[uart] clock_source option (#16486)

Co-authored-by: J. Nick Koston <nick@home-assistant.io>

tests/component_tests/uart/test_clock_source.py

@@ -0,0 +1,112 @@
+"""Tests for UART clock source validation and code generation."""
+
+from collections.abc import Callable
+from pathlib import Path
+
+import pytest
+
+from esphome.components.esp32 import KEY_VARIANT, VARIANTS
+from esphome.components.uart import (
+    CONF_CLOCK_SOURCE,
+    CONFIG_SCHEMA,
+    UART_CLOCK_SOURCES,
+    UART_CLOCK_SOURCES_BY_VARIANT,
+)
+import esphome.config_validation as cv
+from esphome.const import PlatformFramework
+from tests.component_tests.types import SetCoreConfigCallable
+
+
+@pytest.fixture
+def clock_source_validator() -> cv.All:
+    """Find the clock validator without depending on pre-validator ordering."""
+    schema = next(
+        validator
+        for validator in CONFIG_SCHEMA.validators
+        if isinstance(validator, cv.Schema)
+    )
+    return schema.schema[cv.Optional(CONF_CLOCK_SOURCE)]
+
+
+def test_clock_source_table_covers_all_variants() -> None:
+    """New ESP32 variants must declare their supported UART clocks."""
+    assert set(UART_CLOCK_SOURCES_BY_VARIANT) == set(VARIANTS)
+    for sources in UART_CLOCK_SOURCES_BY_VARIANT.values():
+        assert "DEFAULT" in sources
+        assert set(sources) <= UART_CLOCK_SOURCES.keys()
+
+
+@pytest.mark.parametrize(
+    ("variant", "source", "supported"),
+    [
+        ("ESP32", "REF_TICK", True),
+        ("ESP32", "XTAL", False),
+        ("ESP32S2", "REF_TICK", True),
+        ("ESP32S2", "RTC", False),
+        ("ESP32C3", "APB", True),
+        ("ESP32C3", "xtal", True),
+        ("ESP32C3", "REF_TICK", False),
+        ("ESP32S3", "RTC", True),
+        ("ESP32S3", "REF_TICK", False),
+        ("ESP32C2", "APB", False),
+        ("ESP32C6", "APB", False),
+        ("ESP32C6", "DEFAULT", True),
+        ("ESP32C5", "RTC", True),
+        ("ESP32C61", "XTAL", True),
+        ("ESP32H4", "RTC", True),
+        ("ESP32H21", "XTAL", True),
+        ("ESP32S31", "RTC", True),
+        ("ESP32H2", "XTAL", True),
+        ("ESP32P4", "RTC", True),
+        ("ESP32C3", "INVALID", False),
+    ],
+)
+def test_clock_source_validation(
+    variant: str,
+    source: str,
+    supported: bool,
+    set_core_config: SetCoreConfigCallable,
+    clock_source_validator: cv.All,
+) -> None:
+    """Reject unsupported clocks and normalize accepted names."""
+    set_core_config(
+        PlatformFramework.ESP32_IDF,
+        platform_data={KEY_VARIANT: variant},
+    )
+    if supported:
+        assert clock_source_validator(source) == source.upper()
+    else:
+        with pytest.raises(cv.Invalid):
+            clock_source_validator(source)
+
+
+def test_clock_source_requires_esp32(
+    set_core_config: SetCoreConfigCallable,
+    clock_source_validator: cv.All,
+) -> None:
+    """Reject the ESP32-only option before accessing the chip variant."""
+    set_core_config(PlatformFramework.ESP8266_ARDUINO)
+    with pytest.raises(cv.Invalid, match="ESP32"):
+        clock_source_validator("DEFAULT")
+
+
+@pytest.mark.parametrize("source", [None, "default", "xtal"])
+def test_clock_source_codegen(
+    source: str | None,
+    tmp_path: Path,
+    generate_main: Callable[[str | Path], str],
+) -> None:
+    """Emit IDF constants directly and skip the setter when nothing changes."""
+    config = tmp_path / "uart.yaml"
+    config.write_text(
+        "esphome:\n  name: uart-clock-test\n"
+        "esp32:\n  variant: esp32c3\n  framework:\n    type: esp-idf\n"
+        "uart:\n  id: test_uart\n  tx_pin: GPIO4\n  baud_rate: 9600\n"
+        + (f"  clock_source: {source}\n" if source else ""),
+        encoding="utf-8",
+    )
+    main_cpp = generate_main(config)
+    if source in (None, "default"):
+        assert "set_clock_source(" not in main_cpp
+    else:
+        assert f"test_uart->set_clock_source(::UART_SCLK_{source.upper()});" in main_cpp