b861e9c0ac
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
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