I'm in the process of trying to collect coverage for Node.js' own internal libraries, and am running into a few significant problems:

• line counts appear to be all over the place; also we don't collect coverage for the wrap itself on several internal modules. Here's output from assert.js as an example.

  • with coverage: make coverage work for Node.js #23941, we are now collecting coverage for the top level of internal modules.
  • it's still somewhat difficult to figure out the initial offset of files, this is being worked on in (lib: modify NativeModule to use compileFunction #23837, and module: use compileFunction over Module.wrap #21573).
  • coverage can't currently be collected or functions with return statements coverage isn't collected for closing braces in if statements, see: https://bugs.chromium.org/p/v8/issues/detail?id=8381 (@hashseed, @schuay).
    • coverage isn't collected for throw statement.

• the performance of merging 2800 reports is atrocious, I think this is partially because files like loader.js need to get merged over and over again, and also have many 1000s of blocks.

  • @demurgos' work has significantly improved merging performance.

• I'm seeing a few failures for tests that instrument code used by coverage itself; specifically tests that mock the events module.

would love some help getting unblocked from these two issues, very excited to move our own test suite towards built in coverage.

CC: @addaleax, @demurgos, @hashseed, @TimothyGu, @schuay

• Version: >v10.10.0
• Platform :all platforms
• Subsystem: test