angular-cn/packages/compiler-cli/ngcc/test/host
George Kalpakas bd6a39c364 fix(ngcc): correctly detect emitted TS helpers in ES5 (#35191)
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
2020-02-21 09:06:46 -08:00
..
commonjs_host_import_helper_spec.ts refactor(ngcc): use bundle src to create reflection hosts (#34254) 2019-12-18 11:25:01 -08:00
commonjs_host_spec.ts fix(ngcc): correctly detect emitted TS helpers in ES5 (#35191) 2020-02-21 09:06:46 -08:00
esm5_host_import_helper_spec.ts refactor(ngcc): use bundle src to create reflection hosts (#34254) 2019-12-18 11:25:01 -08:00
esm5_host_spec.ts fix(ngcc): correctly detect emitted TS helpers in ES5 (#35191) 2020-02-21 09:06:46 -08:00
esm2015_host_import_helper_spec.ts refactor(ngcc): use bundle src to create reflection hosts (#34254) 2019-12-18 11:25:01 -08:00
esm2015_host_spec.ts fix(ngcc): do not collect private declarations from external packages (#34811) 2020-01-23 13:58:37 -08:00
umd_host_import_helper_spec.ts refactor(ngcc): use bundle src to create reflection hosts (#34254) 2019-12-18 11:25:01 -08:00
umd_host_spec.ts fix(ngcc): correctly detect emitted TS helpers in ES5 (#35191) 2020-02-21 09:06:46 -08:00
util.ts fix(ngcc): properly detect origin of constructor param types (#33901) 2019-11-19 11:38:33 -08:00