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diff --git a/src/ansiblelint/rules/partial_become.py b/src/ansiblelint/rules/partial_become.py
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+++ b/src/ansiblelint/rules/partial_become.py
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+"""Implementation of partial-become rule."""
+# Copyright (c) 2016 Will Thames <will@thames.id.au>
+#
+# Permission is hereby granted, free of charge, to any person obtaining a copy
+# of this software and associated documentation files (the "Software"), to deal
+# in the Software without restriction, including without limitation the rights
+# to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+# copies of the Software, and to permit persons to whom the Software is
+# furnished to do so, subject to the following conditions:
+#
+# The above copyright notice and this permission notice shall be included in
+# all copies or substantial portions of the Software.
+#
+# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+# AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+# OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+# THE SOFTWARE.
+from __future__ import annotations
+
+import sys
+from functools import reduce
+from typing import TYPE_CHECKING, Any
+
+from ansiblelint.constants import LINE_NUMBER_KEY
+from ansiblelint.rules import AnsibleLintRule
+
+if TYPE_CHECKING:
+    from ansiblelint.errors import MatchError
+    from ansiblelint.file_utils import Lintable
+
+
+def _get_subtasks(data: dict[str, Any]) -> list[Any]:
+    result: list[Any] = []
+    block_names = [
+        "tasks",
+        "pre_tasks",
+        "post_tasks",
+        "handlers",
+        "block",
+        "always",
+        "rescue",
+    ]
+    for name in block_names:
+        if data and name in data:
+            result += data[name] or []
+    return result
+
+
+def _nested_search(term: str, data: dict[str, Any]) -> Any:
+    if data and term in data:
+        return True
+    return reduce(
+        (lambda x, y: x or _nested_search(term, y)), _get_subtasks(data), False
+    )
+
+
+def _become_user_without_become(becomeuserabove: bool, data: dict[str, Any]) -> Any:
+    if "become" in data:
+        # If become is in lineage of tree then correct
+        return False
+    if "become_user" in data and _nested_search("become", data):
+        # If 'become_user' on tree and become somewhere below
+        # we must check for a case of a second 'become_user' without a
+        # 'become' in its lineage
+        subtasks = _get_subtasks(data)
+        return reduce(
+            (lambda x, y: x or _become_user_without_become(False, y)), subtasks, False
+        )
+    if _nested_search("become_user", data):
+        # Keep searching down if 'become_user' exists in the tree below current task
+        subtasks = _get_subtasks(data)
+        return len(subtasks) == 0 or reduce(
+            (
+                lambda x, y: x
+                or _become_user_without_become(
+                    becomeuserabove or "become_user" in data, y
+                )
+            ),
+            subtasks,
+            False,
+        )
+    # If at bottom of tree, flag up if 'become_user' existed in the lineage of the tree and
+    # 'become' was not. This is an error if any lineage has a 'become_user' but no become
+    return becomeuserabove
+
+
+class BecomeUserWithoutBecomeRule(AnsibleLintRule):
+    """become_user requires become to work as expected."""
+
+    id = "partial-become"
+    description = "``become_user`` without ``become`` will not actually change user"
+    severity = "VERY_HIGH"
+    tags = ["unpredictability"]
+    version_added = "historic"
+
+    def matchplay(self, file: Lintable, data: dict[str, Any]) -> list[MatchError]:
+        if file.kind == "playbook":
+            result = _become_user_without_become(False, data)
+            if result:
+                return [
+                    self.create_matcherror(
+                        message=self.shortdesc,
+                        filename=file,
+                        linenumber=data[LINE_NUMBER_KEY],
+                    )
+                ]
+        return []
+
+
+# testing code to be loaded only with pytest or when executed the rule file
+if "pytest" in sys.modules:
+    from ansiblelint.rules import RulesCollection  # pylint: disable=ungrouped-imports
+    from ansiblelint.runner import Runner  # pylint: disable=ungrouped-imports
+
+    def test_partial_become_positive() -> None:
+        """Positive test for partial-become."""
+        collection = RulesCollection()
+        collection.register(BecomeUserWithoutBecomeRule())
+        success = "examples/playbooks/rule-partial-become-without-become-pass.yml"
+        good_runner = Runner(success, rules=collection)
+        assert [] == good_runner.run()
+
+    def test_partial_become_negative() -> None:
+        """Negative test for partial-become."""
+        collection = RulesCollection()
+        collection.register(BecomeUserWithoutBecomeRule())
+        failure = "examples/playbooks/rule-partial-become-without-become-fail.yml"
+        bad_runner = Runner(failure, rules=collection)
+        errs = bad_runner.run()
+        assert len(errs) == 3