Merge pull request #43880 from ymqytw/refactor_SMP

Automatic merge from submit-queue (batch tested with PRs 44097, 42772, 43880, 44031, 44066)

Refactor Strategic Merge Patch

Refactor Strategic Merge Patch

```release-note
None
```

staging/src/k8s.io/apimachinery/pkg/util/mergepatch/errors.go

@@ -21,9 +21,23 @@ import (
 	"fmt"
 )
 
-var ErrBadJSONDoc = errors.New("Invalid JSON document")
+var (
-var ErrNoListOfLists = errors.New("Lists of lists are not supported")
+	ErrBadJSONDoc                     = errors.New("Invalid JSON document")
-var ErrBadPatchFormatForPrimitiveList = errors.New("Invalid patch format of primitive list")
+	ErrNoListOfLists                  = errors.New("Lists of lists are not supported")
+	ErrBadPatchFormatForPrimitiveList = errors.New("Invalid patch format of primitive list")
+)
+
+func ErrNoMergeKey(m map[string]interface{}, k string) error {
+	return fmt.Errorf("map: %v does not contain declared merge key: %s", m, k)
+}
+
+func ErrBadArgType(expected, actual string) error {
+	return fmt.Errorf("expected a %s, but received a %s", expected, actual)
+}
+
+func ErrBadPatchType(t interface{}, m map[string]interface{}) error {
+	return fmt.Errorf("unknown patch type: %s in map: %v", t, m)
+}
 
 // IsPreconditionFailed returns true if the provided error indicates
 // a precondition failed.

staging/src/k8s.io/apimachinery/pkg/util/strategicpatch/patch_test.go

@@ -1998,9 +1998,9 @@ func TestStrategicMergePatch(t *testing.T) {
 	testStrategicMergePatchWithCustomArguments(t, "bad patch",
 		"{}", "<THIS IS NOT JSON>", mergeItem, mergepatch.ErrBadJSONDoc)
 	testStrategicMergePatchWithCustomArguments(t, "bad struct",
-		"{}", "{}", []byte("<THIS IS NOT A STRUCT>"), fmt.Errorf(errBadArgTypeFmt, "struct", "slice"))
+		"{}", "{}", []byte("<THIS IS NOT A STRUCT>"), mergepatch.ErrBadArgType("struct", "slice"))
 	testStrategicMergePatchWithCustomArguments(t, "nil struct",
-		"{}", "{}", nil, fmt.Errorf(errBadArgTypeFmt, "struct", "nil"))
+		"{}", "{}", nil, mergepatch.ErrBadArgType("struct", "nil"))
 
 	tc := StrategicMergePatchTestCases{}
 	err := yaml.Unmarshal(createStrategicMergePatchTestCaseData, &tc)