Share one unsupported-toolchain check across platforms

esphome/components/esp32/__init__.py

@@ -1083,11 +1083,7 @@ def _resolve_toolchain(value: ConfigType) -> ConfigType:
     # CORE.toolchain instead of re-resolving it from the config dict.
     if CORE.toolchain is None:
         CORE.toolchain = value.get(CONF_TOOLCHAIN, Toolchain.ESP_IDF)
-    if CORE.toolchain not in (Toolchain.PLATFORMIO, Toolchain.ESP_IDF):
-        raise cv.Invalid(
-            f"Unsupported toolchain '{CORE.toolchain.value}' for ESP32. "
-            "Supported toolchains are 'platformio' and 'esp-idf'."
-        )
+    cv.check_supported_toolchain("ESP32", (Toolchain.PLATFORMIO, Toolchain.ESP_IDF))
     return value
 
 

esphome/components/host/__init__.py

@@ -36,8 +36,8 @@ CONFIG_SCHEMA = cv.All(
             cv.Optional(CONF_MAC_ADDRESS, default="98:35:69:ab:f6:79"): cv.mac_address,
         }
     ),
-    set_core_data,
     cv.require_platformio_toolchain("host"),
+    set_core_data,
 )
 
 

esphome/components/nrf52/__init__.py

@@ -128,11 +128,7 @@ def set_core_data(config: ConfigType) -> ConfigType:
 def _resolve_toolchain(config: ConfigType) -> ConfigType:
     if CORE.toolchain is None:
         CORE.toolchain = config.get(CONF_TOOLCHAIN, Toolchain.SDK_NRF)
-    if CORE.toolchain not in (Toolchain.PLATFORMIO, Toolchain.SDK_NRF):
-        raise cv.Invalid(
-            f"Unsupported toolchain '{CORE.toolchain.value}' for nRF52. "
-            "Supported toolchains are 'platformio' and 'sdk-nrf'."
-        )
+    cv.check_supported_toolchain("nRF52", (Toolchain.PLATFORMIO, Toolchain.SDK_NRF))
     return config
 
 

esphome/components/rp2/__init__.py

@@ -312,8 +312,8 @@ CONFIG_SCHEMA = cv.All(
     ),
     cv.has_at_least_one_key(CONF_BOARD, CONF_VARIANT),
     _detect_variant,
-    set_core_data,
     cv.require_platformio_toolchain("RP2"),
+    set_core_data,
 )
 
 

esphome/config_validation.py

@@ -75,6 +75,7 @@ from esphome.const import (
     TYPE_GIT,
     TYPE_LOCAL,
     Framework,
+    Toolchain,
     __version__ as ESPHOME_VERSION,
 )
 from esphome.core import (
@@ -2532,6 +2533,21 @@ def platformio_version_constraint(value):
     return constraints
 
 
+def check_supported_toolchain(platform_name: str, supported: tuple) -> None:
+    """Raise when the resolved ``CORE.toolchain`` is not in ``supported``.
+
+    One message shape for every platform, so a ``--toolchain`` a platform
+    cannot serve always fails by name instead of silently building with a
+    different backend.
+    """
+    if CORE.toolchain not in supported:
+        names = ", ".join(f"'{tc.value}'" for tc in supported)
+        raise Invalid(
+            f"Unsupported toolchain '{CORE.toolchain.value}' for "
+            f"{platform_name}. Supported: {names}."
+        )
+
+
 def require_platformio_toolchain(platform_name: str):
     """Reject a CLI-selected toolchain other than PlatformIO.
 
@@ -2540,15 +2556,9 @@ def require_platformio_toolchain(platform_name: str):
     """
 
     def validator(config):
-        from esphome.const import Toolchain
-
         if CORE.toolchain is None:
             CORE.toolchain = Toolchain.PLATFORMIO
-        if CORE.toolchain != Toolchain.PLATFORMIO:
-            raise Invalid(
-                f"Unsupported toolchain '{CORE.toolchain.value}' for "
-                f"{platform_name}. The only supported toolchain is 'platformio'."
-            )
+        check_supported_toolchain(platform_name, (Toolchain.PLATFORMIO,))
         return config
 
     return validator

esphome/core/config.py

@@ -557,9 +557,9 @@ def _add_library_str(lib: str) -> None:
 
 @coroutine_with_priority(CoroPriority.FINAL)
 async def _add_platformio_options(pio_options: dict[str, str | list[str]]) -> None:
-    if CORE.using_toolchain_esp_idf or (
-        CORE.using_toolchain_arduino and CORE.is_esp8266
-    ):
+    # Every platform's toolchain validation rejects values it cannot serve,
+    # so using_toolchain_arduino by itself implies the native ESP8266 build.
+    if CORE.using_toolchain_esp_idf or CORE.using_toolchain_arduino:
         # The native builds don't read platformio.ini; honor the options
         # with a native equivalent and warn about the rest, which would
         # otherwise be silently ignored.