[v11.0/forgejo] fix(api): encode empty requested reviewers as an empty array (#7365)

**Backport:** https://codeberg.org/forgejo/forgejo/pulls/7355

- Always initialize `RequestedReviewers` and `RequestedReviewersTeams`, this avoids the JSON encoder from encoding it to the zero value `null` and instead return a empty array.
- Resolves #4108
- Integration test added.

Co-authored-by: ThomasBoom89 <thomasboom89@noreply.codeberg.org>
Reviewed-on: https://codeberg.org/forgejo/forgejo/pulls/7365
Reviewed-by: Gusted <gusted@noreply.codeberg.org>
Co-authored-by: forgejo-backport-action <forgejo-backport-action@noreply.codeberg.org>
Co-committed-by: forgejo-backport-action <forgejo-backport-action@noreply.codeberg.org>

services/convert/pull.go

@@ -91,6 +91,8 @@ func ToAPIPullRequest(ctx context.Context, pr *issues_model.PullRequest, doer *u
 		Created:                 pr.Issue.CreatedUnix.AsTimePtr(),
 		Updated:                 pr.Issue.UpdatedUnix.AsTimePtr(),
 		PinOrder:                apiIssue.PinOrder,
+		RequestedReviewers:      []*api.User{},
+		RequestedReviewersTeams: []*api.Team{},
 
 		AllowMaintainerEdit: pr.AllowMaintainerEdit,
 

tests/integration/api_repo_pulls_test.go

@@ -0,0 +1,34 @@
+// Copyright 2021 The Gitea Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package integration
+
+import (
+	"fmt"
+	"net/http"
+	"testing"
+
+	repo_model "forgejo.org/models/repo"
+	"forgejo.org/models/unittest"
+	api "forgejo.org/modules/structs"
+	"forgejo.org/tests"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestAPIRepoPulls(t *testing.T) {
+	defer tests.PrepareTestEnv(t)()
+
+	// repo = user2/repo1
+	repo := unittest.AssertExistsAndLoadBean(t, &repo_model.Repository{ID: 1})
+
+	// issue id without assigned review member or review team
+	issueID := 5
+	req := NewRequest(t, "GET", fmt.Sprintf("/api/v1/repos/%s/%s/pulls/%d", repo.OwnerName, repo.Name, issueID))
+	res := MakeRequest(t, req, http.StatusOK)
+	var pr *api.PullRequest
+	DecodeJSON(t, res, &pr)
+
+	assert.NotNil(t, pr.RequestedReviewers)
+	assert.NotNil(t, pr.RequestedReviewersTeams)
+}