`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
e648a0c4ca