ng test: Source maps don't match when using --code-coverage

[daelmaak]

🐞 Bug report

Command (mark with an x)

• new
• build
• serve
• test
• e2e
• generate
• add
• update
• lint
• xi18n
• run
• config
• help
• version
• doc

Is this a regression?

Not sure.

Description

When running ng test --code-coverage and then debugging in chrome, the source maps don't match the actual code. On picture, the execution should have stopped at debugger;, which it seemingly doesn't:

🔬 Minimal Reproduction

Using ng cli 10.1.5

1. ng new
2. in the newly created project, run ng test --code-coverage
3. open source file of app.component.ts in the browser controlled by karma
4. place some breakpoints and check whether it is was placed on correct line (which it won't)

🔥 Exception or Error

none

🌍 Your Environment

Angular CLI: 10.1.5
Node: 12.11.0
OS: linux x64

Angular: 10.1.5
... animations, cli, common, compiler, compiler-cli, core, forms
... language-service, platform-browser, platform-browser-dynamic
... platform-server, router, service-worker
Ivy Workspace: Yes

Package                         Version
---------------------------------------------------------
@angular-devkit/architect       0.1001.4
@angular-devkit/build-angular   0.1001.5
@angular-devkit/core            10.1.5
@angular-devkit/schematics      10.1.5
@angular/cdk                    10.2.4
@angular/flex-layout            10.0.0-beta.32
@angular/material               10.2.4
@nguniversal/builders           10.1.0
@nguniversal/common             10.1.0
@nguniversal/express-engine     10.1.0
@schematics/angular             10.1.5
@schematics/update              0.1001.5
rxjs                            6.6.3
typescript                      3.9.7

Anything else relevant?
not to my knowledge

[alan-agius4]

Hi @daelmaak,

Had a quick look at this and from my initial investigation this looks more of an upstream issue. Likely, it's in https://github.com/JS-DevTools/coverage-istanbul-loader or https://github.com/istanbuljs/istanbuljs

[restjohn]

This appears to be the same as #7117. The discussion there indicates the issue is with webpack-contrib/istanbul-instrumenter-loader. Regardless, this makes debugging Angular tests, not even live debugging but just referencing line numbers in test output, impossible when code coverage is enabled, which Angular does by default. Caveat: I'm currently still using Angular 8, though apparently the issue is still outstanding.

[alan-agius4]

I'm sorry, but this issue is not caused by Angular CLI. Please contact the author(s) of the @jsdevtools/coverage-istanbul-loader project or file an issue on their issue tracker.