feat(oxlint/lsp): enable JS plugins

[overlookmotel]

#18727 disabled JS plugins in LSP while we worked out some bugs. As far as I know, we're now reasonably confident it works. We have some flaky tests, but it looks at least likely these are due to vagueries in tests, and not necessarily actual bugs.

In my opinion, at this point, it'd probably be good to enable JS plugins, and get real-world user feedback in advance of JS plugins alpha release.

[overlookmotel]

• feat(oxlint/lsp): enable JS plugins #18834 👈 (View in Graphite)
• fix(linter/plugins): do not destroy workspaces #18833
• fix(linter/plugins): clear state when reloading workspace #18837
• main

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[Copilot]

Pull request overview

Re-enables JavaScript plugin support when running oxlint in LSP mode, reversing the temporary gating introduced in #18727.

Changes:

• Removes the cfg!(feature = "testing") gate that forced external_linter to None in --lsp mode.
• Ensures LSP receives the same external_linter instance as CLI mode (where supported by platform).

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[overlookmotel]

Oh bollocks. I just saw #18802. Looks like we still have problems...

[overlookmotel]

Hopefully #18837 solves that bug, so I've re-opened this.

[Sysix]

I tested on main with the debug build. Maybe it is because of the build, but my responses for a diagnostics are now over one second for the eslint/prefer-const check here on the oxc project. I hoped this would be much faster with the release build (tested without type aware).

All critical bugs are fixed, I could not crash the server anymore. Changing configs in different workspaces will be respected with the new JS config. (Note to myself: only checked severity, but the workspace will be completely rebuilt).

I have somehow a VS Code bug now here: #18729, where I request a diagnostics from the freshly added workspace. Adding the workspace is not the problem, requesting the diagnostics will somehow fail. I skipped the test for now 🤞

I implemented simple LSP tests on the JS NAPI side, all linting tests, expect js-config, are running under 200ms. The JS-Config Test timeouts after 10s :/ Would love to merge the time outed tests before enabling the feature for all users :) #18730

@overlookmotel thank you for all the work on the NAPI side, Your refactoring not only improved the CLI :)

[codspeed-hq]

CodSpeed Performance Report

Merging this PR will not alter performance

_{Comparing om/02-02-feat_oxlint_lsp_enable_js_plugins (9e95b88) with main (9561e7f)}

Summary

✅ 46 untouched benchmarks
⏩ 3 skipped benchmarks¹

Footnotes

1. 3 benchmarks were skipped, so the baseline results were used instead. If they were deleted from the codebase, click here and archive them to remove them from the performance reports. ↩

[overlookmotel]

Running a release build compiled from this PR's branch, I'm seeing about 200ms from pressing save to seeing a red squiggle for a JS plugin rule violation.

It feels fairly snappy!

This is on a Mac Mini M4 Pro, linting Oxc repo. Type-aware linting is enabled. Lint on save (not on type).

From the logs:

2026-02-03 22:17:35.239 [info] [Trace - 22:17:35] Sending notification 'textDocument/didSave'.
2026-02-03 22:17:35.239 [info] Params: {
    "textDocument": {
        "uri": "file:///<redacted>/oxc/apps/oxlint/src-js/package/compat.ts"
    }
}


2026-02-03 22:17:35.240 [info] [Trace - 22:17:35] Sending request 'textDocument/diagnostic - (21)'.
2026-02-03 22:17:35.240 [info] Params: {
    "textDocument": {
        "uri": "file:///<redacted>/oxc/apps/oxlint/src-js/package/compat.ts"
    }
}


2026-02-03 22:17:35.427 [info] [Trace - 22:17:35] Received response 'textDocument/diagnostic - (21)' in 187ms.
2026-02-03 22:17:35.427 [info] Result: {
    "kind": "full",
    "items": [
        {
            "range": {
                "start": {
                    "line": 236,
                    "character": 8
                },
                "end": {
                    "line": 236,
                    "character": 25
                }
            },
            "severity": 1,
            "code": "eslint-js(prefer-const)",
            "source": "oxc",
            "message": "'CHAR_CODE_BRACKET' is never reassigned. Use 'const' instead.",
            "relatedInformation": [
                {
                    "location": {
                        "uri": "file:///<redacted>/oxc/apps/oxlint/src-js/package/compat.ts",
                        "range": {
                            "start": {
                                "line": 236,
                                "character": 8
                            },
                            "end": {
                                "line": 236,
                                "character": 25
                            }
                        }
                    },
                    "message": ""
                }
            ]
        }
    ]
}

Compared to Oxlint 1.43.0 (with JS plugins disabled) approx 190ms:

2026-02-03 22:22:50.900 [info] [Trace - 22:22:50] Sending notification 'textDocument/didSave'.
2026-02-03 22:22:50.900 [info] Params: {
    "textDocument": {
        "uri": "file:///<redacted>/oxc/apps/oxlint/src-js/package/compat.ts"
    }
}


2026-02-03 22:22:50.901 [info] [Trace - 22:22:50] Sending request 'textDocument/diagnostic - (18)'.
2026-02-03 22:22:50.901 [info] Params: {
    "textDocument": {
        "uri": "file:///<redacted>/oxc/apps/oxlint/src-js/package/compat.ts"
    }
}


2026-02-03 22:22:51.091 [info] [Trace - 22:22:51] Received response 'textDocument/diagnostic - (18)' in 190ms.
2026-02-03 22:22:51.091 [info] Result: {
    "kind": "full",
    "items": [
        {
            "range": {
                "start": {
                    "line": 240,
                    "character": 4
                },
                "end": {
                    "line": 240,
                    "character": 13
                }
            },
            "severity": 1,
            "code": "eslint(no-debugger)",
            "codeDescription": {
                "href": "https://oxc.rs/docs/guide/usage/linter/rules/eslint/no-debugger.html"
            },
            "source": "oxc",
            "message": "`debugger` statement is not allowed\nhelp: Remove the debugger statement",
            "relatedInformation": [
                {
                    "location": {
                        "uri": "file:///<redacted>/oxc/apps/oxlint/src-js/package/compat.ts",
                        "range": {
                            "start": {
                                "line": 240,
                                "character": 4
                            },
                            "end": {
                                "line": 240,
                                "character": 13
                            }
                        }
                    },
                    "message": ""
                }
            ]
        }
    ]
}

But am I measuring the right thing?

[overlookmotel]

Like you, I found it much slower with a debug build - about 1 second.

[Sysix]

Your release responses look good 👍 I think after a while it will be faster in the debug build, but this is strange for me :/
I think this is the reason why the NAPI tests-PRs are timed out in the low-performance CI.

[Sysix]

Stack of #18729 is passing now, on my side there are no blockers anymore 🚀

[camc314]

Merge activity

• Feb 6, 12:21 PM UTC: The merge label '0-merge' was detected. This PR will be added to the Graphite merge queue once it meets the requirements.
• Feb 6, 12:21 PM UTC: camc314 added this pull request to the Graphite merge queue.
• Feb 6, 12:28 PM UTC: Merged by the Graphite merge queue.

[yzhe554]

Tested with latest oxlint 1.46.0 and extension 1.45.0, this seems still not available. Any idea? @camc314 @overlookmotel

[camc314]

@yzhe554 can you make an issue with some more details? or reach out on discord? We don't have enough information to action this at the moment

[yzhe554]

@camc314 #19244 it seems the issue is the extension cannot load ts files