From 12b016e3d27b03f88e87c301ca2c29a193be128a Mon Sep 17 00:00:00 2001
From: Jeff Brown <jeff.brown@gmail.com>
Date: Fri, 2 Oct 2026 05:27:29 -0700
Subject: [PATCH] [substitutions] Support !include with a condition (#19455)

Co-authored-by: J. Nick Koston <nick@koston.org>
---
 esphome/components/substitutions/__init__.py  |  19 +-
 esphome/yaml_util.py                          | 114 +++++++--
 .../substitutions/01-include.approved.yaml    |   7 +
 .../substitutions/01-include.input.yaml       |  19 ++
 .../substitutions/12-yaml-merge.input.yaml    |   6 +
 .../fixtures/yaml_util/includes/true.yaml     |   2 +
 .../fixtures/yaml_util/includetest.yaml       |   6 +-
 .../includetest_invalid_condition_type.yaml   |   3 +
 .../yaml_util/includetest_no_file.yaml        |   3 +
 tests/unit_tests/test_bundle.py               |   2 +-
 tests/unit_tests/test_substitutions.py        |  95 +++++++-
 tests/unit_tests/test_yaml_util.py            | 220 +++++++++++++++---
 12 files changed, 420 insertions(+), 76 deletions(-)
 create mode 100644 tests/unit_tests/fixtures/yaml_util/includes/true.yaml
 create mode 100644 tests/unit_tests/fixtures/yaml_util/includetest_invalid_condition_type.yaml
 create mode 100644 tests/unit_tests/fixtures/yaml_util/includetest_no_file.yaml

diff --git a/esphome/components/substitutions/__init__.py b/esphome/components/substitutions/__init__.py
index 5ef7a699eb..d59f39b9c2 100644
--- a/esphome/components/substitutions/__init__.py
+++ b/esphome/components/substitutions/__init__.py
@@ -353,7 +353,7 @@ def resolve_include(
     strict_undefined: bool = True,
     errors: ErrList | None = None,
 ) -> Any:
-    """Resolve an include, substituting the filename if needed.
+    """Resolve an include, substituting the condition and filename if needed.
 
     Note: no path-traversal validation is performed on the resolved filename.
     A substitution that resolves to an absolute path will bypass the parent
@@ -362,6 +362,19 @@ def resolve_include(
     values (including command-line substitutions), so path restrictions are
     an explicit non-goal here.
     """
+    if isinstance(original_condition := include.condition, str):
+        condition = str(
+            _expand_substitutions(
+                original_condition,
+                path + ["condition"],
+                context_vars,
+                strict_undefined,
+                errors,
+            )
+        )
+        if condition != original_condition:
+            include = include.with_condition(condition)
+
     original = include.file
     filename = str(
         _expand_substitutions(
@@ -372,8 +385,8 @@ def resolve_include(
     if substituted:
         include = include.with_file(filename)
     try:
-        return include.load()
-    except esphome.core.EsphomeError as err:
+        return include.load() if include.should_load() else {}
+    except (esphome.core.EsphomeError, cv.Invalid) as err:
         resolved = f" (expanded from '{original}')" if substituted else ""
         raise cv.Invalid(
             f"Error including file '{filename}'{resolved}: {err}"
diff --git a/esphome/yaml_util.py b/esphome/yaml_util.py
index 7c6cf691b9..e892664724 100644
--- a/esphome/yaml_util.py
+++ b/esphome/yaml_util.py
@@ -35,7 +35,7 @@ from esphome.core import (
     TimePeriod,
 )
 from esphome.expression import has_substitution_or_expression
-from esphome.helpers import add_class_to_obj
+from esphome.helpers import FALSY_BOOL_STRINGS, TRUTHY_BOOL_STRINGS, add_class_to_obj
 from esphome.util import OrderedDict, filter_yaml_files
 
 _LOGGER = logging.getLogger(__name__)
@@ -75,6 +75,12 @@ def take_dropped_merge_keys() -> list[tuple[str, str]]:
     return CORE.data.pop(_MERGE_WARNINGS_KEY, [])
 
 
+def _raise_invalid(message: str) -> None:
+    from voluptuous import Invalid
+
+    raise Invalid(message)
+
+
 class SensitiveStr(str):
     """Marker subclass for validated strings that should be masked in
     user-visible YAML output. ``cv.sensitive`` wraps validated values in this
@@ -224,16 +230,18 @@ class IncludeFile:
 
     Created during YAML parsing instead of loading the file immediately,
     allowing substitution variables to appear in the filename path
-    (e.g. ``!include device-${platform}.yaml``). The actual file is
-    loaded on the first call to ``load()``, and the result is cached.
+    (e.g. ``!include device-${platform}.yaml``) and in an optional condition.
+    The actual file is loaded on the first call to ``load()``, and the result
+    is cached. The client is responsible for testing the condition if needed.
     """
 
     def __init__(
         self,
         parent_file: Path,
         file: str,
-        vars: dict[str, Any] | None,
         yaml_loader: Callable[[Path], Any],
+        vars: dict[str, Any] | None = None,
+        condition: bool | str | None = None,
     ) -> None:
         self.parent_file = parent_file
         # The raw include text may be a substitution/Jinja expression, so it
@@ -241,8 +249,9 @@ class IncludeFile:
         # rewrites "/" to "\", which Jinja then decodes as escapes like
         # "\b" -> backspace (issue #18545).
         self.file = file
-        self.vars = vars
         self.yaml_loader = yaml_loader
+        self.vars = vars
+        self.condition = condition
         self._content: Any = _UNSET
 
