SONARPY-2441: Fix NPE when qualified expression is used as keyword argument (#393)

GitOrigin-RevId: 329a636f233c46a099cfa1b70c5c24c08ac2a37e

Author: joke1196

python-frontend/src/main/java/org/sonar/python/api/PythonGrammarBuilder.java

@@ -112,7 +112,7 @@ protected void grammar(LexerfulGrammarBuilder b) {
       POWER)).skipIfOneChild();
     b.rule(POWER).is(b.firstOf(
       b.sequence(b.optional("await"), ATOM, b.zeroOrMore(TRAILER), b.optional("**", FACTOR)),
-      // matches "await" identifier
+      // before python 3.5 "await" can be used as an identifier
       "await")).skipIfOneChild();
 
     b.rule(ATOM).is(b.firstOf(

python-frontend/src/main/java/org/sonar/python/tree/PythonTreeMaker.java

@@ -1584,8 +1584,11 @@ public Argument argument(AstNode astNode) {
     Expression arg = expression(astNode.getLastChild(PythonGrammar.TEST));
     if (assign != null) {
       // Keyword in argument list must be an identifier.
-      AstNode nameNode = astNode.getFirstChild(PythonGrammar.TEST).getFirstChild(PythonGrammar.ATOM).getFirstChild(PythonGrammar.NAME);
-      return new RegularArgumentImpl(name(nameNode), toPyToken(assign.getToken()), arg);
+      return Optional.ofNullable(astNode.getFirstChild(PythonGrammar.TEST))
+        .map(test -> test.getFirstChild(PythonGrammar.ATOM))
+        .map(atom -> atom.getFirstChild(PythonGrammar.NAME))
+        .map(nameNode -> new RegularArgumentImpl(name(nameNode), toPyToken(assign.getToken()), arg))
+        .orElseThrow(() -> new IllegalStateException("Keyword argument must be an identifier"));
     }
     return star == null ? new RegularArgumentImpl(arg) : new UnpackingExpressionImpl(star, arg);
   }

python-frontend/src/test/java/org/sonar/python/tree/PythonTreeMakerTest.java

@@ -120,6 +120,7 @@
 import static org.assertj.core.api.Assertions.assertThat;
 import static org.assertj.core.api.Assertions.assertThatThrownBy;
 import static org.assertj.core.api.Assertions.fail;
+import static org.junit.jupiter.api.Assertions.assertThrowsExactly;
 
 class PythonTreeMakerTest extends RuleTest {
 
@@ -1748,6 +1749,9 @@ void argument() {
     name = (Name) argumentTree.expression();
     assertThat(name.name()).isEqualTo("foo");
     assertThat(argumentTree.children()).hasSize(3).containsExactly(argumentTree.keywordArgument(), argumentTree.equalToken(), argumentTree.expression());
+
+    IllegalStateException exception = assertThrowsExactly(IllegalStateException.class, () -> parse("obj.bar=foo", treeMaker::argument));
+    assertThat(exception.getMessage()).isEqualTo("Keyword argument must be an identifier");
   }
 
   @Test