Plots in CML/CI/automated workflows

[dberenbaum]

What is the best way to make plots outputs available in CML/CI/automated workflows?

There is already --show-vega, which CML uses in its example: https://cml.dev/doc/cml-with-dvc. However, this requires a specific target and doesn't work for image files.

--json has been added to support other products with both vega and paths to image files. However, this is harder to use in cases like the CML example above where the need is to produce a plot in markdown from a vega plot.

See #7093 (comment) for more background.

[pared]

I believe we require 2 flags:

• one (currently json) has to evolve into JSON returning data structure similar to what dvc.plots.collect returns, in order to support vscode requirements, mainly data separated from the template and error handling (plots: return error messages for failed plots #7692)
• second, that would return already filled templates, for use cases where user needs only filled templates, currently, to some extent --show-vega satisfies this requirement but we need it to return all plots for a particular command, probably map plot_id/path -> filled template.

[dberenbaum]

What should each return for image files?

[pared]

--json will return path to image saved in workspace. --show-vega will not do anything.
We can leave it as is, or we can allow also for returning of base64 encoded images.