Fix tsserver protocol parser for TypeScript 5.9.3

[Copilot]

TypeScript 5.9.3 sends multiple tsserver protocol messages in a single stdout chunk. The test harness parser assumed one message per chunk, causing JSON parse failures.

Changes

Rewrote the protocol parser in test/util/lang-server.ts:

• Buffer management: Accumulate data across chunks, process all complete messages
• Content-Length parsing: Use regex to properly delimit messages: /Content-Length: (\d+)\r?\n\r?\n/
• Extracted method: Message processing logic moved to #processMessages() for clarity

Before:

const obj = JSON.parse(data.split('\n', 3)[2]);
// Fails when multiple messages arrive in one chunk

After:

#processMessages() {
  let headerMatch = this.buffer.match(/Content-Length: (\d+)\r?\n\r?\n/);
  while (headerMatch && headerMatch.index !== undefined) {
    // Extract and process each complete message
    // Remove from buffer, continue with next
  }
}

All 10 tests passing.

Warning

Firewall rules blocked me from connecting to one or more addresses (expand for details)

I tried to connect to the following addresses, but was blocked by firewall rules:

• devblogs.microsoft.com
  • Triggering command: /home/REDACTED/work/_temp/ghcca-node/node/bin/node /home/REDACTED/work/_temp/ghcca-node/node/bin/node --enable-source-maps /home/REDACTED/work/_temp/copilot-developer-action-main/dist/index.js (dns block)

If you need me to access, download, or install something from one of these locations, you can either:

• Configure Actions setup steps to set up my environment, which run before the firewall is enabled
• Add the appropriate URLs or hosts to the custom allowlist in this repository's Copilot coding agent settings (admins only)

Original prompt

The branch arthurfiorette/serena has failing unit tests at @packages/ts-html-plugin. Run pnpm build first to build the whole monorepo and then run pnpm test inside the packages/ts-html-plugin first to detect what is going on. This happened once i upgraded the typescript version to a new one. You can enable the debug mode and read the written tsserver log (read packages/ts-html-plugin/test/util/lang-server.ts to understand more). Once you managed to fix what was broken in the ts plugin, open a PR fixing it (you will know that its fixed once all tests start passing again)

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[changeset-bot]

⚠️ No Changeset found

Latest commit: eff90c9

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 100.00%. Comparing base (0830fee) to head (eff90c9).
⚠️ Report is 1 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff            @@
##            master      #455   +/-   ##
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  Coverage   100.00%   100.00%           
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  Files            4         4           
  Lines          434       434           
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  Hits           434       434           

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