jsc.paths regression in 1.3.79

[alexeagle]

Describe the bug

swc re-writes import paths by following symlinks, it seems. I believe this is a regression from one of the changes @realtimetodie made when we originally got SWC working under Bazel.

It now looks like:

require("../../../../../../../private/var/tmp/_bazel_alexeagle/43e97bf6681e7317438fd77d405a1c4b/sandbox/darwin-sandbox/181/execroot/aspect_rules_swc/examples/paths/src/modules/moduleA");

Minimal repro:

1. clone https://github.com/aspect-build/rules_swc
2. npx @bazel/bazelisk build --subcommands examples/paths:compile
3. Open bazel-bin/examples/paths/src/index.js and you'll see the require path is relative
4. update LATEST_SWC_VERSION = "v1.3.78" to v1.3.79 in swc/repositories.bzl
5. repeat step 2 to build again
6. Look at the same index.js file and the require path now contains an absolute path to the root of the filesystem

If you need the minimal repro to not involve Bazel, we can engineer one that creates a similar symlink tree to reproduce the problem without it.

Note, this is my fourth attempt to file an issue here, see prior attempt #8264.

Input code

import { moduleA } from "@modules/moduleA";

moduleA();

Config

{
  "jsc": {
    "parser": {
      "syntax": "typescript"
    },
    "target": "es2021",
    "baseUrl": "./src",
    "paths": {
      "@modules/*": [
        "./modules/*"
      ]
    }
  },
  "module": {
    "type": "commonjs"
  },
  "sourceMaps": true
}

Playground link (or link to the minimal reproduction)

https://github.com/aspect-build/rules_swc/pull/216/files

SWC Info output

swc-darwin-arm64 --version
SWC 0.91.64

Expected behavior

SWC 1.3.78 produces

const _moduleA = require("./modules/moduleA/index");

In #8258 you suggested that we compare with what tsc produces. As I understand it, typescript never attempts to re-write import/require statements. So the result is here

https://github.com/aspect-build/rules_swc/pull/216/files#diff-e3a9eafb3b943b9863d6cea0b348d4ef40bc1b7bb5867a38ac889fcacea0cbf4R3

"use strict";
Object.defineProperty(exports, "__esModule", { value: true });
var moduleA_1 = require("@modules/moduleA");
(0, moduleA_1.moduleA)();

Actual behavior

SWC 1.3.79 produces

const _moduleA = require("../../../../../../../shared/cache/bazel/user_base/09a27d1eeea3b44d1580773090924b4d/sandbox/linux-sandbox/629/execroot/aspect_rules_swc/examples/paths/src/modules/moduleA");

Version

1.3.79

Additional context

In 1.3.78 this worked, so #7852 is the likely culprit, as @kdy1 agrees #8258 (comment)

[kdy1]

I don't think it's culprit 🤣

[kdy1]

Note that I'll investigate, but if fixing this issue results in something which does not match tsc, I'll not fix this and reject patches. Matching the behavior of tsc is more important than satisfying really specific use case.

[kdy1]

Did you try some newer versions? I think it will error with a more useful error complaining about jsc.baseUrl.

[realtimetodie]

Yes, this is a regression. The tsc compiler does not re-write import/require statements to symbolic links. Actually, if you look into the source code of the tsc compiler and how symbolic links are handled, you won't find anything special, because tsc simply relies on the Node.js runtime's path module.

[kdy1]

I can't reproduce it without Bazel

[kdy1]

Yeah actually the TscResolver were written for the bundler, so it patches import path, but I'm not sure if it was a good idea to reuse it for modules transform.

