feat(eslint-plugin): add consistent-type-definitions rule (#463)

Deprecates `prefer-interface`

packages/eslint-plugin/README.md

@@ -131,6 +131,7 @@ Then you should add `airbnb` (or `airbnb-base`) to your `extends` section of `.e
 | [`@typescript-eslint/ban-types`](./docs/rules/ban-types.md)                                               | Enforces that types will not to be used                                                                                                             | :heavy_check_mark: | :wrench: |                   |
 | [`@typescript-eslint/camelcase`](./docs/rules/camelcase.md)                                               | Enforce camelCase naming convention                                                                                                                 | :heavy_check_mark: |          |                   |
 | [`@typescript-eslint/class-name-casing`](./docs/rules/class-name-casing.md)                               | Require PascalCased class and interface names                                                                                                       | :heavy_check_mark: |          |                   |
+| [`@typescript-eslint/consistent-type-definitions`](./docs/rules/consistent-type-definitions.md)           | Consistent with type definition either `interface` or `type`                                                                                        | :heavy_check_mark: | :wrench: |                   |
 | [`@typescript-eslint/explicit-function-return-type`](./docs/rules/explicit-function-return-type.md)       | Require explicit return types on functions and class methods                                                                                        | :heavy_check_mark: |          |                   |
 | [`@typescript-eslint/explicit-member-accessibility`](./docs/rules/explicit-member-accessibility.md)       | Require explicit accessibility modifiers on class properties and methods                                                                            | :heavy_check_mark: |          |                   |
 | [`@typescript-eslint/func-call-spacing`](./docs/rules/func-call-spacing.md)                               | Require or disallow spacing between function identifiers and their invocations                                                                      |                    | :wrench: |                   |
@@ -169,7 +170,6 @@ Then you should add `airbnb` (or `airbnb-base`) to your `extends` section of `.e
 | [`@typescript-eslint/prefer-for-of`](./docs/rules/prefer-for-of.md)                                       | Prefer a ‘for-of’ loop over a standard ‘for’ loop if the index is only used to access the array being iterated                                      |                    |          |                   |
 | [`@typescript-eslint/prefer-function-type`](./docs/rules/prefer-function-type.md)                         | Use function types instead of interfaces with call signatures                                                                                       |                    | :wrench: |                   |
 | [`@typescript-eslint/prefer-includes`](./docs/rules/prefer-includes.md)                                   | Enforce `includes` method over `indexOf` method                                                                                                     |                    | :wrench: | :thought_balloon: |
-| [`@typescript-eslint/prefer-interface`](./docs/rules/prefer-interface.md)                                 | Prefer an interface declaration over a type literal (type T = { ... })                                                                              | :heavy_check_mark: | :wrench: |                   |
 | [`@typescript-eslint/prefer-namespace-keyword`](./docs/rules/prefer-namespace-keyword.md)                 | Require the use of the `namespace` keyword instead of the `module` keyword to declare custom TypeScript modules                                     | :heavy_check_mark: | :wrench: |                   |
 | [`@typescript-eslint/prefer-regexp-exec`](./docs/rules/prefer-regexp-exec.md)                             | Prefer RegExp#exec() over String#match() if no global flag is provided                                                                              |                    |          | :thought_balloon: |
 | [`@typescript-eslint/prefer-string-starts-ends-with`](./docs/rules/prefer-string-starts-ends-with.md)     | Enforce the use of `String#startsWith` and `String#endsWith` instead of other equivalent methods of checking substrings                             |                    | :wrench: | :thought_balloon: |

