[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.

8 files changed, 41 insertions, 12 deletions

diff --git a/src/mbgl/map/map.cpp b/src/mbgl/map/map.cpp
index 2e7dc06e8b..3a307735ab 100644
--- a/src/mbgl/map/map.cpp
+++ b/src/mbgl/map/map.cpp
@@ -38,6 +38,7 @@ public:
     Impl(View&, FileSource&, MapMode, GLContextMode, ConstrainMode, ViewportMode);
 
     void onNeedsRepaint() override;
+    void onStyleError() override;
     void onResourceError(std::exception_ptr) override;
 
     void update();
@@ -316,6 +317,8 @@ void Map::setStyleURL(const std::string& url) {
             } else {
                 Log::Error(Event::Setup, "loading style failed: %s", res.error->message.c_str());
             }
+            impl->onStyleError();
+            impl->onResourceError(std::make_exception_ptr(std::runtime_error(res.error->message)));
         } else if (res.notModified || res.noContent) {
             return;
         } else {
@@ -343,8 +346,8 @@ void Map::setStyleJSON(const std::string& json) {
 }
 
 void Map::Impl::loadStyleJSON(const std::string& json) {
-    style->setJSON(json);
     style->setObserver(this);
+    style->setJSON(json);
     styleJSON = json;
 
     // force style cascade, causing all pending transitions to complete.
@@ -908,6 +911,10 @@ void Map::Impl::onNeedsRepaint() {
     asyncUpdate.send();
 }
 
+void Map::Impl::onStyleError() {
+    view.notifyMapChange(MapChangeDidFailLoadingMap);
+}
+
 void Map::Impl::onResourceError(std::exception_ptr error) {
     if (mode == MapMode::Still && callback) {
         callback(error, {});
diff --git a/src/mbgl/style/observer.hpp b/src/mbgl/style/observer.hpp
index 2c48114669..c4d31ae249 100644
--- a/src/mbgl/style/observer.hpp
+++ b/src/mbgl/style/observer.hpp
@@ -18,6 +18,7 @@ public:
      * and `onNeedsRepaint` will be called.
      */
     void onNeedsRepaint() override {}
+    virtual void onStyleError() {}
     virtual void onResourceError(std::exception_ptr) {}
 };
 
diff --git a/src/mbgl/style/parser.cpp b/src/mbgl/style/parser.cpp
index bc05b5484a..e53fac2667 100644
--- a/src/mbgl/style/parser.cpp
+++ b/src/mbgl/style/parser.cpp
@@ -14,24 +14,27 @@
 
 #include <algorithm>
 #include <set>
+#include <sstream>
 
 namespace mbgl {
 namespace style {
 
 Parser::~Parser() = default;
 
-void Parser::parse(const std::string& json) {
+StyleParseResult Parser::parse(const std::string& json) {
     rapidjson::GenericDocument<rapidjson::UTF8<>, rapidjson::CrtAllocator> document;
     document.Parse<0>(json.c_str());
 
     if (document.HasParseError()) {
-        Log::Error(Event::ParseStyle, "Error parsing style JSON at %i: %s", document.GetErrorOffset(), rapidjson::GetParseError_En(document.GetParseError()));
-        return;
+        std::stringstream message;
+        message <<  document.GetErrorOffset() << " - "
+            << rapidjson::GetParseError_En(document.GetParseError());
+
+        return std::make_exception_ptr(std::runtime_error(message.str()));
     }
 
     if (!document.IsObject()) {
-        Log::Error(Event::ParseStyle, "Style JSON must be an object");
-        return;
+        return std::make_exception_ptr(std::runtime_error("style must be an object"));
     }
 
     if (document.HasMember("version")) {
@@ -100,6 +103,8 @@ void Parser::parse(const std::string& json) {
             glyphURL = { glyphs.GetString(), glyphs.GetStringLength() };
         }
     }
+
+    return nullptr;
 }
 
 void Parser::parseSources(const JSValue& value) {
diff --git a/src/mbgl/style/parser.hpp b/src/mbgl/style/parser.hpp
index a6a71ed817..a05a0b316a 100644
--- a/src/mbgl/style/parser.hpp
+++ b/src/mbgl/style/parser.hpp
@@ -9,6 +9,7 @@
 
 #include <vector>
 #include <memory>
+#include <stdexcept>
 #include <string>
 #include <unordered_map>
 #include <forward_list>
@@ -16,11 +17,13 @@
 namespace mbgl {
 namespace style {
 
+using StyleParseResult = std::exception_ptr;
+
 class Parser {
 public:
     ~Parser();
 
-    void parse(const std::string&);
+    StyleParseResult parse(const std::string&);
 
     std::string spriteURL;
     std::string glyphURL;
diff --git a/src/mbgl/style/style.cpp b/src/mbgl/style/style.cpp
index 1cf64002fb..e04384a96e 100644
--- a/src/mbgl/style/style.cpp
+++ b/src/mbgl/style/style.cpp
@@ -90,7 +90,15 @@ void Style::setJSON(const std::string& json) {
     classes.clear();
 
     Parser parser;
-    parser.parse(json);
+    auto error = parser.parse(json);
+
+    if (error) {
+        Log::Error(Event::ParseStyle, "Failed to parse style: %s", util::toString(error).c_str());
+        observer->onStyleError();
+        observer->onResourceError(error);
+
+        return;
+    }
 
     for (auto& source : parser.sources) {
         addSource(std::move(source));
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() };