Keen Yee Liau 208ef7bd62 refactor(compiler): Remove NullAstVisitor and visitAstChildren (#35619)
This commit removes the `NullAstVisitor` and `visitAstChildren` exported
from `packages/compiler/src/expression_parser/ast.ts` because they
contain duplicate and buggy implementation, and their use cases could be
sufficiently covered by `RecursiveAstVisitor` if the latter implements the
`visit` method. This use case is only needed in the language service.

With this change, any visitor that extends `RecursiveAstVisitor` could
just define their own `visit` function and the parent class will behave
correctly.

A bit of historical context:
In language service, we need a way to tranverse the expression AST in a
selective manner based on where the user's cursor is. This means we need a
"filtering" function to decide which node to visit and which node to not
visit. Instead of refactoring `RecursiveAstVisitor` to support this,
`visitAstChildren` was created. `visitAstChildren` duplicates the
implementation of `RecursiveAstVisitor`, but introduced some bugs along
the way. For example, in `visitKeyedWrite`, it visits
```
obj -> key -> obj
```
instead of
```
obj -> key -> value
```

Moreover, because of the following line
```
visitor.visit && visitor.visit(ast, context) || ast.visit(visitor, context);
```
`visitAstChildren` visits every node *twice*.

PR Close #35619
2020-02-28 07:13:17 -08:00

148 lines
4.4 KiB
TypeScript

/**
* @license
* Copyright Google Inc. 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
*/
import {AbsoluteSourceSpan} from '@angular/compiler';
import * as e from '../../../src/expression_parser/ast';
import * as t from '../../../src/render3/r3_ast';
import {unparse} from '../../expression_parser/utils/unparser';
type HumanizedExpressionSource = [string, AbsoluteSourceSpan];
class ExpressionSourceHumanizer extends e.RecursiveAstVisitor implements t.Visitor {
result: HumanizedExpressionSource[] = [];
private recordAst(ast: e.AST) { this.result.push([unparse(ast), ast.sourceSpan]); }
// This method is defined to reconcile the type of ExpressionSourceHumanizer
// since both RecursiveAstVisitor and Visitor define the visit() method in
// their interfaces.
visit(node: e.AST|t.Node, context?: any) {
if (node instanceof e.AST) {
node.visit(this, context);
} else {
node.visit(this);
}
}
visitASTWithSource(ast: e.ASTWithSource) {
this.recordAst(ast);
this.visitAll([ast.ast], null);
}
visitBinary(ast: e.Binary) {
this.recordAst(ast);
super.visitBinary(ast, null);
}
visitChain(ast: e.Chain) {
this.recordAst(ast);
super.visitChain(ast, null);
}
visitConditional(ast: e.Conditional) {
this.recordAst(ast);
super.visitConditional(ast, null);
}
visitFunctionCall(ast: e.FunctionCall) {
this.recordAst(ast);
super.visitFunctionCall(ast, null);
}
visitImplicitReceiver(ast: e.ImplicitReceiver) {
this.recordAst(ast);
super.visitImplicitReceiver(ast, null);
}
visitInterpolation(ast: e.Interpolation) {
this.recordAst(ast);
super.visitInterpolation(ast, null);
}
visitKeyedRead(ast: e.KeyedRead) {
this.recordAst(ast);
super.visitKeyedRead(ast, null);
}
visitKeyedWrite(ast: e.KeyedWrite) {
this.recordAst(ast);
super.visitKeyedWrite(ast, null);
}
visitLiteralPrimitive(ast: e.LiteralPrimitive) {
this.recordAst(ast);
super.visitLiteralPrimitive(ast, null);
}
visitLiteralArray(ast: e.LiteralArray) {
this.recordAst(ast);
super.visitLiteralArray(ast, null);
}
visitLiteralMap(ast: e.LiteralMap) {
this.recordAst(ast);
super.visitLiteralMap(ast, null);
}
visitMethodCall(ast: e.MethodCall) {
this.recordAst(ast);
super.visitMethodCall(ast, null);
}
visitNonNullAssert(ast: e.NonNullAssert) {
this.recordAst(ast);
super.visitNonNullAssert(ast, null);
}
visitPipe(ast: e.BindingPipe) {
this.recordAst(ast);
super.visitPipe(ast, null);
}
visitPrefixNot(ast: e.PrefixNot) {
this.recordAst(ast);
super.visitPrefixNot(ast, null);
}
visitPropertyRead(ast: e.PropertyRead) {
this.recordAst(ast);
super.visitPropertyRead(ast, null);
}
visitPropertyWrite(ast: e.PropertyWrite) {
this.recordAst(ast);
super.visitPropertyWrite(ast, null);
}
visitSafeMethodCall(ast: e.SafeMethodCall) {
this.recordAst(ast);
super.visitSafeMethodCall(ast, null);
}
visitSafePropertyRead(ast: e.SafePropertyRead) {
this.recordAst(ast);
super.visitSafePropertyRead(ast, null);
}
visitQuote(ast: e.Quote) {
this.recordAst(ast);
super.visitQuote(ast, null);
}
visitTemplate(ast: t.Template) {
t.visitAll(this, ast.children);
t.visitAll(this, ast.templateAttrs);
}
visitElement(ast: t.Element) {
t.visitAll(this, ast.children);
t.visitAll(this, ast.inputs);
t.visitAll(this, ast.outputs);
}
visitReference(ast: t.Reference) {}
visitVariable(ast: t.Variable) {}
visitEvent(ast: t.BoundEvent) { ast.handler.visit(this); }
visitTextAttribute(ast: t.TextAttribute) {}
visitBoundAttribute(ast: t.BoundAttribute) { ast.value.visit(this); }
visitBoundEvent(ast: t.BoundEvent) { ast.handler.visit(this); }
visitBoundText(ast: t.BoundText) { ast.value.visit(this); }
visitContent(ast: t.Content) {}
visitText(ast: t.Text) {}
visitIcu(ast: t.Icu) {}
}
/**
* Humanizes expression AST source spans in a template by returning an array of tuples
* [unparsed AST, AST source span]
* for each expression in the template.
* @param templateAsts template AST to humanize
*/
export function humanizeExpressionSource(templateAsts: t.Node[]): HumanizedExpressionSource[] {
const humanizer = new ExpressionSourceHumanizer();
t.visitAll(humanizer, templateAsts);
return humanizer.result;
}