ngtsc has cyclic import detection, to determine when adding an import to a
directive or pipe would create a cycle. However, this detection must also
account for already inserted imports, as it's possible for both directions
of a circular import to be inserted by Ivy (as opposed to at least one of
those edges existing in the user's program).
This commit fixes the circular import detection for components to take into
consideration already added edges. This is difficult for one critical
reason: only edges to files which will *actually* be imported should be
considered. However, that depends on which directives & pipes are used in
a given template, which is currently only known by running the
TemplateDefinitionBuilder during the 'compile' phase. This is too late; the
decision whether to use remote scoping (which consults the import graph) is
made during the 'resolve' phase, before any compilation has taken place.
Thus, the only way to correctly consider synthetic edges is for the compiler
to know exactly which directives & pipes are used in a template during
'resolve'. There are two ways to achieve this:
1) refactor `TemplateDefinitionBuilder` to do its work in two phases, with
directive matching occurring as a separate step which can be performed
earlier.
2) use the `R3TargetBinder` in the 'resolve' phase to independently bind the
template and get information about used directives.
Option 1 is ideal, but option 2 is currently used for practical reasons. The
cost of binding the template can be shared with template-typechecking.
PR Close#29040
exportAs in @Directive metadata supports multiple values, separated by
commas. Previously it was treated as a single value string.
This commit modifies the compiler to understand that exportAs is a
string[]. It stops short of carrying the multiple values through to the
runtime. Instead, it only emits the first one. A future commit will modify
the runtime to accept all the values.
PR Close#28001
This commit introduces the "t2" API, which processes parsed template ASTs
and performs a number of functions such as binding (the process of
semantically interpreting cross-references within the template) and
directive matching. The API is modeled on TypeScript's TypeChecker API,
with oracle methods that give access to collected metadata.
This work is a prerequisite for the upcoming template type-checking
functionality, and will also become the basis for a refactored
TemplateDefinitionBuilder.
PR Close#26203
