fix(@angular/build): load zone.js dynamically for library unit tests#33478
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This pull request introduces a new 'dynamic-zone' testing strategy to dynamically load 'zone.js' and 'zone.js/testing' when testing a library where polyfills are undefined. It also adds a corresponding integration test. The feedback suggests letting the dynamic import errors propagate instead of catching and logging them, ensuring that the test runner fails fast with a clear stack trace if the imports fail.
When unit testing library targets with the unit-test builder, the build target (ng-packagr) does not have a 'polyfills' configuration. This caused the builder to fall back to the 'dynamic' zone testing strategy, which only dynamically imports zone.js/testing at runtime if Zone is already defined. Since the main zone.js library was never loaded, Zone was undefined, and library tests relying on TestBed/fakeAsync failed. This commit introduces a new 'dynamic-zone' zone testing strategy. If polyfills is undefined (meaning we are running a library target) and zone.js is installed/resolvable, both zone.js and zone.js/testing are dynamically imported at startup, resolving the failure. Fixes angular#33477
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When unit testing library targets with the unit-test builder, the build target (ng-packagr) does not have a 'polyfills' configuration. This caused the builder to fall back to the 'dynamic' zone testing strategy, which only dynamically imports zone.js/testing at runtime if Zone is already defined. Since the main zone.js library was never loaded, Zone was undefined, and library tests relying on TestBed/fakeAsync failed.
This commit introduces a new 'dynamic-zone' zone testing strategy. If polyfills is undefined (meaning we are running a library target) and zone.js is installed/resolvable, both zone.js and zone.js/testing are dynamically imported at startup, resolving the failure.
Fixes #33477