[core] Emit MapChangeDidFailLoadingMap when the style cannot be loaded or parsed

Currently this signal is never emitted, which can cause the Still mode
to starve in case of an invalid style or failed request.

3 files changed, 9 insertions, 4 deletions

diff --git a/test/fixtures/style_parser/non-object.info.json b/test/fixtures/style_parser/non-object.info.json
index d1b67e2ea6..ac6ea00d97 100644
--- a/test/fixtures/style_parser/non-object.info.json
+++ b/test/fixtures/style_parser/non-object.info.json
@@ -1,7 +1,7 @@
 {
     "default": {
         "log": [
-            [1, "ERROR", "ParseStyle", "Style JSON must be an object"]
+            [1, "ERROR", "ParseStyle", "Failed to parse style: style must be an object"]
         ]
     }
-}
\ No newline at end of file
+}
diff --git a/test/map/map.cpp b/test/map/map.cpp
index 2dc8aad927..7e0bbd0234 100644
--- a/test/map/map.cpp
+++ b/test/map/map.cpp
@@ -68,7 +68,7 @@ TEST(Map, SetStyleInvalidJSON) {
     auto observer = Log::removeObserver();
     auto flo = dynamic_cast<FixtureLogObserver*>(observer.get());
     EXPECT_EQ(1u, flo->count({ EventSeverity::Error, Event::ParseStyle, -1,
-        "Error parsing style JSON at 0: Invalid value." }));
+        "Failed to parse style: 0 - Invalid value." }));
     auto unchecked = flo->unchecked();
     EXPECT_TRUE(unchecked.empty()) << unchecked;
 }
diff --git a/test/style/style_parser.cpp b/test/style/style_parser.cpp
index b7806c11cc..3e1149c997 100644
--- a/test/style/style_parser.cpp
+++ b/test/style/style_parser.cpp
@@ -4,6 +4,7 @@
 #include <mbgl/style/parser.hpp>
 #include <mbgl/util/io.hpp>
 #include <mbgl/util/enum.hpp>
+#include <mbgl/util/string.hpp>
 #include <mbgl/util/tileset.hpp>
 
 #include <rapidjson/document.h>
@@ -32,7 +33,11 @@ TEST_P(StyleParserTest, ParseStyle) {
     Log::setObserver(std::unique_ptr<Log::Observer>(observer));
 
     style::Parser parser;
-    parser.parse(util::read_file(base + ".style.json"));
+    auto error = parser.parse(util::read_file(base + ".style.json"));
+
+    if (error) {
+        Log::Error(Event::ParseStyle, "Failed to parse style: %s", util::toString(error).c_str());
+    }
 
     for (auto it = infoDoc.MemberBegin(), end = infoDoc.MemberEnd(); it != end; it++) {
         const std::string name { it->name.GetString(), it->name.GetStringLength() };