In case of new file creation by the MR there is a 404 error on file retrieval by gitlab provider.

It was handled by catching the error and replacing the file string with an empty string.
Type checking was added before byte decoding - necessary in case of the empty string.

pr_agent/git_providers/gitlab_provider.py

@@ -4,6 +4,7 @@ from typing import Optional, Tuple
 from urllib.parse import urlparse
 
 import gitlab
+from gitlab import GitlabGetError
 
 from pr_agent.config_loader import settings
 
@@ -42,7 +43,11 @@ class GitLabProvider(GitProvider):
         self.last_diff = self.mr.diffs.list()[-1]
 
     def _get_pr_file_content(self, file_path: str, branch: str) -> str:
-        return self.gl.projects.get(self.id_project).files.get(file_path, branch).decode()
+        try:
+            return self.gl.projects.get(self.id_project).files.get(file_path, branch).decode()
+        except GitlabGetError:
+            # In case of file creation the method returns GitlabGetError (404 file not found). In this case we return an empty string for the diff.
+            return ''
 
     def get_diff_files(self) -> list[FilePatchInfo]:
         diffs = self.mr.changes()['changes']
@@ -58,8 +63,10 @@ class GitLabProvider(GitProvider):
             elif diff['renamed_file']:
                 edit_type = EDIT_TYPE.RENAMED
             try:
-                original_file_content_str = bytes.decode(original_file_content_str, 'utf-8')
-                new_file_content_str = bytes.decode(new_file_content_str, 'utf-8')
+                if isinstance(original_file_content_str, bytes):
+                    original_file_content_str = bytes.decode(original_file_content_str, 'utf-8')
+                if isinstance(new_file_content_str, bytes):
+                    new_file_content_str = bytes.decode(new_file_content_str, 'utf-8')
             except UnicodeDecodeError:
                 logging.warning(
                     f"Cannot decode file {diff['old_path']} or {diff['new_path']} in merge request {self.id_mr}")