feat(check-template-names): add rule; fixes #1120

.README/rules/check-template-names.md

@@ -0,0 +1,40 @@
+# `check-template-names`
+
+Checks that any `@template` names are actually used in the connected
+`@typedef` or type alias.
+
+Currently checks `TSTypeAliasDeclaration` such as:
+
+```ts
+/**
+ * @template D
+ * @template V
+ */
+export type Pairs<D, V> = [D, V | undefined];
+```
+
+or
+
+```js
+/**
+ * @template D
+ * @template V
+ * @typedef {[D, V | undefined]} Pairs
+ */
+```
+
+|||
+|---|---|
+|Context|everywhere|
+|Tags|`@template`|
+|Recommended|false|
+|Settings||
+|Options||
+
+## Failing examples
+
+<!-- assertions-failing checkTemplateNames -->
+
+## Passing examples
+
+<!-- assertions-passing checkTemplateNames -->

docs/rules/check-template-names.md

@@ -0,0 +1,129 @@
+<a name="user-content-check-template-names"></a>
+<a name="check-template-names"></a>
+# <code>check-template-names</code>
+
+Checks that any `@template` names are actually used in the connected
+`@typedef` or type alias.
+
+Currently checks `TSTypeAliasDeclaration` such as:
+
+```ts
+/**
+ * @template D
+ * @template V
+ */
+export type Pairs<D, V> = [D, V | undefined];
+```
+
+or
+
+```js
+/**
+ * @template D
+ * @template V
+ * @typedef {[D, V | undefined]} Pairs
+ */
+```
+
+|||
+|---|---|
+|Context|everywhere|
+|Tags|`@template`|
+|Recommended|false|
+|Settings||
+|Options||
+
+<a name="user-content-check-template-names-failing-examples"></a>
+<a name="check-template-names-failing-examples"></a>
+## Failing examples
+
+The following patterns are considered problems:
+
+````js
+/**
+ * @template D
+ * @template V
+ */
+type Pairs<X, Y> = [X, Y | undefined];
+// Message: @template D not in use
+
+/**
+ * @template D
+ * @template V
+ */
+export type Pairs<X, Y> = [X, Y | undefined];
+// Message: @template D not in use
+
+/**
+ * @template D
+ * @template V
+ * @typedef {[X, Y | undefined]} Pairs
+ */
+// Message: @template D not in use
+
+/**
+ * @template D
+ * @template V
+ */
+export type Pairs = [number, undefined];
+// Message: @template D not in use
+
+/**
+ * @template D
+ * @template V
+ * @typedef {[undefined]} Pairs
+ */
+// Settings: {"jsdoc":{"mode":"permissive"}}
+// Message: @template D not in use
+
+/**
+ * @template D, U, V
+ */
+export type Extras<D, U> = [D, U | undefined];
+// Message: @template V not in use
+
+/**
+ * @template D, U, V
+ * @typedef {[D, U | undefined]} Extras
+ */
+// Message: @template V not in use
+````
+
+
+
+<a name="user-content-check-template-names-passing-examples"></a>
+<a name="check-template-names-passing-examples"></a>
+## Passing examples
+
+The following patterns are not considered problems:
+
+````js
+/**
+ * @template D
+ * @template V
+ */
+export type Pairs<D, V> = [D, V | undefined];
+
+/**
+ * @template D
+ * @template V
+ * @typedef {[D, V | undefined]} Pairs
+ */
+
+/**
+ * @template D, U, V
+ */
+export type Extras<D, U, V> = [D, U, V | undefined];
+
+/**
+ * @template D, U, V
+ * @typedef {[D, U, V | undefined]} Extras
+ */
+
+/**
+ * @template X
+ * @typedef {[D, U, V | undefined]} Extras
+ * @typedef {[D, U, V | undefined]} Extras
+ */
+````
+

