metrics: Use "metrics.json" as DEFAULT_METRICS_FILE.

[daavoo]

Closes #6168

[daavoo]

I was thinking about how DEFAULT_PARAMS_FILE affects the dvc.yaml definition but I don't think it makes much sense to change metrics to also support a "granular" definition.

Feels overkill to implement:

metrics:
  - metrics.json:
      foo

And use the default file to make it equivalent to:

metrics:
  - foo

[pmrowla]

I know we just use .json for metrics everywhere already in our examples and tests, but I was wondering if it makes sense that we use different default formats for params and metrics. If we are actually going to define a default metrics file now, should we be using yaml for consistency across DVC instead of json?

[dberenbaum]

I was thinking about how DEFAULT_PARAMS_FILE affects the dvc.yaml definition but I don't think it makes much sense to change metrics to also support a "granular" definition.

Agreed that metrics don't need granular support.

should we be using yaml for consistency across DVC instead of json?

There's some related discussion in iterative/dvclive#292. I'd vote to keep as is since we already have it implemented that way in dvclive.

---

@daavoo Is this still desirable given the coming changes in #8371 and iterative/dvclive#311? My concern would be that we are adding defaults that do not match the dvclive outputs.

[daavoo]

@daavoo Is this still desirable given the coming changes in #8371 and iterative/dvclive#311? My concern would be that we are adding defaults that do not match the dvclive outputs.

I was checking how hard was to do this and then combine it with #7939 in comparison to #8371

[dberenbaum]

@daavoo Is this still desirable given the coming changes in #8371 and iterative/dvclive#311? My concern would be that we are adding defaults that do not match the dvclive outputs.

I was checking how hard was to do this and then combine it with #7939 in comparison to #8371

It's more limited (for example, you can't have mutliple dvclive dirs), but I'm open to it as a first step if it's quicker. cc @skshetry

[daavoo]

Closing in favor of top-level metrics