fix: prevent potential NPE in MicroProfileRestClientDiagnosticsParticipant.validateField()

Signed-off-by: Fred Bricon <fbricon@gmail.com>

Author: fbricon

src/main/java/com/redhat/devtools/intellij/lsp4mp4ij/psi/core/utils/PsiTypeUtils.java

@@ -43,6 +43,7 @@
 import com.intellij.psi.util.PsiTreeUtil;
 import com.intellij.psi.util.PsiTypesUtil;
 import com.intellij.psi.util.PsiUtil;
+import org.jetbrains.annotations.Nullable;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
@@ -142,6 +143,7 @@ public static String getSourceMethod(PsiMethod method) {
     }
 
 
+    @Nullable
     public static PsiClass findType(PsiManager manager, String name) {
         JavaPsiFacade facade = JavaPsiFacade.getInstance(manager.getProject());
         return facade.findClass(name, GlobalSearchScope.allScope(manager.getProject()));

src/main/java/com/redhat/devtools/intellij/lsp4mp4ij/psi/internal/restclient/java/MicroProfileRestClientDiagnosticsParticipant.java

@@ -123,6 +123,11 @@ private static void validateField(PsiField field, List<Diagnostic> diagnostics,
 		boolean hasRestClientAnnotation = AnnotationUtils.hasAnnotation(field, REST_CLIENT_ANNOTATION);
 		String fieldTypeName = PsiTypeUtils.getResolvedTypeName(field);
 		PsiClass fieldType = PsiTypeUtils.findType(field.getManager(), fieldTypeName);
+		if (fieldType == null) {
+			// document is in invalid state? better bail now.
+			// See https://github.com/redhat-developer/intellij-quarkus/issues/823
+			return;
+		}
 		boolean hasRegisterRestClient = AnnotationUtils.hasAnnotation(fieldType, REGISTER_REST_CLIENT_ANNOTATION)
 				&& fieldType.isInterface();