[TESTS] coverage for SignInOAuthCallback

(cherry picked from commit f8e1619b993943eafb8ee12bf06f4cdb5862de70)
(cherry picked from commit 46d8bc9bdf68b53767211dc103e6130f55bcdb64)
(cherry picked from commit e0c7b7055f5f4eeca84f1d0b1260b7b9622d3aab)
(cherry picked from commit faab747f8e7eb09262f755445462a77f8a6fb953)
(cherry picked from commit 46acb6a9a79e7ce588b2863aa37bf26805afb2b1)
(cherry picked from commit 22d964e74407c52ffcd3d3a84b0a66e2c186b0fa)
(cherry picked from commit 4c8a6031acf760c2383d9e103c703ee5ececb8e8)
(cherry picked from commit 032e8c7a9a357a13f41410063c2f7fb925dba5ac)
(cherry picked from commit 7a17a3b0fb979e2923019de4b9a7318f578b73b8)
(cherry picked from commit 8ea71c2a31ea7492f5f2e3de529c7fd0b232d3e3)
(cherry picked from commit 4b027e2d37cb91c5951f1d10a018778b19590eb0)
(cherry picked from commit d787089a5de09fa11f8e82a66ec43e4abdde1b2e)
(cherry picked from commit 7b9999357a5d34861b5fd7390cc400f497896246)
(cherry picked from commit 80eb531c380914c66d30a29159b81154e7adefeb)
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(cherry picked from commit 22ec6c11ee779cc06c2e6e6dca3213129033389e)
(cherry picked from commit 3f94b9a111)
(cherry picked from commit a4194c29ff)
(cherry picked from commit aa80ba2ed1e529a85eda01beeb25c6732d2bc9bf)
(cherry picked from commit d349f3e80ec764f6f402ea6183e41511f73cd33f)
(cherry picked from commit ccb073f71ac855b1d7c7dd1e71a29939a14a20c5)
(cherry picked from commit d8a996a9c1052a7c4b7693cb75f10ee0cbce1534)
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(cherry picked from commit 3867b17a485e441198b248be08cbe14bb8bd3946)
(cherry picked from commit 0c48072b2e19f70530d76de459bddd9e7c539c0d)

tests/integration/integration_test.go

@@ -39,6 +39,8 @@ import (
 	"code.gitea.io/gitea/tests"
 
 	"github.com/PuerkitoBio/goquery"
+	"github.com/markbates/goth"
+	"github.com/markbates/goth/gothic"
 	goth_gitlab "github.com/markbates/goth/providers/gitlab"
 	"github.com/stretchr/testify/assert"
 	"github.com/xeipuuv/gojsonschema"
@@ -235,6 +237,14 @@ func getUserToken(t testing.TB, userName string, scope ...auth.AccessTokenScope)
 	return getTokenForLoggedInUser(t, loginUser(t, userName), scope...)
 }
 
+func mockCompleteUserAuth(mock func(res http.ResponseWriter, req *http.Request) (goth.User, error)) func() {
+	old := gothic.CompleteUserAuth
+	gothic.CompleteUserAuth = mock
+	return func() {
+		gothic.CompleteUserAuth = old
+	}
+}
+
 func addAuthSource(t *testing.T, payload map[string]string) *auth.Source {
 	session := loginUser(t, "user1")
 	payload["_csrf"] = GetCSRF(t, session, "/admin/auths/new")

tests/integration/oauth_test.go

@@ -5,15 +5,22 @@ package integration
 
 import (
 	"bytes"
+	"context"
+	"fmt"
 	"io"
 	"net/http"
 	"testing"
 
+	auth_model "code.gitea.io/gitea/models/auth"
+	"code.gitea.io/gitea/models/unittest"
+	user_model "code.gitea.io/gitea/models/user"
 	"code.gitea.io/gitea/modules/json"
 	"code.gitea.io/gitea/modules/setting"
+	"code.gitea.io/gitea/modules/test"
 	"code.gitea.io/gitea/routers/web/auth"
 	"code.gitea.io/gitea/tests"
 
+	"github.com/markbates/goth"
 	"github.com/stretchr/testify/assert"
 )
 
@@ -419,3 +426,46 @@ func TestRefreshTokenInvalidation(t *testing.T) {
 	assert.Equal(t, "unauthorized_client", string(parsedError.ErrorCode))
 	assert.Equal(t, "token was already used", parsedError.ErrorDescription)
 }
+
+func TestSignInOAuthCallbackSignIn(t *testing.T) {
+	defer tests.PrepareTestEnv(t)()
+
+	//
+	// OAuth2 authentication source GitLab
+	//
+	gitlabName := "gitlab"
+	gitlab := addAuthSource(t, authSourcePayloadGitLabCustom(gitlabName))
+
+	//
+	// Create a user as if it had been previously been created by the GitLab
+	// authentication source.
+	//
+	userGitLabUserID := "5678"
+	userGitLab := &user_model.User{
+		Name:        "gitlabuser",
+		Email:       "gitlabuser@example.com",
+		Passwd:      "gitlabuserpassword",
+		Type:        user_model.UserTypeIndividual,
+		LoginType:   auth_model.OAuth2,
+		LoginSource: gitlab.ID,
+		LoginName:   userGitLabUserID,
+	}
+	defer createUser(context.Background(), t, userGitLab)()
+
+	//
+	// A request for user information sent to Goth will return a
+	// goth.User exactly matching the user created above.
+	//
+	defer mockCompleteUserAuth(func(res http.ResponseWriter, req *http.Request) (goth.User, error) {
+		return goth.User{
+			Provider: gitlabName,
+			UserID:   userGitLabUserID,
+			Email:    userGitLab.Email,
+		}, nil
+	})()
+	req := NewRequest(t, "GET", fmt.Sprintf("/user/oauth2/%s/callback?code=XYZ&state=XYZ", gitlabName))
+	resp := MakeRequest(t, req, http.StatusSeeOther)
+	assert.Equal(t, test.RedirectURL(resp), "/")
+	userAfterLogin := unittest.AssertExistsAndLoadBean(t, &user_model.User{ID: userGitLab.ID})
+	assert.Greater(t, userAfterLogin.LastLoginUnix, userGitLab.LastLoginUnix)
+}