feat: export ToSpannerError

The ToSpannerError method should be exported to allow users to create
Spanner errors to use with unit tests. Currently, that was only possible
by creating a struct directly and filling the deprecated Code field. That
is however no longer recommended, as the code field might be removed in a
future release.

Fixes #3122

spanner/client.go

@@ -117,7 +117,7 @@ type ClientConfig struct {
 
 // errDial returns error for dialing to Cloud Spanner.
 func errDial(ci int, err error) error {
-	e := toSpannerError(err).(*Error)
+	e := ToSpannerError(err).(*Error)
 	e.decorate(fmt.Sprintf("dialing fails for channel[%v]", ci))
 	return e
 }
@@ -341,7 +341,7 @@ func (c *Client) BatchReadOnlyTransaction(ctx context.Context, tb TimestampBound
 		},
 	})
 	if err != nil {
-		return nil, toSpannerError(err)
+		return nil, ToSpannerError(err)
 	}
 	tx = res.Id
 	if res.ReadTimestamp != nil {

spanner/client_test.go

@@ -537,7 +537,7 @@ func TestClient_ReadOnlyTransaction_SessionNotFoundOnExecuteStreamingSql(t *test
 	err := testReadOnlyTransaction(t, map[string]SimulatedExecutionTime{
 		MethodExecuteStreamingSql: {Errors: []error{newSessionNotFoundError("projects/p/instances/i/databases/d/sessions/s")}},
 	})
-	want := toSpannerError(newSessionNotFoundError("projects/p/instances/i/databases/d/sessions/s"))
+	want := ToSpannerError(newSessionNotFoundError("projects/p/instances/i/databases/d/sessions/s"))
 	if err == nil {
 		t.Fatalf("missing expected error\nGot: nil\nWant: %v", want)
 	}

spanner/errors.go

@@ -115,8 +115,15 @@ func spannerErrorf(code codes.Code, format string, args ...interface{}) error {
 	}
 }
 
-// toSpannerError converts general Go error to *spanner.Error.
-func toSpannerError(err error) error {
+// ToSpannerError converts a general Go error to *spanner.Error. If the given
+// error is already a *spanner.Error, the original error will be returned.
+//
+// Spanner Errors are normally created by the Spanner client library from the
+// returned status of a RPC. This method can also be used to create Spanner
+// errors for use in tests. The recommended way to create test errors is
+// calling this method with a status error, e.g.
+// ToSpannerError(status.Newf(codes.NotFound, "Table not found").Err())
+func ToSpannerError(err error) error {
 	return toSpannerErrorWithCommitInfo(err, false)
 }
 

spanner/errors_test.go

@@ -63,7 +63,7 @@ func TestToSpannerError(t *testing.T) {
 				wrapped: errors.New("wha?"),
 				msg:     "error with wrapped non-gRPC and non-Spanner error"}},
 	} {
-		err := toSpannerError(test.err)
+		err := ToSpannerError(test.err)
 		errDuringCommit := toSpannerErrorWithCommitInfo(test.err, true)
 		if got, want := ErrCode(err), test.wantCode; got != want {
 			t.Errorf("%v: got %s, want %s", test.err, got, want)

spanner/mutation.go

@@ -179,7 +179,7 @@ func structToMutationParams(in interface{}) ([]string, []interface{}, error) {
 	}
 	fields, err := fieldCache.Fields(t)
 	if err != nil {
-		return nil, nil, toSpannerError(err)
+		return nil, nil, ToSpannerError(err)
 	}
 	var cols []string
 	var vals []interface{}

spanner/pdml.go

@@ -51,7 +51,7 @@ func (c *Client) partitionedUpdate(ctx context.Context, statement Statement, opt
 
 	sh, err := c.idleSessions.take(ctx)
 	if err != nil {
-		return 0, toSpannerError(err)
+		return 0, ToSpannerError(err)
 	}
 	if sh != nil {
 		defer sh.recycle()
@@ -61,7 +61,7 @@ func (c *Client) partitionedUpdate(ctx context.Context, statement Statement, opt
 	// The transaction reference will be added by the executePdml method.
 	params, paramTypes, err := statement.convertParams()
 	if err != nil {
-		return 0, toSpannerError(err)
+		return 0, ToSpannerError(err)
 	}
 	req := &sppb.ExecuteSqlRequest{
 		Session:      sh.getID(),
@@ -107,7 +107,7 @@ func executePdml(ctx context.Context, sh *sessionHandle, req *sppb.ExecuteSqlReq
 		},
 	})
 	if err != nil {
-		return 0, toSpannerError(err)
+		return 0, ToSpannerError(err)
 	}
 	// Add a reference to the PDML transaction on the ExecuteSql request.
 	req.Transaction = &sppb.TransactionSelector{

spanner/read.go

@@ -157,7 +157,7 @@ func (r *RowIterator) Next() (*Row, error) {
 		return row, nil
 	}
 	if err := r.streamd.lastErr(); err != nil {
-		r.err = toSpannerError(err)
+		r.err = ToSpannerError(err)
 	} else if !r.rowd.done() {
 		r.err = errEarlyReadEnd()
 	} else {

spanner/session.go

@@ -1033,13 +1033,13 @@ func (p *sessionPool) takeWriteSession(ctx context.Context) (*sessionHandle, err
 					s.destroy(false)
 					trace.TracePrintf(ctx, map[string]interface{}{"sessionID": s.getID()},
 						"Session not found for write")
-					return nil, toSpannerError(err)
+					return nil, ToSpannerError(err)
 				}
 
