Formatter: Detect line endings (#7054)

Cargo.lock

@@ -2369,6 +2369,7 @@ dependencies = [
  "similar",
  "smallvec",
  "thiserror",
+ "tracing",
  "unicode-width",
 ]
 

crates/ruff_cli/src/commands/format.rs

@@ -12,7 +12,6 @@ use log::{debug, warn};
 use rayon::iter::Either::{Left, Right};
 use rayon::iter::{IntoParallelIterator, ParallelIterator};
 use thiserror::Error;
-use tracing::{span, Level};
 
 use ruff::fs;
 use ruff::logging::LogLevel;
@@ -20,6 +19,7 @@ use ruff::warn_user_once;
 use ruff_formatter::LineWidth;
 use ruff_python_ast::{PySourceType, SourceType};
 use ruff_python_formatter::{format_module, FormatModuleError, PyFormatOptions};
+use ruff_source_file::{find_newline, LineEnding};
 use ruff_workspace::resolver::python_files_in_path;
 
 use crate::args::{FormatArguments, Overrides};
@@ -140,12 +140,18 @@ fn format_path(
 ) -> Result<FormatCommandResult, FormatCommandError> {
     let unformatted = std::fs::read_to_string(path)
         .map_err(|err| FormatCommandError::Read(Some(path.to_path_buf()), err))?;
-    let formatted = {
-        let span = span!(Level::TRACE, "format_path_without_io", path = %path.display());
-        let _enter = span.enter();
-        format_module(&unformatted, options)
-            .map_err(|err| FormatCommandError::FormatModule(Some(path.to_path_buf()), err))?
+
+    let line_ending = match find_newline(&unformatted) {
+        Some((_, LineEnding::Lf)) | None => ruff_formatter::printer::LineEnding::LineFeed,
+        Some((_, LineEnding::Cr)) => ruff_formatter::printer::LineEnding::CarriageReturn,
+        Some((_, LineEnding::CrLf)) => ruff_formatter::printer::LineEnding::CarriageReturnLineFeed,
     };
+
+    let options = options.with_line_ending(line_ending);
+
+    let formatted = format_module(&unformatted, options)
+        .map_err(|err| FormatCommandError::FormatModule(Some(path.to_path_buf()), err))?;
+
     let formatted = formatted.as_code();
     if formatted.len() == unformatted.len() && formatted == unformatted {
         Ok(FormatCommandResult::Unchanged)

crates/ruff_formatter/src/printer/printer_options/mod.rs

@@ -124,7 +124,8 @@ impl SourceMapGeneration {
 }
 
 #[allow(dead_code)]
-#[derive(Clone, Debug, Eq, PartialEq, Default)]
+#[derive(Copy, Clone, Debug, Eq, PartialEq, Default)]
+#[cfg_attr(feature = "serde", derive(serde::Serialize, serde::Deserialize))]
 pub enum LineEnding {
     ///  Line Feed only (\n), common on Linux and macOS as well as inside git repos
     #[default]

crates/ruff_python_formatter/Cargo.toml

@@ -31,6 +31,7 @@ rustc-hash = { workspace = true }
 serde = { workspace = true, optional = true }
 smallvec = { workspace = true }
 thiserror = { workspace = true }
+tracing = { workspace = true }
 unicode-width = { workspace = true }
 
 [dev-dependencies]

crates/ruff_python_formatter/src/lib.rs

@@ -1,4 +1,5 @@
 use thiserror::Error;
+use tracing::Level;
 
 use ruff_formatter::prelude::*;
 use ruff_formatter::{format, FormatError, Formatted, PrintError, Printed, SourceCode};
@@ -119,6 +120,7 @@ impl From<ParseError> for FormatModuleError {
     }
 }
 
+#[tracing::instrument(level=Level::TRACE, skip_all, err)]
 pub fn format_module(
     contents: &str,
     options: PyFormatOptions,

crates/ruff_python_formatter/src/options.rs

@@ -28,6 +28,8 @@ pub struct PyFormatOptions {
     #[cfg_attr(feature = "serde", serde(default = "default_tab_width"))]
     tab_width: TabWidth,
 
+    line_ending: LineEnding,
+
     /// The preferred quote style to use (single vs double quotes).
     quote_style: QuoteStyle,
 
@@ -59,6 +61,7 @@ impl Default for PyFormatOptions {
             line_width: default_line_width(),
             tab_width: default_tab_width(),
             quote_style: QuoteStyle::default(),
+            line_ending: LineEnding::default(),
             magic_trailing_comma: MagicTrailingComma::default(),
             source_map_generation: SourceMapGeneration::default(),
         }
@@ -94,6 +97,10 @@ impl PyFormatOptions {
         self.source_map_generation
     }
 
+    pub fn line_ending(&self) -> LineEnding {
+        self.line_ending
+    }
+
     #[must_use]
     pub fn with_tab_width(mut self, tab_width: TabWidth) -> Self {
         self.tab_width = tab_width;
@@ -123,6 +130,12 @@ impl PyFormatOptions {
         self.line_width = line_width;
         self
     }
+
+    #[must_use]
+    pub fn with_line_ending(mut self, line_ending: LineEnding) -> Self {
+        self.line_ending = line_ending;
+        self
+    }
 }
 
 impl FormatOptions for PyFormatOptions {
@@ -142,7 +155,7 @@ impl FormatOptions for PyFormatOptions {
         PrinterOptions {
             tab_width: self.tab_width,
             line_width: self.line_width,
-            line_ending: LineEnding::LineFeed,
+            line_ending: self.line_ending,
             indent_style: self.indent_style,
             source_map_generation: self.source_map_generation,
         }