Language Server with Definitions Only

[wolmir]

Language server for data pipelines

This PR will introduce the language server module to the extension.

Background

Data Pipelines and dvc.yaml

Data Pipelines
dvc.yaml
Pipelines
Stage command
Original issue

VSCode language support

Language extensions
Available language support list from VSCode with examples

Language Servers

Introduction
Protocol Specification
The Framework to build one
Some extension samples (Look for the ones prefixed by lsp-*)

Demo

The main purpose of this PR is to add the language server scaffolding to the extension project.
However, we also provided a small Go to Definition feature in order to add some value for the user and as an example of how to work in the server module.

The feature works inside strings of dvc.yaml files, and will provide a set of location where the symbols referenced in those strings are found inside a project.

Screen.Recording.2022-09-19.at.14.32.59.mov

[wolmir]

@mattseddon @julieg18 @sroy3

Can you guys skim this and compare with the original PR, please?

The definitions handler is the simplest one, and by removing the others it allowed me to skip that
DvcYaml model entirely.

Plus some other stuff could be removed, like the pythonFiles thing.
In total there were about -800 lines from the original, but I would really like your opinion here.
If they were both ready to go, would you rather merge this one or the original one?

[sroy3]

This looks good to me. All my comments are in the other PR and are mostly for my curiosity, nothing major.

[mattseddon]

@mattseddon @julieg18 @sroy3

Can you guys skim this and compare with the original PR, please?

The definitions handler is the simplest one, and by removing the others it allowed me to skip that DvcYaml model entirely.

Plus some other stuff could be removed, like the pythonFiles thing. In total there were about -800 lines from the original, but I would really like your opinion here. If they were both ready to go, would you rather merge this one or the original one?

@wolmir can you please put a demo and description and open the PR that you would like to be reviewed.

[julieg18]

Looks good to me!

[mattseddon]

The language server is adding definitions in Python files (e.g on re.sub):

With language server

Screen.Recording.2022-09-20.at.9.25.05.am.mov

Expected behaviour

Screen.Recording.2022-09-20.at.9.25.51.am.mov

I would also expect that trying to "Go to definition" inside of the dvc.yaml file would open give the option to open individual files (e.g step into a python file). At least I would expect that the cmd line is split into its component parts and a definition be displayed only for the symbol that is clicked on (e.g for data/features not cmd: ... data/features). It also seems like for example-get-started you cannot go to the params file definitions:

Screen.Recording.2022-09-20.at.9.29.33.am.mov

[wolmir]

This provider is way too simple to add any value, and even an implementation that satisfies the constraints Matt mentioned above is going to complicate the PR again and again

Can we leave the definitions for later as well, and keep only the server skeleton then?
So we have a chance of adding a solid definitions increment?

[wolmir]

This provider is way too simple to add any value, and even an implementation that satisfies the constraints Matt mentioned above is going to complicate the PR again and again

Can we leave the definitions for later as well, and keep only the server skeleton then? So we have a chance of adding a solid definitions increment?

Actually, not really, I'm already fixing it and It's not that much more complicated.

Will update here shortly.

[codeclimate]

Code Climate has analyzed commit 55f89a1 and detected 0 issues on this pull request.

The test coverage on the diff in this pull request is 91.0% (85% is the threshold).

This pull request will bring the total coverage in the repository to 96.9% (0.0% change).

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