[template] Skip the switch optimistic and assumed state setters when they match the default (#19232)

tests/component_tests/template/config/switch_defaults.yaml

@@ -0,0 +1,18 @@
+---
+esphome:
+  name: test
+
+esp32:
+  board: esp32dev
+
+logger:
+
+switch:
+  - platform: template
+    id: plain_switch
+    turn_on_action:
+      - logger.log: "on"
+  - platform: template
+    id: enabled_switch
+    optimistic: true
+    assumed_state: true

tests/component_tests/template/test_template_switch.py

@@ -0,0 +1,17 @@
+"""Tests for the template switch codegen."""
+
+from collections.abc import Callable
+from pathlib import Path
+
+
+def test_default_flags_are_not_emitted(
+    generate_main: Callable[[str | Path], str],
+    component_config_path: Callable[[str], Path],
+) -> None:
+    """Only true optimistic and assumed_state are set; false is the C++ initializer."""
+    main_cpp = generate_main(component_config_path("switch_defaults.yaml"))
+
+    assert "plain_switch->set_optimistic(" not in main_cpp
+    assert "plain_switch->set_assumed_state(" not in main_cpp
+    assert "enabled_switch->set_optimistic(true);" in main_cpp
+    assert "enabled_switch->set_assumed_state(true);" in main_cpp