Merge ~mertkirpici/juju-lint:lp/1993735 into juju-lint:master

[Mert Kirpici]

Close LP #1993735

The callback function `helper_operator_eq_check` for the eq operator, has an overloaded behavior. It first tries regex matching and if that is not successful, it tests for regular string equality checking.

This caused some issues when testing against an empty string. A check value of empty string used to match any kind of input, which is quite counter-intuitive.

With this change we are adding an exception for the empty string case to force string equality check in that case. Also adding a deprecation notice for the overloaded regex checking behavior to inform the users that it will be removed in the future.

[🤖 Canonical IS Merge Bot (canonical-is-mergebot)]

This merge proposal is being monitored by mergebot. Change the status to Approved to merge.

[🤖 prod-jenkaas-bootstack (prod-jenkaas-bootstack)]

FAILED: Continuous integration, rev:318ea5b89eb8c280b8677be58126f1fc4ba23895
https://jenkins.canonical.com/bootstack/job/lp-juju-lint-ci/22/
Executed test runs:
    FAILURE: https://jenkins.canonical.com/bootstack/job/lp-charm-test-functest/1160/
    None: https://jenkins.canonical.com/bootstack/job/lp-update-mp/1579/

Click here to trigger a rebuild:
https://jenkins.canonical.com/bootstack/job/lp-juju-lint-ci/22//rebuild

review: Needs Fixing (continuous-integration)

[Robert Gildein (rgildein)]

One suggestion and I think that we need to rewrite
`test_helper_operator_check` test function.

review: Needs Fixing

[Mert Kirpici (mertkirpici)]

Hi Robert thanks for the review and suggestions. I applied both of them in the update.

[Gabriel Cocenza (gabrielcocenza)]

LGTM

review: Approve

[Robert Gildein (rgildein)]

LGTM

review: Approve

[🤖 Canonical IS Merge Bot (canonical-is-mergebot)]

Change successfully merged at revision 1108dacb9fe66ef726d4764bcd2a3703ef6bfa14

[🤖 prod-jenkaas-bootstack (prod-jenkaas-bootstack)]

PASSED: Continuous integration, rev:ff6c048579ecf261cc2cdb6b3bafecf644af4b71
https://jenkins.canonical.com/bootstack/job/lp-juju-lint-ci/24/
Executed test runs:
    SUCCESS: https://jenkins.canonical.com/bootstack/job/lp-charm-test-functest/1163/
    None: https://jenkins.canonical.com/bootstack/job/lp-update-mp/1581/

Click here to trigger a rebuild:
https://jenkins.canonical.com/bootstack/job/lp-juju-lint-ci/24//rebuild

review: Approve (continuous-integration)

diff --git a/jujulint/lint.py b/jujulint/lint.py
index f73b7ea..4219b2f 100755
--- a/jujulint/lint.py
+++ b/jujulint/lint.py
@@ -60,6 +60,16 @@ ConfigOperator = collections.namedtuple(
 
 def helper_operator_eq_check(check_value, actual_value):
     """Perform the actual equality check for the eq/neq rules."""
+    # An empty string regex matches any string. Therefore
+    # we are handling the empty string as a special case for now
+    # as a workaround.
+    # The overloaded regex matching behavior will be removed in a
+    # future version.
+    #
+    # See LP #1993735
+    if check_value == "":
+        return check_value == actual_value
+
     match = False
     try:
         match = re.match(re.compile(str(check_value)), str(actual_value))
@@ -126,6 +136,11 @@ class Linter:
 
         # collect errors only for non-text output (e.g. json)
         self.collect_errors = True if self.output_format != "text" else False
+        self.logger.warn(
+            "Regex autodetection feature of the eq operator is deprecated. "
+            "It will only check for equality in the future. "
+            "Please use the search operator for regex checks."
+        )
 
     def read_rules(self):
         """Read and parse rules from YAML, optionally processing provided overrides."""
diff --git a/tests/unit/test_jujulint.py b/tests/unit/test_jujulint.py
index c87722d..9f95f43 100644
--- a/tests/unit/test_jujulint.py
+++ b/tests/unit/test_jujulint.py
@@ -1540,25 +1540,22 @@ applications:
         logger_mock.warn.assert_called_once_with(expected_msg)
 
     @pytest.mark.parametrize(
-        "regex_error, check_value, actual_value",
+        "expected_result, check_value, actual_value",
         [
             (True, "same", "same"),
-            (True, "same", "different"),
-            (False, "same", "same"),
             (False, "same", "different"),
+            (False, "same", "Same"),
+            (True, "[sS]ame", "Same"),
+            (True, "[same", "[same"),
+            (False, "", "foo"),
+            (True, "", ""),
         ],
     )
     def test_helper_operator_check(
-        self, regex_error, check_value, actual_value, mocker
+        self, expected_result, check_value, actual_value, mocker
     ):
         """Test comparing values using "helper_operator_check()" function."""
-        if regex_error:
-            mocker.patch.object(lint.re, "match", side_effect=lint.re.error(""))
-
-        expected_result = check_value == actual_value
-
         result = lint.helper_operator_eq_check(check_value, actual_value)
-
         assert bool(result) == expected_result
 
     @pytest.mark.parametrize(