.funcignore pattern src/ also empties node_modules/*/src

Symptom

• The deploy step succeeds and the app's root URL still answers 200.
• A function route (in our case the health check) returns 404, and ARM returns an empty function list for the slot.
• The deployed wwwroot still lists src, test or infra — so it looks as if .funcignore wasn't applied at all.
• The host log has the real reason:

[Error] Error: Worker was unable to load entry point "dist/functions/routes.js": Cannot find module 'C:\home\site\wwwroot\node_modules\debug\src\index.js'. Please verify that the package.json has a valid "main" entry
[Warning] No job functions found. …

Cause

When package points to a folder and respect-funcignore is on, the action globs every entry in that folder, makes each path relative to the package root and deletes it when the ignore library says it's ignored — the same rules as .gitignore:

• src/ has no slash at the start or in the middle, so it matches a src directory at any level — including node_modules/debug/src, so node_modules/debug/src/index.js goes too.
• The glob returns directory entries without a trailing slash, and a pattern ending in / only matches directories, so ignore doesn't match the folder entry itself. The folders stay behind, emptied of the matched files — which is why the deployed root still lists src, test and infra.

Measured with ignore 5.1.9 and 7.0.5 (the version functions-action v1 ships), same result:

Fix

Anchor every pattern to the package root:

/.git*
/.vscode/
/local.settings.json
/src/
/test/
/infra/
/tsconfig.json
/README.md

Keep the rule from coming back with a tiny test in the repository: read .funcignore and fail on any rule that doesn't start with /. An unanchored file pattern such as README.md or tsconfig.json removes the same files from every package in node_modules too — usually harmless, but it's the same trap.

Notes

• When a deployment "succeeds" but no functions appear, read the host log first. With the default fileLoggingMode: debugOnly the host writes log files only while you're debugging in the Azure portal. Turn on always only temporarily — the documentation warns it hurts cold start and throughput — either in host.json ("logging": { "fileLoggingMode": "always" }) or, without a redeploy, through the app setting AzureFunctionsJobHost__logging__fileLoggingMode = always. Or read the traces in Application Insights.
• az functionapp function list has no --slot option; for a deployment slot call ARM directly: GET …/providers/Microsoft.Web/sites/<app>/slots/<slot>/functions?api-version=2023-12-01.
• Sources: functions-action .funcignore handling · gitignore pattern format · host.json fileLoggingMode.