Made empty-string-compare rule opt-in (#1953)

.ansible-lint

@@ -44,6 +44,7 @@ skip_list:
 # Any rule that has the 'opt-in' tag will not be loaded unless its 'id' is
 # mentioned in the enable_list:
 enable_list:
+  - empty-string-compare # opt-in
   - no-log-password # opt-in
   - no-same-owner # opt-in
   # add yaml here if you want to avoid ignoring yaml checks when yamllint

src/ansiblelint/rules/ComparisonToEmptyStringRule.py

@@ -22,7 +22,7 @@ class ComparisonToEmptyStringRule(AnsibleLintRule):
         'conversely ``when: var|length == 0`` rather than ``when: var == ""``)'
     )
     severity = "HIGH"
-    tags = ["idiom"]
+    tags = ["idiom", "opt-in"]
     version_added = "v4.0.0"
 
     empty_string_compare = re.compile("[=!]= ?(\"{2}|'{2})")

test/TestRulesCollection.py

@@ -158,4 +158,4 @@ def test_rules_id_format() -> None:
         assert rule_id_re.match(
             rule.id
         ), f"Rule id {rule.id} did not match our required format."
-    assert len(rules) == 41
+    assert len(rules) == 40