 				s.recycle()
 				trace.TracePrintf(ctx, map[string]interface{}{"sessionID": s.getID()},
 					"Error preparing session for write")
-				return nil, toSpannerError(err)
+				return nil, ToSpannerError(err)
 			}
 		}
 		p.incNumInUse(ctx)
@@ -1506,7 +1506,7 @@ func (hc *healthChecker) worker(i int) {
 				// cycle.
 				// Don't log about permission errors, which may be expected
 				// (e.g. using read-only auth).
-				serr := toSpannerError(err).(*Error)
+				serr := ToSpannerError(err).(*Error)
 				if serr.Code != codes.PermissionDenied {
 					logf(hc.pool.sc.logger, "Failed to prepare session, error: %v", serr)
 				}

spanner/sessionclient.go

@@ -135,7 +135,7 @@ func (sc *sessionClient) createSession(ctx context.Context) (*session, error) {
 		Session:  &sppb.Session{Labels: sc.sessionLabels},
 	})
 	if err != nil {
-		return nil, toSpannerError(err)
+		return nil, ToSpannerError(err)
 	}
 	return &session{valid: true, client: client, id: sid.Name, createTime: time.Now(), md: sc.md, logger: sc.logger}, nil
 }
@@ -227,7 +227,7 @@ func (sc *sessionClient) executeBatchCreateSessions(client *vkit.Client, createC
 		}
 		if ctx.Err() != nil {
 			trace.TracePrintf(ctx, nil, "Context error while creating a batch of %d sessions: %v", createCount, ctx.Err())
-			consumer.sessionCreationFailed(toSpannerError(ctx.Err()), remainingCreateCount)
+			consumer.sessionCreationFailed(ToSpannerError(ctx.Err()), remainingCreateCount)
 			break
 		}
 		response, err := client.BatchCreateSessions(ctx, &sppb.BatchCreateSessionsRequest{
@@ -237,7 +237,7 @@ func (sc *sessionClient) executeBatchCreateSessions(client *vkit.Client, createC
 		})
 		if err != nil {
 			trace.TracePrintf(ctx, nil, "Error creating a batch of %d sessions: %v", remainingCreateCount, err)
-			consumer.sessionCreationFailed(toSpannerError(err), remainingCreateCount)
+			consumer.sessionCreationFailed(ToSpannerError(err), remainingCreateCount)
 			break
 		}
 		actuallyCreated := int32(len(response.Session))

spanner/transaction.go

@@ -489,7 +489,7 @@ func (t *ReadOnlyTransaction) begin(ctx context.Context) error {
 				rts = time.Unix(res.ReadTimestamp.Seconds, int64(res.ReadTimestamp.Nanos))
 			}
 		} else {
-			err = toSpannerError(err)
+			err = ToSpannerError(err)
 		}
 		break
 	}
@@ -827,7 +827,7 @@ func (t *ReadWriteTransaction) update(ctx context.Context, stmt Statement, opts
 	}
 	resultSet, err := sh.getClient().ExecuteSql(contextWithOutgoingMetadata(ctx, sh.getMetadata()), req)
 	if err != nil {
-		return 0, toSpannerError(err)
+		return 0, ToSpannerError(err)
 	}
 	if resultSet.Stats == nil {
 		return 0, spannerErrorf(codes.InvalidArgument, "query passed to Update: %q", stmt.SQL)
@@ -876,7 +876,7 @@ func (t *ReadWriteTransaction) BatchUpdate(ctx context.Context, stmts []Statemen
 		Seqno:       atomic.AddInt64(&t.sequenceNumber, 1),
 	})
 	if err != nil {
-		return nil, toSpannerError(err)
+		return nil, ToSpannerError(err)
 	}
 
 	var counts []int64
@@ -1209,7 +1209,7 @@ func (t *writeOnlyTransaction) applyAtLeastOnce(ctx context.Context, ms ...*Muta
 			break
 		}
 	}
-	return ts, toSpannerError(err)
+	return ts, ToSpannerError(err)
 }
 
 // isAbortedErr returns true if the error indicates that an gRPC call is

spanner/transaction_test.go

@@ -78,7 +78,7 @@ func TestReadOnlyTransaction_RecoverFromFailure(t *testing.T) {
 		})
 
 	_, _, e := txn.acquire(ctx)
-	if wantErr := toSpannerError(errUsr); !testEqual(e, wantErr) {
+	if wantErr := ToSpannerError(errUsr); !testEqual(e, wantErr) {
 		t.Fatalf("Acquire for multi use, got %v, want %v.", e, wantErr)
 	}
 	_, _, e = txn.acquire(ctx)
@@ -238,7 +238,7 @@ func TestTransaction_SessionNotFound(t *testing.T) {
 		t.Fatalf("Expect Read to succeed, got %v, want %v.", got.err, wantErr)
 	}
 
-	wantErr = toSpannerError(newSessionNotFoundError("projects/p/instances/i/databases/d/sessions/s"))
+	wantErr = ToSpannerError(newSessionNotFoundError("projects/p/instances/i/databases/d/sessions/s"))
 	ms := []*Mutation{
 		Insert("Accounts", []string{"AccountId", "Nickname", "Balance"}, []interface{}{int64(1), "Foo", int64(50)}),
 		Insert("Accounts", []string{"AccountId", "Nickname", "Balance"}, []interface{}{int64(2), "Bar", int64(1)}),

spanner/value.go

@@ -2389,7 +2389,7 @@ func decodeStruct(ty *sppb.StructType, pb *proto3.ListValue, ptr interface{}) er
 
 	fields, err := fieldCache.Fields(t)
 	if err != nil {
-		return toSpannerError(err)
+		return ToSpannerError(err)
 	}
 	seen := map[string]bool{}
 	for i, f := range ty.Fields {