From 4cab89bb6819e2592dd4ae8e3a74a78e0e09c382 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Andreas=20M=C3=B6ller?= <am@localheinz.com>
Date: Mon, 24 Jan 2022 18:23:10 +0100
Subject: [PATCH] Enhancement: Add github/add-assignee-to-pull-request action

---
 .github/workflows/merge.yaml                  | 17 +----
 CHANGELOG.md                                  |  5 ++
 .../add-assignee-to-pull-request/action.yaml  | 67 +++++++++++++++++++
 3 files changed, 74 insertions(+), 15 deletions(-)
 create mode 100644 actions/github/add-assignee-to-pull-request/action.yaml

diff --git a/.github/workflows/merge.yaml b/.github/workflows/merge.yaml
index 8e8c57b..74998b8 100644
--- a/.github/workflows/merge.yaml
+++ b/.github/workflows/merge.yaml
@@ -43,23 +43,10 @@ jobs:
             });
 
       - name: "Assign @ergebnis-bot"
-        uses: "actions/github-script@v5"
+        uses: "./.github/actions/github/add-assignee-to-pull-request"
         with:
           github-token: "${{ secrets.ERGEBNIS_BOT_TOKEN }}"
-          script: |
-            const pullRequest = context.payload.workflow_run.pull_requests[0];
-            const repository = context.repo;
-
-            const assignees = [
-              "ergebnis-bot",
-            ];
-
-            await github.rest.issues.addAssignees({
-              owner: repository.owner,
-              repo: repository.repo,
-              assignees: assignees,
-              issue_number: pullRequest.number
-            });
+          assignee: "ergebnis-bot"
 
       - name: "Approve pull request"
         uses: "actions/github-script@v5"
diff --git a/CHANGELOG.md b/CHANGELOG.md
index 6acb40b..5e2cc22 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -8,6 +8,10 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 
 For a full diff see [`1.2.1...main`][1.2.1...main].
 
+### Added
+
+- Added composite action `github/add-assignee-to-pull-request` ([#59]), by [@localheinz]
+
 ## [`1.2.1`][1.2.1]
 
 For a full diff see [`1.2.0...1.2.1`][1.2.0...1.2.1].
@@ -55,5 +59,6 @@ For a full diff see [`1.0.0...main`][1.0.0...main].
 [#48]: https://github.com/ergebnis/.github/pull/48
 [#52]: https://github.com/ergebnis/.github/pull/52
 [#54]: https://github.com/ergebnis/.github/pull/54
+[#59]: https://github.com/ergebnis/.github/pull/59
 
 [@localheinz]: https://github.com/localheinz
diff --git a/actions/github/add-assignee-to-pull-request/action.yaml b/actions/github/add-assignee-to-pull-request/action.yaml
new file mode 100644
index 0000000..6c7d353
--- /dev/null
+++ b/actions/github/add-assignee-to-pull-request/action.yaml
@@ -0,0 +1,67 @@
+# https://docs.github.com/en/actions/creating-actions/creating-a-composite-action
+# https://docs.github.com/en/actions/creating-actions/metadata-syntax-for-github-actions#inputs
+# https://docs.github.com/en/actions/creating-actions/metadata-syntax-for-github-actions#runs-for-composite-run-steps-actions
+# https://docs.github.com/en/rest/reference/issues#add-assignees-to-an-issue
+# https://docs.github.com/en/developers/webhooks-and-events/webhooks/webhook-events-and-payloads#pull_request
+# https://docs.github.com/en/developers/webhooks-and-events/webhooks/webhook-events-and-payloads#workflow_run
+
+name: "Add assignee to pull request"
+
+description: "Adds an assignee to a pull request"
+
+inputs:
+  assignee:
+    description: "Username of user to add as an assignee to a pull request"
+    required: true
+  github-token:
+    description: "GitHub token of a user with permission to add assignees to a pull request"
+    required: true
+
+runs:
+  using: "composite"
+
+  steps:
+    - name: "Determine pull request number"
+      uses: "actions/github-script@v5"
+      with:
+        github-token: "${{ inputs.github-token }}"
+        script: |
+          if (context.eventName == 'pull_request') {
+            core.exportVariable("PULL_REQUEST_NUMBER", context.payload.pull_request.number);
+
+            return;
+          }
+
+          if (context.eventName == 'workflow_run') {
+            core.exportVariable("PULL_REQUEST_NUMBER", context.payload.workflow_run.pull_requests[0].number);
+
+            return;
+          }
+
+          core.setFailed(`Unable to determine the pull request number for event "${context.eventName}"`);
+
+    - name: "Add assignee to pull request"
+      uses: "actions/github-script@v5"
+      with:
+        github-token: "${{ inputs.github-token }}"
+        script: |
+          if (!process.env.PULL_REQUEST_NUMBER) {
+            core.setFailed("The environment variable PULL_REQUEST_NUMBER is not defined.")
+
+            return;
+          }
+
+          const assignees = [
+            "${{ inputs.assignee }}",
+          ];
+
+          try {
+            await github.rest.issues.addAssignees({
+              assignees: assignees,
+              issue_number: process.env.PULL_REQUEST_NUMBER,
+              owner: context.repo.owner,
+              repo: context.repo.repo,
+            });
+          } catch (error) {
+            core.setFailed(error.message);
+          }