     def __repr__(self) -> str:
@@ -256,23 +265,62 @@ class IncludeFile:
         """
         if self._content is not _UNSET:
             return self._content
-        if self.has_unresolved_expressions():
-            from voluptuous import Invalid
-
-            raise Invalid(
+        if self.has_unresolved_file():
+            _raise_invalid(
                 f"Cannot load include with unresolved substitutions: {self.file}"
             )
         self._content = self.yaml_loader(self.parent_file.parent / self.file)
         self._content = add_context(self._content, self.vars)
         return self._content
 
-    def has_unresolved_expressions(self) -> bool:
+    def has_unresolved_file(self) -> bool:
         """Check if the filename contains substitution variables or Jinja expressions."""
         return has_substitution_or_expression(self.file)
 
+    def should_load(self) -> bool:
+        """Evaluates the condition and returns True if the file should be loaded."""
+        if self.condition is None:
+            return True
+        if isinstance(self.condition, bool):
+            return self.condition
+        if self.has_unresolved_condition():
+            _raise_invalid(
+                f"Cannot evaluate include condition for '{self.file}' with unresolved substitutions: {self.condition}"
+            )
+        value = self.condition.lower()
+        if value in TRUTHY_BOOL_STRINGS:
+            return True
+        if value not in FALSY_BOOL_STRINGS:
+            _raise_invalid(
+                f"Cannot convert include condition for '{self.file}' to a boolean, please use 'true' or 'false': {self.condition}"
+            )
+        return False
+
+    def has_unresolved_condition(self) -> bool:
+        """Check if the condition contains substitution variables or Jinja expressions."""
+        return isinstance(self.condition, str) and has_substitution_or_expression(
+            self.condition
+        )
+
     def with_file(self, file: str) -> IncludeFile:
         """Clone this include with *file* as the filename."""
-        return IncludeFile(self.parent_file, file, self.vars, self.yaml_loader)
+        return IncludeFile(
+            self.parent_file,
+            file,
+            self.yaml_loader,
+            vars=self.vars,
+            condition=self.condition,
+        )
+
+    def with_condition(self, condition: bool | str | None) -> IncludeFile:
+        """Clone this include with *condition* as the condition."""
+        return IncludeFile(
+            self.parent_file,
+            self.file,
+            self.yaml_loader,
+            vars=self.vars,
+            condition=condition,
+        )
 
 
 def _is_visible_path(rel: Path) -> bool:
@@ -434,7 +482,7 @@ def force_load_include_files(
         if id(obj) in _seen:
             return
         _seen.add(id(obj))
-        if obj.has_unresolved_expressions():
+        if obj.has_unresolved_file():
             _load_include_candidates(
                 obj,
                 warn_on_unresolved=warn_on_unresolved,
@@ -578,14 +626,21 @@ def _resolve_merge_include(value: Any, node: yaml.Node, value_node: yaml.Node) -
     for _ in range(_MAX_MERGE_INCLUDE_DEPTH):
         if not isinstance(value, IncludeFile):
             break
-        if value.has_unresolved_expressions():
+        if value.has_unresolved_file():
             raise yaml.constructor.ConstructorError(
                 "While constructing a mapping",
                 node.start_mark,
                 "Substitution in include filename with merge keys is not supported yet.",
                 value_node.start_mark,
             )
-        value = value.load()
+        if value.has_unresolved_condition():
+            raise yaml.constructor.ConstructorError(
+                "While constructing a mapping",
+                node.start_mark,
+                "Substitution in include condition with merge keys is not supported yet.",
+                value_node.start_mark,
+            )
+        value = value.load() if value.should_load() else {}
     else:
         raise yaml.constructor.ConstructorError(
             "While constructing a mapping",
@@ -791,11 +846,11 @@ class ESPHomeLoaderMixin:
 
     @_add_data_ref
     def construct_include(self, node: yaml.Node) -> Any:
-        from esphome.const import CONF_VARS
+        from esphome.const import CONF_CONDITION, CONF_FILE, CONF_VARS
 
-        def extract_file_vars(node):
+        def extract_fields(node):
             fields = self.construct_yaml_map(node)
-            file = fields.get("file")
+            file = fields.get(CONF_FILE)
             if file is None:
                 raise yaml.MarkedYAMLError("Must include 'file'", node.start_mark)
             if not isinstance(file, str):
@@ -803,14 +858,21 @@ class ESPHomeLoaderMixin:
                     "Include 'file' must be a string", node.start_mark
                 )
             vars = fields.get(CONF_VARS)
-            return file, vars
+            condition = fields.get(CONF_CONDITION)
+            if condition is not None and not isinstance(condition, (bool, str)):
+                raise yaml.MarkedYAMLError(
+                    "Include 'condition' must be a boolean or string", node.start_mark
+                )
+            return file, vars, condition
 
         if isinstance(node, yaml.nodes.MappingNode):
-            file, vars = extract_file_vars(node)
+            file, vars, condition = extract_fields(node)
         else:
-            file, vars = node.value, None
+            file, vars, condition = node.value, None, None
 
