Truncate `SyntaxError`s before newline character (#4124)

crates/ruff/src/logging.rs

@@ -1,4 +1,4 @@
-use std::fmt::{Display, Formatter};
+use std::fmt::{Display, Formatter, Write};
 use std::path::Path;
 use std::sync::Mutex;
 
@@ -9,7 +9,7 @@ use fern;
 use log::Level;
 use once_cell::sync::Lazy;
 use ruff_python_ast::source_code::SourceCode;
-use rustpython_parser::ParseError;
+use rustpython_parser::{ParseError, ParseErrorType};
 
 pub(crate) static WARNINGS: Lazy<Mutex<Vec<&'static str>>> = Lazy::new(Mutex::default);
 
@@ -150,12 +150,84 @@ impl Display for DisplayParseError<'_> {
         write!(
             f,
             "{header} {path}{colon}{row}{colon}{column}{colon} {inner}",
-            header = "Failed to parse ".bold(),
+            header = "Failed to parse".bold(),
             path = fs::relativize_path(Path::new(&self.error.source_path)).bold(),
             row = source_location.row,
             column = source_location.column,
             colon = ":".cyan(),
-            inner = &self.error.error
+            inner = &DisplayParseErrorType(&self.error.error)
+        )
+    }
+}
+
+pub(crate) struct DisplayParseErrorType<'a>(&'a ParseErrorType);
+
+impl<'a> DisplayParseErrorType<'a> {
+    pub(crate) fn new(error: &'a ParseErrorType) -> Self {
+        Self(error)
+    }
+}
+
+impl Display for DisplayParseErrorType<'_> {
+    fn fmt(&self, f: &mut Formatter<'_>) -> std::fmt::Result {
+        match self.0 {
+            ParseErrorType::Eof => write!(f, "Expected token but reached end of file."),
+            ParseErrorType::ExtraToken(ref tok) => write!(
+                f,
+                "Got extraneous token: {tok}",
+                tok = TruncateAtNewline(&tok)
+            ),
+            ParseErrorType::InvalidToken => write!(f, "Got invalid token"),
+            ParseErrorType::UnrecognizedToken(ref tok, ref expected) => {
+                if let Some(expected) = expected.as_ref() {
+                    write!(
+                        f,
+                        "expected '{expected}', but got {tok}",
+                        tok = TruncateAtNewline(&tok)
+                    )
+                } else {
+                    write!(f, "unexpected token {tok}", tok = TruncateAtNewline(&tok))
+                }
+            }
+            ParseErrorType::Lexical(ref error) => write!(f, "{error}"),
+        }
+    }
+}
+
+/// Truncates the display text before the first newline character to avoid line breaks.
+struct TruncateAtNewline<'a>(&'a dyn Display);
+
+impl Display for TruncateAtNewline<'_> {
+    fn fmt(&self, f: &mut Formatter<'_>) -> std::fmt::Result {
+        struct TruncateAdapter<'a> {
+            inner: &'a mut dyn std::fmt::Write,
+            after_new_line: bool,
+        }
+
+        impl std::fmt::Write for TruncateAdapter<'_> {
+            fn write_str(&mut self, s: &str) -> std::fmt::Result {
+                if self.after_new_line {
+                    Ok(())
+                } else {
+                    if let Some(end) = s.find(['\n', '\r']) {
+                        self.inner.write_str(&s[..end])?;
+                        self.inner.write_str("\u{23ce}...")?;
+                        self.after_new_line = true;
+                        Ok(())
+                    } else {
+                        self.inner.write_str(s)
+                    }
+                }
+            }
+        }
+
+        write!(
+            TruncateAdapter {
+                inner: f,
+                after_new_line: false,
+            },
+            "{}",
+            self.0
         )
     }
 }

crates/ruff/src/rules/pycodestyle/rules/errors.rs

@@ -1,6 +1,7 @@
 use ruff_text_size::{TextLen, TextRange, TextSize};
 use rustpython_parser::ParseError;
 
+use crate::logging::DisplayParseErrorType;
 use ruff_diagnostics::{Diagnostic, Violation};
 use ruff_macros::{derive_message_formats, violation};
 use ruff_python_ast::source_code::Locator;
@@ -50,7 +51,7 @@ pub fn syntax_error(
 
     diagnostics.push(Diagnostic::new(
         SyntaxError {
-            message: parse_error.error.to_string(),
+            message: format!("{}", DisplayParseErrorType::new(&parse_error.error)),
         },
         TextRange::at(parse_error.location, len),
     ));