1 files changed, 80 insertions, 0 deletions
diff --git a/src/ansiblelint/rules/empty_string_compare.py b/src/ansiblelint/rules/empty_string_compare.py
new file mode 100644
index 0000000..5c7cafc
--- /dev/null
+++ b/src/ansiblelint/rules/empty_string_compare.py
@@ -0,0 +1,80 @@
+"""Implementation of empty-string-compare rule."""
+# Copyright (c) 2016, Will Thames and contributors
+# Copyright (c) 2018, Ansible Project
+
+from __future__ import annotations
+
+import re
+import sys
+from typing import TYPE_CHECKING
+
+from ansiblelint.rules import AnsibleLintRule
+from ansiblelint.yaml_utils import nested_items_path
+
+if TYPE_CHECKING:
+    from ansiblelint.file_utils import Lintable
+    from ansiblelint.utils import Task
+
+
+class ComparisonToEmptyStringRule(AnsibleLintRule):
+    """Don't compare to empty string."""
+
+    id = "empty-string-compare"
+    description = (
+        'Use ``when: var|length > 0`` rather than ``when: var != ""`` (or '
+        'conversely ``when: var|length == 0`` rather than ``when: var == ""``)'
+    )
+    severity = "HIGH"
+    tags = ["idiom", "opt-in"]
+    version_added = "v4.0.0"
+
+    empty_string_compare = re.compile("[=!]= ?(\"{2}|'{2})")
+
+    def matchtask(
+        self,
+        task: Task,
+        file: Lintable | None = None,
+    ) -> bool | str:
+        for k, v, _ in nested_items_path(task):
+            if k == "when":
+                if isinstance(v, str):
+                    if self.empty_string_compare.search(v):
+                        return True
+                elif isinstance(v, bool):
+                    pass
+                else:
+                    for item in v:
+                        if isinstance(item, str) and self.empty_string_compare.search(
+                            item,
+                        ):
+                            return True
+
+        return False
+
+
+# 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_rule_empty_string_compare_fail() -> None:
+        """Test rule matches."""
+        rules = RulesCollection()
+        rules.register(ComparisonToEmptyStringRule())
+        results = Runner(
+            "examples/playbooks/rule-empty-string-compare-fail.yml",
+            rules=rules,
+        ).run()
+        assert len(results) == 3
+        for result in results:
+            assert result.message == ComparisonToEmptyStringRule().shortdesc
+
+    def test_rule_empty_string_compare_pass() -> None:
+        """Test rule matches."""
+        rules = RulesCollection()
+        rules.register(ComparisonToEmptyStringRule())
+        results = Runner(
+            "examples/playbooks/rule-empty-string-compare-pass.yml",
+            rules=rules,
+        ).run()
+        assert len(results) == 0, results