-        return IncludeFile(self.name, file, vars, self.yaml_loader)
+        return IncludeFile(
+            self.name, file, self.yaml_loader, vars=vars, condition=condition
+        )
 
     # Directory includes (!include_dir_*) load eagerly during YAML parsing
     # because their paths are directory names, not individual files, and
@@ -967,7 +1029,7 @@ def _load_yaml_internal(fname: Path, *, track_document_range: bool = True) -> An
     # Top-level !include returns a deferred IncludeFile; resolve it so
     # callers always receive the final content.
     if isinstance(res, IncludeFile):
-        res = res.load()
+        res = res.load() if res.should_load() else {}
     return res
 
 
@@ -1358,8 +1420,12 @@ class ESPHomeDumper(yaml.SafeDumper):
         return self.represent_scalar(tag="!remove", value=value.value)
 
     def represent_include_file(self, value):
-        if value.vars:
-            mapping = {"file": value.file, "vars": value.vars}
+        if value.vars or value.condition is not None:
+            mapping = {"file": value.file}
+            if value.vars:
+                mapping["vars"] = value.vars
+            if value.condition is not None:
+                mapping["condition"] = value.condition
             return self.represent_mapping(
                 tag="!include", mapping=mapping, flow_style=False
             )
diff --git a/tests/unit_tests/fixtures/substitutions/01-include.approved.yaml b/tests/unit_tests/fixtures/substitutions/01-include.approved.yaml
index a812fedcfd..e13db65ef7 100644
--- a/tests/unit_tests/fixtures/substitutions/01-include.approved.yaml
+++ b/tests/unit_tests/fixtures/substitutions/01-include.approved.yaml
@@ -13,3 +13,10 @@ test_list:
       - a: alpha
       - b: beta
       - c: The value of C is $c
+  - {}
+  - values:
+      - var1: '1'
+      - a: alpha
+      - b: delta
+      - c: The value of C is saw
+  - {}
diff --git a/tests/unit_tests/fixtures/substitutions/01-include.input.yaml b/tests/unit_tests/fixtures/substitutions/01-include.input.yaml
index d3daa681a4..b30ae5f99e 100644
--- a/tests/unit_tests/fixtures/substitutions/01-include.input.yaml
+++ b/tests/unit_tests/fixtures/substitutions/01-include.input.yaml
@@ -13,3 +13,22 @@ test_list:
     file: inc1.yaml
     vars:
       b: "beta"
+    condition: true
+  - !include
+    file: inc1.yaml
+    vars:
+      b: "gamma"
+      c: "saw"
+    condition: false
+  - !include
+    file: inc1.yaml
+    vars:
+      b: "delta"
+      c: "saw"
+    condition: ${var1 == "1"}
+  - !include
+    file: inc1.yaml
+    vars:
+      b: "epsilon"
+      c: "saw"
+    condition: ${var1 == "2"}
diff --git a/tests/unit_tests/fixtures/substitutions/12-yaml-merge.input.yaml b/tests/unit_tests/fixtures/substitutions/12-yaml-merge.input.yaml
index a03e66e393..3152f8ddf0 100644
--- a/tests/unit_tests/fixtures/substitutions/12-yaml-merge.input.yaml
+++ b/tests/unit_tests/fixtures/substitutions/12-yaml-merge.input.yaml
@@ -7,4 +7,10 @@ test_list:
         file: inc3.yaml
         vars:
           y: 8
+        condition: true
+      <<: !include
+        file: inc3.yaml
+        vars:
+          y: 10
+        condition: false
       after: Content after
diff --git a/tests/unit_tests/fixtures/yaml_util/includes/true.yaml b/tests/unit_tests/fixtures/yaml_util/includes/true.yaml
new file mode 100644
index 0000000000..abd17b22f7
--- /dev/null
+++ b/tests/unit_tests/fixtures/yaml_util/includes/true.yaml
@@ -0,0 +1,2 @@
+---
+true
diff --git a/tests/unit_tests/fixtures/yaml_util/includetest.yaml b/tests/unit_tests/fixtures/yaml_util/includetest.yaml
index 7b01da6a17..6db5c294f4 100644
--- a/tests/unit_tests/fixtures/yaml_util/includetest.yaml
+++ b/tests/unit_tests/fixtures/yaml_util/includetest.yaml
@@ -11,8 +11,8 @@ esphome:
   # should be substituted as 'original',
   # not overwritten by vars in the !include above
   name: ${name}
-  name_add_mac_suffix: true
-  libraries: !include {file: includes/list.yaml, vars: {var1: Wire}}
+  name_add_mac_suffix: !include includes/true.yaml
+  libraries: !include {file: includes/list.yaml, vars: {var1: Wire}, condition: "true"}
 
