database/sql: update the conversion errors to be clearer

There was some ambiguity over which argument was referred to when
a conversion error was returned. Now refer to the argument by
either explicit ordinal position or name if present.

Fixes #15676

Change-Id: Id933196b7e648baa664f4121fa3fb1b07b3c4880
Reviewed-on: https://go-review.googlesource.com/31262
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

src/database/sql/convert.go

@@ -17,6 +17,13 @@ import (
 
 var errNilPtr = errors.New("destination pointer is nil") // embedded in descriptive error
 
+func describeNamedValue(nv *driver.NamedValue) string {
+ if len(nv.Name) == 0 {
+ return fmt.Sprintf("$%d", nv.Ordinal)
+ }
+ return fmt.Sprintf("with name %q", nv.Name)
+}
+
 // driverArgs converts arguments from callers of Stmt.Exec and
 // Stmt.Query into driver Values.
 //
@@ -33,37 +40,39 @@ func driverArgs(ds *driverStmt, args []interface{}) ([]driver.NamedValue, error)
  if !ok {
  for n, arg := range args {
  var err error
- nvargs[n].Ordinal = n + 1
+ nv := &nvargs[n]
+ nv.Ordinal = n + 1
  if np, ok := arg.(NamedParam); ok {
  arg = np.Value
  nvargs[n].Name = np.Name
  }
- nvargs[n].Value, err = driver.DefaultParameterConverter.ConvertValue(arg)
+ nv.Value, err = driver.DefaultParameterConverter.ConvertValue(arg)
 
  if err != nil {
- return nil, fmt.Errorf("sql: converting Exec argument #%d's type: %v", n, err)
+ return nil, fmt.Errorf("sql: converting Exec argument %s type: %v", describeNamedValue(nv), err)
  }
  }
  return nvargs, nil
  }
 
  // Let the Stmt convert its own arguments.
  for n, arg := range args {
- nvargs[n].Ordinal = n + 1
+ nv := &nvargs[n]
+ nv.Ordinal = n + 1
  if np, ok := arg.(NamedParam); ok {
  arg = np.Value
- nvargs[n].Name = np.Name
+ nv.Name = np.Name
  }
  // First, see if the value itself knows how to convert
  // itself to a driver type. For example, a NullString
  // struct changing into a string or nil.
  if vr, ok := arg.(driver.Valuer); ok {
  sv, err := callValuerValue(vr)
  if err != nil {
- return nil, fmt.Errorf("sql: argument index %d from Value: %v", n, err)
+ return nil, fmt.Errorf("sql: argument %s from Value: %v", describeNamedValue(nv), err)
  }
  if !driver.IsValue(sv) {
- return nil, fmt.Errorf("sql: argument index %d: non-subset type %T returned from Value", n, sv)
+ return nil, fmt.Errorf("sql: argument %s: non-subset type %T returned from Value", describeNamedValue(nv), sv)
  }
  arg = sv
  }
@@ -77,14 +86,14 @@ func driverArgs(ds *driverStmt, args []interface{}) ([]driver.NamedValue, error)
  // same error.
  var err error
  ds.Lock()
- nvargs[n].Value, err = cc.ColumnConverter(n).ConvertValue(arg)
+ nv.Value, err = cc.ColumnConverter(n).ConvertValue(arg)
  ds.Unlock()
  if err != nil {
- return nil, fmt.Errorf("sql: converting argument #%d's type: %v", n, err)
+ return nil, fmt.Errorf("sql: converting argument %s type: %v", describeNamedValue(nv), err)
  }
- if !driver.IsValue(nvargs[n].Value) {
- return nil, fmt.Errorf("sql: driver ColumnConverter error converted %T to unsupported type %T",
- arg, nvargs[n].Value)
+ if !driver.IsValue(nv.Value) {
+ return nil, fmt.Errorf("sql: for argument %s, driver ColumnConverter error converted %T to unsupported type %T",
+ describeNamedValue(nv), arg, nv.Value)
  }
  }
 

src/database/sql/sql_test.go

@@ -745,8 +745,8 @@ func TestExec(t *testing.T) {
  {[]interface{}{7, 9}, ""},
 
  // Invalid conversions:
- {[]interface{}{"Brad", int64(0xFFFFFFFF)}, "sql: converting argument #1's type: sql/driver: value 4294967295 overflows int32"},
- {[]interface{}{"Brad", "strconv fail"}, "sql: converting argument #1's type: sql/driver: value \"strconv fail\" can't be converted to int32"},
+ {[]interface{}{"Brad", int64(0xFFFFFFFF)}, "sql: converting argument $2 type: sql/driver: value 4294967295 overflows int32"},
+ {[]interface{}{"Brad", "strconv fail"}, `sql: converting argument $2 type: sql/driver: value "strconv fail" can't be converted to int32`},
 
  // Wrong number of args:
  {[]interface{}{}, "sql: expected 2 arguments, got 0"},