e790c8547e
Prior to this change, each invocation of `loadStandardTestFiles` would load the necessary files from disk. This function is typically called at the top-level of a test module in order to share the result across tests. The `//packages/compiler-cli/test/ngtsc` target has 8 modules where this call occurs, each loading their own copy of `node_modules/typescript` which is ~60MB in size, so the memory overhead used to be significant. This commit loads the individual packages into a standalone `Folder` and mounts this folder into the filesystem of standard test files, such that all file contents are no longer duplicated in memory. PR Close #38909
Virtual file-system layer
To improve cross platform support, all file access (and path manipulation)
is now done through a well known interface (FileSystem).
For testing a number of MockFileSystem implementations are supplied.
These provide an in-memory file-system which emulates operating systems
like OS/X, Unix and Windows.
The current file system is always available via the helper method,
getFileSystem(). This is also used by a number of helper
methods to avoid having to pass FileSystem objects around all the time.
The result of this is that one must be careful to ensure that the file-system
has been initialized before using any of these helper methods.
To prevent this happening accidentally the current file system always starts out
as an instance of InvalidFileSystem, which will throw an error if any of its
methods are called.
You can set the current file-system by calling setFileSystem().
During testing you can call the helper function initMockFileSystem(os)
which takes a string name of the OS to emulate, and will also monkey-patch
aspects of the TypeScript library to ensure that TS is also using the
current file-system.
Finally there is the NgtscCompilerHost to be used for any TypeScript
compilation, which uses a given file-system.
All tests that interact with the file-system should be tested against each of the mock file-systems. A series of helpers have been provided to support such tests:
runInEachFileSystem()- wrap your tests in this helper to run all the wrapped tests in each of the mock file-systems, it callsinitMockFileSystem()for each OS to emulate.loadTestFiles()- use this to add files and their contents to the mock file system for testing.loadStandardTestFiles()- use this to load a mirror image of files on disk into the in-memory mock file-system.loadFakeCore()- use this to load a fake version of@angular/coreinto the mock file-system.
All ngcc and ngtsc source and tests now use this virtual file-system setup.