In ES5 code, TypeScript requires certain helpers (such as
`__spreadArrays()`) to be able to support ES2015+ features. These
helpers can be either imported from `tslib` (by setting the
`importHelpers` TS compiler option to `true`) or emitted inline (by
setting the `importHelpers` and `noEmitHelpers` TS compiler options to
`false`, which is the default value for both).
Ngtsc's `StaticInterpreter` (which is also used during ngcc processing)
is able to statically evaluate some of these helpers (currently
`__assign()`, `__spread()` and `__spreadArrays()`), as long as
`ReflectionHost#getDefinitionOfFunction()` correctly detects the
declaration of the helper. For this to happen, the left-hand side of the
corresponding call expression (i.e. `__spread(...)` or
`tslib.__spread(...)`) must be evaluated as a function declaration for
`getDefinitionOfFunction()` to be called with.
In the case of imported helpers, the `tslib.__someHelper` expression was
resolved to a function declaration of the form
`export declare function __someHelper(...args: any[][]): any[];`, which
allows `getDefinitionOfFunction()` to correctly map it to a TS helper.
In contrast, in the case of emitted helpers (and regardless of the
module format: `CommonJS`, `ESNext`, `UMD`, etc.)), the `__someHelper`
identifier was resolved to a variable declaration of the form
`var __someHelper = (this && this.__someHelper) || function () { ... }`,
which upon further evaluation was categorized as a `DynamicValue`
(prohibiting further evaluation by the `getDefinitionOfFunction()`).
As a result of the above, emitted TypeScript helpers were not evaluated
in ES5 code.
---
This commit changes the detection of TS helpers to leverage the existing
`KnownFn` feature (previously only used for built-in functions).
`Esm5ReflectionHost` is changed to always return `KnownDeclaration`s for
TS helpers, both imported (`getExportsOfModule()`) as well as emitted
(`getDeclarationOfIdentifier()`).
Similar changes are made to `CommonJsReflectionHost` and
`UmdReflectionHost`.
The `KnownDeclaration`s are then mapped to `KnownFn`s in
`StaticInterpreter`, allowing it to statically evaluate call expressions
involving any kind of TS helpers.
Jira issue: https://angular-team.atlassian.net/browse/FW-1689
PR Close#35191
Previously, in cases were values were expensive to compute and would be
used multiple times, a combination of a regular `Map` and a helper
function (`getOrDefault()`) was used to ensure values were only computed
once.
This commit uses a special `Map`-like structure to compute and memoize
such expensive values without the need to a helper function.
PR Close#34512
While different, CommonJS and UMD have a lot in common regarding the
their exports are constructed. Therefore, there was some code
duplication between `CommonJsReflectionHost` and `UmdReflectionHost`.
This commit extracts some of the common bits into a separate file as
helpers to allow reusing the code in both `ReflectionHost`s.
PR Close#34512
When working out the dependencies between entry-points
ngcc must parse the import statements and then resolve the
import path to the actual file. This is complicated because module
resolution is not trivial.
Previously ngcc used the node.js `require.resolve`, with some
hacking to resolve modules. This change refactors the `DependencyHost`
to use a new custom `ModuleResolver`, which is optimized for this use
case.
Moreover, because we are in full control of the resolution,
we can support TS `paths` aliases, where not all imports come from
`node_modules`. This is the case in some CLI projects where there are
compiled libraries that are stored locally in a `dist` folder.
See //FW-1210.
PR Close#29643
George Kalpakas
Pete Bacon Darwin