DVC_STAGE: Added environment variable to track DVC stage name

[rishabhsharma22]

Fixes #10355

• ❗ I have followed the Contributing to DVC checklist.

• 📖 If this PR requires documentation updates, I have created a separate PR (or issue, at least) in dvc.org and linked it here.

Thank you for the contribution - we'll try to review it as soon as possible. 🙏

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 90.68%. Comparing base (017a510) to head (ca4506d).
Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #10357      +/-   ##
==========================================
+ Coverage   90.67%   90.68%   +0.01%     
==========================================
  Files         500      500              
  Lines       38696    38698       +2     
  Branches     5600     5600              
==========================================
+ Hits        35088    35095       +7     
+ Misses       2961     2958       -3     
+ Partials      647      645       -2     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

[shcheklein]

Test fail due to iterative/dvc-s3#80 . I'm fine with this change. We will need to update this https://dvc.org/doc/user-guide/env#environment-variables doc at least after we merge this.

[dberenbaum]

@rishabhsharma22 Could you please create an accompanying docs PR as suggested in the PR template and pointed out by @shcheklein?

[rishabhsharma22]

@dberenbaum I have added the accompanying PR in docs.

[dberenbaum]

@rishabhsharma22 Can you point me to it? I don't see it in https://github.com/iterative/dvc.org/pulls.

[rishabhsharma22]

@dberenbaum seems like something went wrong and the PR didn't go through. I created a new PR. Should be able to see this time. If not here is the link for you. iterative/dvc.org#5191

[skshetry]

Hey, can you provide more example on #10355, please?
Stackoverflow only mentions that you need access to stage name, but it's not clear to me what dvc.api are you using and why you need stage name at all.

If it's to read hyperparameters, I am curious why you do not read the param file directly instead of going this convoluted way? Not to add, your script will be unusable outside dvc, compared to the parametrization example that @shcheklein offered.

[rishabhsharma22]

I attempted to find the stage name while running a command with DVC. However, I couldn't utilize any DVC API for this purpose at that point. Consequently, I didn't use any DVC API at all. I think it would be beneficial to add a feature to access the DVC stage name through its API. Alternatively, incorporating it as a system variable could serve the same purpose.

Now, to address why one might need the stage name: when a lock file generates a stage name for execution, it stores it. The challenge arises when ensuring that this stage name remains synchronized with the lock file if someone passes the stage name as a parameter. Thus, introducing a variable to capture the name of the current running stage would ensure consistency between the stage name generated in the lock file and the stage name needed for reference during execution or reproducibility.

The use cases may vary. In my case, I needed to track specific parameters, and the only identifier available was the stage name, which wasn't accessible through DVC at the time. Therefore, having the DVC stage name as an accessible identifier for the ongoing run would greatly aid in tracking features, parameters, and other relevant aspects. While it's possible to create parameters during execution to track the stage name, incorporating it as a feature ensures consistency and simplifies the process for end users.

I hope this helps answer some of your questions.

[skshetry]

Thanks for the response. It makes sense for dvc to provide something like that, but I still don't understand your usecase. I don't understand what you mean by "synchronizing with the lock file"?

Can you show me an example how you plan to use it?