fix(datastore): Ignore field mismatch errors

datastore/datastore.go

@@ -74,6 +74,7 @@ type Client struct {
 	dataset      string // Called dataset by the datastore API, synonym for project ID.
 	databaseID   string // Default value is empty string
 	readSettings *readSettings
+	config       *datastoreConfig
 }
 
 // NewClient creates a new Client for a given dataset.  If the project ID is
@@ -152,12 +153,15 @@ func NewClientWithDatabase(ctx context.Context, projectID, databaseID string, op
 	if err != nil {
 		return nil, fmt.Errorf("dialing: %w", err)
 	}
+
+	config := newDatastoreConfig(o...)
 	return &Client{
 		connPool:     connPool,
 		client:       newDatastoreClient(connPool, projectID, databaseID),
 		dataset:      projectID,
 		readSettings: &readSettings{},
 		databaseID:   databaseID,
+		config:       &config,
 	}, nil
 }
 
@@ -362,6 +366,48 @@ func checkMultiArg(v reflect.Value) (m multiArgType, elemType reflect.Type) {
 	return multiArgTypeInvalid, nil
 }
 
+// processFieldMismatchError ignore FieldMismatchErr if WithIgnoreFieldMismatch client option is provided by user
+func (c *Client) processFieldMismatchError(err error) error {
+	if c.config == nil || !c.config.ignoreFieldMismatchErrors {
+		return err
+	}
+	return ignoreFieldMismatchErrs(err)
+}
+
+func ignoreFieldMismatchErrs(err error) error {
+	if err == nil {
+		return err
+	}
+
+	multiErr, isMultiErr := err.(MultiError)
+	if isMultiErr {
+		foundErr := false
+		for i, e := range multiErr {
+			multiErr[i] = ignoreFieldMismatchErr(e)
+			if multiErr[i] != nil {
+				foundErr = true
+			}
+		}
+		if !foundErr {
+			return nil
+		}
+		return multiErr
+	}
+
+	return ignoreFieldMismatchErr(err)
+}
+
+func ignoreFieldMismatchErr(err error) error {
+	if err == nil {
+		return err
+	}
+	_, isFieldMismatchErr := err.(*ErrFieldMismatch)
+	if isFieldMismatchErr {
+		return nil
+	}
+	return err
+}
+
 // Close closes the Client. Call Close to clean up resources when done with the
 // Client.
 func (c *Client) Close() error {
@@ -402,9 +448,9 @@ func (c *Client) Get(ctx context.Context, key *Key, dst interface{}) (err error)
 	// as transaction id which can be ignored
 	_, err = c.get(ctx, []*Key{key}, []interface{}{dst}, opts)
 	if me, ok := err.(MultiError); ok {
-		return me[0]
+		return c.processFieldMismatchError(me[0])
 	}
-	return err
+	return c.processFieldMismatchError(err)
 }
 
 // GetMulti is a batch version of Get.
@@ -436,7 +482,7 @@ func (c *Client) GetMulti(ctx context.Context, keys []*Key, dst interface{}) (er
 	// Since opts does not contain Transaction option, 'get' call below will return nil
 	// as transaction id which can be ignored
 	_, err = c.get(ctx, keys, dst, opts)
-	return err
+	return c.processFieldMismatchError(err)
 }
 
 func (c *Client) get(ctx context.Context, keys []*Key, dst interface{}, opts *pb.ReadOptions) ([]byte, error) {

datastore/integration_test.go

@@ -66,8 +66,8 @@ type replayInfo struct {
 var (
 	record = flag.Bool("record", false, "record RPCs")
 
-	newTestClient = func(ctx context.Context, t *testing.T) *Client {
-		return newClient(ctx, t, nil)
+	newTestClient = func(ctx context.Context, t *testing.T, opts ...option.ClientOption) *Client {
+		return newClient(ctx, t, nil, opts...)
 	}
 	testParams map[string]interface{}
 
@@ -109,8 +109,8 @@ func testMain(m *testing.M) int {
 				log.Fatalf("closing recorder: %v", err)
 			}
 		}()
-		newTestClient = func(ctx context.Context, t *testing.T) *Client {
-			return newClient(ctx, t, rec.DialOptions())
+		newTestClient = func(ctx context.Context, t *testing.T, opts ...option.ClientOption) *Client {
+			return newClient(ctx, t, rec.DialOptions(), opts...)
 		}
 		log.Printf("recording to %s", replayFilename)
 	}
@@ -172,7 +172,7 @@ func initReplay() {
 		log.Fatal(err)
 	}
 
-	newTestClient = func(ctx context.Context, t *testing.T) *Client {
+	newTestClient = func(ctx context.Context, t *testing.T, opts ...option.ClientOption) *Client {
 		grpcHeadersEnforcer := &testutil.HeadersEnforcer{
 			OnFailure: t.Fatalf,
 			Checkers: []*testutil.HeaderChecker{
@@ -181,7 +181,8 @@ func initReplay() {
 			},
 		}
 
