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在DART中有没有任何方法可以在预订单、后订单或无序中遍历AST?

dart-analyzer dart

Shubham Kumar · 技术社区 · 7 年前

是否有任何方法来遍历由DART分析器按预序、后序或无序组成的AST。我正在使用访问节点使用generalingastvisitor来遍历AST树,但它只是从代码的顶部到底部递归地遍历它。

import'package:analyzer/src/generated/testing/element_factory.dart';
import 'package:analyzer/analyzer.dart';
import 'dart:io';
import 'package:analyzer/dart/ast/ast.dart';
import 'package:analyzer/dart/ast/token.dart';
import 'package:analyzer/dart/ast/visitor.dart';
import 'package:analyzer/dart/element/element.dart';
import 'package:analyzer/file_system/physical_file_system.dart';
import 'package:analyzer/src/context/builder.dart';
import 'package:analyzer/src/dart/sdk/sdk.dart';
import 'package:analyzer/src/generated/engine.dart';
import 'package:analyzer/src/generated/sdk.dart' show DartSdk;
import 'package:analyzer/src/generated/source.dart';
import 'package:analyzer/src/generated/source_io.dart';
import 'package:analyzer/src/source/source_resource.dart';

main() {
  LibraryElement libElement;
  Source source;
  AnalysisContext context;
  var ast = parseCompilationUnit(src,
      parseFunctionBodies: true, suppressErrors: true);
  print(ast.toSource());
  PhysicalResourceProvider resourceProvider = PhysicalResourceProvider.INSTANCE;
  DartSdk sdk = new FolderBasedDartSdk(resourceProvider,
      resourceProvider.getFolder("/usr/local/opt/dart/libexec"));

  var resolvers = [
    new DartUriResolver(sdk),
  ];
  context = AnalysisEngine.instance.createAnalysisContext()
    ..sourceFactory = new SourceFactory(resolvers);
  source = new FileSource(resourceProvider.getFile(
      "/Users/shubhamkumar/Sites/projects/flutterX/dart_analyser/demo.dart"));
  ChangeSet changeSet = new ChangeSet()..addedSource(source);
  context.applyChanges(changeSet);

  libElement = context.computeLibraryElement(source);
  callAST(context, source, libElement);
}

class Visitor1 extends GeneralizingAstVisitor {
  @override
  visitNode(AstNode node) {
    print("node $node ${node.runtimeType}   ");
    node.childEntities.forEach((n) => print(n));
    return super.visitNode(node);
  }
}

callAST(context, source, libElement) {
  CompilationUnit resolvedUnit =
      context.resolveCompilationUnit(source, libElement);
  var visitor = new Visitor1();
  resolvedUnit.accept(visitor);
}

如果你有任何解决办法,请帮忙。

1 回复 | 直到 7 年前

Mike Fairhurst 7 年前

generalingastvisitor所做的模式是预排序。

顺序遍历在AST上下文中没有意义。按顺序,遍历是左、根、右。但是一个AST分支可以有1到无穷大的子级。因此,最好是按顺序(n)定义一些遍历,在这里您访问第一个孩子、第二个孩子……第n个子级,根级,第n+1子级,第n+2子级…我看不出这样做的目的。

对于后期订单来说,它有点微妙。如果您只想打印节点及其子实体,那么您的解决方案很简单。你只要打电话给超级之前打印节点:

class Visitor2 extends GeneralizingAstVisitor {
  @override
  visitNode(AstNode node) {
    final val = super.visitNode(node);
    print("node $node ${node.runtimeType}   ");
    node.childEntities.forEach((n) => print(n));
    return val;
  }
}

但是,如果您想要为一系列节点类型定制逻辑,则必须在每个访问处理程序中遵循该模式:

class Visitor3 extends GeneralizingAstVisitor {
  @override
  visitAssignmentExpression(AssignmentExpression node) {
    final val = super.visitNode(node);
    // use assignment expression here
    return val;
  }
  @override
  visitBinaryExpression(BinaryExpression node) {
    final val = super.visitNode(node);
    // use binary expression here
    return val;
  }
  // ... more handlers
}

在这种情况下,我会组织访客,使这更容易:

class PostOrderVisitor extends GeneralizingAstVisitor {
  AstVisitor postOrderedVisitor = new Visitor4();
  @override
  visitNode(AstNode node) {
    final val = super.visitNode(node);
    return node.accept(postOrderedVisitor);
  }
}

class Visitor4 extends AstVisitor {
  @override
  visitAssignmentExpression(AssignmentExpression node) {
    // use assignment expression here
  }
  @override
  visitBinaryExpression(BinaryExpression node) {
    // use binary expression here
  }
  // ... more handlers
}

在这种情况下, PostOrderVisitor 处理后期排序,以及 Visitor4 按照该顺序处理单个节点,但不应执行任何递归本身。

对于大多数用例来说,这些应该能够帮助您度过难关,尽管在不知道您要做什么的情况下很难确定。