react-native-devtools-frontend/front_end/entrypoints/formatter_worker/JavaScriptOutline.ts

// Copyright 2016 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

import * as Platform from '../../core/platform/platform.js';
import * as TextUtils from '../../models/text_utils/text_utils.js';
import * as AcornLoose from '../../third_party/acorn-loose/acorn-loose.js';
import * as Acorn from '../../third_party/acorn/acorn.js';

import {ECMA_VERSION} from './AcornTokenizer.js';
import {ESTreeWalker} from './ESTreeWalker.js';
import type {ChunkCallback} from './FormatterWorker.js';

export interface Item {
  title: string;
  subtitle?: string;
  line: number;
  column: number;
}

export function javaScriptOutline(content: string, chunkCallback: ChunkCallback): void {
  const chunkSize = 100000;
  let chunk: Item[] = [];
  let lastReportedOffset = 0;

  let ast;
  try {
    ast = Acorn.parse(content, {ecmaVersion: ECMA_VERSION, ranges: false});
  } catch (e) {
    ast = AcornLoose.AcornLoose.parse(content, {ecmaVersion: ECMA_VERSION, ranges: false});
  }

  const contentLineEndings = Platform.StringUtilities.findLineEndingIndexes(content);
  const textCursor = new TextUtils.TextCursor.TextCursor(contentLineEndings);
  const walker = new ESTreeWalker(beforeVisit);

  // @ts-ignore Technically, the acorn Node type is a subclass of Acorn.ESTree.Node.
  // However, the acorn package currently exports its type without specifying
  // this relationship. So while this is allowed on runtime, we can't properly
  // typecheck it.
  walker.walk(ast);

  chunkCallback({chunk, isLastChunk: true});

  function beforeVisit(node: Acorn.ESTree.Node): undefined {
    if (node.type === 'ClassDeclaration') {
      reportClass((node.id as Acorn.ESTree.Node));
    } else if (node.type === 'VariableDeclarator' && node.init && isClassNode(node.init)) {
      reportClass((node.id as Acorn.ESTree.Node));
    } else if (node.type === 'AssignmentExpression' && isNameNode(node.left) && isClassNode(node.right)) {
      reportClass((node.left as Acorn.ESTree.Node));
    } else if (node.type === 'Property' && isNameNode(node.key) && isClassNode(node.value)) {
      reportClass((node.key as Acorn.ESTree.Node));
    } else if (node.type === 'FunctionDeclaration') {
      reportFunction((node.id as Acorn.ESTree.Node), node);
    } else if (node.type === 'VariableDeclarator' && node.init && isFunctionNode(node.init)) {
      reportFunction((node.id as Acorn.ESTree.Node), (node.init as Acorn.ESTree.Node));
    } else if (node.type === 'AssignmentExpression' && isNameNode(node.left) && isFunctionNode(node.right)) {
      reportFunction((node.left as Acorn.ESTree.Node), (node.right as Acorn.ESTree.Node));
    } else if (
        (node.type === 'MethodDefinition' || node.type === 'Property') && isNameNode(node.key) &&
        isFunctionNode(node.value)) {
      const namePrefix = [];
      if (node.kind === 'get' || node.kind === 'set') {
        namePrefix.push(node.kind);
      }
      if ('static' in node && node.static) {
        namePrefix.push('static');
      }
      reportFunction((node.key as Acorn.ESTree.Node), node.value, namePrefix.join(' '));
    }

    return undefined;
  }

  function reportClass(nameNode: Acorn.ESTree.Node): void {
    const name = 'class ' + stringifyNameNode(nameNode);
    textCursor.advance(nameNode.start);
    addOutlineItem(name);
  }

  function reportFunction(nameNode: Acorn.ESTree.Node, functionNode: Acorn.ESTree.Node, namePrefix?: string): void {
    let name = stringifyNameNode(nameNode);
    const functionDeclarationNode = (functionNode as Acorn.ESTree.FunctionDeclaration);
    if (functionDeclarationNode.generator) {
      name = '*' + name;
    }
    if (namePrefix) {
      name = namePrefix + ' ' + name;
    }
    if (functionDeclarationNode.async) {
      name = 'async ' + name;
    }

    textCursor.advance(nameNode.start);
    addOutlineItem(name, stringifyArguments((functionDeclarationNode.params as Acorn.ESTree.Node[])));
  }

  function isNameNode(node: Acorn.ESTree.Node): boolean {
    if (!node) {
      return false;
    }
    if (node.type === 'MemberExpression') {
      return !node.computed && node.property.type === 'Identifier';
    }
    return node.type === 'Identifier';
  }

  function isFunctionNode(node: Acorn.ESTree.Node): boolean {
    if (!node) {
      return false;
    }
    return node.type === 'FunctionExpression' || node.type === 'ArrowFunctionExpression';
  }

  function isClassNode(node: Acorn.ESTree.Node): boolean {
    return node !== undefined && node.type === 'ClassExpression';
  }

  function stringifyNameNode(node: Acorn.ESTree.Node): string {
    if (node.type === 'MemberExpression') {
      node = (node.property as Acorn.ESTree.Node);
    }
    console.assert(node.type === 'Identifier', 'Cannot extract identifier from unknown type: ' + node.type);
    const identifier = (node as Acorn.ESTree.Identifier);
    return identifier.name;
  }

  function stringifyArguments(params: Acorn.ESTree.Node[]): string {
    const result = [];
    for (const param of params) {
      if (param.type === 'Identifier') {
        result.push(param.name);
      } else if (param.type === 'RestElement' && param.argument.type === 'Identifier') {
        result.push('...' + param.argument.name);
      } else {
        console.error('Error: unexpected function parameter type: ' + param.type);
      }
    }
    return '(' + result.join(', ') + ')';
  }

  function addOutlineItem(title: string, subtitle?: string): void {
    const line = textCursor.lineNumber();
    const column = textCursor.columnNumber();
    chunk.push({title, subtitle, line, column});
    if (textCursor.offset() - lastReportedOffset >= chunkSize) {
      chunkCallback({chunk, isLastChunk: false});
      chunk = [];
      lastReportedOffset = textCursor.offset();
    }
  }
}