DIYgod/RSSHub · error

vm.compileFunction is not supported in Workers

Error message

vm.compileFunction is not supported in Workers

What it means

vmShim.compileFunction() in lib/shims/node-module.ts throws. Workers cannot compile a string into a callable Function at runtime via the vm API (no V8 compileFunction exposed), so the call is hard-fail.

Source

Thrown at lib/shims/node-module.ts:76

        throw new Error('vm.Script.runInThisContext is not supported in Workers');
    }
}

const vmShim = {
    createContext: (sandbox?: object) => sandbox || {},
    runInContext: () => {
        throw new Error('vm.runInContext is not supported in Workers');
    },
    runInNewContext: () => {
        throw new Error('vm.runInNewContext is not supported in Workers');
    },
    runInThisContext: () => {
        throw new Error('vm.runInThisContext is not supported in Workers');
    },
    Script: ScriptShim,
    isContext: () => false,
    compileFunction: () => {
        throw new Error('vm.compileFunction is not supported in Workers');
    },
};

// Child process shim (inline to avoid import cycle)
const child_process = {
    execSync: (_command: string): Buffer => Buffer.from(''),
    exec: () => {
        throw new Error('exec is not supported in Cloudflare Workers');
    },
    spawn: () => {
        throw new Error('spawn is not supported in Cloudflare Workers');
    },
    fork: () => {
        throw new Error('fork is not supported in Cloudflare Workers');
    },
    execFile: () => {
        throw new Error('execFile is not supported in Cloudflare Workers');
    },

View on GitHub (pinned to bed535e087)

Solutions

  1. Replace vm.compileFunction with a build-time compiled function or new Function (only if Workers' CSP allows).
  2. Static-import the compiled result instead.
  3. Keep the code path Node-only.

Example fix

// before
const fn = vm.compileFunction(src, ['x']);
// after
import compiledFn from './compiled'; // produced at build time
Defensive patterns

Strategy: validation

Validate before calling

const vmUsable = typeof process !== 'undefined' && !!process.versions?.node;
if (!vmUsable) {
  // skip vm.compileFunction; use a build-time compiled function
}

Type guard

function isVmShimError(e: unknown): e is Error {
  return e instanceof Error && /not supported in Workers/.test(e.message);
}

Try / catch

try {
  if (vmUsable) return vm.compileFunction(src, ['x']);
  else return precompiled;
} catch (e) {
  if (isVmShimError(e)) return precompiled;
  throw e;
}

Prevention

When it happens

Trigger: Calling vm.compileFunction(source, params) under Workers — used by some module systems and meta-templating libraries to build functions from source.

Common situations: Custom module loaders; DSL/template compilers built on vm.compileFunction.

Related errors

AI-assisted analysis of DIYgod/RSSHub@bed535e087 (2026-08-12). Data as JSON: /api/errors/ace95533b963104c. Report an issue: GitHub.