2019-04-17 11:43:31 +01:00
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/**
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* @license
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2020-05-19 12:08:49 -07:00
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* Copyright Google LLC All Rights Reserved.
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2019-04-17 11:43:31 +01:00
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*
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* Use of this source code is governed by an MIT-style license that can be
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* found in the LICENSE file at https://angular.io/license
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*/
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/**
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2020-06-05 16:27:53 -07:00
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* @fileoverview
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* This file is used as a private API channel to shared Angular FW APIs with @angular/cli.
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*
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* Any changes to this file should be discussed with the Angular CLI team.
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2019-04-17 11:43:31 +01:00
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*/
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fix(compiler-cli): downlevel angular decorators to static properties (#37382)
In v7 of Angular we removed `tsickle` from the default `ngc` pipeline.
This had the negative potential of breaking ES2015 output and SSR due
to a limitation in TypeScript.
TypeScript by default preserves type information for decorated constructor
parameters when `emitDecoratorMetadata` is enabled. For example,
consider this snippet below:
```
@Directive()
export class MyDirective {
constructor(button: MyButton) {}
}
export class MyButton {}
```
TypeScript would generate metadata for the `MyDirective` class it has
a decorator applied. This metadata would be needed in JIT mode, or
for libraries that provide `MyDirective` through NPM. The metadata would
look as followed:
```
let MyDirective = class MyDir {}
MyDirective = __decorate([
Directive(),
__metadata("design:paramtypes", [MyButton]),
], MyDirective);
let MyButton = class MyButton {}
```
Notice that TypeScript generated calls to `__decorate` and
`__metadata`. These calls are needed so that the Angular compiler
is able to determine whether `MyDirective` is actually an directive,
and what types are needed for dependency injection.
The limitation surfaces in this concrete example because `MyButton`
is declared after the `__metadata(..)` call, while `__metadata`
actually directly references `MyButton`. This is illegal though because
`MyButton` has not been declared at this point. This is due to the
so-called temporal dead zone in JavaScript. Errors like followed will
be reported at runtime when such file/code evaluates:
```
Uncaught ReferenceError: Cannot access 'MyButton' before initialization
```
As noted, this is a TypeScript limitation because ideally TypeScript
shouldn't evaluate `__metadata`/reference `MyButton` immediately.
Instead, it should defer the reference until `MyButton` is actually
declared. This limitation will not be fixed by the TypeScript team
though because it's a limitation as per current design and they will
only revisit this once the tc39 decorator proposal is finalized
(currently stage-2 at time of writing).
Given this wontfix on the TypeScript side, and our heavy reliance on
this metadata in libraries (and for JIT mode), we intend to fix this
from within the Angular compiler by downleveling decorators to static
properties that don't need to evaluate directly. For example:
```
MyDirective.ctorParameters = () => [MyButton];
```
With this snippet above, `MyButton` is not referenced directly. Only
lazily when the Angular runtime needs it. This mitigates the temporal
dead zone issue caused by a limitation in TypeScript's decorator
metadata output. See: https://github.com/microsoft/TypeScript/issues/27519.
In the past (as noted; before version 7), the Angular compiler by
default used tsickle that already performed this transformation. We
moved the transformation to the CLI for JIT and `ng-packager`, but now
we realize that we can move this all to a single place in the compiler
so that standalone ngc consumers can benefit too, and that we can
disable tsickle in our Bazel `ngc-wrapped` pipeline (that currently
still relies on tsickle to perform this decorator processing).
This transformation also has another positive side-effect of making
Angular application/library code more compatible with server-side
rendering. In principle, TypeScript would also preserve type information
for decorated class members (similar to how it did that for constructor
parameters) at runtime. This becomes an issue when your application
relies on native DOM globals for decorated class member types. e.g.
```
@Input() panelElement: HTMLElement;
```
Your application code would then reference `HTMLElement` directly
whenever the source file is loaded in NodeJS for SSR. `HTMLElement`
does not exist on the server though, so that will become an invalid
reference. One could work around this by providing global mocks for
these DOM symbols, but that doesn't match up with other places where
dependency injection is used for mocking DOM/browser specific symbols.
More context in this issue: #30586. The TL;DR here is that the Angular
compiler does not care about types for these class members, so it won't
ever reference `HTMLElement` at runtime.
Fixes #30106. Fixes #30586. Fixes #30141.
Resolves FW-2196. Resolves FW-2199.
PR Close #37382
2020-06-05 16:26:23 +02:00
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import * as ts from 'typescript';
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2020-06-05 16:27:53 -07:00
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fix(compiler-cli): downlevel angular decorators to static properties (#37382)
In v7 of Angular we removed `tsickle` from the default `ngc` pipeline.
This had the negative potential of breaking ES2015 output and SSR due
to a limitation in TypeScript.
