fn check_path(
     Ok(checks)
 }
 
-pub fn lint_stdin(path: &Path, stdin: &str, settings: &Settings) -> Result<Vec<Message>> {
+pub fn lint_stdin(
+    path: &Path,
+    stdin: &str,
+    settings: &Settings,
+    autofix: &fixer::Mode,
+) -> Result<Vec<Message>> {
     // Tokenize once.
     let tokens: Vec<LexResult> = tokenize(stdin);
 
@@ -91,14 +98,16 @@ pub fn lint_stdin(path: &Path, stdin: &str, settings: &Settings) -> Result<Vec<M
     let noqa_line_for = noqa::extract_noqa_line_for(&tokens);
 
     // Generate checks.
-    let checks = check_path(
-        path,
-        stdin,
-        tokens,
-        &noqa_line_for,
-        settings,
-        &fixer::Mode::None,
-    )?;
+    let mut checks = check_path(path, stdin, tokens, &noqa_line_for, settings, autofix)?;
+
+    // Apply autofix, write results to stdout.
+    if matches!(autofix, fixer::Mode::Apply) {
+        let output = match fix_file(&mut checks, stdin) {
+            None => stdin.to_string(),
+            Some(content) => content,
+        };
+        io::stdout().write_all(output.as_bytes())?;
+    }
 
     // Convert to messages.
     Ok(checks
@@ -141,7 +150,9 @@ pub fn lint_path(
 
     // Apply autofix.
     if matches!(autofix, fixer::Mode::Apply) {
-        fix_file(&mut checks, &contents, path)?;
+        if let Some(fixed_contents) = fix_file(&mut checks, &contents) {
+            write(path, fixed_contents)?;
+        }
     };
 
     // Convert to messages.

src/main.rs

@@ -81,9 +81,9 @@ fn read_from_stdin() -> Result<String> {
     Ok(buffer)
 }
 
-fn run_once_stdin(settings: &Settings, filename: &Path) -> Result<Vec<Message>> {
+fn run_once_stdin(settings: &Settings, filename: &Path, autofix: bool) -> Result<Vec<Message>> {
     let stdin = read_from_stdin()?;
-    let mut messages = lint_stdin(filename, &stdin, settings)?;
+    let mut messages = lint_stdin(filename, &stdin, settings, &autofix.into())?;
     messages.sort_unstable();
     Ok(messages)
 }
@@ -365,18 +365,20 @@ fn inner_main() -> Result<ExitCode> {
             println!("Formatted {modifications} files.");
         }
     } else {
-        let messages = if cli.files == vec![PathBuf::from("-")] {
-            if cli.fix {
-                eprintln!("Warning: --fix is not enabled when reading from stdin.");
-            }
-
+        let (messages, print_messages) = if cli.files == vec![PathBuf::from("-")] {
             let filename = cli.stdin_filename.unwrap_or_else(|| "-".to_string());
             let path = Path::new(&filename);
-            run_once_stdin(&settings, path)?
+            (
+                run_once_stdin(&settings, path, cli.fix)?,
+                !cli.quiet && !cli.fix,
+            )
         } else {
-            run_once(&cli.files, &settings, !cli.no_cache, cli.fix)?
+            (
+                run_once(&cli.files, &settings, !cli.no_cache, cli.fix)?,
+                !cli.quiet,
+            )
         };
-        if !cli.quiet {
+        if print_messages {
             printer.write_once(&messages)?;
         }
 

tests/integration_test.rs

@@ -39,9 +39,42 @@ fn test_stdin_autofix() -> Result<()> {
     let mut cmd = Command::cargo_bin(crate_name!())?;
     let output = cmd
         .args(&["-", "--fix"])
-        .write_stdin("import os\n")
+        .write_stdin("import os\nimport sys\n\nprint(sys.version)\n")
         .assert()
-        .failure();
-    assert!(str::from_utf8(&output.get_output().stdout)?.contains("-:1:1: F401"));
+        .success();
+    assert_eq!(
+        str::from_utf8(&output.get_output().stdout)?,
+        "import sys\n\nprint(sys.version)\n"
+    );
+    Ok(())
+}
+
+#[test]
+fn test_stdin_autofix_when_not_fixable_should_still_print_contents() -> Result<()> {
+    let mut cmd = Command::cargo_bin(crate_name!())?;
+    let output = cmd
+        .args(&["-", "--fix"])
+        .write_stdin("import os\nimport sys\n\nif (1, 2):\n     print(sys.version)\n")
+        .assert()
+        .failure();
+    assert_eq!(
+        str::from_utf8(&output.get_output().stdout)?,
+        "import sys\n\nif (1, 2):\n     print(sys.version)\n"
+    );
+    Ok(())
+}
+
+#[test]
+fn test_stdin_autofix_when_no_issues_should_still_print_contents() -> Result<()> {
+    let mut cmd = Command::cargo_bin(crate_name!())?;
+    let output = cmd
+        .args(&["-", "--fix"])
+        .write_stdin("import sys\n\nprint(sys.version)\n")
+        .assert()
+        .success();
+    assert_eq!(
+        str::from_utf8(&output.get_output().stdout)?,
+        "import sys\n\nprint(sys.version)\n"
+    );
     Ok(())
 }