fix(no-unused-emit-declarations): error in render functions (#2388)

Author: ntnyq

lib/rules/no-unused-emit-declarations.js

@@ -63,6 +63,7 @@ function hasReferenceId(value, setupContext) {
  * @returns {boolean}
  */
 function isEmitVariableName(name, emitReferenceIds) {
+  if (emitReferenceIds.size === 0) return false
   const emitVariable = emitReferenceIds.values().next().value.name
   return emitVariable === name
 }

tests/lib/rules/no-unused-emit-declarations.js

@@ -369,6 +369,19 @@ tester.run('no-unused-emit-declarations', rule, {
       const m = defineModel('foo')
       </script>
       `
+    },
+    {
+      filename: 'test.vue',
+      code: `
+      <script>
+        export default {
+          emits: ['foo'],
+          setup(_, ctx) {
+            return () => h('button', { onClick: () => ctx.emit('foo') })
+          }
+        }
+      </script>
+      `
     }
   ],
   invalid: [
@@ -750,6 +763,27 @@ tester.run('no-unused-emit-declarations', rule, {
           line: 3
         }
       ]
+    },
+    {
+      filename: 'test.vue',
+      code: `
+      <script>
+        export default {
+          emits: ['foo'],
+          setup(_, ctx) {
+            return () => h('button')
+          }
+        }
+      </script>
+      `,
+      errors: [
+        {
+          messageId: 'unused',
+          line: 4,
+          column: 19,
+          endColumn: 24
+        }
+      ]
     }
   ]
 })