[GITEA] Fix session generation for database

- If the session doesn't exist, it shouldn't be expected that the
variable is non-nil. Define the session variable instead and insert that.
- Add unit tests to test the behavior of the database sessions code .
- Regression caused by dd30d9d5c0.
- Resolves https://codeberg.org/forgejo/forgejo/issues/2042

(cherry picked from commit 90307ad200)
(cherry picked from commit 874ef1978d)
(cherry picked from commit 27d5f035fc)
(cherry picked from commit 65dbc4303b)

[GITEA] Fix session generation for database (squash) timeutil.Mock

because of e743570f65 * Refactor timeutil package (#28623)

(cherry picked from commit acc6b51be2)
(cherry picked from commit 02b74317f2)
(cherry picked from commit 63b9b624bd)
(cherry picked from commit 7752ff8baa)
(cherry picked from commit c0af4d9438)

models/auth/session_test.go

@@ -0,0 +1,142 @@
+// Copyright 2023 The Forgejo Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package auth_test
+
+import (
+	"testing"
+	"time"
+
+	"code.gitea.io/gitea/models/auth"
+	"code.gitea.io/gitea/models/db"
+	"code.gitea.io/gitea/models/unittest"
+	"code.gitea.io/gitea/modules/timeutil"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestAuthSession(t *testing.T) {
+	assert.NoError(t, unittest.PrepareTestDatabase())
+	defer timeutil.MockUnset()
+
+	key := "I-Like-Free-Software"
+
+	t.Run("Create Session", func(t *testing.T) {
+		// Ensure it doesn't exist.
+		ok, err := auth.ExistSession(db.DefaultContext, key)
+		assert.NoError(t, err)
+		assert.False(t, ok)
+
+		preCount, err := auth.CountSessions(db.DefaultContext)
+		assert.NoError(t, err)
+
+		now := time.Date(2021, 1, 1, 0, 0, 0, 0, time.UTC)
+		timeutil.MockSet(now)
+
+		// New session is created.
+		sess, err := auth.ReadSession(db.DefaultContext, key)
+		assert.NoError(t, err)
+		assert.EqualValues(t, key, sess.Key)
+		assert.Empty(t, sess.Data)
+		assert.EqualValues(t, now.Unix(), sess.Expiry)
+
+		// Ensure it exists.
+		ok, err = auth.ExistSession(db.DefaultContext, key)
+		assert.NoError(t, err)
+		assert.True(t, ok)
+
+		// Ensure the session is taken into account for count..
+		postCount, err := auth.CountSessions(db.DefaultContext)
+		assert.NoError(t, err)
+		assert.Greater(t, postCount, preCount)
+	})
+
+	t.Run("Update session", func(t *testing.T) {
+		data := []byte{0xba, 0xdd, 0xc0, 0xde}
+		now := time.Date(2022, 1, 1, 0, 0, 0, 0, time.UTC)
+		timeutil.MockSet(now)
+
+		// Update session.
+		err := auth.UpdateSession(db.DefaultContext, key, data)
+		assert.NoError(t, err)
+
+		timeutil.MockSet(time.Date(2021, 1, 1, 0, 0, 0, 0, time.UTC))
+
+		// Read updated session.
+		// Ensure data is updated and expiry is set from the update session call.
+		sess, err := auth.ReadSession(db.DefaultContext, key)
+		assert.NoError(t, err)
+		assert.EqualValues(t, key, sess.Key)
+		assert.EqualValues(t, data, sess.Data)
+		assert.EqualValues(t, now.Unix(), sess.Expiry)
+
+		timeutil.MockSet(now)
+	})
+
+	t.Run("Delete session", func(t *testing.T) {
+		// Ensure it't exist.
+		ok, err := auth.ExistSession(db.DefaultContext, key)
+		assert.NoError(t, err)
+		assert.True(t, ok)
+
+		preCount, err := auth.CountSessions(db.DefaultContext)
+		assert.NoError(t, err)
+
+		err = auth.DestroySession(db.DefaultContext, key)
+		assert.NoError(t, err)
+
+		// Ensure it doens't exists.
+		ok, err = auth.ExistSession(db.DefaultContext, key)
+		assert.NoError(t, err)
+		assert.False(t, ok)
+
+		// Ensure the session is taken into account for count..
+		postCount, err := auth.CountSessions(db.DefaultContext)
+		assert.NoError(t, err)
+		assert.Less(t, postCount, preCount)
+	})
+
+	t.Run("Cleanup sessions", func(t *testing.T) {
+		timeutil.MockSet(time.Date(2023, 1, 1, 0, 0, 0, 0, time.UTC))
+
+		_, err := auth.ReadSession(db.DefaultContext, "sess-1")
+		assert.NoError(t, err)
+
+		// One minute later.
+		timeutil.MockSet(time.Date(2023, 1, 1, 0, 1, 0, 0, time.UTC))
+		_, err = auth.ReadSession(db.DefaultContext, "sess-2")
+		assert.NoError(t, err)
+
+		// 5 minutes, shouldn't clean up anything.
+		err = auth.CleanupSessions(db.DefaultContext, 5*60)
+		assert.NoError(t, err)
+
+		ok, err := auth.ExistSession(db.DefaultContext, "sess-1")
+		assert.NoError(t, err)
+		assert.True(t, ok)
+
+		ok, err = auth.ExistSession(db.DefaultContext, "sess-2")
+		assert.NoError(t, err)
+		assert.True(t, ok)
+
+		// 1 minute, should clean up sess-1.
+		err = auth.CleanupSessions(db.DefaultContext, 60)
+		assert.NoError(t, err)
+
+		ok, err = auth.ExistSession(db.DefaultContext, "sess-1")
+		assert.NoError(t, err)
+		assert.False(t, ok)
+
+		ok, err = auth.ExistSession(db.DefaultContext, "sess-2")
+		assert.NoError(t, err)
+		assert.True(t, ok)
+
+		// Now, should clean up sess-2.
+		err = auth.CleanupSessions(db.DefaultContext, 0)
+		assert.NoError(t, err)
+
+		ok, err = auth.ExistSession(db.DefaultContext, "sess-2")
+		assert.NoError(t, err)
+		assert.False(t, ok)
+	})
+}