Auto merge of #127455 - Nilstrieb:blazing-tidy, r=jieyouxu

Make tidy problematic const checking fast again

fixes pathological tidy performance described in #127453 by reverting #127428

i think anyone can approve this ASAP, it makes working on this repo significantly worse.

2 files changed, 31 insertions, 27 deletions

diff --git a/src/tools/tidy/src/style.rs b/src/tools/tidy/src/style.rs
index f65001e8de8..8e693c35adc 100644
--- a/src/tools/tidy/src/style.rs
+++ b/src/tools/tidy/src/style.rs
@@ -18,8 +18,9 @@
 // ignore-tidy-dbg
 
 use crate::walk::{filter_dirs, walk};
+use regex::RegexSet;
 use rustc_hash::FxHashMap;
-use std::{ffi::OsStr, path::Path, sync::LazyLock};
+use std::{ffi::OsStr, path::Path};
 
 #[cfg(test)]
 mod tests;
@@ -109,32 +110,16 @@ const ROOT_PROBLEMATIC_CONSTS: &[u32] = &[
     173390526, 721077,
 ];
 
-#[cfg(not(test))]
-const LETTER_DIGIT: &[(char, char)] = &[('A', '4'), ('B', '8'), ('E', '3')];
-
-#[cfg(test)]
-const LETTER_DIGIT: &[(char, char)] = &[('A', '4'), ('B', '8'), ('E', '3'), ('0', 'F')]; // use "futile" F intentionally
-
+// Returns all permutations of problematic consts, over 2000 elements.
 fn generate_problematic_strings(
     consts: &[u32],
     letter_digit: &FxHashMap<char, char>,
 ) -> Vec<String> {
     generate_problems(consts, letter_digit)
-        .flat_map(|v| vec![v.to_string(), format!("{:X}", v)])
+        .flat_map(|v| vec![v.to_string(), format!("{:x}", v), format!("{:X}", v)])
         .collect()
 }
 
-static PROBLEMATIC_CONSTS_STRINGS: LazyLock<Vec<String>> = LazyLock::new(|| {
-    generate_problematic_strings(
-        ROOT_PROBLEMATIC_CONSTS,
-        &FxHashMap::from_iter(LETTER_DIGIT.iter().copied()),
-    )
-});
-
-fn contains_problematic_const(trimmed: &str) -> bool {
-    PROBLEMATIC_CONSTS_STRINGS.iter().any(|s| trimmed.to_uppercase().contains(s))
-}
-
 const INTERNAL_COMPILER_DOCS_LINE: &str = "#### This error code is internal to the compiler and will not be emitted with normal Rust code.";
 
 /// Parser states for `line_is_url`.
@@ -331,6 +316,13 @@ pub fn check(path: &Path, bad: &mut bool) {
         // We only check CSS files in rustdoc.
         path.extension().map_or(false, |e| e == "css") && !is_in(path, "src", "librustdoc")
     }
+    let problematic_consts_strings = generate_problematic_strings(
+        ROOT_PROBLEMATIC_CONSTS,
+        &[('A', '4'), ('B', '8'), ('E', '3')].iter().cloned().collect(),
+    );
+    // This creates a RegexSet as regex contains performance optimizations to be able to deal with these over
+    // 2000 needles efficiently. This runs over the entire source code, so performance matters.
+    let problematic_regex = RegexSet::new(problematic_consts_strings.as_slice()).unwrap();
 
     walk(path, skip, &mut |entry, contents| {
         let file = entry.path();
@@ -400,6 +392,7 @@ pub fn check(path: &Path, bad: &mut bool) {
         let is_test = file.components().any(|c| c.as_os_str() == "tests");
         // scanning the whole file for multiple needles at once is more efficient than
         // executing lines times needles separate searches.
+        let any_problematic_line = problematic_regex.is_match(contents);
         for (i, line) in contents.split('\n').enumerate() {
             if line.is_empty() {
                 if i == 0 {
@@ -469,8 +462,12 @@ pub fn check(path: &Path, bad: &mut bool) {
                 if trimmed.contains("//") && trimmed.contains(" XXX") {
                     err("Instead of XXX use FIXME")
                 }
-                if contains_problematic_const(trimmed) {
-                    err("Don't use magic numbers that spell things (consider 0x12345678)");
+                if any_problematic_line {
+                    for s in problematic_consts_strings.iter() {
+                        if trimmed.contains(s) {
+                            err("Don't use magic numbers that spell things (consider 0x12345678)");
+                        }
+                    }
                 }
             }
             // for now we just check libcore
diff --git a/src/tools/tidy/src/style/tests.rs b/src/tools/tidy/src/style/tests.rs
index 47fec890432..292e23916d2 100644
--- a/src/tools/tidy/src/style/tests.rs
+++ b/src/tools/tidy/src/style/tests.rs
@@ -1,10 +1,17 @@
 use super::*;
 
 #[test]
-fn test_contains_problematic_const() {
-    assert!(contains_problematic_const("786357")); // check with no "decimal" hex digits - converted to integer
-    assert!(contains_problematic_const("589701")); // check with "decimal" replacements - converted to integer
-    assert!(contains_problematic_const("8FF85")); // check for hex display
-    assert!(contains_problematic_const("8fF85")); // check for case-alternating hex display
-    assert!(!contains_problematic_const("1193046")); // check for non-matching value
+fn test_generate_problematic_strings() {
+    let problematic_regex = RegexSet::new(
+        generate_problematic_strings(
+            ROOT_PROBLEMATIC_CONSTS,
+            &[('A', '4'), ('B', '8'), ('E', '3'), ('0', 'F')].iter().cloned().collect(), // use "futile" F intentionally
+        )
+        .as_slice(),
+    )
+    .unwrap();
+    assert!(problematic_regex.is_match("786357")); // check with no "decimal" hex digits - converted to integer
+    assert!(problematic_regex.is_match("589701")); // check with "decimal" replacements - converted to integer
+    assert!(problematic_regex.is_match("8FF85")); // check for hex display
+    assert!(!problematic_regex.is_match("1193046")); // check for non-matching value
 }