fix: repair wasm browser entrypoint

Author: BartWaardenburg

package.json

@@ -28,7 +28,7 @@
     "typos": "typos",
     "deny": "cargo deny check",
     "test": "pnpm run test:rust && pnpm run test:js",
-    "test:js": "node --test packages/codec/__tests__/codec.test.mjs packages/sourcemap/__tests__/sourcemap.test.mjs packages/sourcemap-wasm/__tests__/sourcemap-wasm.test.mjs packages/sourcemap-wasm/__tests__/coverage-utils.test.mjs packages/generator-wasm/__tests__/generator-wasm.test.mjs packages/remapping-wasm/__tests__/remapping-wasm.test.mjs packages/trace-mapping/__tests__/trace-mapping.test.mjs packages/trace-mapping/__tests__/compat.test.mjs packages/source-map/__tests__/source-map.test.mjs packages/gen-mapping/__tests__/gen-mapping.test.mjs packages/gen-mapping/__tests__/gen-mapping.cjs.test.cjs packages/remapping/__tests__/remapping.test.mjs packages/remapping/__tests__/remapping.cjs.test.cjs packages/remapping/__tests__/compat.test.mjs",
+    "test:js": "node --test packages/codec/__tests__/codec.test.mjs packages/sourcemap/__tests__/sourcemap.test.mjs packages/sourcemap-wasm/__tests__/sourcemap-wasm.test.mjs packages/sourcemap-wasm/__tests__/coverage-utils.test.mjs packages/sourcemap-wasm/__tests__/browser.test.mjs packages/generator-wasm/__tests__/generator-wasm.test.mjs packages/remapping-wasm/__tests__/remapping-wasm.test.mjs packages/trace-mapping/__tests__/trace-mapping.test.mjs packages/trace-mapping/__tests__/compat.test.mjs packages/source-map/__tests__/source-map.test.mjs packages/gen-mapping/__tests__/gen-mapping.test.mjs packages/gen-mapping/__tests__/gen-mapping.cjs.test.cjs packages/remapping/__tests__/remapping.test.mjs packages/remapping/__tests__/remapping.cjs.test.cjs packages/remapping/__tests__/compat.test.mjs",
     "test:rust": "cargo test",
     "coverage": "pnpm run coverage:rust && pnpm run coverage:js",
     "coverage:js": "mkdir -p coverage && node --test --experimental-test-coverage --test-reporter=lcov --test-reporter-destination=coverage/js-lcov.info --test-reporter=spec --test-reporter-destination=stdout packages/codec/__tests__/codec.test.mjs packages/sourcemap/__tests__/sourcemap.test.mjs packages/sourcemap-wasm/__tests__/sourcemap-wasm.test.mjs packages/sourcemap-wasm/__tests__/coverage-utils.test.mjs packages/generator-wasm/__tests__/generator-wasm.test.mjs packages/remapping-wasm/__tests__/remapping-wasm.test.mjs packages/trace-mapping/__tests__/trace-mapping.test.mjs packages/trace-mapping/__tests__/compat.test.mjs packages/source-map/__tests__/source-map.test.mjs packages/gen-mapping/__tests__/gen-mapping.test.mjs packages/gen-mapping/__tests__/gen-mapping.cjs.test.cjs packages/remapping/__tests__/remapping.test.mjs packages/remapping/__tests__/remapping.cjs.test.cjs packages/remapping/__tests__/compat.test.mjs",

packages/sourcemap-wasm/README.md

@@ -128,7 +128,17 @@ Parse a source map from a JSON string.
 
 A fast-scan alternative to `SourceMap` that defers VLQ decoding until lookup time. On construction it only parses JSON metadata and byte-scans the mappings string for semicolons (to identify line boundaries). VLQ decoding happens per-line on demand with progressive state tracking. This makes parse time near-instant at the cost of slightly slower first lookups.
 
-`LazySourceMap` does **not** parse `sourcesContent` -- use the fast-scan wrapper (see below) if you need it.
+Import it directly from the supported package entrypoint:
+
+```js
+import { LazySourceMap } from "@srcmap/sourcemap-wasm";
+
+const sm = new LazySourceMap(jsonString);
+const loc = sm.originalPositionFor(42, 10);
+sm.free();
+```
+
+`LazySourceMap` does **not** parse `sourcesContent`. Use `SourceMap` when source contents are required.
 
 #### Static methods
 
@@ -161,59 +171,6 @@ A fast-scan alternative to `SourceMap` that defers VLQ decoding until lookup tim
 | `debugId` | `string \| undefined` | `debugId` proposal field |
 | `lineCount` | `number` | Number of generated lines |
 
