fix: standardize returned errors (#32)

Changes all errors that are created directly by the driver to Spanner errors.

Fixes #14

driver.go

@@ -18,7 +18,6 @@ import (
 	"context"
 	"database/sql"
 	"database/sql/driver"
-	"errors"
 	"fmt"
 	"regexp"
 	"strconv"
@@ -27,6 +26,8 @@ import (
 	"cloud.google.com/go/spanner"
 	"github.com/cloudspannerecosystem/go-sql-spanner/internal"
 	"google.golang.org/api/option"
+	"google.golang.org/grpc/codes"
+	"google.golang.org/grpc/status"
 
 	adminapi "cloud.google.com/go/spanner/admin/database/apiv1"
 	adminpb "google.golang.org/genproto/googleapis/spanner/admin/database/v1"
@@ -114,7 +115,7 @@ func extractConnectorParams(paramsString string) (map[string]string, error) {
 		}
 		keyValue := strings.SplitN(keyValueString, "=", 2)
 		if keyValue == nil || len(keyValue) != 2 {
-			return nil, fmt.Errorf("invalid connection property: %s", keyValueString)
+			return nil, spanner.ToSpannerError(status.Errorf(codes.InvalidArgument, "invalid connection property: %s", keyValueString))
 		}
 		params[strings.ToLower(keyValue[0])] = keyValue[1]
 	}
@@ -326,7 +327,7 @@ func (c *conn) Begin() (driver.Tx, error) {
 
 func (c *conn) BeginTx(ctx context.Context, opts driver.TxOptions) (driver.Tx, error) {
 	if c.inTransaction() {
-		return nil, errors.New("already in a transaction")
+		return nil, spanner.ToSpannerError(status.Errorf(codes.FailedPrecondition, "already in a transaction"))
 	}
 
 	if opts.ReadOnly {

internal/statement_parser.go

@@ -15,9 +15,12 @@
 package internal
 
 import (
-	"fmt"
 	"strings"
 	"unicode"
+
+	"cloud.google.com/go/spanner"
+	"google.golang.org/grpc/codes"
+	"google.golang.org/grpc/status"
 )
 
 var ddlStatements = map[string]bool{"CREATE": true, "DROP": true, "ALTER": true}
@@ -76,7 +79,7 @@ func removeCommentsAndTrim(sql string) (string, error) {
 		c := runes[index]
 		if isInQuoted {
 			if (c == '\n' || c == '\r') && !isTripleQuoted {
-				return "", fmt.Errorf("statement contains an unclosed literal: %s", sql)
+				return "", spanner.ToSpannerError(status.Errorf(codes.InvalidArgument, "statement contains an unclosed literal: %s", sql))
 			} else if c == startQuote {
 				if lastCharWasEscapeChar {
 					lastCharWasEscapeChar = false
@@ -138,7 +141,7 @@ func removeCommentsAndTrim(sql string) (string, error) {
 		index++
 	}
 	if isInQuoted {
-		return "", fmt.Errorf("statement contains an unclosed literal: %s", sql)
+		return "", spanner.ToSpannerError(status.Errorf(codes.InvalidArgument, "statement contains an unclosed literal: %s", sql))
 	}
 	trimmed := strings.TrimSpace(res.String())
 	if len(trimmed) > 0 && trimmed[len(trimmed)-1] == ';' {
@@ -197,7 +200,7 @@ func findParams(sql string) ([]string, error) {
 		c := runes[index]
 		if isInQuoted {
 			if (c == '\n' || c == '\r') && !isTripleQuoted {
-				return nil, fmt.Errorf("statement contains an unclosed literal: %s", sql)
+				return nil, spanner.ToSpannerError(status.Errorf(codes.InvalidArgument, "statement contains an unclosed literal: %s", sql))
 			} else if c == startQuote {
 				if lastCharWasEscapeChar {
 					lastCharWasEscapeChar = false
@@ -248,7 +251,7 @@ func findParams(sql string) ([]string, error) {
 		index++
 	}
 	if isInQuoted {
-		return nil, fmt.Errorf("statement contains an unclosed literal: %s", sql)
+		return nil, spanner.ToSpannerError(status.Errorf(codes.InvalidArgument, "statement contains an unclosed literal: %s", sql))
 	}
 	return res, nil
 }

internal/statement_parser_test.go

@@ -17,7 +17,9 @@ package internal
 import (
 	"testing"
 
