fix: show "merge" form for empty PR (#39640)

fix #39637

routers/web/repo/pull_merge_form.go

@@ -112,7 +112,7 @@ func (prInfo *pullRequestViewInfo) prepareMergeBoxFormProps(ctx *context.Context
 	// if this pr can be merged now, then hide the auto merge
 	generalHideAutoMerge := prInfo.MergeBoxData.canMergeNow && allOverridableChecksOk
 	var mergeStyles []any
-	if pull.IsStatusMergeable() {
+	if pull.IsStatusMergeable() || pull.IsEmpty() {
 		mergeStyles = []any{
 			map[string]any{
 				"name":                  "merge",
@@ -176,7 +176,7 @@ func (prInfo *pullRequestViewInfo) prepareMergeBoxFormProps(ctx *context.Context
 	if len(mergeStyles) > 0 {
 		mergeFormProps["mergeStyles"] = mergeStyles
 		prInfo.MergeBoxData.MergeFormProps = mergeFormProps
-	} else if pull.IsStatusMergeable() {
+	} else if pull.IsStatusMergeable() || pull.IsEmpty() {
 		// no merge style was set in repo setting
 		prInfo.MergeBoxData.infoCommitBlockers.AddInfoItem(
 			svg.RenderHTML("octicon-x", 16, "tw-text-red"),

tests/integration/pull_status_test.go

@@ -17,12 +17,14 @@ import (
 	repo_model "gitea.dev/models/repo"
 	"gitea.dev/models/unittest"
 	"gitea.dev/modules/commitstatus"
+	"gitea.dev/modules/json"
 	"gitea.dev/modules/setting"
 	api "gitea.dev/modules/structs"
 	"gitea.dev/modules/test"
 	"gitea.dev/services/pull"
 
 	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
 )
 
 func TestPullCreate_CommitStatus(t *testing.T) {
@@ -134,6 +136,23 @@ func TestPullCreate_EmptyChangesWithDifferentCommits(t *testing.T) {
 		text := strings.TrimSpace(doc.doc.Find(".merge-section").Text())
 		assert.Contains(t, text, "The changes on this branch are already on the target branch. This will be an empty commit.")
 		assert.Contains(t, text, "This pull request can be merged automatically.")
+		mergeFormProps, exists := doc.doc.Find("#pull-request-merge-form").Attr("data-merge-form-props")
+		require.True(t, exists)
+		var mergeForm struct {
+			EmptyCommit bool `json:"emptyCommit"`
+			CanMergeNow bool `json:"canMergeNow"`
+			MergeStyles []struct {
+				Name    string `json:"name"`
+				Allowed bool   `json:"allowed"`
+			} `json:"mergeStyles"`
+		}
+		require.NoError(t, json.Unmarshal([]byte(mergeFormProps), &mergeForm))
+		assert.True(t, mergeForm.EmptyCommit)
+		assert.True(t, mergeForm.CanMergeNow)
+		assert.Contains(t, mergeForm.MergeStyles, struct {
+			Name    string `json:"name"`
+			Allowed bool   `json:"allowed"`
+		}{Name: "merge", Allowed: true})
 	})
 }