Sourcemaps don't work in vm.Script scripts
Nobody has claimed this yet.
- Dominant language
- JavaScript
- Stars
- 122k
- Forks
- 37.3k
- Avg merge
- 4d 2h
- Merged PRs (30d)
- 283
Description
Version
v21.7.1
Platform
Linux ecls 6.5.0-25-generic #25~22.04.1-Ubuntu SMP PREEMPT_DYNAMIC Tue Feb 20 16:09:15 UTC 2 x86_64 x86_64 x86_64 GNU/Linux
Subsystem
source_map
What steps will reproduce the bug?
This example is adapted from https://github.com/nodejs/node/issues/43047
import vm from 'node:vm';
const comment = '//#';
const code = `// Generated by CoffeeScript 2.7.0
(function() {
throw new Error('hello');
}).call(this);
${comment} sourceMappingURL=data:application/json;base64,eyJ2ZXJzaW9uIjozLCJmaWxlIjoic2ltcGxlLmpzIiwic291cmNlUm9vdCI6IlxcIiwic291cmNlcyI6WyJzaW1wbGUuY29mZmVlIl0sIm5hbWVzIjpbXSwibWFwcGluZ3MiOiI7QUFBQTtFQUFBLE1BQU0sSUFBSSxLQUFKLENBQVUsT0FBVjtBQUFOIiwic291cmNlc0NvbnRlbnQiOlsidGhyb3cgbmV3IEVycm9yICdoZWxsbydcbiJdfQ==
${comment} sourceURL=simple.coffee
`;
// eval(code);
const script = new vm.Script(code, {filename: 'simple.js'})
console.log(script.sourceMapURL)
script.runInNewContext()
How often does it reproduce? Is there a required condition?
Always.
What is the expected behavior? Why is that the expected behavior?
The expected behavior is shown if I uncomment the eval call in foo.js and run the code:
$ node --enable-source-maps foo.js
/simple.coffee:1
throw new Error 'hello'
^
Error: hello
at eval (/simple.coffee:1:7)
at eval (/simple.coffee:1:1)
at file:///home/rrt/Software/ursa/foo.js:13:1
at ModuleJob.run (node:internal/modules/esm/module_job:218:25)
at async ModuleLoader.import (node:internal/modules/esm/loader:329:24)
at async loadESM (node:internal/process/esm_loader:28:7)
at async handleMainPromise (node:internal/modules/run_main:113:12)
Now, the traceback shows the error in the CoffeeScript code.
What do you see instead?
Running this code from file foo.js gives:
$ node --enable-source-maps foo.js
node --enable-source-maps foo.js
data:application/json;base64,eyJ2ZXJzaW9uIjozLCJmaWxlIjoic2ltcGxlLmpzIiwic291cmNlUm9vdCI6IlxcIiwic291cmNlcyI6WyJzaW1wbGUuY29mZmVlIl0sIm5hbWVzIjpbXSwibWFwcGluZ3MiOiI7QUFBQTtFQUFBLE1BQU0sSUFBSSxLQUFKLENBQVUsT0FBVjtBQUFOIiwic291cmNlc0NvbnRlbnQiOlsidGhyb3cgbmV3IEVycm9yICdoZWxsbydcbiJdfQ==
simple.coffee:3
throw new Error('hello');
^
Error: hello
at simple.coffee:3:9
at simple.coffee:5:4
at Script.runInContext (node:vm:133:12)
at Script.runInNewContext (node:vm:138:17)
at file:///home/rrt/Software/ursa/foo.js:17:8
at ModuleJob.run (node:internal/modules/esm/module_job:218:25)
at async ModuleLoader.import (node:internal/modules/esm/loader:329:24)
at async loadESM (node:internal/process/esm_loader:28:7)
at async handleMainPromise (node:internal/modules/run_main:113:12)
Note that the traceback shows the JavaScript source, not the CoffeeScript source.
Additional information
Note that the vm.Script module correctly parses the sourceMappingURL comment, and displays its contents. This led me to believe that the source map would be supported during execution!
I'm sorry if I have overlooked other issues in this area; I have only found the issue I referred to above about adding support for source maps to eval.
Contributor guide
First steps
- Read the whole issue, then the project's contributing guide.
- Comment on the issue to say you are picking it up — it saves two people doing the same work.
- Fork the repository and make your change on a branch.
- Open a pull request that references the issue number.
Research direction
Start with the vm.Script example in foo.js and compare its execution with the eval(code) path under --enable-source-maps. Trace how the sourceMappingURL is parsed versus how stack traces are mapped during script.runInNewContext(); done means the vm.Script traceback points to the CoffeeScript source as the eval traceback does.
Written by the indexing model from the issue text.
Assessment
- Tech stack
- javascript, node.js
- Domain
- backend
- Issue type
- Bug
- Difficulty
- 4/5
- Estimated time
- 3-5 days
- Activity status
- Active
- Clarity
- Mostly clear
- Newbie friendliness
- 55/100