[alexeagle]

@kdy1 I can build a repro without Bazel, the difference is that the input files are staged as symlinks.
(because Bazel tries to make builds reproducible by sandboxing the build steps)

[kdy1]

Ah, it would be nice. I need to create a test case without using Bazel

[alexeagle]

Repro:

1. Download swcx from https://github.com/swc-project/swc/releases/tag/v1.3.79 (we don't use npm or node.js under Bazel to run swc since you have the native CLI)

2. Run this script which emulates a "sandbox" strategy - it makes a tmp dir and symlinks the sources into it to make a more reproducible build just like Bazel does

#!/usr/bin/env bash
set -o errexit -o nounset

TMP=$(mktemp -d)
mkdir -p $TMP/src/modules/moduleA
mkdir -p $TMP/src/modules/moduleB

ln -s $PWD/.swcrc $TMP
ln -s $PWD/src/index.ts $TMP/src
ln -s $PWD/src/modules/moduleA/index.ts $TMP/src/modules/moduleA
ln -s $PWD/src/modules/moduleB/index.ts $TMP/src/modules/moduleB

cd $TMP
ls -alR
~/Downloads/swc-darwin-arm64 compile --source-maps false --config-file .swcrc --out-file src/index.js src/index.ts
grep require src/index.js

Running the script gives this output:

% ./repro.sh 
total 0
drwx------    4 alexeagle  staff    128 Nov 12 11:08 .
drwx------@ 835 alexeagle  staff  26720 Nov 12 11:08 ..
lrwxr-xr-x    1 alexeagle  staff     34 Nov 12 11:08 .swcrc -> /Users/alexeagle/repros/swc/.swcrc
drwxr-xr-x    4 alexeagle  staff    128 Nov 12 11:08 src

./src:
total 0
drwxr-xr-x  4 alexeagle  staff  128 Nov 12 11:08 .
drwx------  4 alexeagle  staff  128 Nov 12 11:08 ..
lrwxr-xr-x  1 alexeagle  staff   40 Nov 12 11:08 index.ts -> /Users/alexeagle/repros/swc/src/index.ts
drwxr-xr-x  4 alexeagle  staff  128 Nov 12 11:08 modules

./src/modules:
total 0
drwxr-xr-x  4 alexeagle  staff  128 Nov 12 11:08 .
drwxr-xr-x  4 alexeagle  staff  128 Nov 12 11:08 ..
drwxr-xr-x  3 alexeagle  staff   96 Nov 12 11:08 moduleA
drwxr-xr-x  3 alexeagle  staff   96 Nov 12 11:08 moduleB

./src/modules/moduleA:
total 0
drwxr-xr-x  3 alexeagle  staff   96 Nov 12 11:08 .
drwxr-xr-x  4 alexeagle  staff  128 Nov 12 11:08 ..
lrwxr-xr-x  1 alexeagle  staff   56 Nov 12 11:08 index.ts -> /Users/alexeagle/repros/swc/src/modules/moduleA/index.ts

./src/modules/moduleB:
total 0
drwxr-xr-x  3 alexeagle  staff   96 Nov 12 11:08 .
drwxr-xr-x  4 alexeagle  staff  128 Nov 12 11:08 ..
lrwxr-xr-x  1 alexeagle  staff   56 Nov 12 11:08 index.ts -> /Users/alexeagle/repros/swc/src/modules/moduleB/index.ts
const _moduleA = require("../../../../../private/var/folders/8n/7cfngjb106sgwb8mr1tytx700000gn/T/tmp.tCjESfPJ/src/modules/moduleA");

Here's a GH repo with the files: https://github.com/alexeagle/swc_8265_repro/

I confirmed that downloading from https://github.com/swc-project/swc/releases/tag/v1.3.78 instead gives the expected require statement.

[kdy1]

I managed to write a test which actually create symlink, and invoke Rust CLI to prevent regression perfectly.

https://github.com/swc-project/swc/pull/8297/files#diff-91e80712ad85568b1133ec3751cb89ec876af4674567542a1c5c506b497e1609

[kdy1]

Feel free to contribute test case to the file.

[alexeagle]

Amazing thank you @kdy1 !

I've never written Rust so I don't think you'd want my contribution to that test case. It looks sufficient already though. Does it need more changes before landing?

[kdy1]

It just needs an approval 😄

[swc-bot]

This closed issue has been automatically locked because it had no new activity for a month. If you are running into a similar issue, please create a new issue with the steps to reproduce. Thank you.