refactor(test): improve type safety for spawned process URLs

[watson]

What does this PR do?

Refactors the spawnProc test helper to improve TypeScript type safety by splitting it into two distinct functions with clear lifecycle expectations and return types.

Motivation

When using spawnProc, TypeScript would complain that proc.url might be undefined, even in cases where we know the process is long-running and will definitely send a port message. This was because the function could return either SpawnedProcess (with url) or void depending on whether the process exited or stayed alive.

This refactoring:

• Makes spawnProc always return SpawnedProcess with a guaranteed url property (rejects if process exits)
• Adds spawnProcAndExpectExit for processes that should run and exit cleanly (returns void on success)
• Implements url as a lazy getter that throws if accessed before the port message is received (prevents timing bugs)
• Provides clear JSDoc documentation explaining when to use each function

This ensures TypeScript correctly understands that proc.url is always defined when using spawnProc, eliminating false-positive type errors.

Additional Notes

This is purely a refactoring of test infrastructure with no impact on production code.

Changes to test helpers:

• Added spawnPluginIntegrationTestProcAndExpectExit wrapper for short-lived plugin integration tests

Updated tests:
Updated various plugin integration tests and other test files to use the appropriate spawn function based on whether they spawn long-running servers (use spawnProc/spawnPluginIntegrationTestProc) or short-lived scripts that run and exit (use spawnProcAndExpectExit/spawnPluginIntegrationTestProcAndExpectExit).

[watson]

• chore(tests): add type annotations to integration test helpers #7240
• refactor(test): improve type safety for spawned process URLs #7219 👈 (View in Graphite)
• master

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 84.56%. Comparing base (3e204e4) to head (47e45ba).

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #7219   +/-   ##
=======================================
  Coverage   84.56%   84.56%           
=======================================
  Files         532      532           
  Lines       22656    22656           
=======================================
  Hits        19159    19159           
  Misses       3497     3497           

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[github-actions]

Overall package size

Self size: 4.39 MB
Deduped: 5.21 MB
No deduping: 5.21 MB

Dependency sizes

| name | version | self size | total size | |------|---------|-----------|------------| | import-in-the-middle | 2.0.0 | 68.46 kB | 797.03 kB | | dc-polyfill | 0.1.10 | 26.73 kB | 26.73 kB |

_{🤖 This report was automatically generated by heaviest-objects-in-the-universe}

[pr-commenter]

Benchmarks

Benchmark execution time: 2026-01-14 13:44:54

Comparing candidate commit 47e45ba in PR branch watson/DEBUG-4402/spawn-proc-refactor with baseline commit 3e204e4 in branch master.

Found 0 performance improvements and 0 performance regressions! Performance is the same for 289 metrics, 31 unstable metrics.

[BridgeAR]

LGTM, as it already improves things further. I believe overload should just be added to all cases to remove even more type error reports.