packages/eslint-plugin/docs/rules/consistent-type-definitions.md

@@ -0,0 +1,74 @@
+# Consistent with type definition either `interface` or `type` (consistent-type-definitions)
+
+There are two ways to define a type.
+
+```ts
+// type alias
+type T1 = {
+  a: string;
+  b: number;
+};
+
+// interface keyword
+interface T2 {
+  a: string;
+  b: number;
+}
+```
+
+## Options
+
+This rule accepts one string option:
+
+- `"interface"`: enforce using `interface`s for object type definitions.
+- `"type"`: enforce using `type`s for object type definitions.
+
+For example:
+
+```CJSON
+{
+    // Use type for object definitions
+    "@typescript-eslint/consistent-type-definitions": ["error", "type"]
+}
+```
+
+## Rule Details
+
+Examples of **incorrect** code with `interface` option.
+
+```ts
+type T = { x: number };
+```
+
+Examples of **correct** code with `interface` option.
+
+```ts
+type T = string;
+type Foo = string | {};
+
+interface T {
+  x: number;
+}
+```
+
+Examples of **incorrect** code with `type` option.
+
+```ts
+interface T {
+  x: number;
+}
+```
+
+Examples of **correct** code with `type` option.
+
+```ts
+type T = { x: number };
+```
+
+## When Not To Use It
+
+If you specifically want to use an interface or type literal for stylistic reasons, you can disable this rule.
+
+## Compatibility
+
+- TSLint: [interface-over-type-literal](https://palantir.github.io/tslint/rules/interface-over-type-literal/)

packages/eslint-plugin/docs/rules/prefer-interface.md

@@ -1,7 +1,9 @@
-# Prefer an interface declaration over a type literal (type T = { ... }) (prefer-interface)
+# Prefer an interface declaration over a type literal (type T = { ... }) (prefer-interface)\
 
 Interfaces are generally preferred over type literals because interfaces can be implemented, extended and merged.
 
+## DEPRECATED - this rule has been deprecated in favour of [`consistent-type-definitions`](./consistent-type-definitions.md)
+
 ## Rule Details
 
 Examples of **incorrect** code for this rule.

packages/eslint-plugin/src/configs/all.json

@@ -9,6 +9,7 @@
     "camelcase": "off",
     "@typescript-eslint/camelcase": "error",
     "@typescript-eslint/class-name-casing": "error",
+    "@typescript-eslint/consistent-type-definitions": "error",
     "@typescript-eslint/explicit-function-return-type": "error",
     "@typescript-eslint/explicit-member-accessibility": "error",
     "func-call-spacing": "off",
@@ -23,11 +24,13 @@
     "@typescript-eslint/no-angle-bracket-type-assertion": "error",
     "no-array-constructor": "off",
     "@typescript-eslint/no-array-constructor": "error",
+    "@typescript-eslint/no-empty-function": "error",
     "@typescript-eslint/no-empty-interface": "error",
     "@typescript-eslint/no-explicit-any": "error",
     "no-extra-parens": "off",
     "@typescript-eslint/no-extra-parens": "error",
     "@typescript-eslint/no-extraneous-class": "error",
+    "@typescript-eslint/no-floating-promises": "error",
     "@typescript-eslint/no-for-in-array": "error",
     "@typescript-eslint/no-inferrable-types": "error",
     "no-magic-numbers": "off",
@@ -53,7 +56,6 @@
     "@typescript-eslint/prefer-for-of": "error",
     "@typescript-eslint/prefer-function-type": "error",
     "@typescript-eslint/prefer-includes": "error",
-    "@typescript-eslint/prefer-interface": "error",
     "@typescript-eslint/prefer-namespace-keyword": "error",
     "@typescript-eslint/prefer-regexp-exec": "error",
     "@typescript-eslint/prefer-string-starts-ends-with": "error",

