feat(eslint-plugin): add consistent-indexed-object-style rule (typescript-eslint#2401)

remcohaszing · web-flow · commit d7dc108580cd · 2020-09-28T11:22:29.000-07:00
diff --git a/packages/eslint-plugin/README.md b/packages/eslint-plugin/README.md
@@ -104,6 +104,7 @@ Pro Tip: For larger codebases you may want to consider splitting our linting int
 | [`@typescript-eslint/ban-tslint-comment`](./docs/rules/ban-tslint-comment.md)                                         | Bans `// tslint:<rule-flag>` comments from being used                                                                   |                    | :wrench: |                   |
 | [`@typescript-eslint/ban-types`](./docs/rules/ban-types.md)                                                           | Bans specific types from being used                                                                                     | :heavy_check_mark: | :wrench: |                   |
 | [`@typescript-eslint/class-literal-property-style`](./docs/rules/class-literal-property-style.md)                     | Ensures that literals on classes are exposed in a consistent style                                                      |                    | :wrench: |                   |
+| [`@typescript-eslint/consistent-indexed-object-style`](./docs/rules/consistent-indexed-object-style.md)               | Enforce or disallow the use of the record type                                                                          |                    | :wrench: |                   |
 | [`@typescript-eslint/consistent-type-assertions`](./docs/rules/consistent-type-assertions.md)                         | Enforces consistent usage of type assertions                                                                            |                    |          |                   |
 | [`@typescript-eslint/consistent-type-definitions`](./docs/rules/consistent-type-definitions.md)                       | Consistent with type definition either `interface` or `type`                                                            |                    | :wrench: |                   |
 | [`@typescript-eslint/consistent-type-imports`](./docs/rules/consistent-type-imports.md)                               | Enforces consistent usage of type imports                                                                               |                    | :wrench: |                   |
diff --git a/packages/eslint-plugin/docs/rules/consistent-indexed-object-style.md b/packages/eslint-plugin/docs/rules/consistent-indexed-object-style.md
@@ -0,0 +1,67 @@
+# Enforce or disallow the use of the record type (`consistent-indexed-object-style`)
+
+TypeScript supports defining object show keys can be flexible using an index signature. TypeScript also has a builtin type named `Record` to create an empty object defining only an index signature. For example, the following types are equal:
+
+```ts
+interface Foo {
+  [key: string]: unknown;
+}
+
+type Foo = {
+  [key: string]: unknown;
+};
+
+type Foo = Record<string, unknown>;
+```
+
+## Options
+
+- `"record"`: Set to `"record"` to only allow the `Record` type. Set to `"index-signature"` to only allow index signatures. (Defaults to `"record"`)
+
+For example:
+
+```CJSON
+{
+    "@typescript-eslint/consistent-type-definitions": ["error", "index-signature"]
+}
+```
+
+## Rule details
+
+This rule enforces a consistent way to define records.
+
+Examples of **incorrect** code with `record` option.
+
+```ts
+interface Foo {
+  [key: string]: unknown;
+}
+
+type Foo = {
+  [key: string]: unknown;
+};
+```
+
+Examples of **correct** code with `record` option.
+
+```ts
+type Foo = Record<string, unknown>;
+```
+
+Examples of **incorrect** code with `index-signature` option.
+
+```ts
+type Foo = Record<string, unknown>;
+```
+
+Examples of **correct** code with `index-signature` option.
