ast.js

/**
 * @fileoverview Utility functions for AST
 */

'use strict';

const estraverse = require('estraverse');

/**
 * Wrapper for estraverse.traverse
 *
 * @param {ASTNode} ASTnode The AST node being checked
 * @param {Object} visitor Visitor Object for estraverse
 */
function traverse(ASTnode, visitor) {
  const opts = Object.assign({}, {
    fallback(node) {
      return Object.keys(node).filter((key) => key === 'children' || key === 'argument');
    }
  }, visitor);

  opts.keys = Object.assign({}, visitor.keys, {
    JSXElement: ['children'],
    JSXFragment: ['children']
  });

  estraverse.traverse(ASTnode, opts);
}

/**
 * Find a return statment in the current node
 *
 * @param {ASTNode} node The AST node being checked
 * @returns {ASTNode | false}
 */
function findReturnStatement(node) {
  if (
    (!node.value || !node.value.body || !node.value.body.body)
    && (!node.body || !node.body.body)
  ) {
    return false;
  }

  const bodyNodes = (node.value ? node.value.body.body : node.body.body);

  return (function loopNodes(nodes) {
    let i = nodes.length - 1;
    for (; i >= 0; i--) {
      if (nodes[i].type === 'ReturnStatement') {
        return nodes[i];
      }
      if (nodes[i].type === 'SwitchStatement') {
        let j = nodes[i].cases.length - 1;
        for (; j >= 0; j--) {
          return loopNodes(nodes[i].cases[j].consequent);
        }
      }
    }
    return false;
  }(bodyNodes));
}

/**
 * Helper function for traversing "returns" (return statements or the
 * returned expression in the case of an arrow function) of a function
 *
 * @param {ASTNode} ASTNode The AST node being checked
 * @param {function} enterFunc Function to execute for each returnStatement found
 * @returns {undefined}
 */
function traverseReturns(ASTNode, enterFunc) {
  const nodeType = ASTNode.type;

  if (nodeType === 'ReturnStatement') {
    return enterFunc(ASTNode);
  }

  if (nodeType === 'ArrowFunctionExpression' && ASTNode.expression) {
    return enterFunc(ASTNode.body);
  }

  if (nodeType !== 'FunctionExpression'
      && nodeType !== 'FunctionDeclaration'
      && nodeType !== 'ArrowFunctionExpression'
      && nodeType !== 'MethodDefinition'
  ) {
    throw new TypeError('only function nodes are expected');
  }

  traverse(ASTNode.body, {
    enter(node) {
      switch (node.type) {
        case 'ReturnStatement':
          this.skip();
          return enterFunc(node);
        case 'FunctionExpression':
        case 'FunctionDeclaration':
        case 'ArrowFunctionExpression':
          return this.skip();
        default:
      }
    }
  });
}

/**
 * Get node with property's name
 * @param {Object} node - Property.
 * @returns {Object} Property name node.
 */
function getPropertyNameNode(node) {
  if (node.key || ['MethodDefinition', 'Property'].indexOf(node.type) !== -1) {
    return node.key;
  }
  if (node.type === 'MemberExpression') {
    return node.property;
  }
  return null;
}

/**
 * Get properties name
 * @param {Object} node - Property.
 * @returns {String} Property name.
 */
function getPropertyName(node) {
  const nameNode = getPropertyNameNode(node);
  return nameNode ? nameNode.name : '';
}

/**
 * Get properties for a given AST node
 * @param {ASTNode} node The AST node being checked.
 * @returns {Array} Properties array.
 */
function getComponentProperties(node) {
  switch (node.type) {
    case 'ClassDeclaration':
    case 'ClassExpression':
      return node.body.body;
    case 'ObjectExpression':
      return node.properties;
    default:
      return [];
  }
}

/**
 * Gets the first node in a line from the initial node, excluding whitespace.
 * @param {Object} context The node to check
 * @param {ASTNode} node The node to check
 * @return {ASTNode} the first node in the line
 */
function getFirstNodeInLine(context, node) {
  const sourceCode = context.getSourceCode();
  let token = node;
  let lines;
  do {
    token = sourceCode.getTokenBefore(token);
    lines = token.type === 'JSXText'
      ? token.value.split('\n')
      : null;
  } while (
    token.type === 'JSXText'
        && /^\s*$/.test(lines[lines.length - 1])
  );
  return token;
}

/**
 * Checks if the node is the first in its line, excluding whitespace.
 * @param {Object} context The node to check
 * @param {ASTNode} node The node to check
 * @return {Boolean} true if it's the first node in its line
 */
function isNodeFirstInLine(context, node) {
  const token = getFirstNodeInLine(context, node);
  const startLine = node.loc.start.line;
  const endLine = token ? token.loc.end.line : -1;
  return startLine !== endLine;
}

