feat: add no-types-missing-flow-annotation (#222)

* feat: disallow types in files missing a file annotation

* chore: add doc entry

* fix: ignore flow files

* fix: renamed to avoid flow auto include the file in some setups

* chore: clean up, add valid test cases

* feat: Allow types in files with an @noflow annotation.

.README/rules/no-types-missing-flow-annotation.md

@@ -0,0 +1,13 @@
+### `no-types-missing-file-annotation`
+
+Disallows Flow type imports, aliases, and annotations in files missing a valid Flow file declaration (or a @noflow annotation).
+
+```js
+{
+    "rules": {
+        "flowtype/no-types-missing-file-annotation": 2
+    }
+}
+```
+
+<!-- assertions noTypesMissingFileAnnotation -->

src/index.js

@@ -3,6 +3,7 @@ import {checkFlowFileAnnotation} from './utilities';
 import defineFlowType from './rules/defineFlowType';
 import genericSpacing from './rules/genericSpacing';
 import noWeakTypes from './rules/noWeakTypes';
+import noTypesMissingFileAnnotation from './rules/noTypesMissingFileAnnotation';
 import requireParameterType from './rules/requireParameterType';
 import requireReturnType from './rules/requireReturnType';
 import requireValidFileAnnotation from './rules/requireValidFileAnnotation';
@@ -30,6 +31,7 @@ const rules = {
   'generic-spacing': genericSpacing,
   'no-dupe-keys': noDupeKeys,
   'no-primitive-constructor-types': noPrimitiveConstructorTypes,
+  'no-types-missing-file-annotation': noTypesMissingFileAnnotation,
   'no-weak-types': noWeakTypes,
   'object-type-delimiter': objectTypeDelimiter,
   'require-parameter-type': requireParameterType,
@@ -51,7 +53,7 @@ export default {
   configs: {
     recommended
   },
-  rules: _.mapValues(rules, (rule) => {
+  rules: _.mapValues(rules, (rule, key) => {
     // Support current and deprecated rule formats
     if (_.isPlainObject(rule)) {
       return {
@@ -60,6 +62,10 @@ export default {
       };
     }
 
+    if (key === 'no-types-missing-file-annotation') {
+      return rule;
+    }
+
     return _.partial(checkFlowFileAnnotation, rule);
   }),
   rulesConfig: {

src/rules/noTypesMissingFileAnnotation.js

@@ -0,0 +1,39 @@
+import {isFlowFile} from '../utilities';
+
+/**
+ * Disallows the use for flow types without a valid file annotation.
+ * Only checks files without a valid flow annotation.
+ */
+
+export default (context) => {
+  // Skip flow files
+  if (isFlowFile(context, false)) {
+    return {};
+  }
+
+  const reporter = (node, type) => {
+    context.report({
+      data: {type},
+      message: 'Type {{type}} require valid Flow declaration.',
+      node
+    });
+  };
+
+  return {
+    ImportDeclaration (node) {
+      if (node.importKind === 'type') {
+        reporter(node, 'imports');
+      }
+      if (node.importKind === 'value' &&
+      node.specifiers.some((specifier) => { return specifier.importKind === 'type'; })) {
+        reporter(node, 'imports');
+      }
+    },
+    TypeAlias (node) {
+      reporter(node, 'aliases');
+    },
+    TypeAnnotation (node) {
+      reporter(node, 'annotations');
+    }
+  };
+};

src/utilities/isFlowFile.js

@@ -1,6 +1,13 @@
 import isFlowFileAnnotation from './isFlowFileAnnotation.js';
-
-export default (context) => {
+/* eslint-disable flowtype/require-valid-file-annotation */
+/**
+ * Checks whether a file has an @flow or @noflow annotation.
+ * @param context
+ * @param [strict] - By default, the function returns true if the file starts with @flow but not if it
+ * starts by @noflow. When the strict flag is set to false, the function returns true if the flag has @noflow also.
+ */
+/* eslint-enable flowtype/require-valid-file-annotation */
+export default (context, strict = true) => {
   const comments = context.getAllComments();
 
   if (!comments.length) {
@@ -9,5 +16,5 @@ export default (context) => {
 
   const firstComment = comments[0];
 
-  return isFlowFileAnnotation(firstComment.value) && !/no/.test(firstComment.value);
+  return isFlowFileAnnotation(firstComment.value) && !(strict && /no/.test(firstComment.value));
 };

tests/rules/assertions/noTypesMissingFileAnnotation.js

@@ -0,0 +1,57 @@
+export default {
+  invalid: [
+    {
+      code: 'const x: number = 42;',
+      errors: [{
+        message: 'Type annotations require valid Flow declaration.'
+      }]
+    },
+    {
+      code: 'type FooType = number;',
+      errors: [{
+        message: 'Type aliases require valid Flow declaration.'
+      }]
+    },
+    {
+      code: 'import type A from "a"',
+      errors: [{
+        message: 'Type imports require valid Flow declaration.'
+      }]
+    },
+    {
+      code: 'import type {A} from "a"',
+      errors: [{
+        message: 'Type imports require valid Flow declaration.'
+      }]
+    },
+    {
+      code: 'import {type A} from "a"',
+      errors: [{
+        message: 'Type imports require valid Flow declaration.'
+      }]
+    },
+    {
+      code: 'function t<T>(): T{}',
+      errors: [{
+        message: 'Type annotations require valid Flow declaration.'
+      }]
+    }
+  ],
+  valid: [
+    {
+      code: '// @flow\nconst x: number = 42;'
+    },
+    {
+      code: '/* @flow weak */\ntype FooType = number;'
+    },
+    {
+      code: '/* @noflow */\ntype FooType = number;'
+    },
+    {
+      code: '/* @noflow */\nimport type A from "a"'
+    },
+    {
+      code: '/* @noflow */\nimport {type A} from "a"'
+    }
+  ]
+};

tests/rules/index.js

@@ -14,6 +14,7 @@ const reportingRules = [
   'no-dupe-keys',
   'no-weak-types',
   'no-primitive-constructor-types',
+  'no-types-missing-file-annotation',
   'object-type-delimiter',
   'require-parameter-type',
   'require-return-type',