Merge pull request #18921 from github/tausbn/python-fix-unused-global-variable-in-forward-annotation-fp

Python: Add support for forward references in unused var query

python/ql/src/Variables/UnusedModuleVariable.ql

@@ -34,6 +34,14 @@ predicate complex_all(Module m) {
   )
 }
 
+predicate used_in_forward_declaration(Name used, Module mod) {
+  exists(StringLiteral s, Annotation annotation |
+    s.getS() = used.getId() and
+    s.getEnclosingModule() = mod and
+    annotation.getASubExpression*() = s
+  )
+}
+
 predicate unused_global(Name unused, GlobalVariable v) {
   not exists(ImportingStmt is | is.contains(unused)) and
   forex(DefinitionNode defn | defn.getNode() = unused |
@@ -55,7 +63,8 @@ predicate unused_global(Name unused, GlobalVariable v) {
     unused.defines(v) and
     not name_acceptable_for_unused_variable(v) and
     not complex_all(unused.getEnclosingModule())
-  )
+  ) and
+  not used_in_forward_declaration(unused, unused.getEnclosingModule())
 }
 
 from Name unused, GlobalVariable v

python/ql/src/change-notes/2025-03-04-fix-forward-annotation-fp-in-unused-global-var-query.md

@@ -0,0 +1,5 @@
+---
+category: fix
+---
+
+- The `py/unused-global-variable` now no longer flags variables that are only used in forward references (e.g. the `Foo` in `def bar(x: "Foo"): ...`).