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feat(compiler-cli): simulate narrowing of signal reads in templates
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packages/compiler-cli/src/ngtsc/typecheck/src/signal_calls.ts
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| /** | ||
| * @license | ||
| * Copyright Google LLC All Rights Reserved. | ||
| * | ||
| * Use of this source code is governed by an MIT-style license that can be | ||
| * found in the LICENSE file at https://angular.io/license | ||
| */ | ||
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| import {AST, AstVisitor, ASTWithSource, Binary, BindingPipe, Call, Chain, Conditional, ImplicitReceiver, Interpolation, KeyedRead, KeyedWrite, LiteralArray, LiteralMap, LiteralPrimitive, NonNullAssert, PrefixNot, PropertyRead, PropertyWrite, SafeCall, SafeKeyedRead, SafePropertyRead, ThisReceiver, Unary,} from '@angular/compiler'; | ||
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| /** | ||
| * The types of nodes potentially corresponding with a signal call in a template. Any call | ||
| * expression without arguments is potentially a signal call, as signal calls cannot be | ||
| * differentiated from regular method calls syntactically. | ||
| */ | ||
| export type PotentialSignalCall = (Call|SafeCall)&{args: []}; | ||
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| /** | ||
| * Tests whether the given call expression may correspond with a signal call. | ||
| */ | ||
| export function isPotentialSignalCall(ast: Call|SafeCall): ast is PotentialSignalCall { | ||
| return ast.args.length === 0; | ||
| } | ||
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| /** | ||
| * Represents a string that identifies a call expression that may represent a signal call. | ||
| */ | ||
| export type SignalCallIdentity = string&{__brand: 'SignalCallIdentity'}; | ||
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| /** | ||
| * Computes the string identity of the provided call expression. Any expression that is witnessed | ||
| * when evaluating the call expression is included in the identity. For implicit reads (e.g. | ||
| * property accesses with `ImplicitReceiver` as receiver) an external identity is requested, to | ||
| * ensure that each local template variable is assigned its own unique identifier. This is important | ||
| * for scenarios like | ||
| * | ||
| * ``` | ||
| * @Component({ | ||
| * template: ` | ||
| * @if (persons[selectedPerson](); as selectedPerson) { | ||
| * {{ persons[selectedPerson]() }} | ||
| * }` | ||
| * }) | ||
| * export class ShadowCmp { | ||
| * persons = { | ||
| * admin: signal('admin'); | ||
| * guest: signal('guest'); | ||
| * }; | ||
| * selectedPerson: keyof ShadowCmp['persons']; | ||
| * } | ||
| * ``` | ||
| * | ||
| * Here, the local alias `selectedPerson` shadows the `ShadowCmp.selectedPerson` field, such that | ||
| * the call expression in the @if's condition expression is not equivalent to the syntactically | ||
| * identical expression within its block. Consequently, different identities have to be computed for | ||
| * both call expressions, which is achieved by letting `identifyImplicitRead` resolve any implicit | ||
| * accesses to a unique identifier for local template variables. | ||
| * | ||
| * @param call The call expression to compute the identity for. | ||
| * @param recurse Callback function to compute the identity of nested signal calls. | ||
| * @param identifyImplicitRead Callback function to determine the identity of implicit reads. | ||
| */ | ||
| export function computeSignalCallIdentity( | ||
| call: PotentialSignalCall, | ||
| recurse: (receiverCall: PotentialSignalCall) => string | null, | ||
| identifyImplicitRead: (expr: AST) => string | null, | ||
| ): SignalCallIdentity|null { | ||
| return call.receiver.visit(new SignalCallIdentification(recurse, identifyImplicitRead)); | ||
| } | ||
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| class SignalCallIdentification implements AstVisitor { | ||
| constructor( | ||
| private recurse: (receiverCall: PotentialSignalCall) => string | null, | ||
| private identifyImplicitRead: (expr: AST) => string | null, | ||
| ) {} | ||
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| visitUnary(ast: Unary): string|null { | ||
| const expr = this.forAst(ast.expr); | ||
| if (expr === null) { | ||
| return null; | ||
| } | ||
| return `${ast.operator}${expr}`; | ||
| } | ||
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| visitBinary(ast: Binary): string|null { | ||
| const left = this.forAst(ast.left); | ||
| const right = this.forAst(ast.right); | ||
| if (left === null || right === null) { | ||
| return null; | ||
| } | ||
| return `${left}${ast.operation}${right}`; | ||
| } | ||
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| visitChain(ast: Chain): string|null { | ||
| return null; | ||