/**
 * Checks if the node is a function or arrow function expression.
 * @param {ASTNode} node The node to check
 * @return {Boolean} true if it's a function-like expression
 */
function isFunctionLikeExpression(node) {
  return node.type === 'FunctionExpression' || node.type === 'ArrowFunctionExpression';
}

/**
 * Checks if the node is a function.
 * @param {ASTNode} node The node to check
 * @return {Boolean} true if it's a function
 */
function isFunction(node) {
  return node.type === 'FunctionExpression' || node.type === 'FunctionDeclaration';
}

/**
 * Checks if the node is a class.
 * @param {ASTNode} node The node to check
 * @return {Boolean} true if it's a class
 */
function isClass(node) {
  return node.type === 'ClassDeclaration' || node.type === 'ClassExpression';
}

/**
 * Removes quotes from around an identifier.
 * @param {string} string the identifier to strip
 * @returns {string}
 */
function stripQuotes(string) {
  return string.replace(/^'|'$/g, '');
}

/**
 * Retrieve the name of a key node
 * @param {Context} context The AST node with the key.
 * @param {ASTNode} node The AST node with the key.
 * @return {string | undefined} the name of the key
 */
function getKeyValue(context, node) {
  if (node.type === 'ObjectTypeProperty') {
    const tokens = context.getFirstTokens(node, 2);
    return (tokens[0].value === '+' || tokens[0].value === '-'
      ? tokens[1].value
      : stripQuotes(tokens[0].value)
    );
  }
  if (node.type === 'GenericTypeAnnotation') {
    return node.id.name;
  }
  if (node.type === 'ObjectTypeAnnotation') {
    return;
  }
  const key = node.key || node.argument;
  if (!key) {
    return;
  }
  return key.type === 'Identifier' ? key.name : key.value;
}

/**
 * Checks if a node is being assigned a value: props.bar = 'bar'
 * @param {ASTNode} node The AST node being checked.
 * @returns {Boolean}
 */
function isAssignmentLHS(node) {
  return (
    node.parent
    && node.parent.type === 'AssignmentExpression'
    && node.parent.left === node
  );
}

/**
 * Extracts the expression node that is wrapped inside a TS type assertion
 *
 * @param {ASTNode} node - potential TS node
 * @returns {ASTNode} - unwrapped expression node
 */
function unwrapTSAsExpression(node) {
  if (node && node.type === 'TSAsExpression') return node.expression;
  return node;
}

function isTSTypeReference(node) {
  if (!node) return false;
  const nodeType = node.type;
  return nodeType === 'TSTypeReference';
}

function isTSTypeAnnotation(node) {
  if (!node) return false;
  const nodeType = node.type;
  return nodeType === 'TSTypeAnnotation';
}

function isTSTypeLiteral(node) {
  if (!node) return false;
  const nodeType = node.type;
  return nodeType === 'TSTypeLiteral';
}

function isTSIntersectionType(node) {
  if (!node) return false;
  const nodeType = node.type;
  return nodeType === 'TSIntersectionType';
}

function isTSInterfaceHeritage(node) {
  if (!node) return false;
  const nodeType = node.type;
  return nodeType === 'TSInterfaceHeritage';
}

function isTSInterfaceDeclaration(node) {
  if (!node) return false;
  const nodeType = node.type;
  return nodeType === 'TSInterfaceDeclaration';
}

function isTSTypeAliasDeclaration(node) {
  if (!node) return false;
  const nodeType = node.type;
  return nodeType === 'TSTypeAliasDeclaration';
}

function isTSParenthesizedType(node) {
  if (!node) return false;
  const nodeType = node.type;
  return nodeType === 'TSTypeAliasDeclaration';
}

function isTSFunctionType(node) {
  if (!node) return false;
  const nodeType = node.type;
  return nodeType === 'TSFunctionType';
}

function isTSTypeQuery(node) {
  if (!node) return false;
  const nodeType = node.type;
  return nodeType === 'TSTypeQuery';
}

function isTSTypeParameterInstantiation(node) {
  if (!node) return false;
  const nodeType = node.type;
  return nodeType === 'TSTypeParameterInstantiation';
}

module.exports = {
  traverse,
  findReturnStatement,
  getFirstNodeInLine,
  getPropertyName,
  getPropertyNameNode,
  getComponentProperties,
  getKeyValue,
  isAssignmentLHS,
  isClass,
  isFunction,
  isFunctionLikeExpression,
  isNodeFirstInLine,
  unwrapTSAsExpression,
  traverseReturns,
  isTSTypeReference,
  isTSTypeAnnotation,
  isTSTypeLiteral,
  isTSIntersectionType,
  isTSInterfaceHeritage,
  isTSInterfaceDeclaration,
  isTSTypeAliasDeclaration,
  isTSParenthesizedType,
  isTSFunctionType,
  isTSTypeQuery,
  isTSTypeParameterInstantiation
};