This optimization builds on a lot of prior work to finally make type-
checking of templates incremental.
Incrementality requires two main components:
- the ability to reuse work from a prior compilation.
- the ability to know when changes in the current program invalidate that
prior work.
Prior to this commit, on every type-checking pass the compiler would
generate new .ngtypecheck files for each original input file in the program.
1. (Build #1 main program): empty .ngtypecheck files generated for each
original input file.
2. (Build #1 type-check program): .ngtypecheck contents overridden for those
which have corresponding components that need type-checked.
3. (Build #2 main program): throw away old .ngtypecheck files and generate
new empty ones.
4. (Build #2 type-check program): same as step 2.
With this commit, the `IncrementalDriver` now tracks template type-checking
_metadata_ for each input file. The metadata contains information about
source mappings for generated type-checking code, as well as some
diagnostics which were discovered at type-check analysis time. The actual
type-checking code is stored in the TypeScript AST for type-checking files,
which is now re-used between programs as follows:
1. (Build #1 main program): empty .ngtypecheck files generated for each
original input file.
2. (Build #1 type-check program): .ngtypecheck contents overridden for those
which have corresponding components that need type-checked, and the
metadata registered in the `IncrementalDriver`.
3. (Build #2 main program): The `TypeCheckShimGenerator` now reuses _all_
.ngtypecheck `ts.SourceFile` shims from build #1's type-check program in
the construction of build #2's main program. Some of the contents of
these files might be stale (if a component's template changed, for
example), but wholesale reuse here prevents unnecessary changes in the
contents of the program at this point and makes TypeScript's job a lot
easier.
4. (Build #2 type-check program): For those input files which have not
"logically changed" (meaning components within are semantically the same
as they were before), the compiler will re-use the type-check file
metadata from build #1, and _not_ generate a new .ngtypecheck shim.
For components which have logically changed or where the previous
.ngtypecheck contents cannot otherwise be reused, code generation happens
as before.
PR Close#36211
ecffc3557f