[MM-42194] Get file information from a deleted post (#20279)

* Introduced inlcude_deleted query parameter to allow admins to retrieve contents of post regardless of deletion status

* Introduced new client route and tests for getting file info of deleted posts

* Fixed tests due to caching of posts

* gofmt

* Small formatting updates

* Invalidating file infos cache on delete of post if post includes files

* Including deleted in migration flow

* Moved invalidating of cache

Co-authored-by: Mattermod <mattermod@users.noreply.github.com>

api4/post.go

@@ -898,7 +898,13 @@ func getFileInfosForPost(c *Context, w http.ResponseWriter, r *http.Request) {
 		return
 	}
 
-	infos, err := c.App.GetFileInfosForPostWithMigration(c.Params.PostId)
+	includeDeleted, _ := strconv.ParseBool(r.URL.Query().Get("include_deleted"))
+	if includeDeleted && !c.App.SessionHasPermissionTo(*c.AppContext.Session(), model.PermissionManageSystem) {
+		c.SetPermissionError(model.PermissionManageSystem)
+		return
+	}
+
+	infos, err := c.App.GetFileInfosForPostWithMigration(c.Params.PostId, includeDeleted)
 	if err != nil {
 		c.Err = err
 		return

api4/post_test.go

@@ -2623,6 +2623,39 @@ func TestGetFileInfosForPost(t *testing.T) {
 	require.Error(t, err)
 	CheckForbiddenStatus(t, resp)
 
+	// Delete post
+	th.SystemAdminClient.DeletePost(post.Id)
+
+	// Normal client should get 404 when trying to access deleted post normally
+	_, resp, err = client.GetFileInfosForPost(post.Id, "")
+	require.Error(t, err)
+	CheckNotFoundStatus(t, resp)
+
+	// Normal client should get unauthorized when trying to access deleted post
+	_, resp, err = client.GetFileInfosForPostIncludeDeleted(post.Id, "")
+	require.Error(t, err)
+	CheckForbiddenStatus(t, resp)
+
+	// System client should get 404 when trying to access deleted post normally
+	_, resp, err = th.SystemAdminClient.GetFileInfosForPost(post.Id, "")
+	require.Error(t, err)
+	CheckNotFoundStatus(t, resp)
+
+	// System client should be able to access deleted post with include_deleted param
+	infos, _, err = th.SystemAdminClient.GetFileInfosForPostIncludeDeleted(post.Id, "")
+	require.NoError(t, err)
+
+	require.Len(t, infos, 3, "missing file infos")
+
+	found = false
+	for _, info := range infos {
+		if info.Id == fileIds[0] {
+			found = true
+		}
+	}
+
+	require.True(t, found, "missing file info")
+
 	client.Logout()
 	_, resp, err = client.GetFileInfosForPost(model.NewId(), "")
 	require.Error(t, err)