Implement Expressions (#9439)

Ports https://github.com/mapbox/mapbox-gl-js/pull/4777 (and its several follow-ups)

3 files changed, 142 insertions, 0 deletions

diff --git a/test/style/conversion/function.test.cpp b/test/style/conversion/function.test.cpp
index 9e8a6b3a7f..a48be2c075 100644
--- a/test/style/conversion/function.test.cpp
+++ b/test/style/conversion/function.test.cpp
@@ -3,6 +3,8 @@
 #include <mbgl/style/conversion/json.hpp>
 #include <mbgl/style/conversion/constant.hpp>
 #include <mbgl/style/conversion/function.hpp>
+#include <mbgl/style/conversion/data_driven_property_value.hpp>
+#include <mbgl/util/rapidjson.hpp>
 
 using namespace mbgl;
 using namespace mbgl::style;
@@ -50,3 +52,29 @@ TEST(StyleConversion, Function) {
     ASSERT_FALSE(fn9);
     ASSERT_EQ("function base must be a number", error.message);
 }
+
+TEST(StyleConversion, CompositeFunctionExpression) {
+    Error error;
+
+    auto parseFunction = [&](const std::string& src) {
+        JSDocument doc;
+        doc.Parse<0>(src);
+        return convert<DataDrivenPropertyValue<float>>(doc, error);
+    };
+
+    auto fn1 = parseFunction(R"(["interpolate", ["linear"], ["zoom"], 0, ["number", ["get", "x"]], 10, 10])");
+    ASSERT_TRUE(fn1);
+    
+    auto fn2 = parseFunction(R"(["coalesce", ["interpolate", ["linear"], ["zoom"], 0, ["number", ["get", "x"]], 10, 10], 0])");
+    ASSERT_TRUE(fn2);
+
+    auto fn3 = parseFunction(R"(["let", "a", 0, ["interpolate", ["linear"], ["zoom"], 0, ["number", ["get", "x"]], 10, 10] ])");
+    ASSERT_TRUE(fn3);
+
+    auto fn4 = parseFunction(R"(["coalesce", ["let", "a", 0, ["interpolate", ["linear"], ["zoom"], 0, ["number", ["get", "x"]], 10, 10], 0 ])");
+    ASSERT_TRUE(fn4);
+
+    auto fn5 = parseFunction(R"(["coalesce", ["interpolate", ["linear"], ["number", ["get", "x"]], 0, ["zoom"], 10, 10], 0])");
+    ASSERT_FALSE(fn5);
+    ASSERT_EQ(R"("zoom" expression may only be used as input to a top-level "step" or "interpolate" expression.)", error.message);
+}
diff --git a/test/style/expression/expression.test.cpp b/test/style/expression/expression.test.cpp
new file mode 100644
index 0000000000..694569695c
--- /dev/null
+++ b/test/style/expression/expression.test.cpp
@@ -0,0 +1,91 @@
+#include <mbgl/test/util.hpp>
+#include <mbgl/util/io.hpp>
+#include <mbgl/style/conversion.hpp>
+#include <mbgl/util/rapidjson.hpp>
+#include <mbgl/style/rapidjson_conversion.hpp>
+#include <mbgl/style/expression/is_expression.hpp>
+
+#include <rapidjson/document.h>
+
+#include <iostream>
+#include <fstream>
+#include <dirent.h>
+
+
+using namespace mbgl;
+using namespace mbgl::style;
+
+TEST(Expression, IsExpression) {
+    rapidjson::GenericDocument<rapidjson::UTF8<>, rapidjson::CrtAllocator> spec;
+    spec.Parse<0>(util::read_file("mapbox-gl-js/src/style-spec/reference/v8.json").c_str());
+    ASSERT_FALSE(spec.HasParseError());
+    ASSERT_TRUE(spec.IsObject() &&
+                spec.HasMember("expression_name") &&
+                spec["expression_name"].IsObject() &&
+                spec["expression_name"].HasMember("values") &&
+                spec["expression_name"]["values"].IsObject());
+    
+    const auto& allExpressions = spec["expression_name"]["values"];
+    
+    for(auto& entry : allExpressions.GetObject()) {
+        const std::string name { entry.name.GetString(), entry.name.GetStringLength() };
+        JSDocument document;
