Add link to user profile in markdown mention only if user exists (#21533)

Previously mentioning a user would link to its profile, regardless of
whether the user existed. This change tests if the user exists and only
if it does - a link to its profile is added.

* Fixes #3444

Signed-off-by: Yarden Shoham <hrsi88@gmail.com>
Co-authored-by: wxiaoguang <wxiaoguang@gmail.com>
Co-authored-by: Lunny Xiao <xiaolunwen@gmail.com>

3 files changed, 68 insertions, 0 deletions

diff --git a/services/markup/main_test.go b/services/markup/main_test.go
new file mode 100644
index 0000000000..8efd08e69d
--- /dev/null
+++ b/services/markup/main_test.go
@@ -0,0 +1,19 @@
+// Copyright 2022 The Gitea Authors. All rights reserved.
+// Use of this source code is governed by a MIT-style
+// license that can be found in the LICENSE file.
+
+package markup
+
+import (
+	"path/filepath"
+	"testing"
+
+	"code.gitea.io/gitea/models/unittest"
+)
+
+func TestMain(m *testing.M) {
+	unittest.MainTest(m, &unittest.TestOptions{
+		GiteaRootPath: filepath.Join("..", ".."),
+		FixtureFiles:  []string{"user.yml"},
+	})
+}
diff --git a/services/markup/processorhelper.go b/services/markup/processorhelper.go
new file mode 100644
index 0000000000..2b1cac2a5b
--- /dev/null
+++ b/services/markup/processorhelper.go
@@ -0,0 +1,29 @@
+// Copyright 2022 The Gitea Authors. All rights reserved.
+// Use of this source code is governed by a MIT-style
+// license that can be found in the LICENSE file.
+
+package markup
+
+import (
+	"context"
+
+	"code.gitea.io/gitea/models/user"
+	"code.gitea.io/gitea/modules/log"
+	"code.gitea.io/gitea/modules/markup"
+)
+
+func ProcessorHelper() *markup.ProcessorHelper {
+	return &markup.ProcessorHelper{
+		IsUsernameMentionable: func(ctx context.Context, username string) bool {
+			// TODO: cast ctx to modules/context.Context and use IsUserVisibleToViewer
+
+			// Only link if the user actually exists
+			userExists, err := user.IsUserExist(ctx, 0, username)
+			if err != nil {
+				log.Error("Failed to validate user in mention %q exists, assuming it does", username)
+				userExists = true
+			}
+			return userExists
+		},
+	}
+}
diff --git a/services/markup/processorhelper_test.go b/services/markup/processorhelper_test.go
new file mode 100644
index 0000000000..386465bc91
--- /dev/null
+++ b/services/markup/processorhelper_test.go
@@ -0,0 +1,20 @@
+// Copyright 2022 The Gitea Authors. All rights reserved.
+// Use of this source code is governed by a MIT-style
+// license that can be found in the LICENSE file.
+
+package markup
+
+import (
+	"context"
+	"testing"
+
+	"code.gitea.io/gitea/models/unittest"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestProcessorHelper(t *testing.T) {
+	assert.NoError(t, unittest.PrepareTestDatabase())
+	assert.True(t, ProcessorHelper().IsUsernameMentionable(context.Background(), "user10"))
+	assert.False(t, ProcessorHelper().IsUsernameMentionable(context.Background(), "no-such-user"))
+}