If no user files changed:
- only type check the changed generated files
Never emit non changed generated files
- we still calculate them, but don’t send them through
TypeScript to emit them but cache the written files instead.
PR Close#19646
This is important to not confuse users nor downstream tools that
consume our source maps. For generated content for which we don’t
have an original source file, we use the generated file now.
Fixes#19538
For now, we always create all generated files, but diff them
before we pass them to TypeScript.
For the user files, we compare the programs and only emit changed
TypeScript files.
This also adds more diagnostic messages if the `—diagnostics` flag
is passed to the command line.
