simplifiy with PR feedback

connor4312 · connor4312 · commit e2f5db12bb57 · 2025-09-10T08:58:31.000-07:00
diff --git a/packages/trace-mapping/src/by-source.ts b/packages/trace-mapping/src/by-source.ts
@@ -1,22 +1,20 @@
 import { COLUMN, SOURCES_INDEX, SOURCE_LINE, SOURCE_COLUMN } from './sourcemap-segment';
-import { memoizedBinarySearch, upperBound } from './binary-search';
 
 import type { ReverseSegment, SourceMapSegment } from './sourcemap-segment';
-import type { MemoState } from './binary-search';
 
 export type Source = {
   __proto__: null;
+  length: number;
   [line: number]: Exclude<ReverseSegment, [number]>[];
 };
 
 // Rebuilds the original source files, with mappings that are ordered by source line/column instead
 // of generated line/column.
 export default function buildBySources(
   decoded: readonly SourceMapSegment[][],
-  memos: MemoState[],
+  sourcesCount: number,
 ): Source[] {
-  const sources: Source[] = memos.map(buildNullArray);
-  const todo: ReverseSegment[][][] = [];
+  const sources: Source[] = Array.from({ length: sourcesCount }, buildNullArray<Source>);
 
   for (let i = 0; i < decoded.length; i++) {
     const line = decoded[i];
@@ -28,58 +26,16 @@ export default function buildBySources(
       const sourceLine = seg[SOURCE_LINE];
       const sourceColumn = seg[SOURCE_COLUMN];
 
-      todo[sourceIndex] ||= [];
-      (todo[sourceIndex][sourceLine] ||= []).push([sourceColumn, i, seg[COLUMN]]);
+      const source = sources[sourceIndex];
+      source.length = Math.max(source.length || 0, sourceLine + 1);
+      (source[sourceLine] ||= []).push([sourceColumn, i, seg[COLUMN]]);
     }
   }
 
-  for (let sourceIndex = 0; sourceIndex < todo.length; sourceIndex++) {
-    const lines = todo[sourceIndex];
-    if (!lines) continue;
-    const originalSource = sources[sourceIndex];
-    const memo = memos[sourceIndex];
-
-    for (let sourceLine = 0; sourceLine < lines.length; sourceLine++) {
-      const segs = lines[sourceLine];
-      if (!segs) continue;
-
-      segs.sort((a, b) => a[0] - b[0]);
-      const originalLine = (originalSource[sourceLine] ||= []);
-
-      let lastIndex = 0;
-      const newOriginalLine: ReverseSegment[] = [];
-      for (let i = 0; i < segs.length; i++) {
-        const seg = segs[i];
-
-        // The binary search either found a match, or it found the left-index just before where the
-        // segment should go. Either way, we want to insert after that. And there may be multiple
-        // generated segments associated with an original location, so there may need to move several
-        // indexes before we find where we need to insert.
-        const originalLineJoint = jointArray(newOriginalLine, originalLine, lastIndex);
-        let index = upperBound(
-          originalLineJoint,
-          seg[0],
-          memoizedBinarySearch(originalLineJoint, seg[0], memo, sourceLine),
-        );
-
-        memo.lastIndex = ++index;
-        if (index <= newOriginalLine.length) {
-          insert(newOriginalLine, index, seg);
-          continue;
-        }
-
-        index = index - newOriginalLine.length + lastIndex;
-        while (lastIndex < index) {
-          newOriginalLine.push(originalLine[lastIndex++]);
-        }
-
-        newOriginalLine.push(seg);
-      }
-
-      while (lastIndex < originalLine.length) {
-        newOriginalLine.push(originalLine[lastIndex++]);
-      }
-      originalSource[sourceLine] = newOriginalLine;
+  for (let sourceIndex = 0; sourceIndex < sources.length; sourceIndex++) {
+    const source = sources[sourceIndex];
+    for (let line = 0; line < source.length; line++) {
+      source[line]?.sort((a, b) => a[0] - b[0]);
     }
   }
 
@@ -94,21 +50,3 @@ export default function buildBySources(
 function buildNullArray<T extends { __proto__: null }>(): T {
   return { __proto__: null } as T;
 }
-
-function jointArray<T>(a: T[], b: T[], bOffset: number): T[] {
-  return new Proxy([], {
-    get(_, p) {
-      if (p === 'length') return a.length + (b.length - bOffset);
-      const index = typeof p === 'symbol' ? NaN : parseInt(p, 10);
-      if (isNaN(index)) return (a as any)[p];
-      return index < a.length ? a[index] : b[index - bOffset];
-    },
-  });
-}
-
-function insert<T>(array: T[], index: number, value: T) {
-  for (let i = array.length; i > index; i--) {
-    array[i] = array[i - 1];
-  }
-  array[index] = value;
-}
diff --git a/packages/trace-mapping/src/trace-mapping.ts b/packages/trace-mapping/src/trace-mapping.ts
@@ -484,10 +484,8 @@ function generatedPosition(
   if (sourceIndex === -1) sourceIndex = resolvedSources.indexOf(source);
   if (sourceIndex === -1) return all ? [] : GMapping(null, null);
 
-  const generated = (cast(map)._bySources ||= buildBySources(
-    decodedMappings(map),
-    (cast(map)._bySourceMemos = sources.map(memoizedState)),
-  ));
+  cast(map)._bySourceMemos = sources.map(memoizedState);
+  const generated = (cast(map)._bySources ||= buildBySources(decodedMappings(map), sources.length));
 
   const segments = generated[sourceIndex][line];
   if (segments == null) return all ? [] : GMapping(null, null);