 esp8266:
-  board: !include {file: includes/scalar.yaml, vars: {var1: nodemcu}}
+  board: !include {file: includes/scalar.yaml, vars: {var1: nodemcu}, condition: true}
diff --git a/tests/unit_tests/fixtures/yaml_util/includetest_invalid_condition_type.yaml b/tests/unit_tests/fixtures/yaml_util/includetest_invalid_condition_type.yaml
new file mode 100644
index 0000000000..94eb7d65ab
--- /dev/null
+++ b/tests/unit_tests/fixtures/yaml_util/includetest_invalid_condition_type.yaml
@@ -0,0 +1,3 @@
+---
+esphome:
+  libraries: !include {file: includes/list.yaml, vars: {var1: Wire}, condition: 1}
diff --git a/tests/unit_tests/fixtures/yaml_util/includetest_no_file.yaml b/tests/unit_tests/fixtures/yaml_util/includetest_no_file.yaml
new file mode 100644
index 0000000000..7724bb301f
--- /dev/null
+++ b/tests/unit_tests/fixtures/yaml_util/includetest_no_file.yaml
@@ -0,0 +1,3 @@
+---
+esphome:
+  libraries: !include {vars: {var1: Wire}}
diff --git a/tests/unit_tests/test_bundle.py b/tests/unit_tests/test_bundle.py
index 1abc7a3ab8..8a2510cf0a 100644
--- a/tests/unit_tests/test_bundle.py
+++ b/tests/unit_tests/test_bundle.py
@@ -1384,7 +1384,7 @@ def test_force_load_skips_duplicate_include_file() -> None:
             self.parent_file = Path("root.yaml")
             self.load_calls = 0
 
-        def has_unresolved_expressions(self) -> bool:
+        def has_unresolved_file(self) -> bool:
             return False
 
         def load(self) -> dict[str, Any]:
diff --git a/tests/unit_tests/test_substitutions.py b/tests/unit_tests/test_substitutions.py
index b94a70443c..198b002d43 100644
--- a/tests/unit_tests/test_substitutions.py
+++ b/tests/unit_tests/test_substitutions.py
@@ -573,6 +573,65 @@ def test_undefined_variable_warning(
     assert "'undefined_var' is undefined" in caplog.text
 
 
+def test_undefined_variable_warning_avoided_by_include_condition(
+    tmp_path: Path, caplog: pytest.LogCaptureFixture
+) -> None:
+    """Compare two different ways to conditionally enable an !include file
+    that defines and uses new variables. One way generates a undefined
+    variable warning when disabled and the other does not."""
+    include_file = tmp_path / "include.yaml"
+    include_file.write_text("substitutions:\n  var: 1\nresult: ${var}\n")
+    method_a_file = tmp_path / "method_a.yaml"
+    method_a_file.write_text(
+        "packages:\n"
+        "  - !include\n"
+        "    file: include.yaml\n"
+        "    condition: ${enable == 'y'}\n"
+    )
+    method_b_file = tmp_path / "method_b.yaml"
+    method_b_file.write_text(
+        "substitutions:\n"
+        "  content: !include include.yaml\n"
+        "packages:\n"
+        "  - ${content if enable == 'y' else {}}\n"
+    )
+
+    def process_file(file, enable):
+        with caplog.at_level(logging.WARNING):
+            args = {"enable": enable}
+            config = yaml_util.load_yaml(file)
+            config = do_packages_pass(config, command_line_substitutions=args)
+            return substitutions.do_substitution_pass(
+                config, command_line_substitutions=args
+            )
+
+    # Case: method A with include enabled produces a result and no warnings
+    config = process_file(method_a_file, "y")
+    assert caplog.text == ""
+    assert config["packages"][0]["result"] == 1
+
+    # Case: method A with include disabled produces no result and no warnings
+    # because the file was not even loaded
+    config = process_file(method_a_file, "n")
+    assert caplog.text == ""
+    assert config["packages"][0] == {}
+
+    # Case: method B with include enabled produces a result and no warnings (same as method A)
+    config = process_file(method_b_file, "y")
+    assert caplog.text == ""
+    assert config["packages"][0]["result"] == 1
+
+    # Case: method B with include disabled produces no result and an undefined variable warning
+    # because the file is loaded into a variable and its own variables cannot be expanded
+    # (different from method A)
+    config = process_file(method_b_file, "n")
+    assert (
+        "Could not resolve substitution variable 'content': 'var' is undefined"
+        in caplog.text
+    )
+    assert config["packages"][0] == {}
+
+
 def test_password_field_warnings_suppressed(
     caplog: pytest.LogCaptureFixture,
 ) -> None:
@@ -717,11 +776,9 @@ def test_resolve_package_max_depth_exceeded(tmp_path: Path) -> None:
     # Each call to the loader returns a fresh IncludeFile pointing at itself,
     # so PACKAGE_SCHEMA always sees an IncludeFile and never a dict.
     def always_returns_include(path: Path) -> yaml_util.IncludeFile:
-        return yaml_util.IncludeFile(parent, path.name, None, always_returns_include)
+        return yaml_util.IncludeFile(parent, path.name, always_returns_include)
 
-    package_config = yaml_util.IncludeFile(
-        parent, "test.yaml", None, always_returns_include
-    )
+    package_config = yaml_util.IncludeFile(parent, "test.yaml", always_returns_include)
     processor = _PackageProcessor({}, None)
     with pytest.raises(
         cv.Invalid,
@@ -791,6 +848,22 @@ def test_include_filename_jinja_expression_with_path_separator(
     assert config["result"] == {"value": 42}
 
