[Feature] Code Coverage Indicators

[sand4rt]

First of all, thank you for this awesome plugin!

It would probably be a lot of work, but it would be great to have code coverage indicators ala Wallaby.js:

When executing your tests and code, Wallaby calculates code coverage to identify which statements of your code have been executed and which statements have not.

Code coverage for your application code is displayed in the left margin of your editor and is updated in real-time. As soon as you start changing your code, the coverage will be automatically updated.

*https://wallabyjs.com/docs/intro/coverage.html#editor-code-coverage-indicators

What the coverage indicators mean:

• Gray: if you see a gray square next to a line of code, it means that the line of code is not covered by any of your tests.
• Yellow: if you see a yellow square next to a line of code, it means that the line of code is only partially covered by your tests.
• Green: if you see a green square next to a line of code, it means that the line of code is covered by at least one of your tests.
• Pink: if you see a pink square next to a line of code, it means that the line of code is on the execution path of a failing test.
• Red: if you see a red square next to a line of code, it means that the line of code is the source of an error or failed expectation, or in the stack of an error.

[jan-xyz]

I am achieving this by using https://github.com/andythigpen/nvim-coverage. You can setup custom arguments for your test runner to export coverage data and then just display it. E.g. for Go I am doing this:

local nt = require("neotest")
local cov = require("coverage")

cov.setup()
nt.setup({
  adapters = {
    require("neotest-go")({
      args = { "-coverprofile=coverage.out" },
    }),
  },
})

and then I run

nt.run.run(vim.fn.getcwd())
cov.load(true)

How it looks like (the green bars are the coverage report):