Deno Compatibility Fix for taglib-wasm

Problem Summary

The taglib-wasm npm package (v0.3.19) was incompatible with Deno due to several issues:

  1. Environment Detection: The Emscripten-generated code incorrectly detected Deno as Node.js because Deno has a process object
  2. Node.js-specific imports: The code tried to use createRequire and Node.js modules (fs, path, url) which don't work in Deno
  3. WebAssembly initialization: The error "RangeError: WebAssembly.Table.get(): invalid address" occurred due to improper environment handling

Root Cause

The Emscripten-generated taglib-wrapper.js file uses this logic:

var ENVIRONMENT_IS_NODE = typeof process == "object" &&
  process.versions?.node && process.type != "renderer";
if (ENVIRONMENT_IS_NODE) {
  const { createRequire } = await import("module");
  var require = createRequire(import.meta.url);
  // ... uses require("fs"), require("path"), etc.
}

Since Deno has a process object (for Node.js compatibility), it gets detected as Node.js, but then fails when trying to use Node.js-specific features.

Solution

Created comprehensive Deno compatibility patches that:

  1. Properly detect Deno: Add ENVIRONMENT_IS_DENO check before ENVIRONMENT_IS_NODE
  2. Avoid Node.js imports in Deno: Only use createRequire when actually in Node.js
  3. Use Deno APIs: Use Deno.readFile() and fetch() for file operations in Deno
  4. Fix WebAssembly loading: Ensure proper environment checks for Wasm instantiation

Implementation

1. Created scripts/fix-deno-compat.js

  • Patches the source build/taglib-wrapper.js after Emscripten compilation
  • Applied during the build process

2. Created scripts/fix-deno-compat-dist.js

  • Patches the distributed dist/taglib-wrapper.js
  • Applied during the postbuild process

3. Updated build scripts

  • build/build-wasm.sh: Uses the new compatibility fix instead of simple sed command
  • scripts/postbuild.js: Applies fixes to distributed files

Testing

Created scripts/test-deno-npm-compat.ts to verify:

  • Local build works with Deno
  • npm package works with Deno
  • Simple API functions correctly

Files Changed

  1. scripts/fix-deno-compat.js - Main compatibility fix script
  2. scripts/fix-deno-compat-dist.js - Distribution-specific fix script
  3. build/build-wasm.sh - Updated to use new fix
  4. scripts/postbuild.js - Updated to apply fixes to dist
  5. scripts/test-deno-npm-compat.ts - Test script for verification

Result

After applying these fixes, taglib-wasm will work correctly in Deno when imported from npm, resolving the WebAssembly initialization errors and Node.js-specific import failures.