[thermostat] Keep presets in shared flash tables (#20080)

tests/component_tests/thermostat/config/presets.yaml

@@ -0,0 +1,53 @@
+---
+esphome:
+  name: test
+
+logger:
+
+esp32:
+  board: esp32dev
+
+sensor:
+  - platform: template
+    id: temp_sensor
+    lambda: return 21.0;
+
+climate:
+  - platform: thermostat
+    id: thermo_a
+    name: Thermo A
+    sensor: temp_sensor
+    min_heating_off_time: 300s
+    min_heating_run_time: 300s
+    min_idle_time: 30s
+    heat_action:
+      - logger.log: heat
+    idle_action:
+      - logger.log: idle
+    preset:
+      - name: Away
+        default_target_temperature_low: 15°C
+        mode: HEAT
+      - name: Eco
+        default_target_temperature_low: 17°C
+      - name: Night Mode
+        default_target_temperature_low: 16°C
+  - platform: thermostat
+    id: thermo_b
+    name: Thermo B
+    sensor: temp_sensor
+    min_heating_off_time: 300s
+    min_heating_run_time: 300s
+    min_idle_time: 30s
+    heat_action:
+      - logger.log: heat
+    idle_action:
+      - logger.log: idle
+    preset:
+      - name: Away
+        default_target_temperature_low: 15°C
+        mode: HEAT
+      - name: Eco
+        default_target_temperature_low: 17°C
+      - name: Night Mode
+        default_target_temperature_low: 16°C

tests/component_tests/thermostat/test_presets.py

@@ -0,0 +1,28 @@
+"""Tests for the thermostat preset codegen."""
+
+from collections.abc import Callable
+from pathlib import Path
+import re
+
+
+def test_presets_shared_progmem_tables(
+    generate_main: Callable[[str | Path], str],
+    component_config_path: Callable[[str], Path],
+) -> None:
+    """Thermostats with the same presets share one PROGMEM table per kind."""
+    main_cpp = generate_main(component_config_path("presets.yaml"))
+
+    standard = re.findall(
+        r"static constexpr thermostat::ThermostatPresetEntry (\w+)\[\] PROGMEM",
+        main_cpp,
+    )
+    custom = re.findall(
+        r"static constexpr thermostat::ThermostatCustomPresetEntry (\w+)\[\] PROGMEM",
+        main_cpp,
+    )
+    assert len(standard) == 1
+    assert len(custom) == 1
+    for var in ("thermo_a", "thermo_b"):
+        assert f"{var}->set_preset_config({standard[0]}, 2);" in main_cpp
+        assert f"{var}->set_custom_preset_config({custom[0]}, 1);" in main_cpp
+    assert "climate::CLIMATE_MODE_HEAT" in main_cpp