parse-postprocess.js

"use strict";

const {
  getLast,
  getNextNonSpaceNonCommentCharacter,
  getShebang,
} = require("../common/util");
const createError = require("../common/parser-create-error");
const { composeLoc, locStart, locEnd } = require("./loc");
const { isTypeCastComment } = require("./comments");

function postprocess(ast, options) {
  if (
    options.parser === "typescript" ||
    options.parser === "flow" ||
    options.parser === "espree"
  ) {
    includeShebang(ast, options);
  }

  // Invalid decorators are removed since `@typescript-eslint/typescript-estree` v4
  // https://github.com/typescript-eslint/typescript-eslint/pull/2375
  if (options.parser === "typescript" && options.originalText.includes("@")) {
    const {
      esTreeNodeToTSNodeMap,
      tsNodeToESTreeNodeMap,
    } = options.tsParseResult;
    ast = visitNode(ast, (node) => {
      const tsNode = esTreeNodeToTSNodeMap.get(node);
      if (!tsNode) {
        return;
      }
      const tsDecorators = tsNode.decorators;
      if (!Array.isArray(tsDecorators)) {
        return;
      }
      // `esTreeNodeToTSNodeMap.get(ClassBody)` and `esTreeNodeToTSNodeMap.get(ClassDeclaration)` has the same tsNode
      const esTreeNode = tsNodeToESTreeNodeMap.get(tsNode);
      if (esTreeNode !== node) {
        return;
      }
      const esTreeDecorators = esTreeNode.decorators;
      if (
        !Array.isArray(esTreeDecorators) ||
        esTreeDecorators.length !== tsDecorators.length ||
        tsDecorators.some((tsDecorator) => {
          const esTreeDecorator = tsNodeToESTreeNodeMap.get(tsDecorator);
          return (
            !esTreeDecorator || !esTreeDecorators.includes(esTreeDecorator)
          );
        })
      ) {
        const { start, end } = esTreeNode.loc;
        throw createError(
          "Leading decorators must be attached to a class declaration",
          {
            start: { line: start.line, column: start.column + 1 },
            end: { line: end.line, column: end.column + 1 },
          }
        );
      }
    });
  }

  // Keep Babel's non-standard ParenthesizedExpression nodes only if they have Closure-style type cast comments.
  if (
    options.parser !== "typescript" &&
    options.parser !== "flow" &&
    options.parser !== "espree" &&
    options.parser !== "meriyah"
  ) {
    const startOffsetsOfTypeCastedNodes = new Set();

    // Comments might be attached not directly to ParenthesizedExpression but to its ancestor.
    // E.g.: /** @type {Foo} */ (foo).bar();
    // Let's use the fact that those ancestors and ParenthesizedExpression have the same start offset.

    ast = visitNode(ast, (node) => {
      if (
        node.leadingComments &&
        node.leadingComments.some(isTypeCastComment)
      ) {
        startOffsetsOfTypeCastedNodes.add(locStart(node));
      }
    });

    ast = visitNode(ast, (node) => {
      if (node.type === "ParenthesizedExpression") {
        const { expression } = node;

        // Align range with `flow`
        if (expression.type === "TypeCastExpression") {
          expression.range = node.range;
          return expression;
        }

        const start = locStart(node);
        if (!startOffsetsOfTypeCastedNodes.has(start)) {
          if (!expression.extra) {
            expression.extra = {};
          }
          expression.extra.parenthesized = true;
          expression.extra.parenStart = start;
          return expression;
        }
      }
    });
  }