+
+```ts
+interface Foo {
+  [key: string]: unknown;
+}
+
+type Foo = {
+  [key: string]: unknown;
+};
+```
diff --git a/packages/eslint-plugin/src/configs/all.ts b/packages/eslint-plugin/src/configs/all.ts
@@ -16,6 +16,7 @@ export = {
     '@typescript-eslint/class-literal-property-style': 'error',
     'comma-spacing': 'off',
     '@typescript-eslint/comma-spacing': 'error',
+    '@typescript-eslint/consistent-indexed-object-style': 'error',
     '@typescript-eslint/consistent-type-assertions': 'error',
     '@typescript-eslint/consistent-type-definitions': 'error',
     '@typescript-eslint/consistent-type-imports': 'error',
diff --git a/packages/eslint-plugin/src/rules/consistent-indexed-object-style.ts b/packages/eslint-plugin/src/rules/consistent-indexed-object-style.ts
@@ -0,0 +1,122 @@
+import { createRule } from '../util';
+import {
+  AST_NODE_TYPES,
+  TSESTree,
+} from '@typescript-eslint/experimental-utils';
+
+type MessageIds = 'preferRecord' | 'preferIndexSignature';
+type Options = ['record' | 'index-signature'];
+
+export default createRule<Options, MessageIds>({
+  name: 'consistent-indexed-object-style',
+  meta: {
+    type: 'suggestion',
+    docs: {
+      description: 'Enforce or disallow the use of the record type',
+      category: 'Stylistic Issues',
+      // too opinionated to be recommended
+      recommended: false,
+    },
+    messages: {
+      preferRecord: 'A record is preferred over an index signature',
+      preferIndexSignature: 'An index signature is preferred over a record.',
+    },
+    fixable: 'code',
+    schema: [
+      {
+        enum: ['record', 'index-signature'],
+      },
+    ],
+  },
+  defaultOptions: ['record'],
+  create(context) {
+    const sourceCode = context.getSourceCode();
+
+    if (context.options[0] === 'index-signature') {
+      return {
+        TSTypeReference(node): void {
+          const typeName = node.typeName;
+          if (typeName.type !== AST_NODE_TYPES.Identifier) {
+            return;
+          }
+          if (typeName.name !== 'Record') {
+            return;
+          }
+
+          const params = node.typeParameters?.params;
+          if (params?.length !== 2) {
+            return;
+          }
+
+          context.report({
+            node,
+            messageId: 'preferIndexSignature',
+            fix(fixer) {
+              const key = sourceCode.getText(params[0]);
+              const type = sourceCode.getText(params[1]);
+              return fixer.replaceText(node, `{ [key: ${key}]: ${type} }`);
+            },
+          });
+        },
+      };
+    }
+
+    function checkMembers(
+      members: TSESTree.TypeElement[],
+      node: TSESTree.Node,
+      prefix: string,
+      postfix: string,
+    ): void {
+      if (members.length !== 1) {
+        return;
+      }
+      const [member] = members;
+
+      if (member.type !== AST_NODE_TYPES.TSIndexSignature) {
+        return;
+      }
+
+      const [parameter] = member.parameters;
+
+      if (!parameter) {
+        return;
+      }
+
+      if (parameter.type !== AST_NODE_TYPES.Identifier) {
+        return;
+      }
+      const keyType = parameter.typeAnnotation;
+      if (!keyType) {
+        return;
+      }
+
+      const valueType = member.typeAnnotation;
+      if (!valueType) {
+        return;
+      }
+
+      context.report({
+        node,
+        messageId: 'preferRecord',
+        fix(fixer) {
+          const key = sourceCode.getText(keyType.typeAnnotation);
+          const value = sourceCode.getText(valueType.typeAnnotation);
+          return fixer.replaceText(
+            node,
+            `${prefix}Record<${key}, ${value}>${postfix}`,
+          );
+        },
+      });
+    }
+
+    return {
+      TSTypeLiteral(node): void {
+        checkMembers(node.members, node, '', '');
+      },
+
+      TSInterfaceDeclaration(node): void {
+        checkMembers(node.body.body, node, `type ${node.id.name} = `, ';');
+      },
+    };
+  },
+});
diff --git a/packages/eslint-plugin/src/rules/index.ts b/packages/eslint-plugin/src/rules/index.ts
@@ -9,6 +9,7 @@ import classLiteralPropertyStyle from './class-literal-property-style';
 import commaDangle from './comma-dangle';
 import commaSpacing from './comma-spacing';
 import confusingNonNullAssertionLikeNotEqual from './no-confusing-non-null-assertion';
+import consistentIndexedObjectStyle from './consistent-indexed-object-style';
 import consistentTypeAssertions from './consistent-type-assertions';
 import consistentTypeDefinitions from './consistent-type-definitions';
 import consistentTypeImports from './consistent-type-imports';
@@ -117,6 +118,7 @@ export default {
   'class-literal-property-style': classLiteralPropertyStyle,
   'comma-dangle': commaDangle,
   'comma-spacing': commaSpacing,
+  'consistent-indexed-object-style': consistentIndexedObjectStyle,
   'consistent-type-assertions': consistentTypeAssertions,
   'consistent-type-definitions': consistentTypeDefinitions,
   'consistent-type-imports': consistentTypeImports,
diff --git a/packages/eslint-plugin/tests/rules/consistent-indexed-object-style.test.ts b/packages/eslint-plugin/tests/rules/consistent-indexed-object-style.test.ts
