[core] Keep templated !include filenames as strings so Windows path normalization cannot corrupt them (#18549)

tests/unit_tests/test_bundle.py

@@ -29,8 +29,9 @@ from esphome.bundle import (
     read_bundle_manifest,
     remap_bundle_path,
 )
+from esphome.components.substitutions import do_substitution_pass
 from esphome.core import CORE, EsphomeError
-from esphome.yaml_util import force_load_include_files
+from esphome.yaml_util import force_load_include_files, load_yaml
 
 # ---------------------------------------------------------------------------
 # Helpers
@@ -1277,6 +1278,59 @@ def test_discover_files_bundles_all_include_candidates(tmp_path: Path) -> None:
     assert "includes/empty.yaml" in paths
 
 
+@pytest.mark.parametrize("enable_proxy", [True, False])
+def test_bundle_roundtrip_templated_include_with_path_separator(
+    tmp_path: Path, enable_proxy: bool
+) -> None:
+    r"""The issue-18545 flow: a Jinja !include whose branches contain "/" still
+    resolves after the bundle is extracted on the build server.
+
+    Windows is the leg that regresses: the raw expression text must survive
+    verbatim, or its separators get rewritten to "\" and Jinja decodes
+    sequences like "\b" as string escapes.
+    """
+    config_dir = _setup_config_dir(
+        tmp_path,
+        files={
+            "includes/boards/board.yaml": (
+                "packages:\n"
+                '  - !include ${ "bluetooth/bluetooth_proxy_single_core.yaml"'
+                ' if enable_bluetooth_proxy else "../empty.yaml" }\n'
+            ),
+            "includes/boards/bluetooth/bluetooth_proxy_single_core.yaml": (
+                "bluetooth_proxy:\n  active: true\n"
+            ),
+            "includes/empty.yaml": "{}\n",
+        },
+    )
+    (config_dir / "test.yaml").write_text(
+        "substitutions:\n"
+        f"  enable_bluetooth_proxy: {str(enable_proxy).lower()}\n"
+        "esphome:\n  name: test\n"
+        "packages:\n  - !include includes/boards/board.yaml\n"
+    )
+
+    result = ConfigBundleCreator({}).create_bundle()
+    bundle_path = tmp_path / "device.esphomebundle.tar.gz"
+    bundle_path.write_bytes(result.data)
+
+    # Both conditional branches must ship in the bundle.
+    paths = [f.path for f in result.files]
+    assert "includes/boards/bluetooth/bluetooth_proxy_single_core.yaml" in paths
+    assert "includes/empty.yaml" in paths
+
+    # Extract to a fresh directory and resolve the config from there, as a
+    # remote build server would.
+    extracted_config = extract_bundle(bundle_path, tmp_path / "remote")
+    config = do_substitution_pass(load_yaml(extracted_config))
+
+    board_pkg = config["packages"][0]["packages"][0]
+    if enable_proxy:
+        assert board_pkg == {"bluetooth_proxy": {"active": True}}
+    else:
+        assert board_pkg == {}
+
+
 def test_discover_files_candidate_outside_config_dir_skipped(
     tmp_path: Path, caplog: pytest.LogCaptureFixture
 ) -> None:

tests/unit_tests/test_substitutions.py

@@ -744,6 +744,25 @@ def test_include_filename_substitution_undefined_var(tmp_path: Path) -> None:
         substitutions.do_substitution_pass(config)
 
 
+def test_include_filename_jinja_expression_with_path_separator(
+    tmp_path: Path,
+) -> None:
+    """A jinja !include whose string literals contain "/" resolves correctly (issue #18545)."""
+    main_file = tmp_path / "main.yaml"
+    main_file.write_text(
+        "substitutions:\n"
+        "  enable_bluetooth_proxy: true\n"
+        "result: !include "
+        '${ "bluetooth/proxy.yaml" if enable_bluetooth_proxy else "../empty.yaml" }\n'
+    )
+    (tmp_path / "bluetooth").mkdir()
+    (tmp_path / "bluetooth" / "proxy.yaml").write_text("value: 42\n")
+
+    config = yaml_util.load_yaml(main_file)
+    config = substitutions.do_substitution_pass(config)
+    assert config["result"] == {"value": 42}
+
+
 def test_raise_first_undefined_logs_extras_at_debug(
     caplog: pytest.LogCaptureFixture,
 ) -> None:

tests/unit_tests/test_yaml_util.py

@@ -701,6 +701,31 @@ def test_include_file_has_unresolved_expressions(
     assert include.has_unresolved_expressions() == expected
 
 
+def test_mapping_include_non_string_file_rejected(tmp_path: Path) -> None:
+    """The mapping !include form rejects a non-string 'file' with a clear error."""
+    entry = tmp_path / "entry.yaml"
+    entry.write_text("wifi: !include\n  file: [not, a, string]\n")
+    with pytest.raises(EsphomeError, match="Include 'file' must be a string"):
+        yaml_util.load_yaml(entry)
+
+
+def test_include_file_templated_filename_stays_raw_string(tmp_path: Path) -> None:
+    """A templated filename keeps its verbatim text (issue #18545)."""
+    parent = tmp_path / "main.yaml"
+    expr = '${ "bluetooth/proxy.yaml" if enable_bluetooth_proxy else "../empty.yaml" }'
+    include = yaml_util.IncludeFile(parent, expr, None, lambda _: {})
+    assert include.file == expr
+    assert include.has_unresolved_expressions()
+    assert repr(include) == f"IncludeFile({expr})"
+
+
+def test_represent_include_file_templated() -> None:
+    """Dumping a templated IncludeFile emits the raw expression unchanged."""
+    expr = '${ "a/b.yaml" if flag else "../c.yaml" }'
+    include = yaml_util.IncludeFile(Path("/fake/main.yaml"), expr, None, lambda _: {})
+    assert yaml_util.dump({"key": include}) == f"key: !include '{expr}'\n"
+
+
 def test_include_in_list_context() -> None:
     """!include of a file returning a list is handled correctly,
     including when that list itself contains a nested IncludeFile."""
@@ -1051,7 +1076,7 @@ class _StubInclude:
     ) -> None:
         # Default parent lives in a nonexistent directory so unresolved
         # stubs never glob real files during candidate expansion.
-        self.file = Path(file)
+        self.file = file
         self.parent_file = parent_file or Path("/nonexistent/parent.yaml")
         self._unresolved = unresolved
         self._load_result = load_result if load_result is not None else {}