[core] Make config-hash independent of machine-local paths (#17523)

tests/unit_tests/core/test_config.py

@@ -1113,6 +1113,48 @@ def test_config_hash_different_for_different_configs() -> None:
     assert hash1 != hash2
 
 
+def test_config_hash_ignores_build_path() -> None:
+    """Test that config_hash does not depend on the build_path value.
+
+    build_path embeds ESPHOME_BUILD_PATH and OS path separators, so it must
+    not make the hash differ between machines.
+    """
+    CORE.reset()
+    CORE.config = {"esphome": {"name": "test", "build_path": "build\\test"}}
+    hash1 = CORE.config_hash
+
+    CORE.reset()
+    CORE.config = {"esphome": {"name": "test", "build_path": "/build/test"}}
+    hash2 = CORE.config_hash
+
+    assert hash1 == hash2
+
+
+def test_config_hash_same_for_different_config_dirs(tmp_path: Path) -> None:
+    """Test that Path values under the config dir hash the same everywhere.
+
+    Simulates the same project checked out at two different locations; the
+    absolute paths differ but the layout relative to the config dir is the
+    same, so the hashes must match.
+    """
+    dir1 = tmp_path / "machine_a" / "project"
+    dir2 = tmp_path / "machine_b" / "somewhere" / "else"
+    dir1.mkdir(parents=True)
+    dir2.mkdir(parents=True)
+
+    CORE.reset()
+    CORE.config_path = dir1 / "device.yaml"
+    CORE.config = {"esphome": {"name": "test"}, "file": dir1 / "fonts" / "arial.ttf"}
+    hash1 = CORE.config_hash
+
+    CORE.reset()
+    CORE.config_path = dir2 / "device.yaml"
+    CORE.config = {"esphome": {"name": "test"}, "file": dir2 / "fonts" / "arial.ttf"}
+    hash2 = CORE.config_hash
+
+    assert hash1 == hash2
+
+
 def test_make_app_name_cpp_no_mac_simple() -> None:
     """Test simple name without MAC suffix returns string literal."""
     cpp_expr, global_decl, byte_len = make_app_name_cpp(

tests/unit_tests/test_main.py

@@ -167,9 +167,9 @@ def setup_core(
     CORE.data[KEY_CORE] = {KEY_TARGET_PLATFORM: platform}
 
     if tmp_path is not None:
-        CORE.config_path = str(tmp_path / f"{name}.yaml")
+        CORE.config_path = tmp_path / f"{name}.yaml"
         CORE.name = name
-        CORE.build_path = str(tmp_path / ".esphome" / "build" / name)
+        CORE.build_path = tmp_path / ".esphome" / "build" / name
 
 
 @pytest.fixture

tests/unit_tests/test_yaml_util.py

@@ -1349,6 +1349,57 @@ def test_sensitive_str__is_a_str_subclass() -> None:
     assert value == "hunter2"
 
 
+def test_dump_path_without_relative_to_is_unchanged() -> None:
+    """Test that Path values dump as str(path) when relative_to is not given."""
+    path = Path("some") / "dir" / "file.ttf"
+    output = yaml_util.dump({"file": path})
+    assert output.strip() == f"file: {path}"
+
+
+def test_dump_path_relative_to_anchor_dir() -> None:
+    """Test that Path values under relative_to dump as relative POSIX paths."""
+    anchor = Path("/config/esphome").absolute()
+    data = {"file": anchor / "fonts" / "arial.ttf"}
+    output = yaml_util.dump(data, relative_to=anchor)
+    assert output.strip() == "file: fonts/arial.ttf"
+
+
+def test_dump_path_outside_anchor_dir_walks_up() -> None:
+    """Test that Path values outside relative_to walk up with ".." segments."""
+    anchor = Path("/config/esphome").absolute()
+    outside = Path("/config/fonts/file.ttf").absolute()
+    output = yaml_util.dump({"file": outside}, relative_to=anchor)
+    assert output.strip() == "file: ../fonts/file.ttf"
+
+
+def test_dump_path_with_dotdot_segments_is_normalized() -> None:
+    """Test that ".." segments do not defeat relativization.
+
+    A path like /config/other/../esphome/fonts/x.ttf is under the anchor
+    once normalized, so it must dump as a plain relative path.
+    """
+    anchor = Path("/config/esphome").absolute()
+    path = Path("/config/other/../esphome/fonts/x.ttf").absolute()
+    output = yaml_util.dump({"file": path}, relative_to=anchor)
+    assert output.strip() == "file: fonts/x.ttf"
+
+
+def test_dump_path_dotdot_reference_outside_anchor() -> None:
+    """Test the relative_config_path("../...") shape stays relative."""
+    anchor = Path("/config/esphome").absolute()
+    path = anchor / ".." / "shared" / "font.ttf"
+    output = yaml_util.dump({"file": path}, relative_to=anchor)
+    assert output.strip() == "file: ../shared/font.ttf"
+
+
+def test_dump_relative_to_does_not_leak_between_calls() -> None:
+    """Test that the relative_to flag is scoped to a single dump call."""
+    anchor = Path("/config/esphome").absolute()
+    path = anchor / "fonts" / "arial.ttf"
+    assert "fonts/arial.ttf" in yaml_util.dump({"file": path}, relative_to=anchor)
+    assert yaml_util.dump({"file": path}).strip() == f"file: {path}"
+
+
 def test_dump__redacts_sensitive_str_by_default() -> None:
     out = yaml_util.dump({"password": SensitiveStr("hunter2")})
     assert "\\033[8mhunter2\\033[28m" in out