+        document.Parse<0>(R"([")" + name + R"("])");
+
+        const JSValue* expression = &document;
+        EXPECT_TRUE(expression::isExpression(conversion::Convertible(expression))) << name;
+    }
+}
+
+class ExpressionEqualityTest : public ::testing::TestWithParam<std::string> {};
+
+TEST_P(ExpressionEqualityTest, ExpressionEquality) {
+    const std::string base = std::string("test/fixtures/expression_equality/") + GetParam();
+
+    std::string error;
+    auto parse = [&](std::string filename, std::string& error_) -> std::unique_ptr<expression::Expression> {
+        rapidjson::GenericDocument<rapidjson::UTF8<>, rapidjson::CrtAllocator> document;
+        document.Parse<0>(util::read_file(filename).c_str());
+        assert(!document.HasParseError());
+        const JSValue* expression = &document;
+        expression::ParsingContext ctx;
+        expression::ParseResult parsed = ctx.parse(conversion::Convertible(expression));
+        if (!parsed) {
+            error_ = ctx.getErrors().size() > 0 ? ctx.getErrors()[0].message : "failed to parse";
+        };
+        return std::move(*parsed);
+    };
+
+    std::unique_ptr<expression::Expression> expression_a1 = parse(base + ".a.json", error);
+    ASSERT_TRUE(expression_a1) << GetParam() << ": " << error;
+
+    std::unique_ptr<expression::Expression> expression_a2 = parse(base + ".a.json", error);
+    ASSERT_TRUE(expression_a2) << GetParam() << ": " << error;
+
+    std::unique_ptr<expression::Expression> expression_b = parse(base + ".b.json", error);
+    ASSERT_TRUE(expression_b) << GetParam() << ": " << error;
+
+
+    EXPECT_TRUE(*expression_a1 == *expression_a2);
+    EXPECT_TRUE(*expression_a1 != *expression_b);
+}
+
+INSTANTIATE_TEST_CASE_P(Expression, ExpressionEqualityTest, ::testing::ValuesIn([] {
+    std::vector<std::string> names;
+    const std::string ending = ".a.json";
+
+    const std::string style_directory = "test/fixtures/expression_equality";
+    DIR *dir = opendir(style_directory.c_str());
+    if (dir != nullptr) {
+        for (dirent *dp = nullptr; (dp = readdir(dir)) != nullptr;) {
+            const std::string name = dp->d_name;
+            if (name.length() >= ending.length() && name.compare(name.length() - ending.length(), ending.length(), ending) == 0) {
+                names.push_back(name.substr(0, name.length() - ending.length()));
+            }
+        }
+        closedir(dir);
+    }
+
+    EXPECT_GT(names.size(), 0u);
+    return names;
+}()));
diff --git a/test/style/expression/util.test.cpp b/test/style/expression/util.test.cpp
new file mode 100644
index 0000000000..0337cd871f
--- /dev/null
+++ b/test/style/expression/util.test.cpp
@@ -0,0 +1,23 @@
+#include <mbgl/test/util.hpp>
+#include <mbgl/style/expression/util.hpp>
+
+using namespace mbgl;
+using namespace mbgl::style::expression;
+
+TEST(Expression, Util_rgba) {
+    Result<Color> valid = rgba(0, 0, 0, 0);
+    ASSERT_TRUE(valid);
+    ASSERT_EQ(valid->r, 0);
+    ASSERT_EQ(valid->g, 0);
+    ASSERT_EQ(valid->b, 0);
+    ASSERT_EQ(valid->a, 0);
+
+    ASSERT_FALSE(rgba(0, 0, 0, -0.1));
+    ASSERT_FALSE(rgba(0, 0, 0, 1.1));
+    ASSERT_FALSE(rgba(0, 0, -1, 1));
+    ASSERT_FALSE(rgba(0, 0, 256, 1));
+    ASSERT_FALSE(rgba(0, -1, 0, 1));
+    ASSERT_FALSE(rgba(0, 256, 0, 1));
+    ASSERT_FALSE(rgba(-1, 1, 0, 1));
+    ASSERT_FALSE(rgba(-256, 1, 0, 1));
+}