  ast = visitNode(ast, (node) => {
    switch (node.type) {
      // Espree
      case "ChainExpression": {
        return transformChainExpression(node.expression);
      }
      case "LogicalExpression": {
        // We remove unneeded parens around same-operator LogicalExpressions
        if (isUnbalancedLogicalTree(node)) {
          return rebalanceLogicalTree(node);
        }
        break;
      }
      // fix unexpected locEnd caused by --no-semi style
      case "VariableDeclaration": {
        const lastDeclaration = getLast(node.declarations);
        if (lastDeclaration && lastDeclaration.init) {
          overrideLocEnd(node, lastDeclaration);
        }
        break;
      }
      // remove redundant TypeScript nodes
      case "TSParenthesizedType": {
        node.typeAnnotation.range = composeLoc(node);
        return node.typeAnnotation;
      }
      case "TSUnionType":
      case "TSIntersectionType":
        if (node.types.length === 1) {
          const [firstType] = node.types;
          // override loc, so that comments are attached properly
          firstType.range = composeLoc(node);
          return firstType;
        }
        break;
      case "TSTypeParameter":
        // babel-ts
        if (typeof node.name === "string") {
          node.name = {
            type: "Identifier",
            name: node.name,
            range: composeLoc(node, node.name.length),
          };
        }
        break;
      case "SequenceExpression": {
        // Babel (unlike other parsers) includes spaces and comments in the range. Let's unify this.
        const lastExpression = getLast(node.expressions);
        if (locEnd(node) > locEnd(lastExpression)) {
          node.range = composeLoc(node, lastExpression);
        }
        break;
      }
      case "ClassProperty":
        // TODO: Temporary auto-generated node type. To remove when typescript-estree has proper support for private fields.
        if (
          node.key &&
          node.key.type === "TSPrivateIdentifier" &&
          getNextNonSpaceNonCommentCharacter(
            options.originalText,
            node.key,
            locEnd
          ) === "?"
        ) {
          node.optional = true;
        }
        break;
    }
  });

  return ast;

  /**
   * - `toOverrideNode` must be the last thing in `toBeOverriddenNode`
   * - do nothing if there's a semicolon on `toOverrideNode.end` (no need to fix)
   */
  function overrideLocEnd(toBeOverriddenNode, toOverrideNode) {
    if (options.originalText[locEnd(toOverrideNode)] === ";") {
      return;
    }
    toBeOverriddenNode.range = composeLoc(toBeOverriddenNode, toOverrideNode);
  }
}

// This is a workaround to transform `ChainExpression` from `espree`, `meriyah`,
// and `typescript` into `babel` shape AST, we should do the opposite,
// since `ChainExpression` is the standard `estree` AST for `optional chaining`
// https://github.com/estree/estree/blob/master/es2020.md
function transformChainExpression(node) {
  if (node.type === "CallExpression") {
    node.type = "OptionalCallExpression";
    node.callee = transformChainExpression(node.callee);
  } else if (node.type === "MemberExpression") {
    node.type = "OptionalMemberExpression";
    node.object = transformChainExpression(node.object);
  }
  // typescript
  else if (node.type === "TSNonNullExpression") {
    node.expression = transformChainExpression(node.expression);
  }
  return node;
}

function visitNode(node, fn) {
  let entries;

  if (Array.isArray(node)) {
    entries = node.entries();
  } else if (
    node &&
    typeof node === "object" &&
    typeof node.type === "string"
  ) {
    entries = Object.entries(node);
  } else {
    return node;
  }

  for (const [key, child] of entries) {
    node[key] = visitNode(child, fn);
  }

  if (Array.isArray(node)) {
    return node;
  }

  return fn(node) || node;
}

function isUnbalancedLogicalTree(node) {
  return (
    node.type === "LogicalExpression" &&
    node.right.type === "LogicalExpression" &&
    node.operator === node.right.operator
  );
}

function rebalanceLogicalTree(node) {
  if (!isUnbalancedLogicalTree(node)) {
    return node;
  }

  return rebalanceLogicalTree({
    type: "LogicalExpression",
    operator: node.operator,
    left: rebalanceLogicalTree({
      type: "LogicalExpression",
      operator: node.operator,
      left: node.left,
      right: node.right.left,
      range: composeLoc(node.left, node.right.left),
    }),
    right: node.right.right,
    range: composeLoc(node),
  });
}

function includeShebang(ast, options) {
  const shebang = getShebang(options.originalText);

  if (shebang) {
    ast.comments.unshift({
      type: "Line",
      value: shebang.slice(2),
      range: [0, shebang.length],
    });
  }
}

module.exports = postprocess;