no-namespace.js

/**
 * @fileoverview Rule to disallow namespace import
 * @author Radek Benkel
 */

import minimatch from 'minimatch';
import docsUrl from '../docsUrl';

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


module.exports = {
  meta: {
    type: 'suggestion',
    docs: {
      url: docsUrl('no-namespace'),
    },
    fixable: 'code',
    schema: [{
      type: 'object',
      properties: {
        ignore: {
          type: 'array',
          items: {
            type: 'string',
          },
          uniqueItems: true,
        },
      },
    }],
  },

  create(context) {
    const firstOption = context.options[0] || {};
    const ignoreGlobs = firstOption.ignore;

    return {
      ImportNamespaceSpecifier(node) {
        if (ignoreGlobs && ignoreGlobs.find(glob => minimatch(node.parent.source.value, glob, { matchBase: true }))) {
          return;
        }

        const scopeVariables = context.getScope().variables;
        const namespaceVariable = scopeVariables.find((variable) => variable.defs[0].node === node);
        const namespaceReferences = namespaceVariable.references;
        const namespaceIdentifiers = namespaceReferences.map(reference => reference.identifier);
        const canFix = namespaceIdentifiers.length > 0 && !usesNamespaceAsObject(namespaceIdentifiers);

        context.report({
          node,
          message: `Unexpected namespace import.`,
          fix: canFix && (fixer => {
            const scopeManager = context.getSourceCode().scopeManager;
            const fixes = [];

            // Pass 1: Collect variable names that are already in scope for each reference we want
            // to transform, so that we can be sure that we choose non-conflicting import names
            const importNameConflicts = {};
            namespaceIdentifiers.forEach((identifier) => {
              const parent = identifier.parent;
              if (parent && parent.type === 'MemberExpression') {
                const importName = getMemberPropertyName(parent);
                const localConflicts = getVariableNamesInScope(scopeManager, parent);
                if (!importNameConflicts[importName]) {
                  importNameConflicts[importName] = localConflicts;
                } else {
                  localConflicts.forEach((c) => importNameConflicts[importName].add(c));
                }
              }
            });

            // Choose new names for each import
            const importNames = Object.keys(importNameConflicts);
            const importLocalNames = generateLocalNames(
              importNames,
              importNameConflicts,
              namespaceVariable.name,
            );

            // Replace the ImportNamespaceSpecifier with a list of ImportSpecifiers
            const namedImportSpecifiers = importNames.map((importName) => (
              importName === importLocalNames[importName]
                ? importName
                : `${importName} as ${importLocalNames[importName]}`
            ));
            fixes.push(fixer.replaceText(node, `{ ${namedImportSpecifiers.join(', ')} }`));

            // Pass 2: Replace references to the namespace with references to the named imports
            namespaceIdentifiers.forEach((identifier) => {
              const parent = identifier.parent;
              if (parent && parent.type === 'MemberExpression') {
                const importName = getMemberPropertyName(parent);
                fixes.push(fixer.replaceText(parent, importLocalNames[importName]));
              }
            });

            return fixes;
          }),
        });
      },
    };
  },
};

/**
 * @param {Identifier[]} namespaceIdentifiers
 * @returns {boolean} `true` if the namespace variable is more than just a glorified constant
 */
function usesNamespaceAsObject(namespaceIdentifiers) {
  return !namespaceIdentifiers.every((identifier) => {
    const parent = identifier.parent;

    // `namespace.x` or `namespace['x']`
    return (
      parent && parent.type === 'MemberExpression' &&
      (parent.property.type === 'Identifier' || parent.property.type === 'Literal')
    );
  });
}

/**
 * @param {MemberExpression} memberExpression
 * @returns {string} the name of the member in the object expression, e.g. the `x` in `namespace.x`
 */
function getMemberPropertyName(memberExpression) {
  return memberExpression.property.type === 'Identifier'
    ? memberExpression.property.name
    : memberExpression.property.value;
}

/**
 * @param {ScopeManager} scopeManager
 * @param {ASTNode} node
 * @return {Set<string>}
 */
function getVariableNamesInScope(scopeManager, node) {
  let currentNode = node;
  let scope = scopeManager.acquire(currentNode);
  while (scope == null) {
    currentNode = currentNode.parent;
    scope = scopeManager.acquire(currentNode, true);
  }
  return new Set([
    ...scope.variables.map(variable => variable.name),
    ...scope.upper.variables.map(variable => variable.name),
  ]);
}

/**
 *
 * @param {*} names
 * @param {*} nameConflicts
 * @param {*} namespaceName
 */
function generateLocalNames(names, nameConflicts, namespaceName) {
  const localNames = {};
  names.forEach((name) => {
    let localName;
    if (!nameConflicts[name].has(name)) {
      localName = name;
    } else if (!nameConflicts[name].has(`${namespaceName}_${name}`)) {
      localName = `${namespaceName}_${name}`;
    } else {
      for (let i = 1; i < Infinity; i++) {
        if (!nameConflicts[name].has(`${namespaceName}_${name}_${i}`)) {
          localName = `${namespaceName}_${name}_${i}`;
          break;
        }
      }
    }
    localNames[name] = localName;
  });
  return localNames;
}