chore(spanner): enable Go 1.13 error wrapping (#6795)

spanner/spannertest/db.go

@@ -1089,7 +1089,7 @@ func valForType(v *structpb.Value, t spansql.Type) (interface{}, error) {
 		if ok {
 			x, err := strconv.ParseInt(sv.StringValue, 10, 64)
 			if err != nil {
-				return nil, fmt.Errorf("bad int64 string %q: %v", sv.StringValue, err)
+				return nil, fmt.Errorf("bad int64 string %q: %w", sv.StringValue, err)
 			}
 			return x, nil
 		}
@@ -1116,7 +1116,7 @@ func valForType(v *structpb.Value, t spansql.Type) (interface{}, error) {
 			s := sv.StringValue
 			d, err := parseAsDate(s)
 			if err != nil {
-				return nil, fmt.Errorf("bad DATE string %q: %v", s, err)
+				return nil, fmt.Errorf("bad DATE string %q: %w", s, err)
 			}
 			return d, nil
 		}
@@ -1130,7 +1130,7 @@ func valForType(v *structpb.Value, t spansql.Type) (interface{}, error) {
 			}
 			t, err := parseAsTimestamp(s)
 			if err != nil {
-				return nil, fmt.Errorf("bad TIMESTAMP string %q: %v", s, err)
+				return nil, fmt.Errorf("bad TIMESTAMP string %q: %w", s, err)
 			}
 			return t, nil
 		}

spanner/spannertest/db_eval.go

@@ -649,7 +649,7 @@ func (ec evalContext) coerceString(target spansql.Expr, slit spansql.StringLiter
 	case spansql.Date:
 		d, err := parseAsDate(string(slit))
 		if err != nil {
-			return nil, fmt.Errorf("coercing string literal %q to DATE: %v", slit, err)
+			return nil, fmt.Errorf("coercing string literal %q to DATE: %w", slit, err)
 		}
 		return coercedValue{
 			val:  d,
@@ -658,7 +658,7 @@ func (ec evalContext) coerceString(target spansql.Expr, slit spansql.StringLiter
 	case spansql.Timestamp:
 		t, err := parseAsTimestamp(string(slit))
 		if err != nil {
-			return nil, fmt.Errorf("coercing string literal %q to TIMESTAMP: %v", slit, err)
+			return nil, fmt.Errorf("coercing string literal %q to TIMESTAMP: %w", slit, err)
 		}
 		return coercedValue{
 			val:  t,
@@ -758,7 +758,7 @@ func paramAsInteger(p spansql.Param, params queryParams) (int64, error) {
 	case string:
 		x, err := strconv.ParseInt(v, 10, 64)
 		if err != nil {
-			return 0, fmt.Errorf("bad int64 string %q: %v", v, err)
+			return 0, fmt.Errorf("bad int64 string %q: %w", v, err)
 		}
 		return x, nil
 	}

spanner/spannertest/db_query.go

@@ -582,7 +582,7 @@ func (d *database) evalSelect(sel spansql.Select, qc *queryContext) (si *selIter
 				if !starArg {
 					ci, err := ec.colInfo(fexpr.Args[0])
 					if err != nil {
-						return nil, fmt.Errorf("evaluating aggregate function %s arg type: %v", fexpr.Name, err)
+						return nil, fmt.Errorf("evaluating aggregate function %s arg type: %w", fexpr.Name, err)
 					}
 					argType = ci.Type
 				}
@@ -717,7 +717,7 @@ func (d *database) evalSelectFrom(qc *queryContext, ec evalContext, sf spansql.S
 		// TODO: Do all relevant types flow through here? Path expressions might be tricky here.
 		col, err := ec.colInfo(sf.Expr)
 		if err != nil {
-			return ec, nil, fmt.Errorf("evaluating type of UNNEST arg: %v", err)
+			return ec, nil, fmt.Errorf("evaluating type of UNNEST arg: %w", err)
 		}
 		if !col.Type.Array {
 			return ec, nil, fmt.Errorf("type of UNNEST arg is non-array %s", col.Type.SQL())
@@ -729,7 +729,7 @@ func (d *database) evalSelectFrom(qc *queryContext, ec evalContext, sf spansql.S
 		// Evaluate the expression, and yield a virtual table with one column.
 		e, err := ec.evalExpr(sf.Expr)
 		if err != nil {
-			return ec, nil, fmt.Errorf("evaluating UNNEST arg: %v", err)
+			return ec, nil, fmt.Errorf("evaluating UNNEST arg: %w", err)
 		}
 		arr, ok := e.([]interface{})
 		if !ok {

spanner/value.go

@@ -818,7 +818,7 @@ func (n *NullJSON) UnmarshalJSON(payload []byte) error {
 	var v interface{}
 	err := json.Unmarshal(payload, &v)
 	if err != nil {
-		return fmt.Errorf("payload cannot be converted to a struct: got %v, err: %s", string(payload), err)
+		return fmt.Errorf("payload cannot be converted to a struct: got %v, err: %w", string(payload), err)
 	}
 	n.Value = v
 	n.Valid = true