From 180b3f125f191d1912d152d1064228013f39552f Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Konstantin=20K=C3=A4fer?= <mail@kkaefer.com>
Date: Thu, 7 Jan 2016 12:05:51 +0100
Subject: [PATCH] [core] don't mark tiles with failed requests as obsolete

Otherwise, this will remove them from the map and overwrite the old data. This could happen e.g. when we have connection trouble and a tile needs to be refreshed, or we're displaying stale information and the connection is down.
---
 src/mbgl/map/source.cpp           | 2 +-
 src/mbgl/map/tile_data.hpp        | 4 ++++
 src/mbgl/map/vector_tile_data.cpp | 6 +++++-
 3 files changed, 10 insertions(+), 2 deletions(-)

diff --git a/src/mbgl/map/source.cpp b/src/mbgl/map/source.cpp
index 4432b3a49..613972e93 100644
--- a/src/mbgl/map/source.cpp
+++ b/src/mbgl/map/source.cpp
@@ -531,7 +531,7 @@ void Source::tileLoadingCompleteCallback(const TileID& tileID, const TransformSt
         return;
     }
 
-    if (tileData->getState() == TileData::State::obsolete && tileData->getError()) {
+    if (tileData->hasError()) {
         observer->onTileError(*this, tileID, tileData->getError());
         return;
     }
diff --git a/src/mbgl/map/tile_data.hpp b/src/mbgl/map/tile_data.hpp
index 2bb11054a..e31cced96 100644
--- a/src/mbgl/map/tile_data.hpp
+++ b/src/mbgl/map/tile_data.hpp
@@ -88,6 +88,10 @@ public:
         return state;
     }
 
+    bool hasError() const {
+        return error.operator bool();
+    }
+
     std::exception_ptr getError() const {
         return error;
     }
diff --git a/src/mbgl/map/vector_tile_data.cpp b/src/mbgl/map/vector_tile_data.cpp
index f44dc7598..ee43373a6 100644
--- a/src/mbgl/map/vector_tile_data.cpp
+++ b/src/mbgl/map/vector_tile_data.cpp
@@ -33,12 +33,16 @@ VectorTileData::VectorTileData(const TileID& id_,
                                                         Seconds expires_) {
         if (err) {
             error = err;
-            state = State::obsolete;
             callback();
             return;
         }
 
+        // Reset the error if we didn't receive one for this request. This is to prevent old error
+        // messages from being displayed again, e.g. after a connection trouble cleared up.
+        error = nullptr;
+
         if (!tile) {
+            // This is a 404 response. We're treating these as empty tiles.
             state = State::parsed;
             buckets.clear();
             callback();