Python: Handle if-then-else definitions in import resolution

Author: RasmusWL

python/ql/lib/change-notes/2023-02-16-import-if-then-else.md

@@ -0,0 +1,4 @@
+---
+category: minorAnalysis
+---
+* Fixed module resolution so we properly recognize definitions made within if-then-else statements.

python/ql/lib/semmle/python/dataflow/new/internal/ImportResolution.qll

@@ -71,13 +71,19 @@ module ImportResolution {
    */
   pragma[nomagic]
   predicate module_export(Module m, string name, DataFlow::CfgNode defn) {
-    exists(EssaVariable v |
+    exists(EssaVariable v, EssaDefinition essaDef |
       v.getName() = name and
-      v.getAUse() = ImportStar::getStarImported*(m).getANormalExit()
+      v.getAUse() = ImportStar::getStarImported*(m).getANormalExit() and
+      (
+        essaDef = v.getDefinition()
+        or
+        // to handle definitions guarded by if-then-else
+        essaDef = v.getDefinition().(PhiFunction).getAnInput()
+      )
     |
-      defn.getNode() = v.getDefinition().(AssignmentDefinition).getValue()
+      defn.getNode() = essaDef.(AssignmentDefinition).getValue()
       or
-      defn.getNode() = v.getDefinition().(ArgumentRefinement).getArgument()
+      defn.getNode() = essaDef.(ArgumentRefinement).getArgument()
     )
     or
     exists(Alias a |

python/ql/test/experimental/import-resolution/main.py

@@ -91,7 +91,7 @@ def local_import():
 
 # check that definitions from within if-then-else are found
 from if_then_else import if_then_else_defined
-check("if_then_else_defined", if_then_else_defined, "if_defined", globals()) #$ MISSING: prints=if_defined prints=else_defined_1 prints=else_defined_2
+check("if_then_else_defined", if_then_else_defined, "if_defined", globals()) #$ prints=if_defined prints=else_defined_1 prints=else_defined_2
 
 exit(__file__)