css: log parser warnings with the Source and a byte position

src/bun_core/string/immutable.rs

@@ -56,8 +56,9 @@ mod wtf8_text;
 pub use wtf8_text::{
     Wtf8Codepoints, codepoint_len_utf16, push_codepoint_wtf8_joined, push_wtf8,
     push_wtf8_well_formed, utf8_decoded_len_utf16, utf8_lossy_len_utf16, wtf8_codepoint_at,
-    wtf8_codepoint_count, wtf8_codepoints, wtf8_first_codepoint, wtf8_has_surrogate,
-    wtf8_len_utf16, wtf8_offset_of_utf16_index, wtf8_slice_by_utf16, wtf8_to_utf16, wtf16_to_wtf8,
+    wtf8_codepoint_count, wtf8_codepoint_start, wtf8_codepoints, wtf8_first_codepoint,
+    wtf8_has_surrogate, wtf8_len_utf16, wtf8_offset_of_utf16_index, wtf8_slice_by_utf16,
+    wtf8_to_utf16, wtf16_to_wtf8,
 };
 
 // UTF-16 surrogate primitives. The single implementation lives in the

src/bun_core/string/immutable/wtf8_text.rs

@@ -31,6 +31,14 @@ pub fn wtf8_codepoint_at(text: &[u8], at: usize) -> (u32, usize) {
     (UNICODE_REPLACEMENT, 1)
 }
 
+/// Where the code point starts that `at` is in the middle of. `at` itself if it is not.
+pub fn wtf8_codepoint_start(text: &[u8], at: usize) -> usize {
+    (1..=3)
+        .filter_map(|back| at.checked_sub(back))
+        .find(|&start| wtf8_codepoint_at(text, start).1 > at - start)
+        .unwrap_or(at)
+}
+
 /// The code points of `text`, each with the offset in bytes where it starts: `[...text]`. See
 /// [`wtf8_codepoint_at`].
 #[inline]

src/bundler/ParseTask.rs

@@ -1273,7 +1273,6 @@ pub mod parse_worker {
             Loader::Css => {
                 // make css ast
                 let mut import_records = Vec::<ImportRecord>::default();
-                let source_code = &source.contents;
                 let mut temp_log = Log::init();
                 // `temp_log` is flushed into `log` on every exit path via linear
                 // control flow (scopeguard would alias `log`/`temp_log`).
@@ -1293,7 +1292,7 @@ pub mod parse_worker {
 
                 let (mut css_ast, extra) = match bun_css::BundlerStyleSheet::parse_bundler(
                     bump,
-                    source_code,
+                    source,
                     parser_options,
                     &mut import_records,
                     bun_ast::Index::source(source.index.0),

src/bundler/transpiler.rs

@@ -3059,9 +3059,10 @@ impl<'a> Transpiler<'a> {
         // `'bump`-threading note).
         let alloc: &'static Arena = unsafe { bun_ptr::detach_lifetime_ref::<Arena>(self.arena) };
 
+        let source = bun_ast::Source::init_path_string(file_path_text, entry.contents());
         let (mut sheet, extra) = match bun_css::StyleSheet::<bun_css::DefaultAtRule>::parse(
             alloc,
-            entry.contents(),
+            &source,
             opts,
             None,
             bun_ast::Index::source(0u32),