tests: add regression test for variadic interface chain forwarding

vlib/v/tests/fns/variadic_interface_chain_forwarding_test.v

@@ -0,0 +1,138 @@
+import arrays
+
+// Regression test for https://github.com/vlang/v/issues/26760
+// Interface values passed through variadic parameter chains must preserve
+// their type tags and data pointers.
+
+interface Value {}
+
+fn process_params(params []Value) string {
+	mut result := []string{}
+	for i := 0; i < params.len; i++ {
+		param := params[i]
+		match param {
+			string {
+				result << 'string:${param}'
+			}
+			i32 {
+				result << 'i32:${param}'
+			}
+			[]u8 {
+				result << '[]u8:${param.len}'
+			}
+			else {
+				result << 'unknown'
+			}
+		}
+	}
+	return result.join(', ')
+}
+
+struct Statement {
+mut:
+	handle int
+}
+
+struct Transaction {
+mut:
+	handle int
+}
+
+fn (mut stmt Statement) execute(params ...Value) !string {
+	return process_params(params)
+}
+
+fn (stmt Statement) close() ! {}
+
+fn (mut t Transaction) prepare(query string) !Statement {
+	return Statement{ handle: 1 }
+}
+
+fn (mut t Transaction) execute(query string, params ...Value) !string {
+	mut stmt := t.prepare(query)!
+	result := stmt.execute(...params)!
+	stmt.close()!
+	return result
+}
+
+struct ListParams {
+	email  ?string
+	role   ?string
+	offset i32
+	fetch  i32
+}
+
+fn get_conditions(p ListParams) (string, []Value) {
+	mut conditions := []string{}
+	mut params := []Value{}
+
+	if email := p.email {
+		conditions = arrays.concat(conditions, 'email = ?')
+		params = arrays.concat(params, email)
+	}
+
+	if role := p.role {
+		conditions = arrays.concat(conditions, 'role = ?')
+		params = arrays.concat(params, role)
+	}
+
+	return conditions.join(' AND '), params
+}
+
+fn test_variadic_interface_forwarding_with_match() ! {
+	p := ListParams{
+		email:  'info@peony.com'
+		offset: 0
+		fetch:  10
+	}
+
+	conditions, mut params := get_conditions(p)
+	params = arrays.concat(params, p.offset, p.fetch)
+
+	mut tx := Transaction{ handle: 1 }
+	result := tx.execute('SELECT * FROM users WHERE ${conditions}', ...params)!
+	assert result == 'string:info@peony.com, i32:0, i32:10', 'got: ${result}'
+}
+
+fn test_variadic_interface_forwarding_single_param() ! {
+	p := ListParams{
+		email:  'info@peony.com'
+		offset: 0
+		fetch:  10
+	}
+
+	conditions, params := get_conditions(p)
+
+	mut tx := Transaction{ handle: 1 }
+	result := tx.execute('SELECT COUNT(*) FROM users WHERE ${conditions}', ...params)!
+	assert result == 'string:info@peony.com', 'got: ${result}'
+}
+
+fn test_variadic_interface_forwarding_with_byte_arrays() ! {
+	user_id_bin := [u8(1), 2, 3, 4]
+	email := 'info@peony.com'
+
+	mut params := [Value(user_id_bin), email]
+
+	mut tx := Transaction{ handle: 1 }
+	result := tx.execute('INSERT INTO users', ...params)!
+	assert result == '[]u8:4, string:info@peony.com', 'got: ${result}'
+}
+
+fn test_variadic_interface_forwarding_repeated() ! {
+	for _ in 0 .. 100 {
+		p := ListParams{
+			email:  'info@peony.com'
+			role:   'admin'
+			offset: 5
+			fetch:  20
+		}
+
+		conditions, mut params := get_conditions(p)
+		params = arrays.concat(params, p.offset, p.fetch)
+
+		mut tx := Transaction{ handle: 1 }
+		result := tx.execute('SELECT * FROM users WHERE ${conditions}', ...params)!
+		assert result == 'string:info@peony.com, string:admin, i32:5, i32:20', 'got: ${result}'
+	}
+}