 
+def test_include_condition_substitution_undefined_var(tmp_path: Path) -> None:
+    """!include with an undefined substitution variable raises cv.Invalid.
+
+    The error message must reference the unresolved condition template so the
+    user knows which include failed, rather than seeing a bare file-not-found.
+    """
+    main_file = tmp_path / "main.yaml"
+    main_file.write_text(
+        "result: !include\n  file: file.yaml\n  condition: ${undefined_var}\n"
+    )
+
+    config = yaml_util.load_yaml(main_file)
+    with pytest.raises(cv.Invalid, match=r"\$\{undefined_var\}"):
+        substitutions.do_substitution_pass(config)
+
+
 def test_raise_first_undefined_logs_extras_at_debug(
     caplog: pytest.LogCaptureFixture,
 ) -> None:
@@ -838,7 +911,7 @@ def test_do_substitution_pass_included_substitutions_must_be_mapping(
     def loader(path: Path):
         return ["not", "a", "mapping"]
 
-    include = yaml_util.IncludeFile(parent, "subs.yaml", None, loader)
+    include = yaml_util.IncludeFile(parent, "subs.yaml", loader)
     config = OrderedDict({CONF_SUBSTITUTIONS: include})
 
     with pytest.raises(
@@ -861,7 +934,7 @@ def test_do_packages_pass_included_substitutions_must_be_mapping(
     def loader(path: Path):
         return ["not", "a", "mapping"]
 
-    include = yaml_util.IncludeFile(parent, "subs.yaml", None, loader)
+    include = yaml_util.IncludeFile(parent, "subs.yaml", loader)
     config = OrderedDict(
         {
             CONF_SUBSTITUTIONS: include,
@@ -888,9 +961,7 @@ def test_resolve_package_undefined_var_in_include_filename(tmp_path: Path) -> No
     def loader(path: Path):
         raise EsphomeError(f"Error reading file {path}: No such file")
 
-    package_config = yaml_util.IncludeFile(
-        parent, "${undefined_var}.yaml", None, loader
-    )
+    package_config = yaml_util.IncludeFile(parent, "${undefined_var}.yaml", loader)
     processor = _PackageProcessor({}, None)
     with pytest.raises(cv.Invalid, match="unresolved substitutions"):
         processor.resolve_package(package_config, substitutions.ContextVars(), [])
@@ -906,7 +977,7 @@ def test_resolve_include_error_shows_expanded_from_when_substituted(
     def failing_loader(_path: Path) -> None:
         raise EsphomeError("File not found")
 
-    include = yaml_util.IncludeFile(parent, "${device}.yaml", None, failing_loader)
+    include = yaml_util.IncludeFile(parent, "${device}.yaml", failing_loader)
     context = substitutions.ContextVars({"device": "my_device"})
 
     with pytest.raises(cv.Invalid) as exc_info:
@@ -927,7 +998,7 @@ def test_resolve_include_error_no_expanded_from_for_literal_filename(
     def failing_loader(_path: Path) -> None:
         raise EsphomeError("File not found")
 
-    include = yaml_util.IncludeFile(parent, "literal.yaml", None, failing_loader)
+    include = yaml_util.IncludeFile(parent, "literal.yaml", failing_loader)
 
     with pytest.raises(cv.Invalid) as exc_info:
         substitutions.resolve_include(include, [], substitutions.ContextVars())
@@ -946,7 +1017,7 @@ def test_include_vars_applied_to_lambda_value(tmp_path: Path) -> None:
     included.write_text('!lambda |-\n  return "${foo}";\n')
 
     include = yaml_util.IncludeFile(
-        tmp_path / "main.yaml", "lambda.yaml", {"foo": "bar"}, yaml_util.load_yaml
+        tmp_path / "main.yaml", "lambda.yaml", yaml_util.load_yaml, vars={"foo": "bar"}
     )
     config = OrderedDict({"value": include.load()})
     result = substitutions.do_substitution_pass(config)
diff --git a/tests/unit_tests/test_yaml_util.py b/tests/unit_tests/test_yaml_util.py
index f3f73ea4dc..e1c3080e29 100644
--- a/tests/unit_tests/test_yaml_util.py
+++ b/tests/unit_tests/test_yaml_util.py
@@ -43,17 +43,37 @@ def clear_core_frontmatter() -> None:
     core.CORE.frontmatter = {}
 
 
-def test_include_with_vars(fixture_path: Path) -> None:
+def test_include(fixture_path: Path) -> None:
+    """Test !include with and without vars, with and without conditions"""
     yaml_file = fixture_path / "yaml_util" / "includetest.yaml"
 
     actual = yaml_util.load_yaml(yaml_file)
     actual = substitutions.do_substitution_pass(actual, None)
     assert actual["esphome"]["name"] == "original"
+    assert actual["esphome"]["name_add_mac_suffix"]
     assert actual["esphome"]["libraries"][0] == "Wire"
     assert actual["esp8266"]["board"] == "nodemcu"
     assert actual["wifi"]["ssid"] == "my_custom_ssid"
 
