Plots: render dots with annotations without Vega spec

[aguschin]

If Vega spec is present, Studio render plots with nice annotations with exact value at Y-axis when you hover your mouse over the plot. But if we don't have that spec, Studio won't show them. It would be nice to do that!

Example with annotations rendered

https://studio.iterative.ai/user/aguschin/views/fashion_mnist_project-i4tmmlg2aq

Example where we do not have annotations

https://studio.iterative.ai/user/aguschin/views/example-get-started-w3o8p2cq0o

Thanks to @mvshmakov for investigation on the issue origin.

[dberenbaum]

Thanks, @aguschin! @shcheklein is there a priority for this for Studio?

[shcheklein]

@dberenbaum in Studio plots improvements are considered p1 at the moment. I think it would be great to invest time into improving plots in DVC (as we do with images, live plots already) along the way. Products might affect each other. I would not ruin or disrupt any existing large priorities though for this. In Studio we'll be iterating on basic large features for the next month at least.

[dberenbaum]

Thanks, good to know. Agreed that improving in DVC makes sense. This looks like a very minor change, so it shouldn't disrupt much.

[dberenbaum]

Related comment from @pared about the default template in https://github.com/iterative/dvc/pull/4975/files#r531031121:

I would consider dropping this one at some point, for sake of interactive linear to become the default, though one thing that is stopping me from proposing it right away is the simplicity of the default plot, which definitely makes the learning curve for custom plots smoother.

I would suggest that we make "linear" the default and rename the current default template to something like "simple" or "basic" and document that it's a simplified linear plot included as an easy starting point for creating custom templates.

The docs only mention the templates in https://dvc.org/doc/command-reference/plots#plot-templates, and the default is listed as "linear plot," with no explanation of the difference between "default.json" and "linear.json," so I think this would clarify and shouldn't create issues for existing users.

[pared]

This issue makes me doubt that the current state of plots (writing json templates into files under .dvc/plots in particular) is the proper way to go. If we change default now, only the repos created after the next release will have interactive default. We should probably load default templates from within the DVC itself.