-		opts := append(grpcHeadersEnforcer.CallOptions(), option.WithGRPCConn(conn))
+		opts = append(opts, grpcHeadersEnforcer.CallOptions()...)
+		opts = append(opts, option.WithGRPCConn(conn))
 		client, err := NewClientWithDatabase(ctx, ri.ProjectID, testParams["databaseID"].(string), opts...)
 		if err != nil {
 			t.Fatalf("NewClientWithDatabase: %v", err)
@@ -191,7 +192,7 @@ func initReplay() {
 	log.Printf("replaying from %s", replayFilename)
 }
 
-func newClient(ctx context.Context, t *testing.T, dialOpts []grpc.DialOption) *Client {
+func newClient(ctx context.Context, t *testing.T, dialOpts []grpc.DialOption, opts ...option.ClientOption) *Client {
 	if testing.Short() {
 		t.Skip("Integration tests skipped in short mode")
 	}
@@ -207,7 +208,8 @@ func newClient(ctx context.Context, t *testing.T, dialOpts []grpc.DialOption) *C
 			xGoogReqParamsHeaderChecker,
 		},
 	}
-	opts := append(grpcHeadersEnforcer.CallOptions(), option.WithTokenSource(ts))
+	opts = append(opts, grpcHeadersEnforcer.CallOptions()...)
+	opts = append(opts, option.WithTokenSource(ts))
 	for _, opt := range dialOpts {
 		opts = append(opts, option.WithGRPCDialOption(opt))
 	}
@@ -264,6 +266,130 @@ func TestIntegration_Basics(t *testing.T) {
 	}
 }
 
+type OldX struct {
+	I int
+	J int
+}
+type NewX struct {
+	I int
+	j int
+}
+
+func TestIntegration_IgnoreFieldMismatch(t *testing.T) {
+	ctx := context.Background()
+	client := newTestClient(ctx, t, WithIgnoreFieldMismatch())
+	t.Cleanup(func() {
+		client.Close()
+	})
+
+	// Save entities with an extra field
+	keys := []*Key{
+		NameKey("X", "x1", nil),
+		NameKey("X", "x2", nil),
+	}
+	entitiesOld := []OldX{
+		{I: 10, J: 20},
+		{I: 30, J: 40},
+	}
+	_, gotErr := client.PutMulti(ctx, keys, entitiesOld)
+	if gotErr != nil {
+		t.Fatalf("Failed to save: %v\n", gotErr)
+	}
+
+	var wants []NewX
+	for _, oldX := range entitiesOld {
+		wants = append(wants, []NewX{{I: oldX.I}}...)
+	}
+
+	t.Cleanup(func() {
+		client.DeleteMulti(ctx, keys)
+	})
+
+	tests := []struct {
+		desc    string
+		client  *Client
+		wantErr error
+	}{
+		{
+			desc:   "Without IgnoreFieldMismatch option",
+			client: newTestClient(ctx, t),
+			wantErr: &ErrFieldMismatch{
+				StructType: reflect.TypeOf(NewX{}),
+				FieldName:  "J",
+				Reason:     "no such struct field",
+			},
+		},
+		{
+			desc:   "With IgnoreFieldMismatch option",
+			client: newTestClient(ctx, t, WithIgnoreFieldMismatch()),
+		},
+	}
+	for _, test := range tests {
+		t.Run(test.desc, func(t *testing.T) {
+			defer test.client.Close()
+			// FieldMismatch error in Next
+			query := NewQuery("X").FilterField("I", ">=", 10)
+			it := test.client.Run(ctx, query)
+			resIndex := 0
+			for {
+				var newX NewX
+				_, err := it.Next(&newX)
+				if err == iterator.Done {
+					break
+				}
+
+				compareIgnoreFieldMismatchResults(t, []NewX{wants[resIndex]}, []NewX{newX}, test.wantErr, err, "Next")
+				resIndex++
+			}
+
+			// FieldMismatch error in Get
+			var getX NewX
+			gotErr = test.client.Get(ctx, keys[0], &getX)
+			compareIgnoreFieldMismatchResults(t, []NewX{wants[0]}, []NewX{getX}, test.wantErr, gotErr, "Get")
+
+			// FieldMismatch error in GetAll
+			var getAllX []NewX
+			_, gotErr = test.client.GetAll(ctx, query, &getAllX)
+			compareIgnoreFieldMismatchResults(t, wants, getAllX, test.wantErr, gotErr, "GetAll")
+
+			// FieldMismatch error in GetMulti
+			getMultiX := make([]NewX, len(keys))
+			gotErr = test.client.GetMulti(ctx, keys, getMultiX)
+			compareIgnoreFieldMismatchResults(t, wants, getMultiX, test.wantErr, gotErr, "GetMulti")
+
+			tx, err := test.client.NewTransaction(ctx)
+			if err != nil {
+				t.Fatalf("tx.GetMulti got: %v, want: nil\n", err)
+			}
+
+			// FieldMismatch error in tx.Get
+			var txGetX NewX
+			err = tx.Get(keys[0], &txGetX)
+			compareIgnoreFieldMismatchResults(t, []NewX{wants[0]}, []NewX{txGetX}, test.wantErr, err, "tx.Get")
+
+			// FieldMismatch error in tx.GetMulti
+			txGetMultiX := make([]NewX, len(keys))
+			err = tx.GetMulti(keys, txGetMultiX)
+			compareIgnoreFieldMismatchResults(t, wants, txGetMultiX, test.wantErr, err, "tx.GetMulti")
+
+			tx.Commit()
+
+		})
+	}
+
+}
+
+func compareIgnoreFieldMismatchResults(t *testing.T, wantX []NewX, gotX []NewX, wantErr error, gotErr error, errPrefix string) {
+	if !equalErrs(gotErr, wantErr) {
+		t.Errorf("%v: error got: %v, want: %v", errPrefix, gotErr, wantErr)
+	}
+	for resIndex := 0; resIndex < len(wantX) && gotErr == nil; resIndex++ {
+		if wantX[resIndex].I != gotX[resIndex].I {
+			t.Fatalf("%v %v: got: %v, want: %v\n", errPrefix, resIndex, wantX[resIndex].I, gotX[resIndex].I)
+		}
+	}
+}
+
 func TestIntegration_GetWithReadTime(t *testing.T) {
 	ctx, cancel := context.WithTimeout(context.Background(), time.Second*20)
 	client := newTestClient(ctx, t)

