Python: Handle @pytest.fixture decorations with arguments as well

Not the prettiest of solutions, but it seems to work well enough.

Author: tausbn

python/ql/src/Imports/UnusedImport.ql

@@ -15,14 +15,24 @@ import Variables.Definition
 import semmle.python.ApiGraphs
 
 private predicate is_pytest_fixture(Import imp, Variable name) {
-  exists(Alias a |
+  exists(Alias a, API::Node pytest_fixture, API::Node decorator |
+    pytest_fixture = API::moduleImport("pytest").getMember("fixture") and
+    // The additional `.getReturn()` is to account for the difference between
+    // ```
+    // @pytest.fixture
+    // def foo():
+    //    ...
+    // ```
+    // and
+    // ```
+    // @pytest.fixture(some, args, here)
+    // def foo():
+    //    ...
+    // ```
+    decorator in [pytest_fixture, pytest_fixture.getReturn()] and
     a = imp.getAName() and
     a.getAsname().(Name).getVariable() = name and
-    API::moduleImport("pytest")
-        .getMember("fixture")
-        .getReturn()
-        .getAValueReachableFromSource()
-        .asExpr() = a.getValue()
+    a.getValue() = decorator.getReturn().getAValueReachableFromSource().asExpr()
   )
 }
 

python/ql/test/query-tests/Imports/unused/UnusedImport.expected

@@ -6,5 +6,3 @@
 | imports_test.py:27:1:27:25 | Import | Import of 'func2' is not used. |
 | imports_test.py:34:1:34:14 | Import | Import of 'module2' is not used. |
 | imports_test.py:116:1:116:41 | Import | Import of 'not_a_fixture' is not used. |
-| imports_test.py:118:1:118:68 | Import | Import of 'session_fixture' is not used. |
-| imports_test.py:118:1:118:68 | Import | Import of 'wrapped_autouse_fixture' is not used. |

python/ql/test/query-tests/Imports/unused/imports_test.py

@@ -115,4 +115,4 @@ def baz() -> Optional['subexpression_return_type']:
 
 from pytest_fixtures import not_a_fixture  # BAD
 from pytest_fixtures import fixture, wrapped_fixture  # GOOD (pytest fixtures are used implicitly by pytest)
-from pytest_fixtures import session_fixture, wrapped_autouse_fixture  # GOOD [FALSE POSITIVE]
+from pytest_fixtures import session_fixture, wrapped_autouse_fixture  # GOOD (pytest fixtures are used implicitly by pytest)