fix: prevent RowsAffected double-counting when triggers fire

rowsaffected_test.go

@@ -0,0 +1,143 @@
+package mssql
+
+import (
+	"context"
+	"fmt"
+	"math/rand"
+	"testing"
+)
+
+// TestRowsAffectedWithTrigger verifies that RowsAffected returns the correct
+// count for the outermost DML statement even when AFTER triggers fire and
+// produce their own intermediate DONEINPROC row counts. See #204.
+func TestRowsAffectedWithTrigger(t *testing.T) {
+	conn, logger := open(t)
+	defer conn.Close()
+	defer logger.StopLogging()
+
+	ctx := context.Background()
+
+	suffix := fmt.Sprintf("%d", rand.Intn(999999))
+	tbl := "test_ra204_" + suffix
+	audit := "test_ra204_audit_" + suffix
+	trg := "tr_ra204_" + suffix
+
+	cleanup := func() {
+		conn.ExecContext(ctx, "drop trigger if exists "+trg)
+		conn.ExecContext(ctx, "drop table if exists "+audit)
+		conn.ExecContext(ctx, "drop table if exists "+tbl)
+	}
+	cleanup()
+	defer cleanup()
+
+	_, err := conn.ExecContext(ctx, "create table "+tbl+" (id int primary key, value nvarchar(100))")
+	if err != nil {
+		t.Fatal("create table failed:", err)
+	}
+
+	_, err = conn.ExecContext(ctx, "insert into "+tbl+" values (1, 'old'), (2, 'old'), (3, 'old')")
+	if err != nil {
+		t.Fatal("insert failed:", err)
+	}
+
+	// Scenario 1: Basic update without trigger
+	result, err := conn.ExecContext(ctx, "update "+tbl+" set value = 'test' where id = 1")
+	if err != nil {
+		t.Fatal("update failed:", err)
+	}
+	rowsAffected, _ := result.RowsAffected()
+	if rowsAffected != 1 {
+		t.Errorf("basic update: expected RowsAffected=1, got %d", rowsAffected)
+	}
+
+	// Create audit table and trigger without NOCOUNT
+	_, err = conn.ExecContext(ctx, "create table "+audit+" (id int identity, action nvarchar(50))")
+	if err != nil {
+		t.Fatal("create audit table failed:", err)
+	}
+	_, err = conn.ExecContext(ctx, "create trigger "+trg+" on "+tbl+" after update as begin insert into "+audit+" (action) select 'updated' from inserted end")
+	if err != nil {
+		t.Fatal("create trigger failed:", err)
+	}
+
+	// Scenario 2: Update with trigger (no NOCOUNT) - trigger produces extra DONEINPROC
+	result, err = conn.ExecContext(ctx, "update "+tbl+" set value = 'triggered' where id = 1")
+	if err != nil {
+		t.Fatal("triggered update failed:", err)
+	}
+	rowsAffected, _ = result.RowsAffected()
+	if rowsAffected != 1 {
+		t.Errorf("trigger without NOCOUNT: expected RowsAffected=1, got %d", rowsAffected)
+	}
+
+	// Scenario 3: Recreate trigger with NOCOUNT
+	conn.ExecContext(ctx, "drop trigger "+trg)
+	_, err = conn.ExecContext(ctx, "create trigger "+trg+" on "+tbl+" after update as begin set nocount on; insert into "+audit+" (action) select 'updated' from inserted end")
+	if err != nil {
+		t.Fatal("create nocount trigger failed:", err)
+	}
+
+	result, err = conn.ExecContext(ctx, "update "+tbl+" set value = 'nocount' where id = 1")
+	if err != nil {
+		t.Fatal("nocount triggered update failed:", err)
+	}
+	rowsAffected, _ = result.RowsAffected()
+	if rowsAffected != 1 {
+		t.Errorf("trigger with NOCOUNT: expected RowsAffected=1, got %d", rowsAffected)
+	}
+
+	// Scenario 4: Update all rows with trigger
+	result, err = conn.ExecContext(ctx, "update "+tbl+" set value = 'all'")
+	if err != nil {
+		t.Fatal("bulk update failed:", err)
+	}
+	rowsAffected, _ = result.RowsAffected()
+	if rowsAffected != 3 {
+		t.Errorf("bulk update with trigger: expected RowsAffected=3, got %d", rowsAffected)
+	}
+}
+
+// TestMultiStatementBatchRowsAffected verifies that RowsAffected returns the
+// last statement's count for a multi-statement batch. The assignment (=)
+// semantics in doneStruct processing mean each DONE token replaces (not
+// accumulates) the row count, so the final DONE is authoritative.
+func TestMultiStatementBatchRowsAffected(t *testing.T) {
+	conn, logger := open(t)
+	defer conn.Close()
+	defer logger.StopLogging()
+
+	ctx := context.Background()
+
+	suffix := fmt.Sprintf("%d", rand.Intn(999999))
+	tbl := "test_msbatch_" + suffix
+
+	cleanup := func() {
+		conn.ExecContext(ctx, "drop table if exists "+tbl)
+	}
+	cleanup()
+	defer cleanup()
+
+	_, err := conn.ExecContext(ctx, "create table "+tbl+" (id int primary key, value nvarchar(100))")
+	if err != nil {
+		t.Fatal("create table failed:", err)
+	}
+
+	// Seed 5 rows.
+	_, err = conn.ExecContext(ctx, "insert into "+tbl+" values (1,'a'),(2,'b'),(3,'c'),(4,'d'),(5,'e')")
+	if err != nil {
+		t.Fatal("insert failed:", err)
+	}
+
+	// Multi-statement batch: first UPDATE touches 3 rows, second touches 2.
+	// RowsAffected should be 2 (the last statement), not 5 (the sum).
+	batch := "update " + tbl + " set value='x' where id <= 3; " +
+		"update " + tbl + " set value='y' where id > 3"
+	result, err := conn.ExecContext(ctx, batch)
+	if err != nil {
+		t.Fatal("multi-statement batch failed:", err)
+	}
+	rowsAffected, _ := result.RowsAffected()
+	if rowsAffected != 2 {
+		t.Errorf("multi-statement batch: expected RowsAffected=2 (last stmt), got %d", rowsAffected)
+	}
+}

