feat: added option to persist auto-generated Dockerfile

[AliLordLoss]

Fix for #12938

Adds persist_dockerfile and dockerfile_output_path parameters to the build_docker_image
step. This allows users to keep the auto-generated Dockerfile for inspection or reuse.

By default, the Dockerfile is still deleted after the build unless persist_dockerfile is set to True.

Closes #12938

Checklist

• This pull request references any related issue by including "closes <link to issue>"
  • If no issue exists and your change is not a small fix, please create an issue first.
• If this pull request adds new functionality, it includes unit tests that cover the changes
• If this pull request removes docs files, it includes redirect settings in mint.json.
• If this pull request adds functions or classes, it includes helpful docstrings.

[desertaxle]

Thanks for the PR, @AliLordLoss — this is shaping up nicely!

I have two small requests to help make this even better:

1. In build_docker_image, could you add a log message when the generated Dockerfile is saved? It would be helpful to let users know they should update the dockerfile field in their configuration, since otherwise a new file will be generated on each run.
2. Could you add a couple of tests to cover the new functionality?

Let me know if you have any questions or need help with either!

[AliLordLoss]

Thanks for the PR, @AliLordLoss — this is shaping up nicely!

I have two small requests to help make this even better:

1. In build_docker_image, could you add a log message when the generated Dockerfile is saved? It would be helpful to let users know they should update the dockerfile field in their configuration, since otherwise a new file will be generated on each run.
2. Could you add a couple of tests to cover the new functionality?

Let me know if you have any questions or need help with either!

Hi there @desertaxle, I'll certainly try to address your requests.
Thanks for the guidance, I'll make sure to let you know if I had any sort of problem.

[AliLordLoss]

@desertaxle I added some tests but they're failing, it seems like it's using the old version of the build_docker_image rather than the one with my modifications.
Should I modify a different test file? E.g. src/integrations/prefect-docker/tests/deployments/test_steps.py??? I tried doing it but couldn't even run the file, it complained about not being able to import prefect_docker.

[desertaxle]

Yep, you should add tests to src/integrations/prefect-docker/tests/deployments/test_steps.py. You can install an editable version of prefect-docker by going into src/integrations/prefect-docker and running uv sync. After that, you can run the prefect-docker tests by running uv run pytest tests.

[desertaxle]

This is closer to the log message I had in mind:

Suggested change

	"Persisting auto-generated Dockerfile to disk. You can use `dockerfile_output_path` to specify the output path."
	f"Persisting auto-generated Dockerfile to {dockerfile_output_path or 'Dockerfile.generated'}. Please update your 'dockerfile' value to use this Dockerfile for subsequent runs."

[desertaxle]

Hey @AliLordLoss, I think you might have accidentally reverted your code changes instead of the changes to tests/cli/test_deploy.py 😅

[AliLordLoss]

Hey @AliLordLoss, I think you might have accidentally reverted your code changes instead of the changes to tests/cli/test_deploy.py 😅

Yeah, sorry 😅
Fixed it

[desertaxle]

Thanks for sticking with the @AliLordLoss! I have one more small nit, but once that's addressed, this will be good to merge!

[AliLordLoss]

Thanks for sticking with the @AliLordLoss! I have one more small nit, but once that's addressed, this will be good to merge!

You're welcome! That's done as well.

[desertaxle]

LGTM! Thanks @AliLordLoss!