+	"cloud.google.com/go/spanner"
 	"github.com/google/go-cmp/cmp"
+	"google.golang.org/grpc/codes"
 )
 
 func TestRemoveCommentsAndTrim(t *testing.T) {
@@ -660,3 +662,25 @@ func TestIsDdl(t *testing.T) {
 		}
 	}
 }
+
+func TestRemoveCommentsAndTrim_Errors(t *testing.T) {
+	_, err := removeCommentsAndTrim("SELECT 'Hello World FROM SomeTable")
+	if g, w := spanner.ErrCode(err), codes.InvalidArgument; g != w {
+		t.Errorf("error code mismatch\nGot: %v\nWant: %v\n", g, w)
+	}
+	_, err = removeCommentsAndTrim("SELECT 'Hello World\nFROM SomeTable")
+	if g, w := spanner.ErrCode(err), codes.InvalidArgument; g != w {
+		t.Errorf("error code mismatch\nGot: %v\nWant: %v\n", g, w)
+	}
+}
+
+func TestFindParams_Errors(t *testing.T) {
+	_, err := findParams("SELECT 'Hello World FROM SomeTable WHERE id=@id")
+	if g, w := spanner.ErrCode(err), codes.InvalidArgument; g != w {
+		t.Errorf("error code mismatch\nGot: %v\nWant: %v\n", g, w)
+	}
+	_, err = findParams("SELECT 'Hello World\nFROM SomeTable WHERE id=@id")
+	if g, w := spanner.ErrCode(err), codes.InvalidArgument; g != w {
+		t.Errorf("error code mismatch\nGot: %v\nWant: %v\n", g, w)
+	}
+}

stmt.go

@@ -17,11 +17,11 @@ package spannerdriver
 import (
 	"context"
 	"database/sql/driver"
-	"errors"
-	"fmt"
 
 	"cloud.google.com/go/spanner"
 	"github.com/cloudspannerecosystem/go-sql-spanner/internal"
+	"google.golang.org/grpc/codes"
+	"google.golang.org/grpc/status"
 )
 
 type stmt struct {
@@ -39,15 +39,15 @@ func (s *stmt) NumInput() int {
 }
 
 func (s *stmt) Exec(args []driver.Value) (driver.Result, error) {
-	return nil, fmt.Errorf("use ExecContext instead")
+	return nil, spanner.ToSpannerError(status.Errorf(codes.Unimplemented, "use ExecContext instead"))
 }
 
 func (s *stmt) ExecContext(ctx context.Context, args []driver.NamedValue) (driver.Result, error) {
 	return s.conn.ExecContext(ctx, s.query, args)
 }
 
 func (s *stmt) Query(args []driver.Value) (driver.Rows, error) {
-	return nil, fmt.Errorf("use QueryContext instead")
+	return nil, spanner.ToSpannerError(status.Errorf(codes.Unimplemented, "use QueryContext instead"))
 }
 
 func (s *stmt) QueryContext(ctx context.Context, args []driver.NamedValue) (driver.Rows, error) {
@@ -75,7 +75,7 @@ func prepareSpannerStmt(q string, args []driver.NamedValue) (spanner.Statement,
 		return spanner.Statement{}, err
 	}
 	if len(names) != len(args) {
-		return spanner.Statement{}, fmt.Errorf("got %v argument values, but found %v parameters in the sql string", len(args), len(names))
+		return spanner.Statement{}, spanner.ToSpannerError(status.Errorf(codes.InvalidArgument, "got %v argument values, but found %v parameters in the sql string", len(args), len(names)))
 	}
 	ss := spanner.NewStatement(q)
 	for i, v := range args {
@@ -93,7 +93,7 @@ type result struct {
 }
 
 func (r *result) LastInsertId() (int64, error) {
-	return 0, errors.New("spanner doesn't autogenerate IDs")
+	return 0, spanner.ToSpannerError(status.Errorf(codes.Unimplemented, "Cloud Spanner does not support auto-generated ids"))
 }
 
 func (r *result) RowsAffected() (int64, error) {

transaction.go

@@ -18,7 +18,6 @@ import (
 	"bytes"
 	"context"
 	"encoding/gob"
-	"fmt"
 
 	"cloud.google.com/go/spanner"
 	sppb "google.golang.org/genproto/googleapis/spanner/v1"
@@ -87,7 +86,7 @@ func (tx *readOnlyTransaction) Query(ctx context.Context, stmt spanner.Statement
 }
 
 func (tx *readOnlyTransaction) ExecContext(_ context.Context, stmt spanner.Statement) (int64, error) {
-	return 0, fmt.Errorf("read-only transactions cannot write")
+	return 0, spanner.ToSpannerError(status.Errorf(codes.FailedPrecondition, "read-only transactions cannot write"))
 }
 
 // ErrAbortedDueToConcurrentModification is returned by a read/write transaction