no-named-as-default-member.js

/**
 * @fileoverview Rule to warn about potentially confused use of name exports
 * @author Desmond Brand
 * @copyright 2016 Desmond Brand. All rights reserved.
 * See LICENSE in root directory for full license.
 */
import Exports from '../ExportMap';
import importDeclaration from '../importDeclaration';
import docsUrl from '../docsUrl';

//------------------------------------------------------------------------------
// Rule Definition
//------------------------------------------------------------------------------

module.exports = {
  meta: {
    type: 'suggestion',
    docs: {
      url: docsUrl('no-named-as-default-member'),
    },
    schema: [],
  },

  create(context) {

    const fileImports = new Map();
    const allPropertyLookups = new Map();

    function handleImportDefault(node) {
      const declaration = importDeclaration(context);
      const exportMap = Exports.get(declaration.source.value, context);
      if (exportMap == null) return;

      if (exportMap.errors.length) {
        exportMap.reportErrors(context, declaration);
        return;
      }

      fileImports.set(node.local.name, {
        exportMap,
        sourcePath: declaration.source.value,
      });
    }

    function storePropertyLookup(objectName, propName, node) {
      const lookups = allPropertyLookups.get(objectName) || [];
      lookups.push({ node, propName });
      allPropertyLookups.set(objectName, lookups);
    }

    function handlePropLookup(node) {
      const objectName = node.object.name;
      const propName = node.property.name;
      storePropertyLookup(objectName, propName, node);
    }

    function handleDestructuringAssignment(node) {
      const isDestructure = (
        node.id.type === 'ObjectPattern' &&
        node.init != null &&
        node.init.type === 'Identifier'
      );
      if (!isDestructure) return;

      const objectName = node.init.name;
      for (const { key } of node.id.properties) {
        if (key == null) continue;  // true for rest properties
        storePropertyLookup(objectName, key.name, key);
      }
    }

    function handleProgramExit() {
      allPropertyLookups.forEach((lookups, objectName) => {
        const fileImport = fileImports.get(objectName);
        if (fileImport == null) return;

        for (const { propName, node } of lookups) {
          // the default import can have a "default" property
          if (propName === 'default') continue;
          if (!fileImport.exportMap.namespace.has(propName)) continue;

          context.report({
            node,
            message: (
              `Caution: \`${objectName}\` also has a named export ` +
              `\`${propName}\`. Check if you meant to write ` +
              `\`import {${propName}} from '${fileImport.sourcePath}'\` ` +
              'instead.'
            ),
          });
        }
      });
    }

    return {
      'ImportDefaultSpecifier': handleImportDefault,
      'MemberExpression': handlePropLookup,
      'VariableDeclarator': handleDestructuringAssignment,
      'Program:exit': handleProgramExit,
    };
  },
};