| } | ||
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| visitConditional(ast: Conditional): string|null { | ||
| return null; | ||
| } | ||
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| visitThisReceiver(ast: ThisReceiver): string|null { | ||
| return 'this'; | ||
| } | ||
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| visitImplicitReceiver(ast: ImplicitReceiver): string|null { | ||
| return 'this'; | ||
| } | ||
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| visitInterpolation(ast: Interpolation): string|null { | ||
| return null; | ||
| } | ||
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| visitKeyedRead(ast: KeyedRead): string|null { | ||
| const receiver = this.forAst(ast.receiver); | ||
| const key = this.forAst(ast.key); | ||
| if (receiver === null || key === null) { | ||
| return null; | ||
| } | ||
| return `${receiver}[${key}]`; | ||
| } | ||
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| visitKeyedWrite(ast: KeyedWrite): string|null { | ||
| return null; | ||
| } | ||
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| visitLiteralArray(ast: LiteralArray): string|null { | ||
| return null; | ||
| } | ||
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| visitLiteralMap(ast: LiteralMap): string|null { | ||
| return null; | ||
| } | ||
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| visitLiteralPrimitive(ast: LiteralPrimitive): string|null { | ||
| return `${ast.value}`; | ||
| } | ||
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| visitPipe(ast: BindingPipe): string|null { | ||
| // Don't enable narrowing when pipes are being evaluated. | ||
| return null; | ||
| } | ||
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| visitPrefixNot(ast: PrefixNot): string|null { | ||
| const expression = this.forAst(ast.expression); | ||
| if (expression === null) { | ||
| return expression; | ||
| } | ||
| return `!${expression}`; | ||
| } | ||
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| visitNonNullAssert(ast: NonNullAssert): string|null { | ||
| return this.forAst(ast.expression); | ||
| } | ||
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| visitPropertyRead(ast: PropertyRead): string|null { | ||
| const receiver = this.identifyReceiver(ast); | ||
| if (receiver === null) { | ||
| return null; | ||
| } | ||
| return `${receiver}.${ast.name}`; | ||
| } | ||
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| visitPropertyWrite(ast: PropertyWrite): string|null { | ||
| return null; | ||
| } | ||
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| visitSafePropertyRead(ast: SafePropertyRead): string|null { | ||
| const receiver = this.identifyReceiver(ast); | ||
| if (receiver === null) { | ||
| return null; | ||
| } | ||
| return `${receiver}?.${ast.name}`; | ||
| } | ||
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| visitSafeKeyedRead(ast: SafeKeyedRead): string|null { | ||
| const receiver = this.forAst(ast.receiver) | ||
| if (receiver === null) { | ||
| return null; | ||
| } | ||
| return `${receiver}?.[${this.forAst(ast.key)}]`; | ||
| } | ||
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| visitCall(ast: Call): string|null { | ||
| if (ast.args.length > 0) { | ||
| // Don't enable narrowing for complex calls. | ||
| return null; | ||
| } | ||
| const receiver = this.forAst(ast.receiver); | ||
| if (receiver === null) { | ||
| return null; | ||
| } | ||
| return `${receiver}()`; | ||
| } | ||
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| visitSafeCall(ast: SafeCall): string|null { | ||
| if (ast.args.length > 0) { | ||
| // Don't enable narrowing for complex calls. | ||
| return null; | ||
| } | ||
| const receiver = this.forAst(ast.receiver); | ||
| if (receiver === null) { | ||
| return null; | ||
| } | ||
| return `${receiver}?.()`; | ||
| } | ||
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| visitASTWithSource(ast: ASTWithSource): string|null { | ||
| return this.forAst(ast.ast); | ||
| } | ||
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| private identifyReceiver(ast: PropertyRead|SafePropertyRead): string|null { | ||
| const receiver = ast.receiver; | ||
| if (receiver instanceof ImplicitReceiver && !(receiver instanceof ThisReceiver)) { | ||
| const implicitIdentity = this.identifyImplicitRead(ast); | ||
| if (implicitIdentity !== null) { | ||
| return implicitIdentity; | ||
| } | ||
| } | ||
| return this.forAst(receiver); | ||
| } | ||
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| private forAst(ast: AST): string|null { | ||
| if ((ast instanceof Call || ast instanceof SafeCall) && isPotentialSignalCall(ast)) { | ||
| const result = this.recurse(ast); | ||
| if (result !== null) { | ||
| return `ɵ${result}`; | ||
| } | ||
| } | ||
| return ast.visit(this); | ||
| } | ||
| } |
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