TypeScript by default preserves type information for decorated constructor
parameters when `emitDecoratorMetadata` is enabled. For example,
consider this snippet below:
```
@Directive()
export class MyDirective {
constructor(button: MyButton) {}
}
export class MyButton {}
```
TypeScript would generate metadata for the `MyDirective` class it has
a decorator applied. This metadata would be needed in JIT mode, or
for libraries that provide `MyDirective` through NPM. The metadata would
look as followed:
```
let MyDirective = class MyDir {}
MyDirective = __decorate([
Directive(),
__metadata("design:paramtypes", [MyButton]),
], MyDirective);
let MyButton = class MyButton {}
```
Notice that TypeScript generated calls to `__decorate` and
`__metadata`. These calls are needed so that the Angular compiler
is able to determine whether `MyDirective` is actually an directive,
and what types are needed for dependency injection.
The limitation surfaces in this concrete example because `MyButton`
is declared after the `__metadata(..)` call, while `__metadata`
actually directly references `MyButton`. This is illegal though because
`MyButton` has not been declared at this point. This is due to the
so-called temporal dead zone in JavaScript. Errors like followed will
be reported at runtime when such file/code evaluates:
```
Uncaught ReferenceError: Cannot access 'MyButton' before initialization
```
As noted, this is a TypeScript limitation because ideally TypeScript
shouldn't evaluate `__metadata`/reference `MyButton` immediately.
Instead, it should defer the reference until `MyButton` is actually
declared. This limitation will not be fixed by the TypeScript team
though because it's a limitation as per current design and they will
only revisit this once the tc39 decorator proposal is finalized
(currently stage-2 at time of writing).
Given this wontfix on the TypeScript side, and our heavy reliance on
this metadata in libraries (and for JIT mode), we intend to fix this
from within the Angular compiler by downleveling decorators to static
properties that don't need to evaluate directly. For example:
```
MyDirective.ctorParameters = () => [MyButton];
```
With this snippet above, `MyButton` is not referenced directly. Only
lazily when the Angular runtime needs it. This mitigates the temporal
dead zone issue caused by a limitation in TypeScript's decorator
metadata output. See: https://github.com/microsoft/TypeScript/issues/27519.
In the past (as noted; before version 7), the Angular compiler by
default used tsickle that already performed this transformation. We
moved the transformation to the CLI for JIT and `ng-packager`, but now
we realize that we can move this all to a single place in the compiler
so that standalone ngc consumers can benefit too, and that we can
disable tsickle in our Bazel `ngc-wrapped` pipeline (that currently
still relies on tsickle to perform this decorator processing).
This transformation also has another positive side-effect of making
Angular application/library code more compatible with server-side
rendering. In principle, TypeScript would also preserve type information
for decorated class members (similar to how it did that for constructor
parameters) at runtime. This becomes an issue when your application
relies on native DOM globals for decorated class member types. e.g.
```
@Input() panelElement: HTMLElement;
```
Your application code would then reference `HTMLElement` directly
whenever the source file is loaded in NodeJS for SSR. `HTMLElement`
does not exist on the server though, so that will become an invalid
reference. One could work around this by providing global mocks for
these DOM symbols, but that doesn't match up with other places where
dependency injection is used for mocking DOM/browser specific symbols.
More context in this issue: #30586. The TL;DR here is that the Angular
compiler does not care about types for these class members, so it won't
ever reference `HTMLElement` at runtime.
Fixes #30106. Fixes #30586. Fixes #30141.
Resolves FW-2196. Resolves FW-2199.
PR Close #37382
2020-06-05 16:26:23 +02:00
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import {TypeScriptReflectionHost} from './ngtsc/reflection';
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import {getDownlevelDecoratorsTransform} from './transformers/downlevel_decorators_transform';
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2020-06-05 16:27:53 -07:00
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2019-04-17 11:43:31 +01:00
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/**
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* Known values for global variables in `@angular/core` that Terser should set using
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* https://github.com/terser-js/terser#conditional-compilation
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*/
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export const GLOBAL_DEFS_FOR_TERSER = {
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ngDevMode: false,
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ngI18nClosureMode: false,
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};
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fix(ivy): retain JIT metadata unless JIT mode is explicitly disabled (#33671)
NgModules in Ivy have a definition which contains various different bits
of metadata about the module. In particular, this metadata falls into two
categories:
* metadata required to use the module at runtime (for bootstrapping, etc)
in AOT-only applications.
* metadata required to depend on the module from a JIT-compiled app.
The latter metadata consists of the module's declarations, imports, and
exports. To support JIT usage, this metadata must be included in the
generated code, especially if that code is shipped to NPM. However, because
this metadata preserves the entire NgModule graph (references to all
directives and components in the app), it needs to be removed during
optimization for AOT-only builds.
Previously, this was done with a clever design:
1. The extra metadata was added by a function called `setNgModuleScope`.
A call to this function was generated after each NgModule.
2. This function call was marked as "pure" with a comment and used
`noSideEffects` internally, which causes optimizers to remove it.
The effect was that in dev mode or test mode (which use JIT), no optimizer
runs and the full NgModule metadata was available at runtime. But in
production (presumably AOT) builds, the optimizer runs and removes the JIT-
specific metadata.
However, there are cases where apps that want to use JIT in production, and
still make an optimized build. In this case, the JIT-specific metadata would
be erroneously removed. This commit solves that problem by adding an
`ngJitMode` global variable which guards all `setNgModuleScope` calls. An
optimizer can be configured to statically define this global to be `false`
for AOT-only builds, causing the extra metadata to be stripped.
