chore: init frontend-source directory with tooling scaffold

Former-commit-id: 435fb8e3e4f8e334ad3b0e95052edbdd9547d197

frontend-source/scripts/node_modules/@jridgewell/trace-mapping/src/by-source.ts

@@ -0,0 +1,41 @@
+import { COLUMN, SOURCES_INDEX, SOURCE_LINE, SOURCE_COLUMN } from './sourcemap-segment';
+import { sortComparator } from './sort';
+
+import type { ReverseSegment, SourceMapSegment } from './sourcemap-segment';
+
+export type Source = ReverseSegment[][];
+
+// 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: unknown[],
+): Source[] {
+  const sources: Source[] = memos.map(() => []);
+
+  for (let i = 0; i < decoded.length; i++) {
+    const line = decoded[i];
+    for (let j = 0; j < line.length; j++) {
+      const seg = line[j];
+      if (seg.length === 1) continue;
+
+      const sourceIndex = seg[SOURCES_INDEX];
+      const sourceLine = seg[SOURCE_LINE];
+      const sourceColumn = seg[SOURCE_COLUMN];
+
+      const source = sources[sourceIndex];
+      const segs = (source[sourceLine] ||= []);
+      segs.push([sourceColumn, i, seg[COLUMN]]);
+    }
+  }
+
+  for (let i = 0; i < sources.length; i++) {
+    const source = sources[i];
+    for (let j = 0; j < source.length; j++) {
+      const line = source[j];
+      if (line) line.sort(sortComparator);
+    }
+  }
+
+  return sources;
+}