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fix JS and TS executors to await Promise in context execution #246

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fix JS and TS executors to await Promise in context execution #246

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0fbf830
fix JS and TS executors to await Promise in context execution
whoiskatrin Nov 25, 2025
0fd5dc1
adding tests to verify promise resolution
whoiskatrin Nov 25, 2025
43d9b86
fix small nits
whoiskatrin Nov 25, 2025
e1c3e86
Update executor to await Promises in context execution
whoiskatrin Nov 25, 2025
2b7481a
update tests
whoiskatrin Nov 25, 2025
e4aa98a
top level await
whoiskatrin Nov 28, 2025
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5 changes: 5 additions & 0 deletions .changeset/heavy-bananas-dream.md
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Original file line number Diff line number Diff line change
@@ -0,0 +1,5 @@
---
"@cloudflare/sandbox": patch
---

fix JS and TS executors to await Promise in context execution
47 changes: 32 additions & 15 deletions package-lock.json
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1 change: 1 addition & 0 deletions packages/sandbox-container/package.json
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Original file line number Diff line number Diff line change
Expand Up @@ -13,6 +13,7 @@
},
"dependencies": {
"@repo/shared": "*",
"acorn": "^8.14.0",
"esbuild": "^0.27.0",
"zod": "^3.22.3"
},
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11 changes: 10 additions & 1 deletion packages/sandbox-container/src/runtime/executors/javascript/node_executor.ts
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Expand Up @@ -7,6 +7,8 @@ import { fileURLToPath } from 'node:url';
import * as util from 'node:util';
import * as vm from 'node:vm';
import type { RichOutput } from '../../process-pool';
import { transformForAsyncExecution } from '../shared/code-transformer';
import { isThenable } from '../shared/thenable';

// Create CommonJS-like globals for the sandbox
const __filename = fileURLToPath(import.meta.url);
Expand Down Expand Up @@ -83,7 +85,14 @@ rl.on('line', async (line: string) => {
options.timeout = timeout;
}

result = vm.runInContext(code, context, options);
// Transform code to support top-level await and capture last expression
const wrappedCode = transformForAsyncExecution(code);
result = vm.runInContext(wrappedCode, context, options);

// Result is always a Promise from async IIFE - await it
if (isThenable(result)) {
result = await result;
}
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@claude claude bot Nov 25, 2025

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Critical timeout bypass: vm.runInContext timeout only applies to sync execution. When awaiting the Promise here, long-running or infinite Promises ignore the timeout entirely.

Wrap in Promise.race:

if (isThenable(result)) {
  if (timeout !== undefined) {
    const timeoutPromise = new Promise((_, reject) => 
      setTimeout(() => reject(new Error('Execution timeout')), timeout)
    );
    result = await Promise.race([result, timeoutPromise]);
  } else {
    result = await result;
  }
}

} catch (error: unknown) {
const err = error as Error;
stderr += err.stack || err.toString();
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