fix(theme): ignore atomic-write tmp files in the theme dev watcher

[andershagbard]

Summary

This is an error which happens because Claude Code generates these tmp files. Not sure if other tools use the same method or naming.

• Editor tools (including AI coding assistants) create temporary files like blocks/foo.liquid.tmp.93809.4dbd82e0b95a during atomic save operations and delete them within milliseconds.
• Because the per-event debounce fires independently for add and unlink events, the file watcher sees the add, tries to upload the invalid asset key to Shopify, and crashes shopify theme dev — requiring a manual restart.
• Adds **/*.tmp.* to DEFAULT_IGNORE_PATTERNS so chokidar never emits events for these files.

Root cause

queueFsEvent debounces per ${fileKey}:${eventName}, meaning add and unlink are queued separately. By the time the 250ms debounce fires for add, the file is already gone — but Shopify still gets the upload attempt with an invalid key.

Test plan

• New unit test asserting **/*.tmp.* is present in chokidar's ignored option
• All 44 existing theme-fs tests pass
• Type-check passes
• Lint passes

🤖 Generated with Claude Code

[graygilmore]

Thanks for this @andershagbard. We're just having a discussion internally here because there are going to be themes that already contain files with .tmp. in the name that this would break.

The purpose behind the PR makes sense but we need to think of how to make sure our fix doesn't break existing themes.

[andershagbard]

I added this because the devserver will crash because the API doesn't accept that file name. I assume it's blocked serverside, and therefore these files would not exist?

[andershagbard]

Correct me if I am wrong, but I think this can be enforced in all folders except assets.

I am getting these errors in the theme editor:

FileSaveError: Must have a .liquid file extension

FileSaveError: "sections/test.json.tmp.1231231" contains illegal characters

[graygilmore]

You’re right that files like sections/test.json.tmp.1231231 are not valid theme files and won’t be accepted server-side.

The piece I’m worried about is the breadth of **/*.tmp.*. DEFAULT_IGNORE_PATTERNS is used for the initial file glob too, so this can hide real files (e.g. snippets/test.tmp.liquid).

Maybe we can narrow this to non-asset theme folders and only ignore files where the temp suffix is appended after a valid extension?

[
  '**/blocks/**/*.liquid.tmp.*',
  '**/layout/**/*.liquid.tmp.*',
  '**/snippets/**/*.liquid.tmp.*',
  '**/config/**/*.json.tmp.*',
  '**/locales/**/*.json.tmp.*',
  '**/sections/**/*.{liquid,json}.tmp.*',
  '**/templates/**/*.{liquid,json}.tmp.*',
]

That should catch sections/test.json.tmp.1231231 and blocks/foo.liquid.tmp.93809.4dbd82e0b95a, but not ignore valid files like snippets/test.tmp.liquid or any legitimate assets/* files.

As a personal workaround for now you could also add the following to your .shopifyignore:

/\.tmp\.[0-9]+(\.[0-9a-fA-F]+)?$/

Meant to just comment