SONARPY-228 Fix FP in UnusedLocalVariableCheck when "locals()" is used (SonarSource#117)

pynicolas · alban-auzeill · commit 691b8a56372a · 2018-01-02T15:32:04.000+01:00
diff --git a/its/ruling/src/test/resources/expected/python-S1481.json b/its/ruling/src/test/resources/expected/python-S1481.json
@@ -166,12 +166,6 @@
 'project:django-1.4/django/core/cache/__init__.py':[
 133,
 ],
-'project:django-1.4/django/db/backends/oracle/base.py':[
-93,
-94,
-95,
-96,
-],
 'project:django-1.4/django/db/backends/sqlite3/creation.py':[
 84,
 ],
diff --git a/python-checks/src/main/java/org/sonar/python/checks/UnusedLocalVariableCheck.java b/python-checks/src/main/java/org/sonar/python/checks/UnusedLocalVariableCheck.java
@@ -40,11 +40,22 @@ public Set<AstNodeType> subscribedKinds() {
 
   @Override
   public void visitNode(AstNode functionTree) {
+    // https://docs.python.org/3/library/functions.html#locals
+    if (isCallingLocalsFunction(functionTree)) {
+      return;
+    }
     for (Symbol symbol : getContext().symbolTable().symbols(functionTree)) {
       checkSymbol(symbol);
     }
   }
 
+  private static boolean isCallingLocalsFunction(AstNode functionTree) {
+    return functionTree
+      .getDescendants(PythonGrammar.NAME)
+      .stream()
+      .anyMatch(node -> "locals".equals(node.getTokenValue()));
+  }
+
   private void checkSymbol(Symbol symbol) {
     if (symbol.readUsages().isEmpty()) {
       for (AstNode writeUsage : symbol.writeUsages()) {
diff --git a/python-checks/src/test/resources/checks/unusedLocalVariable.py b/python-checks/src/test/resources/checks/unusedLocalVariable.py
@@ -10,3 +10,8 @@ def f(unread_param):
     read_in_nested_function = 1
     def nested_function():
         print(read_in_nested_function)
+
+def using_locals(a, b):
+  c = a + b
+  # "locals" will include the "c" value
+  return locals()
