[esp8266] Fail fast when Rosetta 2 is missing on Apple Silicon Macs (#17737)

esphome/__main__.py

@@ -776,6 +776,13 @@ def compile_program(args: ArgsProtocol, config: ConfigType) -> int:
 
         check_placeholder_credentials(config)
 
+    # Keep this here, NOT in codegen: config-hash and --only-generate must keep
+    # working on machines that cannot run the toolchain.
+    if CORE.is_esp8266:
+        from esphome.components.esp8266 import check_rosetta
+
+        check_rosetta()
+
     # NOTE: "Build path:" format is parsed by script/ci_memory_impact_extract.py
     # If you change this format, update the regex in that script as well
     _LOGGER.info("Compiling app... Build path: %s", CORE.build_path)

esphome/components/esp8266/__init__.py

@@ -1,5 +1,6 @@
 import logging
 from pathlib import Path
+import platform
 import re
 import subprocess
 
@@ -20,9 +21,15 @@ from esphome.const import (
     PLATFORM_ESP8266,
     ThreadModel,
 )
-from esphome.core import CORE, CoroPriority, Lambda, coroutine_with_priority
+from esphome.core import (
+    CORE,
+    CoroPriority,
+    EsphomeError,
+    Lambda,
+    coroutine_with_priority,
+)
 from esphome.core.config import BOARD_MAX_LENGTH
-from esphome.helpers import copy_file_if_changed
+from esphome.helpers import IS_MACOS, copy_file_if_changed
 from esphome.types import ConfigType
 
 from .boards import BOARDS, ESP8266_LD_SCRIPTS
@@ -237,6 +244,32 @@ CONFIG_SCHEMA = cv.All(
 )
 
 
+def check_rosetta() -> None:
+    """Fail fast when the x86_64 ESP8266 toolchain cannot run on this Mac.
+
+    There is no native arm64 build of the xtensa-lx106 toolchain; on Apple
+    Silicon it runs under Rosetta 2, which macOS updates can remove.
+    """
+    if not IS_MACOS or platform.machine() != "arm64":
+        return
+    try:
+        result = subprocess.run(
+            ["/usr/bin/arch", "-x86_64", "/usr/bin/true"],
+            capture_output=True,
+            close_fds=False,
+            check=False,
+        )
+    except OSError:
+        return  # arch(1) unavailable; let the build proceed
+    if result.returncode != 0:
+        raise EsphomeError(
+            "ESP8266 builds on Apple Silicon Macs use an Intel (x86_64) "
+            "compiler that requires Rosetta 2, which is not installed on "
+            "this system. Install it with:\n"
+            "  softwareupdate --install-rosetta --agree-to-license"
+        )
+
+
 @coroutine_with_priority(CoroPriority.PLATFORM)
 async def to_code(config):
     cg.add(esp8266_ns.setup_preferences())

tests/unit_tests/components/test_esp8266.py

@@ -1,9 +1,15 @@
 """Tests for ESP8266 component."""
 
+from __future__ import annotations
+
+from collections.abc import Generator
+from unittest.mock import MagicMock, patch
+
 import pytest
 
-from esphome.components.esp8266 import lambdas_use_scanf_float
-from esphome.core import Lambda
+from esphome.components import esp8266
+from esphome.components.esp8266 import check_rosetta, lambdas_use_scanf_float
+from esphome.core import EsphomeError, Lambda
 from esphome.types import ConfigType
 
 
@@ -60,3 +66,54 @@ def test_lambdas_use_scanf_float_nested() -> None:
     """Test detection in deeply nested config."""
     config: ConfigType = {"a": {"b": {"c": [Lambda('sscanf(buf, "%f", &v)')]}}}
     assert lambdas_use_scanf_float(config) is True
+
+
+@pytest.fixture
+def apple_silicon_run(monkeypatch: pytest.MonkeyPatch) -> Generator[MagicMock]:
+    """Simulate an Apple Silicon Mac and yield the mocked subprocess.run."""
+    monkeypatch.setattr(esp8266, "IS_MACOS", True)
+    with (
+        patch("esphome.components.esp8266.platform.machine", return_value="arm64"),
+        patch("esphome.components.esp8266.subprocess.run") as mock_run,
+    ):
+        yield mock_run
+
+
+@pytest.mark.parametrize(
+    ("is_macos", "machine"),
+    [
+        (False, "arm64"),
+        (True, "x86_64"),
+    ],
+)
+def test_check_rosetta_skips_other_systems(
+    monkeypatch: pytest.MonkeyPatch, is_macos: bool, machine: str
+) -> None:
+    """The check only probes on Apple Silicon Macs."""
+    monkeypatch.setattr(esp8266, "IS_MACOS", is_macos)
+    with (
+        patch("esphome.components.esp8266.platform.machine", return_value=machine),
+        patch("esphome.components.esp8266.subprocess.run") as mock_run,
+    ):
+        check_rosetta()
+    mock_run.assert_not_called()
+
+
+def test_check_rosetta_installed(apple_silicon_run: MagicMock) -> None:
+    """No error when the x86_64 probe succeeds (Rosetta present)."""
+    apple_silicon_run.return_value = MagicMock(returncode=0)
+    check_rosetta()
+    apple_silicon_run.assert_called_once()
+
+
+def test_check_rosetta_missing(apple_silicon_run: MagicMock) -> None:
+    """A failing x86_64 probe raises an actionable error."""
+    apple_silicon_run.return_value = MagicMock(returncode=1)
+    with pytest.raises(EsphomeError, match="softwareupdate --install-rosetta"):
+        check_rosetta()
+
+
+def test_check_rosetta_arch_unavailable(apple_silicon_run: MagicMock) -> None:
+    """The build proceeds when arch(1) cannot be executed."""
+    apple_silicon_run.side_effect = OSError("no such file")
+    check_rosetta()

tests/unit_tests/test_main.py

@@ -5450,6 +5450,43 @@ def _setup_build_info_test(
     return build_info_path, firmware_path
 
 
+def test_compile_program_esp8266_runs_rosetta_check(tmp_path: Path) -> None:
+    """Test that compile_program runs the Rosetta preflight for ESP8266 targets."""
+    setup_core(platform=PLATFORM_ESP8266, tmp_path=tmp_path, name="test_device")
+
+    config: dict[str, Any] = {CONF_ESPHOME: {CONF_NAME: "test_device"}}
+    args = MockArgs()
+
+    with (
+        patch(
+            "esphome.components.esp8266.check_rosetta",
+            side_effect=EsphomeError("Rosetta 2 is not installed"),
+        ) as mock_check,
+        pytest.raises(EsphomeError, match="Rosetta 2 is not installed"),
+    ):
+        compile_program(args, config)
+
+    mock_check.assert_called_once()
+
+
+def test_compile_program_skips_rosetta_check_on_other_platforms(
+    tmp_path: Path,
+    mock_compile_build_info_run_compile: Mock,
+    mock_compile_build_info_get_idedata: Mock,
+) -> None:
+    """Test that the Rosetta preflight does not run for non-ESP8266 targets."""
+    _setup_build_info_test(tmp_path, firmware_first=True)
+
+    config: dict[str, Any] = {CONF_ESPHOME: {CONF_NAME: "test_device"}}
+    args = MockArgs()
+
+    with patch("esphome.components.esp8266.check_rosetta") as mock_check:
+        result = compile_program(args, config)
+
+    assert result == 0
+    mock_check.assert_not_called()
+
+
 def test_compile_program_emits_build_info_when_firmware_rebuilt(
     tmp_path: Path,
     caplog: pytest.LogCaptureFixture,