Make MLAllowlist opt-in

Analysis.__init_subclass__ put every subclass into Analysis.ALL, and
fickling/__init__.py transitively imported fickling.ml via hook.py, wich
registered MLAllowlist.

The shorten_code() shadowing bug (GHSA-cffv-grgg-g429) made it dead code
until the previous commit, and now it conflicts with other default
analysis passes.

This commit makes MLAllowlist opt-in; use `check_safety(analyze=...)`
if you need it.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: thomas-chauchefoin-tob

fickling/analysis.py

@@ -170,8 +170,10 @@ def __str__(self):
 class Analysis(ABC):
     ALL: list[Analysis] = []
 
-    def __init_subclass__(cls, **kwargs):
-        Analysis.ALL.append(cls())
+    def __init_subclass__(cls, *, register: bool = True, **kwargs):
+        super().__init_subclass__(**kwargs)
+        if register:
+            Analysis.ALL.append(cls())
 
     @abstractmethod
     def analyze(self, context: AnalysisContext) -> Iterator[AnalysisResult]:

fickling/ml.py

@@ -288,7 +288,7 @@
 }
 
 
-class MLAllowlist(Analysis):
+class MLAllowlist(Analysis, register=False):
     def __init__(self):
         super().__init__()
         self.allowlist = ML_ALLOWLIST

test/test_analysis.py

@@ -0,0 +1,19 @@
+from unittest import TestCase
+
+import fickling.fickle as op
+from fickling.analysis import Severity, check_safety
+from fickling.fickle import Pickled
+
+
+class TestAnalysis(TestCase):
+    def test_benign_pickle(self):
+        pickled = Pickled(
+            [
+                op.Proto.create(4),
+                op.ShortBinUnicode("collections"),
+                op.ShortBinUnicode("deque"),
+                op.StackGlobal(),
+                op.Stop(),
+            ]
+        )
+        self.assertEqual(check_safety(pickled).severity, Severity.LIKELY_SAFE)

test/test_bypasses.py

@@ -2,8 +2,9 @@
 from unittest import TestCase
 
 import fickling.fickle as op
-from fickling.analysis import Severity, UnsafeImportsML, check_safety
+from fickling.analysis import Analyzer, Severity, UnsafeImportsML, check_safety
 from fickling.fickle import Pickled
+from fickling.ml import MLAllowlist
 
 
 class TestBypasses(TestCase):
@@ -697,7 +698,8 @@ def test_ml_allowlist_not_shadowed_by_unsafe_imports_ml(self):
                 op.Stop(),
             ]
         )
-        res = check_safety(pickled)
+        analyzer = Analyzer([UnsafeImportsML(), MLAllowlist()])
+        res = check_safety(pickled, analyzer=analyzer)
         self.assertGreater(res.severity, Severity.LIKELY_SAFE)
         detailed = res.detailed_results().get("AnalysisResult", {})
         self.assertIsNotNone(