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fix(ngcc): correctly detect emitted TS helpers in ES5 (#35191)

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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
This commit is contained in:
George Kalpakas
2020-02-06 18:44:49 +02:00
committed by Miško Hevery
parent 14744f27c5
commit bd6a39c364
15 changed files with 1194 additions and 453 deletions
Download Patch File Download Diff File Expand all files Collapse all files

4
packages/compiler-cli/ngcc/src/host/umd_host.ts
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@ -12,7 +12,7 @@ import {absoluteFrom} from '../../../src/ngtsc/file_system';
import {Declaration, Import} from '../../../src/ngtsc/reflection';
import {Logger} from '../logging/logger';
import {BundleProgram} from '../packages/bundle_program';
import {FactoryMap, stripExtension} from '../utils';
import {FactoryMap, getTsHelperFnFromIdentifier, stripExtension} from '../utils';
import {ExportDeclaration, ExportStatement, ReexportStatement, findNamespaceOfIdentifier, findRequireCallReference, isExportStatement, isReexportStatement, isRequireCall} from './commonjs_umd_utils';
import {Esm5ReflectionHost, stripParentheses} from './esm5_host';
@ -215,7 +215,7 @@ export class UmdReflectionHost extends Esm5ReflectionHost {
// We need to add the `viaModule` because the `getExportsOfModule()` call
// did not know that we were importing the declaration.
return {node: importedFile, known: null, viaModule: importInfo.from};
return {node: importedFile, known: getTsHelperFnFromIdentifier(id), viaModule: importInfo.from};
}
private resolveModuleName(moduleName: string, containingFile: ts.SourceFile): ts.SourceFile