Facing an error while creating and merge a gitlab mr using python script

General
1

I’m trying to create and merge a gitlab mr using python script, the mr was created without any error, but I got an error message while trying to merge it "422, {"message":"Branch cannot be merged"}", how can i get more details about the error? Is there any issue with my script? Thanks

The functions used to create and merge it:

def create_merge_request(token, project_id, source_branch, target_branch, title, description):
    """Créer une Merge Request sur GitLab."""
    url = f"{GITLAB_HOST_HTTPS}/api/v4/projects/{project_id}/merge_requests"
    headers = {"PRIVATE-TOKEN": token}
    data = {
        "source_branch": source_branch,
        "target_branch": target_branch,
        "title": title,
        "description": description,
        "merge_when_pipeline_succeeds": False,  # Désactiver la fusion conditionnelle
        "remove_source_branch": True,   # Supprimer la branche source après fusion
        "squash": True                        # Ne pas écraser les commits
    }

    response = requests.post(url, headers=headers, json=data)

    if response.status_code == 201:
        mr_data = response.json()
        print(f"Merge Request créée avec succès : {mr_data.get('web_url')}")
        return mr_data  # Retourne les détails de la MR
    else:
        print(f"Erreur lors de la création de la Merge Request : {response.json()}")
        return None

def merge_mr(token, project_id, merge_request_iid):
    """Fusionner une Merge Request via l'API GitLab."""
    url = f"{GITLAB_HOST_HTTPS}/api/v4/projects/{project_id}/merge_requests/{merge_request_iid}/merge"
    headers = {"PRIVATE-TOKEN": token}

    print(f"URL utilisée pour le merge : {url}")
    response = requests.put(url, headers=headers) #, json=data

    if response.status_code == 200:
        print("Merge Request mergée avec succès.")
        return response.json()
    elif response.status_code == 405:
        print("Erreur 405 : Méthode non autorisée. Vérifiez la méthode HTTP (PUT).")
    else:
        print(f"Erreur lors de la Merge : {response.status_code}, {response.text}")
    return None
def create_and_merge_mr(token, project_id, source_branch, target_branch, title, description):
    """Créer une MR et la merger immédiatement si possible."""
    # Étape 1 : Créer la MR
    mr_data = create_merge_request(token, project_id, source_branch, target_branch, title, description)
    if not mr_data:
        print("Échec de la création de la Merge Request.")
        return
    
    # Étape 2 : Récupérer l'ID interne de la MR (iid)
    merge_request_iid = mr_data.get('iid')
    if not merge_request_iid:
        print("Impossible de récupérer l'ID interne de la Merge Request.")
        return
    
    # Étape 3 : Fusionner la MR
    merge_result = merge_mr(token, project_id, merge_request_iid)
    if merge_result:
        print("MR mergée avec succès.")
    else:
        print("Échec de la merge de la MR.")

def main():
    parser = ArgumentParser()
    parser.add_argument("--client_group_name", help="Nom du groupe client à filtrer", default=None)
    parser.add_argument("--yaml_file", help="Chemin du fichier YAML pour les topics", default="nature-topics.yaml")
    parser.add_argument("--gitlab_token", help="GitLab token for authentication", required=True)
    parser.add_argument("--nature", help="Nature of the environment (e.g., dev, qa)", required=True)
    args = parser.parse_args()


    #1.
    #2.
    #3.
    #4.



    # 9. merge la MR
    # git_merge_branches(local_repo_path, new_branch, branch)
    create_and_merge_mr(
        args.gitlab_token, 
        project_id, 
        new_branch, 
        branch, 
        "xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx", 
        "yyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyy" 
    )

if __name__ == "__main__":
    main()
2

The error message "422, {"message":"Branch cannot be merged"} typically occurs in GitLab when there is an issue preventing the merge operation. Common reasons for this include:

Possible Causes for “Branch cannot be merged”

  1. Conflicts: The source branch and target branch have merge conflicts.
  2. Pipeline Failures: If the project is configured to require successful pipelines before merging, and the pipeline has failed or is not finished, the merge will be blocked.
  3. Protected Branch Restrictions: The target branch (e.g., main or master) may have restrictions, such as requiring approvals or disallowing direct merges.
  4. Merge Rules: GitLab settings may enforce rules like requiring a specific number of approvals or preventing merges without discussions.
  5. Stale Source Branch: The source branch might be out of date with the target branch.
  6. Permissions: The GitLab user associated with the API token might lack permissions to merge into the target branch.

Steps to Troubleshoot

1. Check Merge Conflicts

Add the following endpoint to check for conflicts in the merge request:

def check_conflicts(token, project_id, merge_request_iid):
    """Check if a merge request has conflicts."""
    url = f"{GITLAB_HOST_HTTPS}/api/v4/projects/{project_id}/merge_requests/{merge_request_iid}"
    headers = {"PRIVATE-TOKEN": token}
    
    response = requests.get(url, headers=headers)
    if response.status_code == 200:
        mr_data = response.json()
        if mr_data.get("has_conflicts"):
            print("The merge request has conflicts. Resolve them before merging.")
        else:
            print("No conflicts found.")
        print(f"Merge Status: {mr_data.get('merge_status')}")
    else:
        print(f"Failed to check conflicts: {response.status_code}, {response.text}")

Call this function before merging:

check_conflicts(token, project_id, merge_request_iid)

2. Verify Pipeline Status

Check if the pipeline is complete and successful. Add a function to check the pipeline status:

def check_pipeline_status(token, project_id, merge_request_iid):
    """Check the pipeline status of a merge request."""
    url = f"{GITLAB_HOST_HTTPS}/api/v4/projects/{project_id}/merge_requests/{merge_request_iid}/pipelines"
    headers = {"PRIVATE-TOKEN": token}
    
    response = requests.get(url, headers=headers)
    if response.status_code == 200:
        pipelines = response.json()
        if not pipelines:
            print("No pipelines found for the merge request.")
            return
        latest_pipeline = pipelines[0]  # Get the latest pipeline
        print(f"Pipeline status: {latest_pipeline.get('status')}")
    else:
        print(f"Failed to fetch pipeline status: {response.status_code}, {response.text}")

Call this function to validate the pipeline:

check_pipeline_status(token, project_id, merge_request_iid)

3. Verify Permissions

Ensure the token used has sufficient permissions:

  • The token should have at least Developer permissions for the project.
  • If protected branches are configured, the token needs Maintainer or appropriate permissions to merge.

Enhancing the Script

Update the merge_mr function to check the merge status:

def merge_mr(token, project_id, merge_request_iid):
    """Fusionner une Merge Request via l'API GitLab."""
    url = f"{GITLAB_HOST_HTTPS}/api/v4/projects/{project_id}/merge_requests/{merge_request_iid}"
    headers = {"PRIVATE-TOKEN": token}

    # Check merge request details
    response = requests.get(url, headers=headers)
    if response.status_code == 200:
        mr_data = response.json()
        print(f"Merge Status: {mr_data.get('merge_status')}")
        if mr_data.get("has_conflicts"):
            print("The merge request has conflicts. Resolve them before merging.")
            return None
        if mr_data.get("merge_status") != "can_be_merged":
            print("Merge request cannot be merged. Check GitLab rules or pipeline status.")
            return None
    else:
        print(f"Failed to fetch merge request details: {response.status_code}, {response.text}")
        return None

    # Attempt to merge
    merge_url = f"{url}/merge"
    response = requests.put(merge_url, headers=headers)
    if response.status_code == 200:
        print("Merge Request merged successfully.")
        return response.json()
    else:
        print(f"Error during merge: {response.status_code}, {response.text}")
        return None

Debugging the Issue

  1. Use check_conflicts to ensure there are no merge conflicts.
  2. Use check_pipeline_status to confirm the pipeline is successful.
  3. Update the merge_mr function to print additional details from the merge request (e.g., merge_status and has_conflicts).
  4. Double-check branch protection rules in GitLab (e.g., settings that prevent direct merging).

Example Output

If the issue persists, the enhanced script will provide more details such as:

  • Whether the source branch is up-to-date.
  • Whether the pipeline has succeeded.
  • Whether there are conflicts.
  • If the token lacks permissions.

This will help pinpoint the cause and make necessary adjustments to your project settings or process. Let me know if you’d like further assistance!