feat: add require-indexer-name rule (#425)

* Add require-indexer-name rule

* Add require-indexer-name docs

.README/README.md

@@ -174,6 +174,7 @@ When `true`, only checks files with a [`@flow` annotation](http://flowtype.org/d
 {"gitdown": "include", "file": "./rules/object-type-delimiter.md"}
 {"gitdown": "include", "file": "./rules/require-compound-type-alias.md"}
 {"gitdown": "include", "file": "./rules/require-exact-type.md"}
+{"gitdown": "include", "file": "./rules/require-indexer-name.md"}
 {"gitdown": "include", "file": "./rules/require-inexact-type.md"}
 {"gitdown": "include", "file": "./rules/require-parameter-type.md"}
 {"gitdown": "include", "file": "./rules/require-readonly-react-props.md"}

.README/rules/require-indexer-name.md

@@ -0,0 +1,23 @@
+### `require-indexer-name`
+
+This rule validates Flow object indexer name.
+
+#### Options
+
+The rule has a string option:
+
+* `"never"` (default): Never report files that are missing an indexer key name.
+* `"always"`: Always report files that are missing an indexer key name.
+
+```js
+{
+  "rules": {
+    "flowtype/require-indexer-name": [
+      2,
+      "always"
+    ]
+  }
+}
+```
+
+<!-- assertions requireIndexerName -->

src/index.js

@@ -17,6 +17,7 @@ import noUnusedExpressions from './rules/noUnusedExpressions';
 import noWeakTypes from './rules/noWeakTypes';
 import noMixed from './rules/noMixed';
 import objectTypeDelimiter from './rules/objectTypeDelimiter';
+import requireIndexerName from './rules/requireIndexerName';
 import requireCompoundTypeAlias from './rules/requireCompoundTypeAlias';
 import requireInexactType from './rules/requireInexactType';
 import requireExactType from './rules/requireExactType';
@@ -61,6 +62,7 @@ const rules = {
   'object-type-delimiter': objectTypeDelimiter,
   'require-compound-type-alias': requireCompoundTypeAlias,
   'require-exact-type': requireExactType,
+  'require-indexer-name': requireIndexerName,
   'require-inexact-type': requireInexactType,
   'require-parameter-type': requireParameterType,
   'require-readonly-react-props': requireReadonlyReactProps,

src/rules/requireIndexerName.js

@@ -0,0 +1,33 @@
+import {getParameterName} from '../utilities';
+
+const schema = [
+  {
+    enum: ['always', 'never'],
+    type: 'string',
+  },
+];
+
+const create = (context) => {
+  const always = (context.options[0] || 'always') === 'always';
+
+  if (always) {
+    return {
+      ObjectTypeIndexer (node) {
+        const id = getParameterName(node, context);
+        if (id === null) {
+          context.report({
+            message: 'All indexers must be declared with key name.',
+            node,
+          });
+        }
+      },
+    };
+  } else {
+    return {};
+  }
+};
+
+export default {
+  create,
+  schema,
+};

src/utilities/getParameterName.js

@@ -33,6 +33,30 @@ export default (identifierNode, context) => {
     return context.getSourceCode().getFirstToken(identifierNode, tokenIndex).value;
   }
 
+  if (identifierNode.type === 'ObjectTypeIndexer') {
+    let tokenIndex;
+
+    tokenIndex = 0;
+
+    if (identifierNode.static) {
+      tokenIndex++;
+    }
+
+    if (identifierNode.variance) {
+      tokenIndex++;
+    }
+
+    tokenIndex++;
+
+    const id = context.getSourceCode().getFirstToken(identifierNode, tokenIndex);
+    const colonOrBrace = context.getSourceCode().getTokenAfter(id);
+    if (colonOrBrace.value === ':') {
+      return id.value;
+    } else {
+      return null;
+    }
+  }
+
   if (identifierNode.type === 'FunctionTypeParam') {
     return context.getSourceCode().getFirstToken(identifierNode).value;
   }

tests/rules/assertions/requireIndexerName.js

@@ -0,0 +1,26 @@
+export default {
+  invalid: [
+    {
+      code: 'type foo = { [string]: number };',
+      errors: [
+        {message: 'All indexers must be declared with key name.'},
+      ],
+    },
+  ],
+  valid: [
+    {
+      code: 'type foo = { [key: string]: number };',
+      errors: [],
+    },
+    {
+      code: 'type foo = { [key: string]: number };',
+      errors: [],
+      options: ['never'],
+    },
+    {
+      code: 'type foo = { [string]: number };',
+      errors: [],
+      options: ['never'],
+    },
+  ],
+};

tests/rules/index.js

@@ -31,6 +31,7 @@ const reportingRules = [
   'object-type-delimiter',
   'require-compound-type-alias',
   'require-inexact-type',
+  'require-indexer-name',
   'require-exact-type',
   'require-parameter-type',
   'require-readonly-react-props',