Deleted file referenced in existing BUILD file causes ./pants tailor to fail

[bmcandr]

We are in the process of introducing pants to our Python monorepo, but I ran into an issue where ./pants tailor throws the following error when a file referenced in a BUILD file has been deleted or moved to a new location:

[ERROR] 1 Exception encountered:

  Exception: Unmatched glob from path/to:file's `entry_point` field: "path/to/file.py"

Do the file(s) exist? If so, check if the file(s) are in your `.gitignore` or the global `pants_ignore` option, which may result in Pants not being able to see the file(s) even though they exist on disk. Refer to https://www.pantsbuild.org/v2.10/docs/troubleshooting#pants-cannot-find-a-file-in-your-project.

Assume the following initial structure:

|-- path
|   |-- to
|   |   |-- BUILD
|   |   |-- file.py
|   |   |-- other_file.py

Then, we delete or move file.py to some other location.

At this point BUILD still contains a reference to the deleted/moved file:

pex_binary(
    name="file",
    entry_point="file.py",
)

pex_binary(
    name="other_file",
    entry_point="other_file.py",
)

python_sources()

Running ./pants tailor throws the error shown above and I can resolve this by deleting the BUILD file and regenerating it.

Is there a way to force ./pants tailor to overwrite existing BUILD files?

[sureshjoshi]

@bmcandr - I hope you were able to solve this, but if not, Slack is the best approach for troubleshooting questions.

Discussions are currently used moreso for larger feature/design-specific questions where we want to keep a history.

All the one-off questions are nailed pretty quick in Slack
https://www.pantsbuild.org/docs/getting-help

[bmcandr]

@sureshjoshi, thanks. I did end up getting help from the Slack channel.

[Eric-Arellano]

Hi there, @bmcandr - pardon the delay response! Thanks @sureshjoshi for the reply.

This is expected behavior, but I can see why it's confusing. What would you expect Pants to do in this situation?

[bmcandr]

Sorry for the even longer delayed response! Glad to know this is expected behavior. I'm still new to pants and thought ./pants tailor might be able to handle moved/deleted files. Sounds like we just need to manually modify BUILD files when things get moved around or deleted.

[Eric-Arellano]

No worries! Indeed: tailor only every creates new BUILD files and adds to existing ones. It never deletes things. It's very conservative - we don't want to accidentally delete things that you manually set, since BUILD files are human editable.