Python: Fix "unused disjunct" warnings

tausbn · web-flow · commit 74f0bdfc7985 · 2022-03-04T12:14:57.000Z
For the most part, these boil down to "some global property holds, and
so this relation contains all instances of class `X`". The fix is to
explicitly build the cartesian product (which we were already building
implicitly anyway) by adding `and exists(var)` to the disjunct that did
not mention `var`.

Note that these cartesian products are always with singletons on one
side, and so should be unproblematic.
diff --git a/python/ql/lib/semmle/python/Module.qll b/python/ql/lib/semmle/python/Module.qll
@@ -196,7 +196,7 @@ private predicate isPotentialSourcePackage(Folder f) {
 private predicate isPotentialPackage(Folder f) {
   exists(f.getFile("__init__.py"))
   or
-  py_flags_versioned("options.respect_init", "False", _) and major_version() = 2
+  py_flags_versioned("options.respect_init", "False", _) and major_version() = 2 and exists(f)
 }
 
 private string moduleNameFromBase(Container file) {
diff --git a/python/ql/lib/semmle/python/dataflow/old/Legacy.qll b/python/ql/lib/semmle/python/dataflow/old/Legacy.qll
@@ -15,7 +15,7 @@ deprecated class CallContext extends TaintTrackingContext {
       )
     )
     or
-    this.isTop()
+    this.isTop() and exists(s)
   }
 }
 
diff --git a/python/ql/lib/semmle/python/pointsto/Base.qll b/python/ql/lib/semmle/python/pointsto/Base.qll
@@ -124,7 +124,7 @@ int version_tuple_compare(Object t) {
 predicate baseless_is_new_style(ClassObject cls) {
   cls.isBuiltin()
   or
-  major_version() = 3
+  major_version() = 3 and exists(cls)
   or
   exists(cls.declaredMetaClass())
 }
diff --git a/python/ql/lib/semmle/python/pointsto/MRO.qll b/python/ql/lib/semmle/python/pointsto/MRO.qll
@@ -329,7 +329,7 @@ private class ClassListList extends TClassListList {
       result = ConsList(removed_head, removed_tail)
     )
     or
-    this = EmptyList() and result = EmptyList()
+    this = EmptyList() and result = EmptyList() and exists(cls)
   }
 
   pragma[nomagic]
diff --git a/python/ql/lib/semmle/python/pointsto/PointsTo.qll b/python/ql/lib/semmle/python/pointsto/PointsTo.qll
@@ -1076,7 +1076,7 @@ module InterProceduralPointsTo {
   /** Helper for default_parameter_points_to */
   pragma[noinline]
   private predicate context_for_default_value(ParameterDefinition def, PointsToContext context) {
-    context.isRuntime()
+    context.isRuntime() and exists(def)
     or
     exists(PointsToContext caller, CallNode call, PythonFunctionObjectInternal func, int n |
       context.fromCall(call, func, caller) and
@@ -2286,7 +2286,7 @@ module Types {
       func != six_add_metaclass_function() and result = false
     )
     or
-    not exists(Module m | m.getName() = "six") and result = false
+    not exists(Module m | m.getName() = "six") and result = false and exists(cls)
     or
     exists(Class pycls |
       pycls = cls.getScope() and

Original file line number	Diff line number	Diff line change
`@@ -196,7 +196,7 @@ private predicate isPotentialSourcePackage(Folder f) {`
`196`	`196`	`private predicate isPotentialPackage(Folder f) {`
`197`	`197`	`exists(f.getFile("__init__.py"))`
`198`	`198`	`or`
`199`		`- py_flags_versioned("options.respect_init", "False", _) and major_version() = 2`
	`199`	`+ py_flags_versioned("options.respect_init", "False", _) and major_version() = 2 and exists(f)`
`200`	`200`	`}`
`201`	`201`
`202`	`202`	`private string moduleNameFromBase(Container file) {`
Original file line number	Diff line number	Diff line change
`@@ -15,7 +15,7 @@ deprecated class CallContext extends TaintTrackingContext {`
`15`	`15`	`)`
`16`	`16`	`)`
`17`	`17`	`or`
`18`		`- this.isTop()`
	`18`	`+ this.isTop() and exists(s)`
`19`	`19`	`}`
`20`	`20`	`}`
`21`	`21`
Original file line number	Diff line number	Diff line change
`@@ -124,7 +124,7 @@ int version_tuple_compare(Object t) {`
`124`	`124`	`predicate baseless_is_new_style(ClassObject cls) {`
`125`	`125`	`cls.isBuiltin()`
`126`	`126`	`or`
`127`		`- major_version() = 3`
	`127`	`+ major_version() = 3 and exists(cls)`
`128`	`128`	`or`
`129`	`129`	`exists(cls.declaredMetaClass())`
`130`	`130`	`}`
Original file line number	Diff line number	Diff line change
`@@ -329,7 +329,7 @@ private class ClassListList extends TClassListList {`
`329`	`329`	`result = ConsList(removed_head, removed_tail)`
`330`	`330`	`)`
`331`	`331`	`or`
`332`		`- this = EmptyList() and result = EmptyList()`
	`332`	`+ this = EmptyList() and result = EmptyList() and exists(cls)`
`333`	`333`	`}`
`334`	`334`
`335`	`335`	`pragma[nomagic]`