src/index.js

@@ -7,6 +7,7 @@ import checkParamNames from './rules/checkParamNames.js';
 import checkPropertyNames from './rules/checkPropertyNames.js';
 import checkSyntax from './rules/checkSyntax.js';
 import checkTagNames from './rules/checkTagNames.js';
+import checkTemplateNames from './rules/checkTemplateNames.js';
 import checkTypes from './rules/checkTypes.js';
 import checkValues from './rules/checkValues.js';
 import convertToJsdocComments from './rules/convertToJsdocComments.js';
@@ -81,6 +82,7 @@ const index = {
     'check-property-names': checkPropertyNames,
     'check-syntax': checkSyntax,
     'check-tag-names': checkTagNames,
+    'check-template-names': checkTemplateNames,
     'check-types': checkTypes,
     'check-values': checkValues,
     'convert-to-jsdoc-comments': convertToJsdocComments,
@@ -155,6 +157,7 @@ const createRecommendedRuleset = (warnOrError, flatName) => {
       'jsdoc/check-property-names': warnOrError,
       'jsdoc/check-syntax': 'off',
       'jsdoc/check-tag-names': warnOrError,
+      'jsdoc/check-template-names': 'off',
       'jsdoc/check-types': warnOrError,
       'jsdoc/check-values': warnOrError,
       'jsdoc/convert-to-jsdoc-comments': 'off',

src/rules/checkTemplateNames.js

@@ -0,0 +1,101 @@
+import {
+  parse as parseType,
+  traverse,
+  tryParse as tryParseType,
+} from '@es-joy/jsdoccomment';
+import iterateJsdoc from '../iterateJsdoc.js';
+
+export default iterateJsdoc(({
+  context,
+  utils,
+  node,
+  settings,
+  report,
+}) => {
+  const {
+    mode
+  } = settings;
+
+  const templateTags = utils.getTags('template');
+
+  const usedNames = new Set();
+  /**
+   * @param {import('@typescript-eslint/types').TSESTree.TSTypeAliasDeclaration} aliasDeclaration
+   */
+  const checkParameters = (aliasDeclaration) => {
+    /* c8 ignore next -- Guard */
+    const {params} = aliasDeclaration.typeParameters ?? {params: []};
+    for (const {name: {name}} of params) {
+      usedNames.add(name);
+    }
+    for (const tag of templateTags) {
+      const {name} = tag;
+      const names = name.split(/,\s*/);
+      for (const name of names) {
+        if (!usedNames.has(name)) {
+          report(`@template ${name} not in use`, null, tag);
+        }
+      }
+    }
+  };
+
+  const handleTypeAliases = () => {
+    const nde = /** @type {import('@typescript-eslint/types').TSESTree.Node} */ (
+      node
+    );
+    if (!nde) {
+      return;
+    }
+    switch (nde.type) {
+    case 'ExportNamedDeclaration':
+      if (nde.declaration?.type === 'TSTypeAliasDeclaration') {
+        checkParameters(nde.declaration);
+      }
+      break;
+    case 'TSTypeAliasDeclaration':
+      checkParameters(nde);
+      break;
+    }
+  };
+
+  const typedefTags = utils.getTags('typedef');
+  if (!typedefTags.length || typedefTags.length >= 2) {
+    handleTypeAliases();
+    return;
+  }
+
+  const potentialType = typedefTags[0].type;
+  const parsedType = mode === 'permissive' ?
+    tryParseType(/** @type {string} */ (potentialType)) :
+    parseType(/** @type {string} */ (potentialType), mode)
+
+  traverse(parsedType, (nde) => {
+    const {
+      type,
+      value,
+    } = /** @type {import('jsdoc-type-pratt-parser').NameResult} */ (nde);
+    if (type === 'JsdocTypeName' && (/^[A-Z]$/).test(value)) {
+      usedNames.add(value);
+    }
+  });
+
+  for (const tag of templateTags) {
+    const {name} = tag;
+    const names = name.split(/,\s*/);
+    for (const name of names) {
+      if (!usedNames.has(name)) {
+        report(`@template ${name} not in use`, null, tag);
+      }
+    }
+  }
+}, {
+  iterateAllJsdocs: true,
+  meta: {
+    docs: {
+      description: 'Checks that any `@template` names are actually used in the connected `@typedef` or type alias.',
+      url: 'https://github.com/gajus/eslint-plugin-jsdoc/blob/main/docs/rules/require-template.md#repos-sticky-header',
+    },
+    schema: [],
+    type: 'suggestion',
+  },
+});