Change line-ending default to auto

crates/ruff_cli/tests/format.rs

@@ -94,6 +94,35 @@ if condition:
     Ok(())
 }
 
+#[test]
+fn mixed_line_endings() -> Result<()> {
+    let tempdir = TempDir::new()?;
+
+    fs::write(
+        tempdir.path().join("main.py"),
+        "from test import say_hy\n\nif __name__ == \"__main__\":\n    say_hy(\"dear Ruff contributor\")\n",
+    )?;
+
+    fs::write(
+        tempdir.path().join("test.py"),
+        "def say_hy(name: str):\r\n    print(f\"Hy {name}\")\r\n",
+    )?;
+
+    assert_cmd_snapshot!(Command::new(get_cargo_bin(BIN_NAME))
+        .current_dir(tempdir.path())
+        .args(["format", "--diff", "--isolated"])
+        .arg("."), @r###"
+    success: true
+    exit_code: 0
+    ----- stdout -----
+
+    ----- stderr -----
+    warning: `ruff format` is not yet stable, and subject to change in future versions.
+    2 files left unchanged
+    "###);
+    Ok(())
+}
+
 #[test]
 fn exclude() -> Result<()> {
     let tempdir = TempDir::new()?;

crates/ruff_workspace/src/options.rs

@@ -2623,16 +2623,16 @@ pub struct FormatOptions {
 
     /// The character Ruff uses at the end of a line.
     ///
+    /// * `auto`: The newline style is detected automatically on a file per file basis. Files with mixed line endings will be converted to the first detected line ending. Defaults to `\n` for files that contain no line endings.
     /// * `lf`: Line endings will be converted to `\n`. The default line ending on Unix.
     /// * `cr-lf`: Line endings will be converted to `\r\n`. The default line ending on Windows.
-    /// * `auto`: The newline style is detected automatically on a file per file basis. Files with mixed line endings will be converted to the first detected line ending. Defaults to `\n` for files that contain no line endings.
     /// * `native`: Line endings will be converted to `\n` on Unix and `\r\n` on Windows.
     #[option(
-        default = r#"lf"#,
-        value_type = r#""lf" | "cr-lf" | "auto" | "native""#,
+        default = r#"auto"#,
+        value_type = r#""auto" | "lf" | "cr-lf" | "native""#,
         example = r#"
-            # Automatically detect the line ending on a file per file basis.
-            line-ending = "auto"
+            # Use `\n` line endings for all files
+            line-ending = "lf"
         "#
     )]
     pub line_ending: Option<LineEnding>,

crates/ruff_workspace/src/settings.rs

@@ -168,7 +168,7 @@ impl Default for FormatterSettings {
             exclude: FilePatternSet::default(),
             preview: PreviewMode::Disabled,
             line_width: default_options.line_width(),
-            line_ending: LineEnding::Lf,
+            line_ending: LineEnding::Auto,
             indent_style: default_options.indent_style(),
             indent_width: default_options.indent_width(),
             quote_style: default_options.quote_style(),
@@ -183,18 +183,18 @@ impl Default for FormatterSettings {
 #[serde(rename_all = "kebab-case")]
 #[cfg_attr(feature = "schemars", derive(schemars::JsonSchema))]
 pub enum LineEnding {
-    ///  Line endings will be converted to `\n` as is common on Unix.
+    /// The newline style is detected automatically on a file per file basis.
+    /// Files with mixed line endings will be converted to the first detected line ending.
+    /// Defaults to [`LineEnding::Lf`] for a files that contain no line endings.
     #[default]
+    Auto,
+
+    ///  Line endings will be converted to `\n` as is common on Unix.
     Lf,
 
     /// Line endings will be converted to `\r\n` as is common on Windows.
     CrLf,
 
-    /// The newline style is detected automatically on a file per file basis.
-    /// Files with mixed line endings will be converted to the first detected line ending.
-    /// Defaults to [`LineEnding::Lf`] for a files that contain no line endings.
-    Auto,
-
     /// Line endings will be converted to `\n` on Unix and `\r\n` on Windows.
     Native,
 }