As a performance optimization, this commit splits the single
__ngtypecheck__.ts file which was previously added to the user's program as
a container for all template type-checking code into multiple .ngtypecheck
shim files, one for each original file in the user's program.
In larger applications, the generation, parsing, and checking of this single
type-checking file was a huge performance bottleneck, with the file often
exceeding 1 MB in text content. Particularly in incremental builds,
regenerating this single file for the entire application proved especially
expensive.
This commit introduces a new strategy for template type-checking code which
makes use of a new interface, the `TypeCheckingProgramStrategy`. This
interface abstracts the process of creating a new `ts.Program` to type-check
a particular compilation, and allows the mechanism there to be kept separate
from the more complex logic around dealing with multiple .ngtypecheck files.
A new `TemplateTypeChecker` hosts that logic and interacts with the
`TypeCheckingProgramStrategy` to actually generate and return diagnostics.
The `TypeCheckContext` class, previously the workhorse of template type-
checking, is now solely focused on collecting and generating type-checking
file contents.
A side effect of implementing the new `TypeCheckingProgramStrategy` in this
way is that the API is designed to be suitable for use by the Angular
Language Service as well. The LS also needs to type-check components, but
has its own method for constructing a `ts.Program` with type-checking code.
Note that this commit does not make the actual checking of templates at all
_incremental_ just yet. That will happen in a future commit.
PR Close#36211
b861e9c0ac