Closes #3020

Summary

If MarkText is started with --user-data-dir while an instance using that directory is already running, the file is not opened. For example, the report starts portable MarkText twice:

MarkText.exe .\TestDoc1.md --user-data-dir .\Data
MarkText.exe .\TestDoc2.md --user-data-dir .\Data

Instead of opening TestDoc2.md in a new tab, the running instance shows ArgError: option requires argument: --user-data-dir.

Cause. The running instance parses the argv of the second-instance event. Electron documents that this argv "will not be exactly the same list of arguments as those passed to the second instance. The order might change and additional arguments might be appended" (see electron/electron#32933, closed as not planned). On develop (Electron 42, macOS), the running instance receives:

[<exe>, '--user-data-dir', '--allow-file-access-from-files', '--enable-avfoundation', <app path>, 'TestDoc2.md', 'Data']

Switches come first, so --user-data-dir is separated from Data. It is also followed by another switch, so arg throws. Only the --user-data-dir=Data form survives this.

Fix. Electron's recommendation is additionalData.

• A starting instance passes its own process.argv to app.requestSingleInstanceLock({ argv }).
• The second-instance handler parses that unchanged copy. If a second instance from a version without this change sends no data, the handler falls back to argv as before.

Type of change

• Bug fix (non-breaking, fixes an issue)
• New feature (non-breaking, adds functionality)
• Breaking change (causes existing functionality to change)
• Documentation update

Test plan

• New tests added
  • issue-3020-second-instance-args.spec.ts (e2e, built app) opens a document, then starts a second instance with second.md --user-data-dir <same dir>. It checks that the second instance exits with 0 (the failure message includes its output), that the running instance receives one second-instance event and its listeners throw nothing, and that second.md opens as a tab without a new window.
  • On develop it fails with ArgError: option requires argument: --user-data-dir. With this change it passes (3/3 repeated runs).
• A standalone probe on the built app tried five argument forms for the second instance: file --user-data-dir dir, --user-data-dir dir file, --user-data-dir=dir file, --user-data-dir dir --new-window file, and file --user-data-dir dir --allow-file-access-from-files. On develop, every form except --user-data-dir=dir threw ArgError and opened nothing. With this change all five open the file, and --new-window opens it in a new window.
• pnpm run typecheck passes, eslint reports 0 errors on the changed files, all desktop unit tests pass (818/818), and launch.spec.ts + tabs.spec.ts pass.
• Tested on: macOS (built app via Playwright). The e2e job covers Linux. Windows was not run.

Notes for reviewers

• Listener wrapper in the spec. An exception thrown by a main-process listener hangs an Electron app driven by Playwright. The spec therefore wraps the app's own second-instance listeners in a try/catch that records what they throw. Without the wrapper, the running instance hangs and never acknowledges the second instance. The second instance then carries on as an instance of its own, so the spec would time out instead of reporting the ArgError.
• --no-sandbox on Linux. Playwright launches Electron with --no-sandbox on Linux, because the CI runner can't use Chromium's SUID sandbox. The spec passes the same switch to the second instance; without it, the second instance aborts at startup there, before it reaches the running instance.
• Conflict with fix(desktop): launch normally when NODE_ENV=development is set (#5053) #5374. This PR and fix(desktop): launch normally when NODE_ENV=development is set (#5053) #5374 (error.unexpectedErrorWithMessage #5053) change adjacent lines in packages/desktop/src/main/index.ts: that PR changes the if around the lock, this one changes the lock call. Whichever merges second needs a trivial rebase.

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