e648a0c4ca
`NgCompiler` is the heart of ngtsc and can be used to analyze and compile Angular programs in a variety of environments. Most of these integrations rely on `NgProgram` and the creation of an `NgCompilerHost` in order to create a `ts.Program` with the right shape for `NgCompiler`. However, certain environments (such as the Angular Language Service) have their own mechanisms for creating `ts.Program`s that don't make use of a `ts.CompilerHost`. In such environments, an `NgCompilerHost` does not make sense. This commit breaks the dependency of `NgCompiler` on `NgCompilerHost` and extracts the specific interface of the host on which `NgCompiler` depends into a new interface, `NgCompilerAdapter`. This interface includes methods from `ts.CompilerHost`, the `ExtendedTsCompilerHost`, as well as APIs from `NgCompilerHost`. A consumer such as the language service can implement this API without needing to jump through hoops to create an `NgCompilerHost` implementation that somehow wraps its specific environment. PR Close #37118
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.