refactor(linter/plugins): ensure debug assertions always shaken out of release build

[overlookmotel]

The assert* functions are no-ops in release builds, and minifier removes them as dead code.

However, there's an annoyance - we have to ensure that they're only used in files which end up in the plugins.js chunk. If we use those assertions elsewhere (e.g. in cli.ts), TSDown creates a shared chunk containing them, and then minifier can't see that they can be removed, and leaves all the assertions in the output.

Fix this problem by adding a plugin to TSDown for the release build which replaces imports from asserts.ts with inlined empty functions.

// Original code
import { assertIs, assertIsNonNull } from '../utils/asserts.ts';

// After transform
function assertIs() {}
function assertIsNonNull() {}

This allows us to use the assertion functions anywhere, and minifier can always remove them as dead code.

[overlookmotel]

• build(linter/plugins): simplify TSDown config #15948
• refactor(linter/plugins): replace ! with assertIsNonNull #15947
• refactor(linter/plugins): ensure debug assertions always shaken out of release build #15946 👈 (View in Graphite)
• refactor(linter/plugins): move assertions into own file #15945
• main

---

How to use the Graphite Merge Queue

Add either label to this PR to merge it via the merge queue:

• 0-merge - adds this PR to the back of the merge queue
• hotfix - for urgent hot fixes, skip the queue and merge this PR next

You must have a Graphite account in order to use the merge queue. Sign up using this link.

An organization admin has enabled the Graphite Merge Queue in this repository.

Please do not merge from GitHub as this will restart CI on PRs being processed by the merge queue.

This stack of pull requests is managed by Graphite. Learn more about stacking.

[camc314]

@overlookmotel do you have a repro for why this is needed?

I tried the following, on the 11-21-refactor_linter_plugins_move_assertions_into_own_file branch (without this change)

$ git diff
diff --git a/apps/oxlint/src-js/plugins/lint.ts b/apps/oxlint/src-js/plugins/lint.ts
index 70cd9f15e5..517fa4d3c7 100644
--- a/apps/oxlint/src-js/plugins/lint.ts
+++ b/apps/oxlint/src-js/plugins/lint.ts
@@ -79,6 +79,7 @@ function lintFileImpl(
   ruleIds: number[],
   settingsJSON: string,
 ) {
+  assertIsNonNull("");
   // If new buffer, add it to `buffers` array. Otherwise, get existing buffer from array.
   // Do this before checks below, to make sure buffer doesn't get garbage collected when not expected
   // if there's an error.

This yields:

$ rg "function lintFileImpl" ./dist ./debug -A 3
./debug/plugins.js
14632:function lintFileImpl(filePath$1, bufferId, buffer$1, ruleIds, settingsJSON$1) {
14633-  if (assertIsNonNull(""), buffer$1 === null) buffer$1 = buffers[bufferId];
14634-  else {
14635-          let { buffer: arrayBuffer, byteOffset } = buffer$1;

./dist/plugins.js
14624:function lintFileImpl(filePath$1, bufferId, buffer$1, ruleIds, settingsJSON$1) {
14625-  if (buffer$1 === null) buffer$1 = buffers[bufferId];
14626-  else {
14627-          let { buffer: arrayBuffer, byteOffset } = buffer$1;

Only in the debugBuild is assertIsNonNull called.

If we're worred about this regressing, I think it'd be better to write a plugin that executes after everythings done that checks that assertIsNonNull doesn't exist anymore.

Edit: oh nevermind, i see if you import it in cli.ts, it still gets brought in. I think we should try speaking with the rolldown team to get this working. I think i've heard of solutions to this or other people running into the same issue

[camc314]

Merge activity

• Nov 21, 2:54 PM UTC: The merge label '0-merge' was detected. This PR will be added to the Graphite merge queue once it meets the requirements.
• Nov 21, 2:56 PM UTC: camc314 added this pull request to the Graphite merge queue.
• Nov 21, 3:05 PM UTC: Merged by the Graphite merge queue.

[Copilot]

Copilot encountered an error and was unable to review this pull request. You can try again by re-requesting a review.

[overlookmotel]

Only in the debugBuild is assertIsNonNull called.

Yes, that's the idea. But in release build it's removed entirely.

I think we should try speaking with the rolldown team to get this working. I think i've heard of solutions to this or other people running into the same issue

I tried a few things to prevent TSDown producing a shared chunks (manual chunking options etc). But nothing worked.

Looks like it's already tracked here: rolldown/rolldown#4437