Make DENO_COVERAGE_DIR public

[caspervonb]

The DENO_UNSTABLE_COVERAGE_DIR is the environment variable that actually controls if coverage collection takes place or not. It has a terrible name and is not documented anywhere as it is not considered public at the moment.

Using an environment variable is the most common way to determine if coverage should be collected and where it should be collected too.

This implies that we remove deno test --coverage which was kept for backwards compatibility in 1.x.
The removal of the coverage flag would probably have to be a 2.0 change.

Usage would be:

export DENO_COVERAGE_DIR="some/path"
deno run ...
deno test ...
deno test ...
deno coverage --lcov > cov.lcov

[bartlomieju]

What are use cases for making this env var public?

[lowlighter]

It could be useful for apps that spawns external v8 instances to know whether coverage should be collected or not.

I'm mostly thinking about astral (lino-levan/astral#13) where some functions may be evaluated in a browser context.

Not sure if duplicated references are properly now handled (it uses to only treat first occurrence), but if it is, it'd may allow unified coverage which would be really nice

[bartlomieju]

I'm fine making this env var public