----
-
-### Fast-scan mode (`fast.js`)
-
-The `fast.js` entry point wraps `LazySourceMap` with lazy `sourcesContent` extraction from the original JSON string. It exposes a `SourceMap` class with the same interface you would expect, but internally:
-
-1. Parses using fast-scan mode (no VLQ decode at parse time).
-2. Keeps the raw JSON string on the JS side and only calls `JSON.parse()` to extract `sourcesContent` on first access (then releases the JSON for GC).
-3. Forwards all lookups to the underlying `LazySourceMap`.
-
-This is ideal when you only need to look up a few positions and want the fastest possible parse time.
-
-```js
-const { SourceMap } = require('@srcmap/sourcemap-wasm/pkg/fast.js');
-
-const sm = new SourceMap(jsonString);
-
-// Lookups work the same as the regular SourceMap
-const loc = sm.originalPositionFor(42, 10);
-
-// sourcesContent is extracted lazily from JSON on first access
-const content = sm.sourceContentFor(0);
-
-sm.free();
-```
-
-#### Instance methods
-
-| Method | Returns | Description |
-|--------|---------|-------------|
-| `originalPositionFor(line, column)` | `{ source, line, column, name } \| null` | Forward lookup (0-based) |
-| `originalPositionFlat(line, column)` | `Int32Array` | Forward lookup returning flat indices |
-| `originalPositionBuf(line, column)` | `boolean` | Zero-allocation lookup via static buffer |
-| `originalPositionsFor(positions: Int32Array)` | `Int32Array` | Batch forward lookup |
-| `source(index)` | `string \| null` | Resolve source index to filename |
-| `name(index)` | `string \| null` | Resolve name index to string |
-| `sourceContentFor(index)` | `string \| null` | Get source content by index (triggers lazy JSON parse on first call) |
-| `isIgnoredIndex(index)` | `boolean` | Check if a source index is in the `ignoreList` |
-| `free()` | `void` | Release WASM memory |
-
-#### Instance properties
-
-| Property | Type | Description |
-|----------|------|-------------|
-| `sources` | `string[]` | All source filenames |
-| `names` | `string[]` | All names |
-| `sourcesContent` | `(string \| null)[] \| null` | Source file contents (lazily extracted from JSON on first access) |
-| `ignoreList` | `number[]` | Source ignore list indices |
-| `file` | `string \| undefined` | Output filename |
-| `sourceRoot` | `string \| undefined` | Source root prefix |
-| `debugId` | `string \| undefined` | `debugId` proposal field |
-| `lineCount` | `number` | Number of generated lines |
-
 ## Performance
 
 ### Batch API vs trace-mapping
@@ -231,7 +188,7 @@ The batch API (`originalPositionsFor`) returns a flat `Int32Array`, avoiding per
 | Use case | Recommended package |
 |----------|-------------------|
 | Batch lookups (error stacks, coverage) | **@srcmap/sourcemap-wasm** (batch API) |
-| Few lookups, fast parse | **@srcmap/sourcemap-wasm** (fast-scan mode via `fast.js`) |
+| Few lookups, fast parse | **@srcmap/sourcemap-wasm** (`LazySourceMap`) |
 | Few individual lookups | `@jridgewell/trace-mapping` (lower per-call overhead) |
 | Native Node.js addons | `@srcmap/sourcemap` (NAPI) |
 | Browser environments | **@srcmap/sourcemap-wasm** |

packages/sourcemap-wasm/__tests__/browser.test.mjs

@@ -0,0 +1,23 @@
+import assert from "node:assert/strict";
+import { readFileSync } from "node:fs";
+import { it } from "node:test";
+import init, { LazySourceMap, SourceMap, resultPtr, wasmMemory } from "../browser/index.mjs";
+
+it("exposes the browser API as static ESM exports before initialization", () => {
+  assert.equal(typeof init, "function");
+  assert.equal(typeof SourceMap, "function");
+  assert.equal(typeof LazySourceMap, "function");
+  assert.equal(typeof resultPtr, "function");
+  assert.equal(typeof wasmMemory, "function");
+});
+
+it("initializes the generated module only once", async () => {
+  const wasm = readFileSync(new URL("../web/srcmap_sourcemap_wasm_bg.wasm", import.meta.url));
+
+  const input = { module_or_path: wasm };
+  const first = init(input);
+  const second = init(input);
+
+  assert.equal(second, first);
+  await first;
+});

packages/sourcemap-wasm/browser/index.mjs

@@ -11,31 +11,27 @@
  * call init() before using any exports.
  */
 
-let initialized = false;
+import initWasm, {
+  LazySourceMap,
+  SourceMap,
+  resultPtr,
+  wasmMemory,
+} from "../web/srcmap_sourcemap_wasm.js";
+
+export { LazySourceMap, SourceMap, resultPtr, wasmMemory };
+
 let initPromise = null;
 
 /**
  * Initialize the WASM module. Must be called before using any exports.
- * Safe to call multiple times — subsequent calls return immediately.
- * @param {string|URL|Request|BufferSource} [input] - Optional WASM module source
+ * Safe to call multiple times, subsequent calls return the same promise.
+ * @param {string|URL|Request|BufferSource} [input] Optional WASM module source
  * @returns {Promise<void>}
  */
-export default async function init(input) {
-  if (initialized) return;
-  if (initPromise) return initPromise;
-
-  initPromise = (async () => {
-    const wasm = await import("../web/srcmap_sourcemap_wasm.js");
-    await wasm.default(input);
-    initialized = true;
-
-    // Re-export all WASM exports
-    Object.assign(exports, wasm);
-  })();
+export default function init(input) {
+  if (!initPromise) {
+    initPromise = initWasm(input).then(() => undefined);
+  }
 
   return initPromise;
 }
-
-const exports = {};
-
-export { exports as wasm };

packages/sourcemap-wasm/package.json

@@ -51,7 +51,7 @@
     "build:web": "wasm-pack build --target web --out-dir web",
     "build:bundler": "wasm-pack build --target bundler --out-dir bundler",
     "build:all": "pnpm run build && pnpm run build:web",
-    "test": "node --test __tests__/sourcemap-wasm.test.mjs __tests__/coverage-utils.test.mjs",
+    "test": "node --test __tests__/sourcemap-wasm.test.mjs __tests__/coverage-utils.test.mjs __tests__/browser.test.mjs",
     "test:coverage": "mkdir -p coverage && node --test --experimental-test-coverage --test-reporter=lcov --test-reporter-destination=coverage/lcov.info --test-reporter=spec --test-reporter-destination=stdout __tests__/sourcemap-wasm.test.mjs __tests__/coverage-utils.test.mjs"
   }
 }