fix(mysqldump): unescape generation expressions from INFORMATION_SCHEMA

internal/mysqldump/escape.go

@@ -4,6 +4,16 @@ import (
 	"bytes"
 )
 
+var unescapeMap = map[byte]byte{
+	'0':  0,
+	'n':  '\n',
+	'r':  '\r',
+	'\\': '\\',
+	'\'': '\'',
+	'"':  '"',
+	'Z':  '\032',
+}
+
 func escape(str string) string {
 	var esc string
 	var buf bytes.Buffer
@@ -34,3 +44,18 @@ func escape(str string) string {
 	_, _ = buf.WriteString(str[last:])
 	return buf.String()
 }
+
+func unescape(str string) string {
+	var buf bytes.Buffer
+	for i := 0; i < len(str); i++ {
+		if str[i] == '\\' && i+1 < len(str) {
+			if unescaped, ok := unescapeMap[str[i+1]]; ok {
+				buf.WriteByte(unescaped)
+				i++
+				continue
+			}
+		}
+		buf.WriteByte(str[i])
+	}
+	return buf.String()
+}

internal/mysqldump/escape_test.go

@@ -12,3 +12,39 @@ func TestEscape(t *testing.T) {
 	result := escape(input)
 	assert.Equal(t, expected, result)
 }
+
+func TestUnescape(t *testing.T) {
+	input := `\0\n\r\\\'\"\Za`
+	expected := string([]byte{0, '\n', '\r', '\\', '\'', '"', '\032', 'a'})
+	result := unescape(input)
+	assert.Equal(t, expected, result)
+}
+
+func TestEscapeUnescape_RoundTrip(t *testing.T) {
+	testCases := []string{
+		"simple text",
+		"text with\nnewline",
+		"text with\rcarriage return",
+		`text with "double quotes"`,
+		"text with 'single quotes'",
+		`text with \backslash`,
+		"null\x00byte",
+		`json_extract(\'$.taxStatus\')`,
+	}
+
+	for _, original := range testCases {
+		escaped := escape(original)
+		unescaped := unescape(escaped)
+		assert.Equal(t, original, unescaped, "round-trip failed for: %q", original)
+	}
+}
+
+func TestUnescape_UnknownSequencePassthrough(t *testing.T) {
+	input := `abc\xyz`
+	assert.Equal(t, input, unescape(input))
+}
+
+func TestUnescape_TrailingBackslashPassthrough(t *testing.T) {
+	input := "abc\\"
+	assert.Equal(t, input, unescape(input))
+}

internal/mysqldump/schema.go

@@ -212,7 +212,8 @@ func (col *ColumnSchema) writeCharsetAndCollation(b *strings.Builder, tableColla
 func (col *ColumnSchema) writeGeneratedOrDefault(b *strings.Builder) {
 	if col.GenerationExpr.Valid && col.GenerationExpr.String != "" {
 		b.WriteString(" GENERATED ALWAYS AS (")
-		b.WriteString(col.GenerationExpr.String)
+		// INFORMATION_SCHEMA can return escaped quotes in generation expressions.
+		b.WriteString(unescape(col.GenerationExpr.String))
 		b.WriteString(")")
 		if col.IsVirtual {
 			b.WriteString(" VIRTUAL")

internal/mysqldump/schema_test.go

@@ -211,6 +211,37 @@ func TestTableSchema_BuildCreateTableSQL_GeneratedColumn(t *testing.T) {
 	assert.Contains(t, sql, "GENERATED ALWAYS AS (CONCAT(first_name, ' ', last_name)) VIRTUAL")
 }
 
+func TestTableSchema_BuildCreateTableSQL_GeneratedColumn_WithEscapedQuotes(t *testing.T) {
+	// This test covers issue #846: generation expressions from INFORMATION_SCHEMA.COLUMNS
+	// contain escaped quotes that need to be unescaped
+	schema := &TableSchema{
+		Name:      "b2b_components_pending_order",
+		Engine:    "InnoDB",
+		Charset:   "utf8mb4",
+		Collation: "utf8mb4_unicode_ci",
+		Columns: []ColumnSchema{
+			{Name: "id", Type: "int", Nullable: false, Extra: "AUTO_INCREMENT"},
+			{Name: "price", Type: "json", Nullable: false},
+			{
+				Name:     "tax_status",
+				Type:     "varchar(255)",
+				Nullable: true,
+				// This simulates what MySQL's INFORMATION_SCHEMA.COLUMNS returns with escaped quotes
+				GenerationExpr: sql.NullString{String: "json_unquote(json_extract(`price`,_utf8mb4\\'$.taxStatus\\'))", Valid: true},
+				IsVirtual:      true,
+			},
+		},
+		PrimaryKey: []string{"id"},
+	}
+
+	sql := schema.BuildCreateTableSQL()
+
+	// The output should have unescaped quotes
+	assert.Contains(t, sql, "GENERATED ALWAYS AS (json_unquote(json_extract(`price`,_utf8mb4'$.taxStatus'))) VIRTUAL")
+	// Ensure the broken version with backslash-escaped quotes is NOT in the output
+	assert.NotContains(t, sql, "\\'")
+}
+
 func TestTableSchema_BuildCreateTableSQL_ColumnCollation(t *testing.T) {
 	schema := &TableSchema{
 		Name:      "test",