From ca5b36ba80312766b694dabb32f8788125bff8ae Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Konstantin=20K=C3=A4fer?= <mail@kkaefer.com>
Date: Fri, 29 Jun 2018 11:47:03 -0700
Subject: [core] fix crash when trying to parse legacy filters

Legacy filters aren't part of the style specification, but you can generate them by parsing a legacy filter in a stylesheet, and obtaining the parsed Filter and serializing it.
---
 src/mbgl/style/expression/is_constant.cpp | 5 +++++
 test/style/filter.test.cpp                | 4 ++++
 2 files changed, 9 insertions(+)

diff --git a/src/mbgl/style/expression/is_constant.cpp b/src/mbgl/style/expression/is_constant.cpp
index 0ebb37faa9..577ecf8cb6 100644
--- a/src/mbgl/style/expression/is_constant.cpp
+++ b/src/mbgl/style/expression/is_constant.cpp
@@ -4,6 +4,8 @@ namespace mbgl {
 namespace style {
 namespace expression {
 
+constexpr static const char filter[] = "filter-";
+
 bool isFeatureConstant(const Expression& expression) {
     if (auto e = dynamic_cast<const CompoundExpressionBase*>(&expression)) {
         const std::string name = e->getName();
@@ -12,6 +14,9 @@ bool isFeatureConstant(const Expression& expression) {
             return false;
         } else if (name == "has" && parameterCount && *parameterCount == 1) {
             return false;
+        } else if (std::equal(std::begin(filter), std::end(filter) - 1, name.begin())) {
+            // Legacy filters begin with "filter-" and are never constant.
+            return false;
         } else if (
             name == "properties" ||
             name == "geometry-type" ||
diff --git a/test/style/filter.test.cpp b/test/style/filter.test.cpp
index c8f1d3b808..bac3801223 100644
--- a/test/style/filter.test.cpp
+++ b/test/style/filter.test.cpp
@@ -192,3 +192,7 @@ TEST(Filter, ZoomExpressionNested) {
     ASSERT_TRUE(filter(R"(["==", ["get", "two"], ["zoom"]])", {{"two", int64_t(2)}}, {}, FeatureType::Point, {}, 2.0f));
     ASSERT_FALSE(filter(R"(["==", ["get", "two"], ["+", ["zoom"], 1]])", {{"two", int64_t(2)}}, {}, FeatureType::Point, {}, 2.0f));
 }
+
+TEST(Filter, Internal) {
+    filter(R"(["filter-==","class","snow"])");
+}
-- 
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