 
+def test_include_with_no_file(fixture_path: Path) -> None:
+    """Ensure that an error is emitted when the file field is missing."""
+    yaml_file = fixture_path / "yaml_util" / "includetest_no_file.yaml"
+
+    with pytest.raises(EsphomeError, match=r"Must include 'file'"):
+        yaml_util.load_yaml(yaml_file)
+
+
+def test_include_with_invalid_condition_type(fixture_path: Path) -> None:
+    """Ensure that an error is emitted when the condition field is an invalid type."""
+    yaml_file = fixture_path / "yaml_util" / "includetest_invalid_condition_type.yaml"
+
+    with pytest.raises(
+        EsphomeError, match=r"Include 'condition' must be a boolean or string"
+    ):
+        yaml_util.load_yaml(yaml_file)
+
+
 def test_loading_a_missing_file(fixture_path):
     """We throw EsphomeError when loading a missing file."""
     yaml_file = fixture_path / "yaml_util" / "missing.yaml"
@@ -64,7 +84,7 @@ def test_loading_a_missing_file(fixture_path):
 
 def test_parsing_with_custom_loader(fixture_path):
     """Test custom loader used for vscode connection
-    Default loader is tested in test_include_with_vars
+    Default loader is tested in test_include
     """
     yaml_file = fixture_path / "yaml_util" / "includetest.yaml"
 
@@ -78,10 +98,11 @@ def test_parsing_with_custom_loader(fixture_path):
         # substitute config to expand includes:
         substitutions.substitute(config, [], substitutions.ContextVars(), False)
 
-    assert len(loader_calls) == 3
+    assert len(loader_calls) == 4
     assert loader_calls[0].parts[-2:] == ("includes", "included.yaml")
-    assert loader_calls[1].parts[-2:] == ("includes", "list.yaml")
-    assert loader_calls[2].parts[-2:] == ("includes", "scalar.yaml")
+    assert loader_calls[1].parts[-2:] == ("includes", "true.yaml")
+    assert loader_calls[2].parts[-2:] == ("includes", "list.yaml")
+    assert loader_calls[3].parts[-2:] == ("includes", "scalar.yaml")
 
 
 def test_construct_secret_simple(fixture_path: Path) -> None:
@@ -570,7 +591,7 @@ def test_represent_remove() -> None:
 def test_represent_include_file() -> None:
     """Test that IncludeFile objects are dumped as !include scalars."""
     include = yaml_util.IncludeFile(
-        Path("/fake/main.yaml"), "path/to/file.yaml", None, lambda _: {}
+        Path("/fake/main.yaml"), "path/to/file.yaml", lambda _: {}
     )
     assert yaml_util.dump({"key": include}) == "key: !include 'path/to/file.yaml'\n"
 
@@ -580,13 +601,27 @@ def test_represent_include_file_with_vars() -> None:
     include = yaml_util.IncludeFile(
         Path("/fake/main.yaml"),
         "path/to/file.yaml",
-        {"key": "value"},
         lambda _: {},
+        vars={"key": "value"},
+    )
+    assert (
+        yaml_util.dump({"key": include})
+        == "key: !include\n  file: path/to/file.yaml\n  vars:\n    key: value\n"
+    )
+
+
+def test_represent_include_file_with_condition() -> None:
+    """Test that IncludeFile with condition is dumped as !include mapping form."""
+    include = yaml_util.IncludeFile(
+        Path("/fake/main.yaml"),
+        "path/to/file.yaml",
+        lambda _: {},
+        condition="true",
+    )
+    assert (
+        yaml_util.dump({"key": include})
+        == "key: !include\n  file: path/to/file.yaml\n  condition: 'true'\n"
     )
-    result = yaml_util.dump({"key": include})
-    assert "!include" in result
-    assert "file: path/to/file.yaml" in result
-    assert "key: value" in result
 
 
 def test_represent_include_file_with_data_base_mixin() -> None:
@@ -596,7 +631,7 @@ def test_represent_include_file_with_data_base_mixin() -> None:
     subclass. add_multi_representer must match this subclass through the MRO.
     """
     include = yaml_util.IncludeFile(
-        Path("/fake/main.yaml"), "common/spi.yaml", None, lambda _: {}
+        Path("/fake/main.yaml"), "common/spi.yaml", lambda _: {}
     )
     wrapped = yaml_util.make_data_base(include)
     assert isinstance(wrapped, yaml_util.ESPHomeDataBase)
@@ -609,7 +644,7 @@ def test_represent_include_file_with_data_base_mixin() -> None:
 def test_include_file_repr(tmp_path: Path) -> None:
     """repr() includes the filename so it appears usefully in error messages."""
     parent = tmp_path / "main.yaml"
-    include = yaml_util.IncludeFile(parent, "some/nested.yaml", None, lambda _: {})
+    include = yaml_util.IncludeFile(parent, "some/nested.yaml", lambda _: {})
     assert repr(include) == "IncludeFile(some/nested.yaml)"
 
 
@@ -624,7 +659,7 @@ def test_include_file_load_caches_result(tmp_path: Path) -> None:
         call_count += 1
         return content
 
-    include = yaml_util.IncludeFile(parent, "child.yaml", None, counting_loader)
+    include = yaml_util.IncludeFile(parent, "child.yaml", counting_loader)
     first = include.load()
     second = include.load()
 
@@ -641,7 +676,7 @@ def test_include_file_load_caches_none_result(tmp_path: Path) -> None:
         nonlocal call_count
         call_count += 1
 
