Alex Rickabaugh 3613e7c4e5 test(compiler-cli): move testing utils to separate package (#39594)
ngtsc has a robust suite of testing utilities, designed for in-memory
testing of a TypeScript compiler. Previously these utilities lived in the
`test` directory for the compiler-cli package.

This commit moves those utilities to an `ngtsc/testing` package, enabling
them to be depended on separately and opening the door for using them from
the upcoming language server testing infrastructure.

As part of this refactoring, the `fake_core` package (a lightweight API
replacement for @angular/core) is expanded to include functionality needed
for Language Service test use cases.

PR Close #39594
2020-11-17 11:59:56 -08:00

893 B

fake_core is a library designed to expose some of the same symbols as @angular/core, without requiring compilation of the whole of @angular/core. This enables unit tests for the compiler to be written without incurring long rebuilds for every change.

  • @angular/core is compiled with @angular/compiler-cli, and therefore has an implicit dependency on it. Therefore core must be rebuilt if the compiler changes.
  • Tests for the compiler which intend to build code that depends on @angular/core must have a data dependency on @angular/core. Therefore core must be built to run the compiler tests, and thus rebuilt if the compiler changes.

This rebuild cycle is expensive and slow. fake_core avoids this by exposing a subset of the @angular/core API, which enables applications to be built by the ngtsc compiler without needing a full version of core present at compile time.