Coverage not generated with ts_project

[subnova]

🐞 bug report

Affected Rule

ts_project

Is this a regression?

Regression between ts_library and ts_project.

Description

Coverage reports are not generated when (test) code is built using ts_project.

🔬 Minimal Reproduction

The issue is demonstrated by the repository https://github.com/subnova/coverage_test (minus the patch that resolves the issue).

🌍 Your Environment

Operating System:

  
    System Version:	macOS 10.15.7 (19H1217)
    Kernel Version:	Darwin 19.6.0
  

Output of bazel version:

  
Build label: 4.0.0
Build target: bazel-out/darwin-opt/bin/src/main/java/com/google/devtools/build/lib/bazel/BazelServer_deploy.jar
Build time: Thu Jan 21 07:38:50 2021 (1611214730)
Build timestamp: 1611214730
Build timestamp as int: 1611214730
  

Rules_nodejs version:

(Please check that you have matching versions between WORKSPACE file and @bazel/* npm packages.)

  
3.5.1
  

[Toxicable]

If anyone comes accross this, you may also need to enable:
tsconfig: inlineSourceMap, inlineSources
.bazelrc: coverage --instrument_test_targets --experimental_forward_instrumented_files_info_by_default