fix(sec): add tests for private issues on projects

- Add integration and unit tests to ensure that private issues on
projects are not shown in any way, shape or form when the doer has no
access to it.

(cherry picked from commit 55dcc1d06cb12ddb750a0289fbb6e212f93957a8)

models/issues/issue_project_test.go

@@ -0,0 +1,100 @@
+// Copyright 2025 The Forgejo Authors. All rights reserved.
+// SPDX-License-Identifier: GPL-3.0-or-later
+
+package issues_test
+
+import (
+	"testing"
+
+	"code.gitea.io/gitea/models/db"
+	"code.gitea.io/gitea/models/issues"
+	"code.gitea.io/gitea/models/organization"
+	"code.gitea.io/gitea/models/project"
+	"code.gitea.io/gitea/models/unittest"
+	user_model "code.gitea.io/gitea/models/user"
+	"code.gitea.io/gitea/modules/optional"
+	"code.gitea.io/gitea/tests"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+func TestPrivateIssueProjects(t *testing.T) {
+	defer tests.AddFixtures("models/fixtures/PrivateIssueProjects/")()
+	require.NoError(t, unittest.PrepareTestDatabase())
+
+	user2 := unittest.AssertExistsAndLoadBean(t, &user_model.User{ID: 2})
+	t.Run("Organization project", func(t *testing.T) {
+		org := unittest.AssertExistsAndLoadBean(t, &organization.Organization{ID: 3})
+		orgProject := unittest.AssertExistsAndLoadBean(t, &project.Project{ID: 1001, OwnerID: org.ID})
+		board := unittest.AssertExistsAndLoadBean(t, &project.Board{ID: 1001, ProjectID: orgProject.ID})
+
+		t.Run("Authenticated user", func(t *testing.T) {
+			defer tests.PrintCurrentTest(t)()
+			issueList, err := issues.LoadIssuesFromBoard(db.DefaultContext, board, user2, org, optional.None[bool]())
+			require.NoError(t, err)
+			assert.Len(t, issueList, 1)
+			assert.EqualValues(t, 6, issueList[0].ID)
+
+			issuesNum, err := issues.NumIssuesInProject(db.DefaultContext, orgProject, user2, org, optional.None[bool]())
+			require.NoError(t, err)
+			assert.EqualValues(t, 1, issuesNum)
+
+			issuesNum, err = issues.NumIssuesInProject(db.DefaultContext, orgProject, user2, org, optional.Some(true))
+			require.NoError(t, err)
+			assert.EqualValues(t, 0, issuesNum)
+
+			issuesNum, err = issues.NumIssuesInProject(db.DefaultContext, orgProject, user2, org, optional.Some(false))
+			require.NoError(t, err)
+			assert.EqualValues(t, 1, issuesNum)
+		})
+
+		t.Run("Anonymous user", func(t *testing.T) {
+			defer tests.PrintCurrentTest(t)()
+			issueList, err := issues.LoadIssuesFromBoard(db.DefaultContext, board, nil, org, optional.None[bool]())
+			require.NoError(t, err)
+			assert.Empty(t, issueList)
+
+			issuesNum, err := issues.NumIssuesInProject(db.DefaultContext, orgProject, nil, org, optional.None[bool]())
+			require.NoError(t, err)
+			assert.EqualValues(t, 0, issuesNum)
+		})
+	})
+
+	t.Run("User project", func(t *testing.T) {
+		userProject := unittest.AssertExistsAndLoadBean(t, &project.Project{ID: 1002, OwnerID: user2.ID})
+		board := unittest.AssertExistsAndLoadBean(t, &project.Board{ID: 1002, ProjectID: userProject.ID})
+
+		t.Run("Authenticated user", func(t *testing.T) {
+			defer tests.PrintCurrentTest(t)()
+			issueList, err := issues.LoadIssuesFromBoard(db.DefaultContext, board, user2, nil, optional.None[bool]())
+			require.NoError(t, err)
+			assert.Len(t, issueList, 1)
+			assert.EqualValues(t, 7, issueList[0].ID)
+
+			issuesNum, err := issues.NumIssuesInProject(db.DefaultContext, userProject, user2, nil, optional.None[bool]())
+			require.NoError(t, err)
+			assert.EqualValues(t, 1, issuesNum)
+
+			issuesNum, err = issues.NumIssuesInProject(db.DefaultContext, userProject, user2, nil, optional.Some(true))
+			require.NoError(t, err)
+			assert.EqualValues(t, 0, issuesNum)
+
+			issuesNum, err = issues.NumIssuesInProject(db.DefaultContext, userProject, user2, nil, optional.Some(false))
+			require.NoError(t, err)
+			assert.EqualValues(t, 1, issuesNum)
+		})
+
+		t.Run("Anonymous user", func(t *testing.T) {
+			defer tests.PrintCurrentTest(t)()
+
+			issueList, err := issues.LoadIssuesFromBoard(db.DefaultContext, board, nil, nil, optional.None[bool]())
+			require.NoError(t, err)
+			assert.Empty(t, issueList)
+
+			issuesNum, err := issues.NumIssuesInProject(db.DefaultContext, userProject, nil, nil, optional.None[bool]())
+			require.NoError(t, err)
+			assert.EqualValues(t, 0, issuesNum)
+		})
+	})
+}