token.go

@@ -1242,7 +1242,12 @@ func (t *tokenProcessor) iterateResponse() error {
 					}
 				case doneStruct:
 					if token.Status&doneCount != 0 {
-						t.rowCount += int64(token.RowCount)
+						// Assignment (not +=) so the final DONE token's count
+						// is authoritative. Prevents double-counting when AFTER
+						// triggers fire without SET NOCOUNT ON (#204).
+						// For multi-statement batches, this means RowsAffected()
+						// returns the last statement's count, not the sum.
+						t.rowCount = int64(token.RowCount)
 					}
 					if token.isError() && t.firstError == nil {
 						t.firstError = token.getError()

token_test.go

@@ -467,3 +467,49 @@ func TestNextToken_CancelDrainClosedChannelStartsSecondResponse(t *testing.T) {
 		t.Fatal("expected attention packet to be written")
 	}
 }
+
+// TestRowCountAssignmentNotAccumulation verifies that iterateResponse uses
+// assignment (=) for doneStruct row counts, not accumulation (+=). This
+// prevents double-counting when AFTER triggers fire without SET NOCOUNT ON.
+func TestRowCountAssignmentNotAccumulation(t *testing.T) {
+	tokChan := make(chan tokenStruct, 10)
+	tp := &tokenProcessor{
+		tokChan: tokChan,
+		ctx:     context.Background(),
+		sess:    &tdsSession{},
+	}
+
+	// Simulate trigger scenario: DONEINPROC from trigger (1 row), then
+	// final DONE from the outer UPDATE (also 1 row). With +=, rowCount
+	// would be 2. With =, it should be 1.
+	tokChan <- doneInProcStruct{Status: doneCount, RowCount: 1}
+	tokChan <- doneStruct{Status: doneFinal | doneCount, RowCount: 1}
+	close(tokChan)
+
+	err := tp.iterateResponse()
+	assert.NoError(t, err)
+	assert.Equal(t, int64(1), tp.rowCount,
+		"rowCount should be 1 (assigned), not 2 (accumulated)")
+}
+
+// TestRowCountMultiStatement verifies that for multi-statement batches, the
+// final DONE token's count wins (last statement), not the sum.
+func TestRowCountMultiStatement(t *testing.T) {
+	tokChan := make(chan tokenStruct, 10)
+	tp := &tokenProcessor{
+		tokChan: tokChan,
+		ctx:     context.Background(),
+		sess:    &tdsSession{},
+	}
+
+	// First statement: DONE with 3 rows
+	tokChan <- doneStruct{Status: doneCount, RowCount: 3}
+	// Second statement: DONE with 2 rows (final)
+	tokChan <- doneStruct{Status: doneFinal | doneCount, RowCount: 2}
+	close(tokChan)
+
+	err := tp.iterateResponse()
+	assert.NoError(t, err)
+	assert.Equal(t, int64(2), tp.rowCount,
+		"rowCount should be 2 (last statement), not 5 (sum)")
+}