packages/eslint-plugin/src/rules/consistent-type-definitions.ts

@@ -0,0 +1,103 @@
+import { TSESLint, TSESTree } from '@typescript-eslint/experimental-utils';
+import * as util from '../util';
+
+export default util.createRule({
+  name: 'consistent-type-definitions',
+  meta: {
+    type: 'suggestion',
+    docs: {
+      description:
+        'Consistent with type definition either `interface` or `type`',
+      category: 'Stylistic Issues',
+      recommended: 'error',
+    },
+    messages: {
+      interfaceOverType: 'Use an `interface` instead of a `type`',
+      typeOverInterface: 'Use a `type` instead of an `interface`',
+    },
+    schema: [
+      {
+        enum: ['interface', 'type'],
+      },
+    ],
+    fixable: 'code',
+  },
+  defaultOptions: ['interface'],
+  create(context, [option]) {
+    const sourceCode = context.getSourceCode();
+
+    return {
+      // VariableDeclaration with kind type has only one VariableDeclarator
+      "TSTypeAliasDeclaration[typeAnnotation.type='TSTypeLiteral']"(
+        node: TSESTree.TSTypeAliasDeclaration,
+      ) {
+        if (option === 'interface') {
+          context.report({
+            node: node.id,
+            messageId: 'interfaceOverType',
+            fix(fixer) {
+              const typeNode = node.typeParameters || node.id;
+              const fixes: TSESLint.RuleFix[] = [];
+
+              const firstToken = sourceCode.getFirstToken(node);
+              if (firstToken) {
+                fixes.push(fixer.replaceText(firstToken, 'interface'));
+                fixes.push(
+                  fixer.replaceTextRange(
+                    [typeNode.range[1], node.typeAnnotation.range[0]],
+                    ' ',
+                  ),
+                );
+              }
+
+              const afterToken = sourceCode.getTokenAfter(node.typeAnnotation);
+              if (
+                afterToken &&
+                afterToken.type === 'Punctuator' &&
+                afterToken.value === ';'
+              ) {
+                fixes.push(fixer.remove(afterToken));
+              }
+
+              return fixes;
+            },
+          });
+        }
+      },
+      TSInterfaceDeclaration(node) {
+        if (option === 'type') {
+          context.report({
+            node: node.id,
+            messageId: 'typeOverInterface',
+            fix(fixer) {
+              const typeNode = node.typeParameters || node.id;
+              const fixes: TSESLint.RuleFix[] = [];
+
+              const firstToken = sourceCode.getFirstToken(node);
+              if (firstToken) {
+                fixes.push(fixer.replaceText(firstToken, 'type'));
+                fixes.push(
+                  fixer.replaceTextRange(
+                    [typeNode.range[1], node.body.range[0]],
+                    ' = ',
+                  ),
+                );
+              }
+
+              if (node.extends) {
+                node.extends.forEach(heritage => {
+                  const typeIdentifier = sourceCode.getText(heritage);
+                  fixes.push(
+                    fixer.insertTextAfter(node.body, ` & ${typeIdentifier}`),
+                  );
+                });
+              }
+
+              return fixes;
+            },
+          });
+        }
+      },
+    };
+  },
+});

packages/eslint-plugin/src/rules/index.ts

@@ -5,6 +5,7 @@ import banTsIgnore from './ban-ts-ignore';
 import banTypes from './ban-types';
 import camelcase from './camelcase';
 import classNameCasing from './class-name-casing';
+import consistentTypeDefinitions from './consistent-type-definitions';
 import explicitFunctionReturnType from './explicit-function-return-type';
 import explicitMemberAccessibility from './explicit-member-accessibility';
 import funcCallSpacing from './func-call-spacing';
@@ -63,6 +64,7 @@ export default {
   'ban-types': banTypes,
   camelcase: camelcase,
   'class-name-casing': classNameCasing,
+  'consistent-type-definitions': consistentTypeDefinitions,
   'explicit-function-return-type': explicitFunctionReturnType,
   'explicit-member-accessibility': explicitMemberAccessibility,
   'func-call-spacing': funcCallSpacing,

packages/eslint-plugin/src/rules/prefer-interface.ts

@@ -16,6 +16,8 @@ export default util.createRule({
       interfaceOverType: 'Use an interface instead of a type literal.',
     },
     schema: [],
+    deprecated: true,
+    replacedBy: ['consistent-type-definitions'],
   },
   defaultOptions: [],
   create(context) {