chore(prefer-to-have-length): convert to typescript (#396)

src/rules/__tests__/prefer-to-have-length.test.js → src/rules/__tests__/prefer-to-have-length.test.ts

@@ -1,19 +1,31 @@
-import { RuleTester } from 'eslint';
+import { TSESLint } from '@typescript-eslint/experimental-utils';
 import rule from '../prefer-to-have-length';
 
-const ruleTester = new RuleTester();
+const ruleTester = new TSESLint.RuleTester({
+  parserOptions: {
+    ecmaVersion: 2015,
+  },
+});
 
 ruleTester.run('prefer-to-have-length', rule, {
   valid: [
     'expect(files).toHaveLength(1);',
     "expect(files.name).toBe('file');",
+    "expect(files[`name`]).toBe('file');",
     'expect(result).toBe(true);',
     `expect(user.getUserName(5)).resolves.toEqual('Paul')`,
     `expect(user.getUserName(5)).rejects.toEqual('Paul')`,
     'expect(a);',
+    'expect(files["length"]).toBe(1);',
   ],
 
   invalid: [
+    // todo: support this
+    // {
+    //   code: 'expect(files["length"]).toBe(1);',
+    //   errors: [{ messageId: 'useToHaveLength', column: 22, line: 1 }],
+    //   output: 'expect(files).toHaveLength(1);',
+    // },
     {
       code: 'expect(files.length).toBe(1);',
       errors: [{ messageId: 'useToHaveLength', column: 22, line: 1 }],

src/rules/prefer-to-have-length.ts

@@ -0,0 +1,80 @@
+import { AST_NODE_TYPES } from '@typescript-eslint/experimental-utils';
+import {
+  createRule,
+  isExpectCall,
+  isParsedEqualityMatcherCall,
+  isSupportedAccessor,
+  parseExpectCall,
+} from './tsUtils';
+
+export default createRule({
+  name: __filename,
+  meta: {
+    docs: {
+      category: 'Best Practices',
+      description: 'Suggest using `toHaveLength()`',
+      recommended: false,
+    },
+    messages: {
+      useToHaveLength: 'Use toHaveLength() instead',
+    },
+    fixable: 'code',
+    type: 'suggestion',
+    schema: [],
+  },
+  defaultOptions: [],
+  create(context) {
+    return {
+      CallExpression(node) {
+        if (!isExpectCall(node)) {
+          return;
+        }
+
+        const {
+          expect: {
+            arguments: [argument],
+          },
+          matcher,
+        } = parseExpectCall(node);
+
+        if (
+          !matcher ||
+          !isParsedEqualityMatcherCall(matcher) ||
+          !argument ||
+          argument.type !== AST_NODE_TYPES.MemberExpression ||
+          !isSupportedAccessor(argument.property, 'length') ||
+          argument.property.type !== AST_NODE_TYPES.Identifier
+        ) {
+          return;
+        }
+
+        context.report({
+          fix(fixer) {
+            const propertyDot = context
+              .getSourceCode()
+              .getFirstTokenBetween(
+                argument.object,
+                argument.property,
+                token => token.value === '.',
+              );
+
+            /* istanbul ignore next */
+            if (propertyDot === null) {
+              throw new Error(
+                `Unexpected null when attempting to fix ${context.getFilename()} - please file a github issue at https://github.com/jest-community/eslint-plugin-jest`,
+              );
+            }
+
+            return [
+              fixer.remove(propertyDot),
+              fixer.remove(argument.property),
+              fixer.replaceText(matcher.node.property, 'toHaveLength'),
+            ];
+          },
+          messageId: 'useToHaveLength',
+          node: matcher.node.property,
+        });
+      },
+    };
+  },
+});