From 2f1d3f8299fe7b8239e8a0af4aa0fad018ded3e6 Mon Sep 17 00:00:00 2001
From: "J. Nick Koston" <nick@koston.org>
Date: Sun, 30 Aug 2026 17:34:16 -0500
Subject: [PATCH] [core] Deduplicate the host program path lookup (#18897)

---
 esphome/__main__.py           | 33 +++++++++++-----------
 tests/unit_tests/test_main.py | 52 +++++++++++++++++++++++++++++++++++
 2 files changed, 68 insertions(+), 17 deletions(-)

diff --git a/esphome/__main__.py b/esphome/__main__.py
index 632d2ba3d0..1ebf194205 100644
--- a/esphome/__main__.py
+++ b/esphome/__main__.py
@@ -1670,20 +1670,26 @@ def command_compile(args: ArgsProtocol, config: ConfigType) -> int | None:
     if exit_code != 0:
         return exit_code
     if CORE.is_host:
-        if CORE.using_toolchain_esp_idf:
-            from esphome.espidf import toolchain
-
-            program_path = str(toolchain.get_elf_path())
-        else:
-            from esphome.platformio.toolchain import get_idedata
-
-            program_path = str(get_idedata(config).firmware_elf_path)
-        _LOGGER.info("Successfully compiled program to path '%s'", program_path)
+        _LOGGER.info(
+            "Successfully compiled program to path '%s'", _host_program_path(config)
+        )
     else:
         _LOGGER.info("Successfully compiled program.")
     return 0
 
 
+def _host_program_path(config: ConfigType) -> str:
+    """Return the compiled host ELF path."""
+    if CORE.using_toolchain_esp_idf:
+        from esphome.espidf import toolchain
+
+        return str(toolchain.get_elf_path())
+    from esphome.platformio.toolchain import get_idedata
+
+    # Memoized by compile_program's own call; this is a dict lookup
+    return str(get_idedata(config).firmware_elf_path)
+
+
 def command_upload(args: ArgsProtocol, config: ConfigType) -> int | None:
     # Get devices, resolving special identifiers like OTA
     devices = choose_upload_log_host(
@@ -1728,14 +1734,7 @@ def command_run(args: ArgsProtocol, config: ConfigType) -> int | None:
         return exit_code
     _LOGGER.info("Successfully compiled program.")
     if CORE.is_host:
-        if CORE.using_toolchain_esp_idf:
-            from esphome.espidf import toolchain
-
-            program_path = str(toolchain.get_elf_path())
-        else:
-            from esphome.platformio.toolchain import get_idedata
-
-            program_path = str(get_idedata(config).firmware_elf_path)
+        program_path = _host_program_path(config)
         _LOGGER.info("Running program from path '%s'", program_path)
         return run_external_process(program_path)
 
diff --git a/tests/unit_tests/test_main.py b/tests/unit_tests/test_main.py
index 08c99e2119..15b1105ed0 100644
--- a/tests/unit_tests/test_main.py
+++ b/tests/unit_tests/test_main.py
@@ -112,6 +112,7 @@ from esphome.const import (
     PLATFORM_BK72XX,
     PLATFORM_ESP32,
     PLATFORM_ESP8266,
+    PLATFORM_HOST,
     PLATFORM_NRF52,
     PLATFORM_RP2,
     Toolchain,
@@ -7254,3 +7255,54 @@ async def test_wrap_to_code_comment_is_insertion_order_independent() -> None:
     assert first == second
     assert second.index("alpha") < second.index("beta")
     assert second.index("a: 2") < second.index("z: 1")
+
+
+def test_host_program_path_platformio_toolchain() -> None:
+    """Host + PlatformIO toolchain reads the memoized idedata path."""
+    setup_core(platform=PLATFORM_HOST)
+    idedata = SimpleNamespace(firmware_elf_path="/build/x/.pioenvs/x/program")
+    with patch(
+        "esphome.platformio.toolchain.get_idedata", return_value=idedata
+    ) as mock_get:
+        assert main._host_program_path({}) == "/build/x/.pioenvs/x/program"
+    mock_get.assert_called_once_with({})
+
+
+def test_host_program_path_esp_idf_toolchain() -> None:
+    """Host + native ESP-IDF toolchain asks the espidf toolchain for the ELF."""
+    setup_core(platform=PLATFORM_HOST)
+    CORE.toolchain = Toolchain.ESP_IDF
+    with patch(
+        "esphome.espidf.toolchain.get_elf_path", return_value=Path("/b/app.elf")
+    ):
+        assert main._host_program_path({}) == str(Path("/b/app.elf"))
+
+
+def test_command_compile_host_logs_program_path(
+    caplog: pytest.LogCaptureFixture,
+) -> None:
+    """command_compile on host logs the compiled program path."""
+    setup_core(platform=PLATFORM_HOST)
+    with (
+        patch.object(main, "write_cpp", return_value=0),
+        patch.object(main, "compile_program", return_value=0),
+        patch.object(main, "_host_program_path", return_value="/b/program"),
+        caplog.at_level(logging.INFO),
+    ):
+        assert main.command_compile(SimpleNamespace(only_generate=False), {}) == 0
+    assert "Successfully compiled program to path '/b/program'" in caplog.text
+
+
+def test_command_run_host_executes_program(caplog: pytest.LogCaptureFixture) -> None:
+    """command_run on host logs and executes the compiled program directly."""
+    setup_core(platform=PLATFORM_HOST)
+    with (
+        patch.object(main, "write_cpp", return_value=0),
+        patch.object(main, "compile_program", return_value=0),
+        patch.object(main, "_host_program_path", return_value="/b/program"),
+        patch.object(main, "run_external_process", return_value=0) as mock_run,
+        caplog.at_level(logging.INFO),
+    ):
+        assert main.command_run(SimpleNamespace(), {}) == 0
+    mock_run.assert_called_with("/b/program")
+    assert "Running program from path '/b/program'" in caplog.text