Fix false negatives when using handler property in vue/no-arrow-functions-in-watch rule (#1368)

Author: ota-meshi

Diff for: lib/rules/no-arrow-functions-in-watch.js

@@ -28,14 +28,18 @@ module.exports = {
         return
       }
       for (const property of watchValue.properties) {
-        if (
-          property.type === 'Property' &&
-          property.value.type === 'ArrowFunctionExpression'
-        ) {
-          context.report({
-            node: property,
-            message: 'You should not use an arrow function to define a watcher.'
-          })
+        if (property.type !== 'Property') {
+          continue
+        }
+
+        for (const handler of utils.iterateWatchHandlerValues(property)) {
+          if (handler.type === 'ArrowFunctionExpression') {
+            context.report({
+              node: handler,
+              message:
+                'You should not use an arrow function to define a watcher.'
+            })
+          }
         }
       }
     })

Diff for: lib/rules/no-unused-properties.js

@@ -634,24 +634,17 @@ module.exports = {
             if (watcher.type === 'object') {
               const property = watcher.property
               if (property.kind === 'init') {
-                /** @type {Expression | null} */
-                let handlerValueNode = null
-                if (property.value.type === 'ObjectExpression') {
-                  const handler = utils.findProperty(property.value, 'handler')
-                  if (handler) {
-                    handlerValueNode = handler.value
-                  }
-                } else {
-                  handlerValueNode = property.value
-                }
-                if (
-                  handlerValueNode &&
-                  (handlerValueNode.type === 'Literal' ||
-                    handlerValueNode.type === 'TemplateLiteral')
-                ) {
-                  const name = utils.getStringLiteralValue(handlerValueNode)
-                  if (name != null) {
-                    watcherUsedProperties.add(name)
+                for (const handlerValueNode of utils.iterateWatchHandlerValues(
+                  property
+                )) {
+                  if (
+                    handlerValueNode.type === 'Literal' ||
+                    handlerValueNode.type === 'TemplateLiteral'
+                  ) {
+                    const name = utils.getStringLiteralValue(handlerValueNode)
+                    if (name != null) {
+                      watcherUsedProperties.add(name)
+                    }
                   }
                 }
               }
@@ -699,11 +692,11 @@ module.exports = {
                 if (
                   utils.getStaticPropertyName(parentParentProperty) !==
                     'computed' ||
-                  utils.getStaticPropertyName(property) !== 'handler'
+                  utils.getStaticPropertyName(property) !== 'get'
                 ) {
                   return
                 }
-                // check { computed: { foo: { handler: (vm) => vm.prop } } }
+                // check { computed: { foo: { get: () => vm.prop } } }
               } else {
                 return
               }

Diff for: lib/utils/index.js

@@ -1476,6 +1476,13 @@ module.exports = {
     }
   },
 
+  /**
+   * Return generator with the all handler nodes defined in the given watcher property.
+   * @param {Property|Expression} property
+   * @returns {IterableIterator<Expression>}
+   */
+  iterateWatchHandlerValues,
+
   /**
    * Wraps composition API trace map in both 'vue' and '@vue/composition-api' imports
    * @param {import('eslint-utils').TYPES.TraceMap} map
@@ -1990,3 +1997,26 @@ function getComponentComments(context) {
   componentComments.set(context, tokens)
   return tokens
 }
+
+/**
+ * Return generator with the all handler nodes defined in the given watcher property.
+ * @param {Property|Expression} property
+ * @returns {IterableIterator<Expression>}
+ */
+function* iterateWatchHandlerValues(property) {
+  const value = property.type === 'Property' ? property.value : property
+  if (value.type === 'ObjectExpression') {
+    const handler = findProperty(value, 'handler')
+    if (handler) {
+      yield handler.value
+    }
+  } else if (value.type === 'ArrayExpression') {
+    for (const element of value.elements.filter(isDef)) {
+      if (element.type !== 'SpreadElement') {
+        yield* iterateWatchHandlerValues(element)
+      }
+    }
+  } else {
+    yield value
+  }
+}

Diff for: tests/lib/rules/no-arrow-functions-in-watch.js

@@ -218,6 +218,51 @@ ruleTester.run('no-arrow-functions-in-watch', rule, {
           line: 15
         }
       ]
+    },
+    {
+      filename: 'test.vue',
+      code: `
+      export default {
+        watch: {
+          foo:{
+            handler: function() {},
+          },
+          bar:{
+            handler: () => {}
+          }
+        }
+      }`,
+      errors: [
+        {
+          message: 'You should not use an arrow function to define a watcher.',
+          line: 8
+        }
+      ]
+    },
+    {
+      filename: 'test.vue',
+      code: `
+      export default {
+        watch: {
+          e: [
+            'handle1',
+            (val, oldVal) => { /* ... */ },
+            {
+              handler: (val, oldVal) => { /* ... */ },
+            }
+          ],
+        }
+      }`,
+      errors: [
+        {
+          message: 'You should not use an arrow function to define a watcher.',
+          line: 6
+        },
+        {
+          message: 'You should not use an arrow function to define a watcher.',
+          line: 8
+        }
+      ]
     }
   ]
 })

Diff for: tests/lib/rules/no-unused-properties.js

@@ -263,6 +263,29 @@ tester.run('no-unused-properties', rule, {
         </script>
       `
     },
+    {
+      filename: 'test.vue',
+      code: `
+        <script>
+          export default {
+            props: ['foo'],
+            watch: {
+              foo: [
+                'bar',
+                {
+                  handler: 'baz'
+                }
+              ],
+            },
+            methods: {
+              bar () {},
+              baz () {},
+            }
+          };
+        </script>
+      `,
+      options: allOptions
+    },
 
     // data used as a template identifier
     {
@@ -1114,7 +1137,7 @@ tester.run('no-unused-properties', rule, {
           props: ['x'],
           computed: {
             y: {
-              handler: (vm) => vm.x * 2
+              get: () => this.x * 2
             }
           }
         };