-    include = yaml_util.IncludeFile(parent, "empty.yaml", None, counting_loader)
+    include = yaml_util.IncludeFile(parent, "empty.yaml", counting_loader)
     first = include.load()
     second = include.load()
 
@@ -653,7 +688,7 @@ def test_include_file_load_caches_none_result(tmp_path: Path) -> None:
 def test_include_file_load_raises_on_unresolved_expressions(tmp_path: Path) -> None:
     """load() raises if the filename contains unresolved substitutions or expressions."""
     parent = tmp_path / "main.yaml"
-    include = yaml_util.IncludeFile(parent, "${undefined_var}.yaml", None, lambda _: {})
+    include = yaml_util.IncludeFile(parent, "${undefined_var}.yaml", lambda _: {})
     with pytest.raises(cv.Invalid, match="unresolved"):
         include.load()
 
@@ -670,13 +705,83 @@ def test_include_file_load_raises_on_unresolved_expressions(tmp_path: Path) -> N
         ("price-100$.yaml", False),  # $ at end, not followed by valid substitution
     ],
 )
-def test_include_file_has_unresolved_expressions(
+def test_include_file_has_unresolved_file(
     tmp_path: Path, filename: str, expected: bool
 ) -> None:
-    """has_unresolved_expressions() detects substitution patterns in the filename."""
+    """has_unresolved_file() detects substitution patterns in the filename."""
     parent = tmp_path / "main.yaml"
-    include = yaml_util.IncludeFile(parent, filename, None, lambda _: {})
-    assert include.has_unresolved_expressions() == expected
+    include = yaml_util.IncludeFile(parent, filename, lambda _: {})
+    assert include.has_unresolved_file() == expected
+
+
+@pytest.mark.parametrize(
+    ("condition", "expected"),
+    [
+        (None, False),
+        (True, False),
+        (False, False),
+        ("true", False),
+        ("false", False),
+        ("$has_feature", True),  # whole substitution
+        ("${has_feature}", True),  # whole substitution
+        ("tr$ue", True),  # partial substitution
+        ("$.", False),  # malformed substitution
+        ("${1 == 1}", True),  # Jinja expression
+        ("${", False),  # malformed expression
+    ],
+)
+def test_include_file_has_unresolved_condition(
+    tmp_path: Path, condition: bool | str | None, expected: bool
+) -> None:
+    """has_unresolved_condition() detects substitution patterns in the condition."""
+    parent = tmp_path / "main.yaml"
+    include = yaml_util.IncludeFile(
+        parent, "device.yaml", lambda _: {}, condition=condition
+    )
+    assert include.has_unresolved_condition() == expected
+
+
+@pytest.mark.parametrize(
+    ("condition", "expected_result_or_error"),
+    [
+        (None, True),
+        (True, True),
+        (False, False),
+        ("true", True),
+        ("True", True),
+        ("TRUE", True),
+        ("yes", True),
+        ("on", True),
+        ("enable", True),
+        ("false", False),
+        ("False", False),
+        ("FALSE", False),
+        ("no", False),
+        ("off", False),
+        ("disable", False),
+        (
+            "$sub",
+            "Cannot evaluate include condition for 'device.yaml' with unresolved substitutions",
+        ),
+        ("", "Cannot convert include condition for 'device.yaml' to a boolean"),
+        ("trues", "Cannot convert include condition for 'device.yaml' to a boolean"),
+    ],
+)
+def test_include_file_should_load(
+    tmp_path: Path,
+    condition: bool | str | None,
+    expected_result_or_error: bool | str,
+) -> None:
+    """should_load() evaluates the condition and raises an error if it is malformed."""
+    parent = tmp_path / "main.yaml"
+    include = yaml_util.IncludeFile(
+        parent, "device.yaml", lambda _: {}, condition=condition
+    )
+    if isinstance(expected_result_or_error, bool):
+        assert include.should_load() == expected_result_or_error
+    else:
+        with pytest.raises(cv.Invalid, match=expected_result_or_error):
+            include.should_load()
 
 
 def test_mapping_include_non_string_file_rejected(tmp_path: Path) -> None:
@@ -691,16 +796,16 @@ def test_include_file_templated_filename_stays_raw_string(tmp_path: Path) -> Non
     """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 _: {})
+    include = yaml_util.IncludeFile(parent, expr, lambda _: {})
     assert include.file == expr
-    assert include.has_unresolved_expressions()
+    assert include.has_unresolved_file()
     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 _: {})
+    include = yaml_util.IncludeFile(Path("/fake/main.yaml"), expr, lambda _: {})
     assert yaml_util.dump({"key": include}) == f"key: !include '{expr}'\n"
 
 
@@ -710,12 +815,12 @@ def test_include_in_list_context() -> None:
     parent = Path("/fake/main.yaml")
 
     # The nested IncludeFile resolves to a plain string value
-    inner = yaml_util.IncludeFile(parent, "inner.yaml", None, lambda _: "gamma")
+    inner = yaml_util.IncludeFile(parent, "inner.yaml", lambda _: "gamma")
 
