fix: don't panic when a PR branch is deleted (#385)

internal/scm/github/pullrequest.go

@@ -21,7 +21,12 @@ func convertPullRequest(pr *github.PullRequest) pullRequest {
 }
 
 func convertGraphQLPullRequest(pr graphqlPR) pullRequest {
-	combinedStatus := pr.Commits.Nodes[0].Commit.StatusCheckRollup.State
+	var combinedStatus *graphqlPullRequestState
+	nodes := pr.Commits.Nodes
+	if len(nodes) > 0 {
+		combinedStatus = nodes[0].Commit.StatusCheckRollup.State
+	}
+
 	status := scm.PullRequestStatusUnknown
 
 	if pr.Merged {

internal/scm/github/pullrequest_test.go

@@ -0,0 +1,66 @@
+package github
+
+import (
+	"testing"
+
+	"github.com/lindell/multi-gitter/internal/scm"
+	"github.com/stretchr/testify/assert"
+)
+
+func Test_convertGraphQLPullRequest(t *testing.T) {
+	scenarios := []struct {
+		name     string
+		pr       graphqlPR
+		expected pullRequest
+	}{{
+		name: "should return status 'closed' when the PR branch is deleted",
+		pr: graphqlPR{
+			Number:      1,
+			HeadRefName: "dummy_branch",
+			Closed:      true,
+			URL:         "http://dummy.url",
+			Merged:      false,
+			BaseRepository: struct {
+				Name  string "json:\"name\""
+				Owner struct {
+					Login string "json:\"login\""
+				} "json:\"owner\""
+			}{
+				Name: "base_repo",
+				Owner: struct {
+					Login string "json:\"login\""
+				}{Login: "dummy_user"},
+			},
+			HeadRepository: struct {
+				Name  string "json:\"name\""
+				Owner struct {
+					Login string "json:\"login\""
+				} "json:\"owner\""
+			}{
+				Name: "pr_owner",
+				Owner: struct {
+					Login string "json:\"login\""
+				}{Login: "dummy_owner"},
+			},
+		},
+		expected: pullRequest{
+			status:      scm.PullRequestStatusClosed,
+			ownerName:   "dummy_user",
+			repoName:    "base_repo",
+			branchName:  "dummy_branch",
+			prOwnerName: "dummy_owner",
+			prRepoName:  "pr_owner",
+			number:      1,
+			guiURL:      "http://dummy.url",
+		},
+	}}
+
+	for _, scenario := range scenarios {
+		t.Run(scenario.name, func(t *testing.T) {
+			got := convertGraphQLPullRequest(scenario.pr)
+			if got != scenario.expected {
+				assert.Equal(t, scenario.expected, got)
+			}
+		})
+	}
+}