From 13c6a41c57037333722f627ddb876768cc1e854c Mon Sep 17 00:00:00 2001
From: Charlie Marsh <charlie.r.marsh@gmail.com>
Date: Mon, 5 Feb 2024 22:25:31 -0500
Subject: [PATCH] Try fast-path for tab detection

---
 .../pycodestyle/rules/tab_indentation.rs      | 33 +++++++++++++++----
 1 file changed, 26 insertions(+), 7 deletions(-)

diff --git a/crates/ruff_linter/src/rules/pycodestyle/rules/tab_indentation.rs b/crates/ruff_linter/src/rules/pycodestyle/rules/tab_indentation.rs
index 153caab6484563..d7adb6a8d0e405 100644
--- a/crates/ruff_linter/src/rules/pycodestyle/rules/tab_indentation.rs
+++ b/crates/ruff_linter/src/rules/pycodestyle/rules/tab_indentation.rs
@@ -3,7 +3,7 @@ use ruff_macros::{derive_message_formats, violation};
 use ruff_python_index::Indexer;
 use ruff_python_parser::lexer::LexResult;
 use ruff_python_parser::Tok;
-use ruff_python_trivia::leading_indentation;
+use ruff_python_trivia::{is_python_whitespace, leading_indentation};
 use ruff_source_file::Locator;
 use ruff_text_size::{TextLen, TextRange, TextSize};
 
@@ -52,6 +52,11 @@ pub(crate) fn tab_indentation(
     locator: &Locator,
     indexer: &Indexer,
 ) {
+    // If there are no tabs in the file, give up.
+    if memchr::memchr(b'\t', locator.contents().as_bytes()).is_none() {
+        return;
+    }
+
     // Always check the first line for tab indentation as there's no newline
     // token before it.
     tab_indentation_at_line_start(diagnostics, locator, TextSize::default());
@@ -81,11 +86,25 @@ fn tab_indentation_at_line_start(
     locator: &Locator,
     line_start: TextSize,
 ) {
-    let indent = leading_indentation(locator.after(line_start));
-    if indent.find('\t').is_some() {
-        diagnostics.push(Diagnostic::new(
-            TabIndentation,
-            TextRange::at(line_start, indent.text_len()),
-        ));
+    let mut contains_tab = false;
+    for (i, char) in locator.after(line_start).as_bytes().iter().enumerate() {
+        match char {
+            // If we find a tab character, report it as a violation.
+            b'\t' => {
+                contains_tab = true;
+            }
+            // If we find a space, continue.
+            b' ' | b'\x0C' => {}
+            // If we find a non-whitespace character, stop.
+            _ => {
+                if contains_tab {
+                    diagnostics.push(Diagnostic::new(
+                        TabIndentation,
+                        TextRange::at(line_start, TextSize::try_from(i).unwrap()),
+                    ));
+                }
+                return;
+            }
+        }
     }
 }