     # The outer IncludeFile returns a list whose last element is itself an IncludeFile,
     # exercising the substitution pass's ability to recurse into loaded content.
     outer = yaml_util.IncludeFile(
-        parent, "items.yaml", None, lambda _: ["alpha", "beta", inner]
+        parent, "items.yaml", lambda _: ["alpha", "beta", inner]
     )
 
     config = OrderedDict({"values": outer})
@@ -736,15 +841,48 @@ def test_top_level_include_resolved_by_load_yaml(tmp_path: Path) -> None:
     assert result["key"] == "value"
 
 
+@pytest.mark.parametrize(
+    ("condition", "expected_result_or_error"),
+    [
+        ("true", True),
+        ("false", False),
+        ('"TRUE"', True),
+        ('"FALSE"', False),
+        ('"x"', "Cannot convert include condition for 'child.yaml' to a boolean"),
+        (
+            "$sub",
+            "Cannot evaluate include condition for 'child.yaml' with unresolved substitutions",
+        ),
+    ],
+)
+def test_top_level_include_with_condition_resolved_by_load_yaml(
+    tmp_path: Path, condition: bool | str | None, expected_result_or_error: bool | str
+) -> None:
+    """load_yaml evaluates the condition for a top-level !include."""
+    child = tmp_path / "child.yaml"
+    child.write_text("key: value\n")
+    main = tmp_path / "main.yaml"
+    main.write_text(f"!include {{ file: child.yaml, condition: {condition} }}\n")
+
+    if isinstance(expected_result_or_error, bool):
+        result = yaml_util.load_yaml(main)
+        assert isinstance(result, dict)
+        if expected_result_or_error:
+            assert result["key"] == "value"
+        else:
+            assert result == {}
+    else:
+        with pytest.raises(cv.Invalid, match=expected_result_or_error):
+            result = yaml_util.load_yaml(main)
+
+
 def test_include_plain_filename_loads_after_deferred_refactor() -> None:
     """!include with a plain filename (no $ expressions) still loads correctly.
 
     Regression guard: the deferred-loading refactor must not break the simple case.
     """
     parent = Path("/fake/main.yaml")
-    include = yaml_util.IncludeFile(
-        parent, "child.yaml", None, lambda _: {"answer": 42}
-    )
+    include = yaml_util.IncludeFile(parent, "child.yaml", lambda _: {"answer": 42})
 
     config = OrderedDict({"result": include})
     config = substitutions.do_substitution_pass(config)
@@ -756,7 +894,23 @@ def test_yaml_merge_include_with_filename_substitution_raises() -> None:
     """<<: !include ${expr} raises a clear error — substitutions in merge-key filenames
     are not yet supported, and the error message must say so."""
     yaml_text = "base:\n  existing: value\n  <<: !include ${filename}.yaml\n"
-    with pytest.raises(EsphomeError, match="not supported yet"):
+    with pytest.raises(
+        EsphomeError,
+        match="Substitution in include filename with merge keys is not supported yet",
+    ):
+        yaml_util.parse_yaml(
+            Path("/fake/main.yaml"), io.StringIO(yaml_text), lambda _: {}
+        )
+
+
+def test_yaml_merge_include_with_condition_substitution_raises() -> None:
+    """<<: !include { file: ${expr}, condition: {} } raises a clear error — substitutions in merge-key conditions
+    are not yet supported, and the error message must say so."""
+    yaml_text = "base:\n  existing: value\n  <<: !include\n    file: filename.yaml\n    condition: ${expr}\n"
+    with pytest.raises(
+        EsphomeError,
+        match="Substitution in include condition with merge keys is not supported yet",
+    ):
         yaml_util.parse_yaml(
             Path("/fake/main.yaml"), io.StringIO(yaml_text), lambda _: {}
         )
@@ -775,8 +929,8 @@ def test_yaml_merge_chain_include_resolves() -> None:
     """Chained includes in merge keys resolve through multiple IncludeFile layers."""
     parent = Path("/fake/main.yaml")
 
-    inner = yaml_util.IncludeFile(parent, "inner.yaml", None, lambda _: {"x": 1})
-    outer = yaml_util.IncludeFile(parent, "outer.yaml", None, lambda _: inner)
+    inner = yaml_util.IncludeFile(parent, "inner.yaml", lambda _: {"x": 1})
+    outer = yaml_util.IncludeFile(parent, "outer.yaml", lambda _: inner)
 
     yaml_text = "base:\n  existing: value\n  <<: !include outer.yaml\n"
     config = yaml_util.parse_yaml(parent, io.StringIO(yaml_text), lambda _: outer)
@@ -791,7 +945,7 @@ def test_yaml_merge_chain_include_depth_exceeded() -> None:
     parent = Path("/fake/main.yaml")
 
     def self_referencing_loader(path: Path) -> yaml_util.IncludeFile:
-        return yaml_util.IncludeFile(parent, path.name, None, self_referencing_loader)
+        return yaml_util.IncludeFile(parent, path.name, self_referencing_loader)
 
     yaml_text = "base:\n  <<: !include loop.yaml\n"
     with pytest.raises(EsphomeError, match="Maximum include chain depth"):
@@ -1061,7 +1215,7 @@ class _StubInclude:
         self._raise = raise_on_load
         self.load_calls = 0
 
-    def has_unresolved_expressions(self) -> bool:
+    def has_unresolved_file(self) -> bool:
         return self._unresolved
 
     def load(self) -> object: