Accepted Merge Request Events" trigger also fires on merge request updates when triggerOpenMergeRequestOnPush is unset

[barbaluc]

Jenkins and plugins versions report

Bug description

When only "Accepted Merge Request Events" is checked in the GitLab trigger configuration (and "Trigger open merge requests" is left to its default/unset value), the job incorrectly triggers on any merge request update (e.g. pushing new commits, editing the MR description, etc.), not just when the MR is actually merged/accepted.

Steps to reproduce

1. Create a Jenkins pipeline/freestyle job with the GitLab trigger enabled
2. Uncheck "Build when a change is pushed to GitLab"
3. Uncheck "Opened Merge Request Events"
4. Check "Accepted Merge Request Events"
5. Leave "Trigger open merge requests on push to source branch" at its default (unspecified)
6. Update a merge request (push a commit, edit description, etc.)
7. Observed: the job triggers
8. Expected: the job should only trigger when the MR is merged (action=merge)

Root cause

In MergeRequestHookTriggerHandlerFactory.java, the field triggerOpenMergeRequestOnPush in GitLabPushTrigger is declared without a default value, so it is null at runtime.

The trigger chain conditions compared against TriggerOpenMergeRequest.never without null-checking:

// Before fix — null != never evaluates to true
chain.rejectUnless(
        triggerOpenMergeRequest != TriggerOpenMergeRequest.never, // null != never → true
        of(State.opened, State.updated),
        of(Action.update))
    .acceptIf(
        triggerOpenMergeRequest != TriggerOpenMergeRequest.never, // null != never → true
        of(State.updated), of(Action.update))
    .acceptIf(
        triggerOpenMergeRequest != TriggerOpenMergeRequest.never && triggerOpenMergeRequest != null,
        of(State.opened),
        of(Action.update))

When triggerOpenMergeRequest is null:

• The reject rule for update events is not added (rejectUnless(true, ...) is a no-op)
• An accept rule for state=updated, action=update is added

This causes any MR update event to pass the filter and trigger the build.

Ironically, the third condition already had a null check (&& triggerOpenMergeRequest != null), but the first two did not.

Fix

Extract the three conditions into a single boolean that properly null-guards:

boolean triggerOnOpenMergeRequestEnabled =
        triggerOpenMergeRequest != null && triggerOpenMergeRequest != TriggerOpenMergeRequest.never;

Then use this boolean consistently for all three chain rules.

A regression test has been added for the exact scenario: triggerOnAcceptedMergeRequest=true with default (null) triggerOpenMergeRequestOnPush, receiving a state=updated, action=update event.

Affected file

• src/main/java/com/dabsquared/gitlabjenkins/trigger/handler/merge/MergeRequestHookTriggerHandlerFactory.java

PR

Incoming

What Operating System are you using (both controller, and any agents involved in the problem)?

Linux

Reproduction steps

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Expected Results

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Actual Results

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Anything else?

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Are you interested in contributing a fix?

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