params: show only params files that are actually used

[pared]

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• 📖 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. 🙏

Closes #5539

[skshetry]

Looks good to me. But this default behaviour has been there since we introduced params, same as #5451 (introduced in #3631), so cc'ing @efiop if this was intended.

[efiop]

It was intended originally, but now it is a mixup. Need to take a closer look and also look at the docs, as those might be affected. IIRC the logic was that people might use it without our pipelines (similar to same assumptions/discussions around metrics/plots). I don't feel comfortable just disabling this behavior, because it might turn out that it is needed in some scenario. We might need to double check params workflow first.

[skshetry]

@efiop, isn't expecting a params.yaml file at the root of a git repository quite an assumption? 🙂

There's --targets for this usecase already.

[efiop]

@skshetry Hard to tell. Params/metrics and plots are all filled with assumptions that were provided by users while developing it, and I also get constantly confused by it. The change seems logical, but we just need to make sure it fits into the workflow and we def need to check the docs.

[pared]

@efiop

So the whole issue started in #5451, where user has quite extensive pipeline, and running exp show yielded unwanted results. This change was a prerequisite to make sure only used parameters are shown.

Params/metrics and plots are all filled with assumptions that were provided by users while developing it, and I also get constantly confused by it.

I guess we all are.
I think I jumped the horse here. The way to fix #5451 and not break just released 2.0.0 is to provide new flag that will allow user to show only used params, and keep this issue in mind when releasing 3.0. That way we keep the default behaviour.

[pared]

Closing, we do not intend to change default behaviour for now.
Context:
#5451 (comment)