[llvm] [workflows] issue-write: Avoid race condition when PR branch is deleted (PR #87118)

[via llvm-commits]

llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-github-workflow

Author: Tom Stellard (tstellar)

<details>
<summary>Changes</summary>

Fixes #<!-- -->87102 .

---
Full diff: https://github.com/llvm/llvm-project/pull/87118.diff


1 Files Affected:

- (modified) .github/workflows/issue-write.yml (+9) 


``````````diff
diff --git a/.github/workflows/issue-write.yml b/.github/workflows/issue-write.yml
index 02a5f7c213e898..cb5a96caf8e91e 100644
--- a/.github/workflows/issue-write.yml
+++ b/.github/workflows/issue-write.yml
@@ -77,6 +77,15 @@ jobs:
             }
             const gql_result = await github.graphql(gql_query, gql_variables);
             console.log(gql_result);
+            // If the branch for the PR was deleted before this job has a chance
+            // to run, then the ref will be null.  This can happen if someone:
+            // 1. Rebase the PR, which triggers some workflow.
+            // 2. Immediately merges the PR and deletes the branch.
+            // 3. The workflow finishes and triggers this job.
+            if (!gql_result.repository.ref) {
+              console.log("Ref has been deleted");
+              return;
+            }
             console.log(gql_result.repository.ref.associatedPullRequests.nodes);
 
             var pr_number = 0;

``````````

</details>


https://github.com/llvm/llvm-project/pull/87118