From cb8d04981c76951872e323ab1250b06ccd0897cc Mon Sep 17 00:00:00 2001
From: Hannes Schmidt <hannes@ucsc.edu>
Date: Thu, 30 Jan 2025 22:09:06 -0800
Subject: [PATCH] [2/2] Fix: GitHub CI workflow selects dev when building prod
 branch (#5428)

---
 scripts/check_branch.py   | 29 +++++++++++-
 test/test_check_branch.py | 93 ++++++++++++++++++++++++++++++++-------
 2 files changed, 105 insertions(+), 17 deletions(-)

diff --git a/scripts/check_branch.py b/scripts/check_branch.py
index bc2e490ece..0342f453ed 100644
--- a/scripts/check_branch.py
+++ b/scripts/check_branch.py
@@ -52,7 +52,32 @@ def target_branch() -> str | None:
     built or, if the build is for a feature branch involving a pull request, the
     base branch of that feature branch.
     """
-    for variable in 'CI_COMMIT_REF_NAME', 'GITHUB_BASE_REF', 'GITHUB_HEAD_REF':
+    # The comments on the environment variable names below are taken from
+    #
+    # https://docs.github.com/en/actions/writing-workflows/choosing-what-your-workflow-does/store-information-in-variables
+    #
+    # and
+    #
+    # https://docs.gitlab.com/ee/ci/variables/predefined_variables.html
+    #
+    for variable in [
+        # The name of the base ref or target branch of the pull request in a
+        # workflow run. This is only set when the event that triggers a workflow
+        # run is either pull_request or pull_request_target. For example, main.
+        #
+        'GITHUB_BASE_REF',
+
+        # The short ref name of the branch or tag that triggered the workflow
+        # run. This value matches the branch or tag name shown on GitHub. For
+        # example, feature-branch-1. For pull requests, the format is
+        # <pr_number>/merge.
+        #
+        'GITHUB_REF_NAME',
+
+        # The branch or tag name for which project is built.
+        #
+        'CI_COMMIT_REF_NAME',
+    ]:
         try:
             branch = os.environ[variable]
         except KeyError:
@@ -60,7 +85,7 @@ def target_branch() -> str | None:
         else:
             return branch
     repo = git.Repo(config.project_root)
-    return None if repo.head.is_detached else repo.active_branch.name
+    return None if repo.head.is_detached else repo.head.reference.name
 
 
 def main(argv):
diff --git a/test/test_check_branch.py b/test/test_check_branch.py
index 2f044042f3..3a80e6ca83 100644
--- a/test/test_check_branch.py
+++ b/test/test_check_branch.py
@@ -1,9 +1,12 @@
 import json
 import os
 from unittest.mock import (
+    PropertyMock,
     patch,
 )
 
+import git
+
 from azul.modules import (
     load_script,
 )
@@ -14,7 +17,7 @@
 
 class TestCheckBranch(AzulUnitTestCase):
 
-    def test(self):
+    def test_check_branch(self):
         script = load_script('check_branch')
         check_branch = script.check_branch
 
@@ -71,17 +74,77 @@ def expect_exception(branch, deployment, message):
                              "Branch 'feature/foo' cannot be deployed to 'prod', "
                              "only one of {'sandbox'} or personal deployments.")
 
-        variables = ['CI_COMMIT_REF_NAME', 'GITHUB_BASE_REF', 'GITHUB_HEAD_REF']
-
-        for variable in variables:
-            if variable == 'GITHUB_HEAD_REF':
-                branches = ['foo/bar']
-            else:
-                branches = ['develop', 'prod']
-            for branch in branches:
-                with patch.dict(os.environ) as env:
-                    for var in variables:
-                        env.pop(var, None)
-                    env[var] = branch
-                    with self.subTest(branch=branch, variable=variable):
-                        self.assertEqual(branch, script.target_branch())
+    def test_target_branch(self):
+        script = load_script('check_branch')
+
+        develop, prod = 'develop', 'prod'
+        feature, merge = 'issues/foo/1234-bar', '2345/merge'
+        cases = [
+            (
+                'Local build',
+                feature,
+                {},
+                feature
+            ),
+            (
+                'Local build with detached head',
+                None,
+                {},
+                None
+            ),
+            (
+                'GitHub building develop',
+                develop,
+                {'GITHUB_REF_NAME': develop},
+                develop
+            ),
+            (
+                'GitHub building prod',
+                prod,
+                {'GITHUB_REF_NAME': prod},
+                prod
+            ),
+            (
+                'GitHub PR against develop',
+                merge,
+                {
+                    'GITHUB_REF_NAME': merge,
+                    'GITHUB_HEAD_REF': feature,
+                    'GITHUB_BASE_REF': develop
+                },
+                develop
+            ),
+            (
+                'GitHub PR against prod',
+                merge,
+                {
+                    'GITHUB_REF_NAME': merge,
+                    'GITHUB_HEAD_REF': feature,
+                    'GITHUB_BASE_REF': prod
+                },
+                prod
+            ),
+            (
+                'Sandbox build on GitLab',
+                None,
+                {'CI_COMMIT_REF_NAME': feature},
+                feature
+            ),
+            (
+                'Non-sandbox build on GitLab',
+                None,
+                {'CI_COMMIT_REF_NAME': develop},
+                develop
+            ),
+        ]
+        variables = {v for case in cases for v in case[2]}
+        for sub_test, current_branch, new_env, target_branch in cases:
+            with self.subTest(sub_test):
+                with patch.object(git.Repo, 'head', new_callable=PropertyMock) as head:
+                    head.return_value.is_detached = current_branch is None
+                    head.return_value.reference.name = current_branch
+                    with patch.dict(os.environ) as env:
+                        for variable in variables:
+                            env.pop(variable, None)
+                        env.update(new_env)
+                        self.assertEqual(target_branch, script.target_branch())