A configuration for Terser used by the CLI is provided in `tooling.ts` which
sets `ngJitMode` to `false` when building AOT apps.
PR Close #33671
2019-11-07 14:18:44 -08:00
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export const GLOBAL_DEFS_FOR_TERSER_WITH_AOT = {
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...GLOBAL_DEFS_FOR_TERSER,
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ngJitMode: false,
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};
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fix(compiler-cli): downlevel angular decorators to static properties (#37382)
In v7 of Angular we removed `tsickle` from the default `ngc` pipeline.
This had the negative potential of breaking ES2015 output and SSR due
to a limitation in TypeScript.
TypeScript by default preserves type information for decorated constructor
parameters when `emitDecoratorMetadata` is enabled. For example,
consider this snippet below:
```
@Directive()
export class MyDirective {
constructor(button: MyButton) {}
}
export class MyButton {}
```
TypeScript would generate metadata for the `MyDirective` class it has
a decorator applied. This metadata would be needed in JIT mode, or
for libraries that provide `MyDirective` through NPM. The metadata would
look as followed:
```
let MyDirective = class MyDir {}
MyDirective = __decorate([
Directive(),
__metadata("design:paramtypes", [MyButton]),
], MyDirective);
let MyButton = class MyButton {}
```
Notice that TypeScript generated calls to `__decorate` and
`__metadata`. These calls are needed so that the Angular compiler
is able to determine whether `MyDirective` is actually an directive,
and what types are needed for dependency injection.
The limitation surfaces in this concrete example because `MyButton`
is declared after the `__metadata(..)` call, while `__metadata`
actually directly references `MyButton`. This is illegal though because
`MyButton` has not been declared at this point. This is due to the
so-called temporal dead zone in JavaScript. Errors like followed will
be reported at runtime when such file/code evaluates:
```
Uncaught ReferenceError: Cannot access 'MyButton' before initialization
```
As noted, this is a TypeScript limitation because ideally TypeScript
shouldn't evaluate `__metadata`/reference `MyButton` immediately.
Instead, it should defer the reference until `MyButton` is actually
declared. This limitation will not be fixed by the TypeScript team
though because it's a limitation as per current design and they will
only revisit this once the tc39 decorator proposal is finalized
(currently stage-2 at time of writing).
Given this wontfix on the TypeScript side, and our heavy reliance on
this metadata in libraries (and for JIT mode), we intend to fix this
from within the Angular compiler by downleveling decorators to static
properties that don't need to evaluate directly. For example:
```
MyDirective.ctorParameters = () => [MyButton];
```
With this snippet above, `MyButton` is not referenced directly. Only
lazily when the Angular runtime needs it. This mitigates the temporal
dead zone issue caused by a limitation in TypeScript's decorator
metadata output. See: https://github.com/microsoft/TypeScript/issues/27519.
In the past (as noted; before version 7), the Angular compiler by
default used tsickle that already performed this transformation. We
moved the transformation to the CLI for JIT and `ng-packager`, but now
we realize that we can move this all to a single place in the compiler
so that standalone ngc consumers can benefit too, and that we can
disable tsickle in our Bazel `ngc-wrapped` pipeline (that currently
still relies on tsickle to perform this decorator processing).
This transformation also has another positive side-effect of making
Angular application/library code more compatible with server-side
rendering. In principle, TypeScript would also preserve type information
for decorated class members (similar to how it did that for constructor
parameters) at runtime. This becomes an issue when your application
relies on native DOM globals for decorated class member types. e.g.
```
@Input() panelElement: HTMLElement;
```
Your application code would then reference `HTMLElement` directly
whenever the source file is loaded in NodeJS for SSR. `HTMLElement`
does not exist on the server though, so that will become an invalid
reference. One could work around this by providing global mocks for
these DOM symbols, but that doesn't match up with other places where
dependency injection is used for mocking DOM/browser specific symbols.
More context in this issue: #30586. The TL;DR here is that the Angular
compiler does not care about types for these class members, so it won't
ever reference `HTMLElement` at runtime.
Fixes #30106. Fixes #30586. Fixes #30141.
Resolves FW-2196. Resolves FW-2199.
PR Close #37382
2020-06-05 16:26:23 +02:00
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/**
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* Transform for downleveling Angular decorators and Angular-decorated class constructor
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* parameters for dependency injection. This transform can be used by the CLI for JIT-mode
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* compilation where decorators should be preserved, but downleveled so that apps are not
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* exposed to the ES2015 temporal dead zone limitation in TypeScript's metadata.
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* See https://github.com/angular/angular-cli/pull/14473 for more details.
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*/
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export function decoratorDownlevelTransformerFactory(program: ts.Program):
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ts.TransformerFactory<ts.SourceFile> {
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const typeChecker = program.getTypeChecker();
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const reflectionHost = new TypeScriptReflectionHost(typeChecker);
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return getDownlevelDecoratorsTransform(
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typeChecker, reflectionHost, [], /* isCore */ false,
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/* enableClosureCompiler */ false);
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}
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