fix(reactivity): clear on readonly collections return undefined

packages/reactivity/__tests__/readonly.spec.ts

@@ -275,6 +275,14 @@ describe('reactivity/readonly', () => {
             expect(isReactive(value)).toBe(true)
           }
         })
+
+        test('should return undefined from Map.clear() call', () => {
+          const wrapped = readonly(new Collection())
+          expect(wrapped.clear()).toBeUndefined()
+          expect(
+            `Clear operation failed: target is readonly.`
+          ).toHaveBeenWarned()
+        })
       }
     })
   })
@@ -332,6 +340,14 @@ describe('reactivity/readonly', () => {
             expect(isReadonly(v2)).toBe(true)
           }
         })
+
+        test('should return undefined from Set.clear() call', () => {
+          const wrapped = readonly(new Collection())
+          expect(wrapped.clear()).toBeUndefined()
+          expect(
+            `Clear operation failed: target is readonly.`
+          ).toHaveBeenWarned()
+        })
       }
     })
   })

packages/reactivity/__tests__/shallowReadonly.spec.ts

@@ -113,6 +113,12 @@ describe('reactivity/shallowReadonly', () => {
         ).not.toHaveBeenWarned()
       })
     })
+
+    test('should return undefined from Map.clear() call', () => {
+      const sroMap = shallowReadonly(new Map())
+      expect(sroMap.clear()).toBeUndefined()
+      expect(`Clear operation failed: target is readonly.`).toHaveBeenWarned()
+    })
   })
 
   describe('collection/Set', () => {
@@ -197,5 +203,11 @@ describe('reactivity/shallowReadonly', () => {
         ).not.toHaveBeenWarned()
       })
     })
+
+    test('should return undefined from Set.clear() call', () => {
+      const sroSet = shallowReadonly(new Set())
+      expect(sroSet.clear()).toBeUndefined()
+      expect(`Clear operation failed: target is readonly.`).toHaveBeenWarned()
+    })
   })
 })

packages/reactivity/src/collectionHandlers.ts

@@ -223,7 +223,11 @@ function createReadonlyMethod(type: TriggerOpTypes): Function {
         toRaw(this)
       )
     }
-    return type === TriggerOpTypes.DELETE ? false : this
+    return type === TriggerOpTypes.DELETE
+      ? false
+      : type === TriggerOpTypes.CLEAR
+      ? undefined
+      : this
   }
 }