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lsp.client: multi-mime LanguageServerProvider class registrations start one server process per MIME (reuse map is instance-keyed)

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評価

難易度
4/5
見積もり時間
3〜5日
初心者へのやさしさ
48/100
issue の種類
バグ
明瞭さ
おおむね明確
活発さ
活発
技術スタック
java
領域
developer-experience, tooling

調査の方向性

まず、LSPBindings.buildBindings と、LanguageServerProvider インスタンスの解決に関係する MimeLookup/layer 登録を読んでください。text/javascript と text/typescript に登録された 1 つの provider で問題を再現し、その後 pgrep でプロセスを確認してください。同じプロジェクトが 1 つの language-server プロセスを使用し、複数 MIME の登録と再利用を回帰テストでカバーできれば完了です。

索引モデルが issue の本文から書いたものです。

説明

LSP
Apache NetBeans version

Apache NetBeans 25 (observed on RELEASE300, still present on RELEASE310)

Bug description

Summary: When one LanguageServerProvider is registered for multiple MIME types with a class-level @MimeLookup.Registration / layer class registration, LSPBindings starts one language-server process per MIME type instead of reusing the running server, because its server-reuse map is keyed by provider instance — and a class registration places a separate .instance in each mime folder, each instantiated independently.

Measured effect (in a NetBeans-Platform-based IDE using ide/lsp.client, with providers registered for both text/javascript and text/typescript):

  • two typescript-language-server processes for a single mixed JS/TS project,
  • two deno lsp processes for one deno workspace,
  • two ngserver processes in an Angular project with a component (.ts) and its template open.

Each extra process is a full tsserver-class JVM/node footprint per project, silently.

Mechanism (from reading the RELEASE300/310 LSPBindings source/bytecode): buildBindings files a started server under every declared mime only when the same provider instance is presented for each mime folder. With a class-level registration, the second mime folder resolves a different instance of the same provider class, misses the reuse map, and a second server process is spawned. Shutdown being GC-driven (LSPReference + keep-alive) means both processes then live for the session.

Workaround we ship: converting every multi-mime provider registration to a static singleton factory method (methodvalue registration), so every mime folder resolves the same object. That fixes it completely — A/B measured 2 processes → 1 — but the requirement is undocumented and very easy to violate (we re-introduced it once via a three-mime CSS provider before gating registrations structurally).

Steps to reproduce
  1. Register one LanguageServerProvider class for two mimes (e.g. text/javascript and text/typescript) with a plain class-level registration.
  2. Open one file of each mime from the same project.
  3. Observe two identical language-server processes for the project (e.g. pgrep -fl typescript-language-server).
Expected behavior

One server process per project for a provider declared on multiple mimes — or, failing that, a documented requirement that multi-mime providers must be registered as singletons.

Suggested fix directions: key the reuse map by provider class (or by the provider's declared mime set), or have MimeLookup resolution for LanguageServerProvider treated as singleton-per-class in LSPBindings. Happy to provide more detail or test against a patch — we carry a structural test (registrations == getMimeTypes(), no class-instance backdoor) that could inform one upstream.

Context

Found while building NMOX Studio (Apache-2.0, NetBeans-Platform based): https://github.com/NMOX/NMOX-Studio — details in our engineering ledger entry 83 (docs/engineering/tech-debt.md).

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