datastore/option.go

@@ -0,0 +1,65 @@
+// Copyright 2024 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package datastore
+
+import (
+	"google.golang.org/api/option"
+	"google.golang.org/api/option/internaloption"
+)
+
+// datastoreConfig contains the Datastore client option configuration that can be
+// set through datastoreClientOptions.
+type datastoreConfig struct {
+	ignoreFieldMismatchErrors bool
+}
+
+// newDatastoreConfig generates a new datastoreConfig with all the given
+// datastoreClientOptions applied.
+func newDatastoreConfig(opts ...option.ClientOption) datastoreConfig {
+	var conf datastoreConfig
+	for _, opt := range opts {
+		if datastoreOpt, ok := opt.(datastoreClientOption); ok {
+			datastoreOpt.applyDatastoreOpt(&conf)
+		}
+	}
+	return conf
+}
+
+// A datastoreClientOption is an option for a Google Datastore client.
+type datastoreClientOption interface {
+	option.ClientOption
+	applyDatastoreOpt(*datastoreConfig)
+}
+
+// WithIgnoreFieldMismatch allows ignoring ErrFieldMismatch error while
+// reading or querying data.
+// WARNING: Ignoring ErrFieldMismatch can cause data loss while writing
+// back to Datastore. E.g.
+// if entity written to Datastore is {X: 1, Y:2} and it is read into
+// type NewStruct struct{X int}, then {X:1} is returned.
+// Now, if this is written back to Datastore, there will be no Y field
+// left for this entity in Datastore
+func WithIgnoreFieldMismatch() option.ClientOption {
+	return &withIgnoreFieldMismatch{ignoreFieldMismatchErrors: true}
+}
+
+type withIgnoreFieldMismatch struct {
+	internaloption.EmbeddableAdapter
+	ignoreFieldMismatchErrors bool
+}
+
+func (w *withIgnoreFieldMismatch) applyDatastoreOpt(c *datastoreConfig) {
+	c.ignoreFieldMismatchErrors = true
+}

datastore/query.go

@@ -825,7 +825,7 @@ func (c *Client) GetAllWithOptions(ctx context.Context, q *Query, dst interface{
 		}
 		res.Keys = append(res.Keys, k)
 	}
-	return res, errFieldMismatch
+	return res, c.processFieldMismatchError(errFieldMismatch)
 }
 
 // Run runs the given query in the given context
@@ -1061,7 +1061,7 @@ func (t *Iterator) Next(dst interface{}) (k *Key, err error) {
 	if dst != nil && !t.keysOnly {
 		err = loadEntityProto(dst, e)
 	}
-	return k, err
+	return k, t.client.processFieldMismatchError(err)
 }
 
 func (t *Iterator) next() (*Key, *pb.Entity, error) {

datastore/transaction.go

@@ -571,7 +571,7 @@ func (t *Transaction) get(spanName string, keys []*Key, dst interface{}) (err er
 	if txnID != nil && err == nil {
 		t.setToInProgress(txnID)
 	}
-	return err
+	return t.client.processFieldMismatchError(err)
 }
 
 // Get is the transaction-specific version of the package function Get.
@@ -582,9 +582,9 @@ func (t *Transaction) get(spanName string, keys []*Key, dst interface{}) (err er
 func (t *Transaction) Get(key *Key, dst interface{}) (err error) {
 	err = t.get("cloud.google.com/go/datastore.Transaction.Get", []*Key{key}, []interface{}{dst})
 	if me, ok := err.(MultiError); ok {
-		return me[0]
+		return t.client.processFieldMismatchError(me[0])
 	}
-	return err
+	return t.client.processFieldMismatchError(err)
 }
 
 // GetMulti is a batch version of Get.