[core] Implement image expression (#15877)

* [core] Bump gl-js version
* [core] Implement image expression
* [core] Use new image expression
* [core] Coerce image expression to / from string
* [core] Serialize evaluated image
* [core] Pass available images to layout
* [core] Pass images to evaluation context
* [core] Set available flag value based on image availability
* [core] Allow image coercion to boolean to indicate image availability
* [core] Coalesce image expression
* [core] Add image expression to next build system
* [core] Align serialization format and evaluated type with gl-js
* [core] Add images to expression evaluation method
* [core] Add support for Image expression to expression test runner
* [core] Unskip image expression tests
* [core] Update unit tests
* [core] Use image expression in annotation manager
* [core] Add string to ImageExpression conversion
* [core] Add image expression to expression dsl
* [core] Convert tokens for implicitly created Image literal
* [core] Fix clang format
* [core] Split generated style code lines that are over 120 characters
* [core] Add unit test for image expression equality
* [core] Add image property expression evaluation unit test
* [core] Unskip image expression render test
* [core] Skip 'in' expression tests
* [core] Ignore fill-pattern/update-feature-state render test
* [core] Rename Image::serialize to Image::toValue

17 files changed, 188 insertions, 55 deletions

diff --git a/include/mbgl/style/conversion/function.hpp b/include/mbgl/style/conversion/function.hpp
index 47ce6843b5..9ceeb979ce 100644
--- a/include/mbgl/style/conversion/function.hpp
+++ b/include/mbgl/style/conversion/function.hpp
@@ -12,6 +12,7 @@ namespace conversion {
 
 bool hasTokens(const std::string&);
 std::unique_ptr<expression::Expression> convertTokenStringToFormatExpression(const std::string&);
+std::unique_ptr<expression::Expression> convertTokenStringToImageExpression(const std::string&);
 std::unique_ptr<expression::Expression> convertTokenStringToExpression(const std::string&);
 
 optional<std::unique_ptr<expression::Expression>> convertFunctionToExpression(expression::type::Type, const Convertible&, Error&, bool convertTokens);
diff --git a/include/mbgl/style/conversion/property_value.hpp b/include/mbgl/style/conversion/property_value.hpp
index 9d619f7a02..61360b7440 100644
--- a/include/mbgl/style/conversion/property_value.hpp
+++ b/include/mbgl/style/conversion/property_value.hpp
@@ -39,6 +39,12 @@ struct Converter<PropertyValue<T>> {
             ? PropertyValue<T>(PropertyExpression<T>(convertTokenStringToFormatExpression(firstUnformattedSection)))
             : PropertyValue<T>(t);
     }
+
+    PropertyValue<T> maybeConvertTokens(const expression::Image& image) const {
+        return hasTokens(image.id())
+                   ? PropertyValue<T>(PropertyExpression<T>(convertTokenStringToImageExpression(image.id())))
+                   : PropertyValue<T>(image);
+    }
 };
 
 } // namespace conversion
diff --git a/include/mbgl/style/conversion_impl.hpp b/include/mbgl/style/conversion_impl.hpp
index 3e1b8455e5..73d83302a0 100644
--- a/include/mbgl/style/conversion_impl.hpp
+++ b/include/mbgl/style/conversion_impl.hpp
@@ -2,6 +2,7 @@
 
 #include <mbgl/style/color_ramp_property_value.hpp>
 #include <mbgl/style/conversion.hpp>
+#include <mbgl/style/expression/image.hpp>
 #include <mbgl/style/layer.hpp>
 #include <mbgl/style/property_value.hpp>
 #include <mbgl/style/transition_options.hpp>
diff --git a/include/mbgl/style/expression/dsl.hpp b/include/mbgl/style/expression/dsl.hpp
index 4abeac7989..347861abc9 100644
--- a/include/mbgl/style/expression/dsl.hpp
+++ b/include/mbgl/style/expression/dsl.hpp
@@ -49,6 +49,7 @@ std::unique_ptr<Expression> toString(std::unique_ptr<Expression>,
                                      std::unique_ptr<Expression> def = nullptr);
 std::unique_ptr<Expression> toFormatted(std::unique_ptr<Expression>,
                                         std::unique_ptr<Expression> def = nullptr);
+std::unique_ptr<Expression> toImage(std::unique_ptr<Expression>, std::unique_ptr<Expression> def = nullptr);
 
 std::unique_ptr<Expression> get(const char* value);
 std::unique_ptr<Expression> get(std::unique_ptr<Expression>);
@@ -89,6 +90,9 @@ std::unique_ptr<Expression> concat(std::vector<std::unique_ptr<Expression>> inpu
 std::unique_ptr<Expression> format(const char* value);
 std::unique_ptr<Expression> format(std::unique_ptr<Expression>);
 
+std::unique_ptr<Expression> image(const char* value);
+std::unique_ptr<Expression> image(std::unique_ptr<Expression>);
+
 } // namespace dsl
 } // namespace expression
 } // namespace style
diff --git a/include/mbgl/style/expression/expression.hpp b/include/mbgl/style/expression/expression.hpp
index 1341a8d041..9893daa8c4 100644
--- a/include/mbgl/style/expression/expression.hpp
+++ b/include/mbgl/style/expression/expression.hpp
@@ -28,9 +28,7 @@ public:
     EvaluationContext() = default;
     explicit EvaluationContext(float zoom_) : zoom(zoom_) {}
     explicit EvaluationContext(GeometryTileFeature const * feature_) : feature(feature_) {}
-    EvaluationContext(float zoom_, GeometryTileFeature const * feature_) :
-        zoom(zoom_), feature(feature_)
-    {}
+    EvaluationContext(float zoom_, GeometryTileFeature const* feature_) : zoom(zoom_), feature(feature_) {}
     EvaluationContext(optional<mbgl::Value> accumulated_, GeometryTileFeature const * feature_) :
         accumulated(std::move(accumulated_)), feature(feature_)
     {}
@@ -50,6 +48,11 @@ public:
         return *this;
     };
 
+    EvaluationContext& withAvailableImages(const std::set<std::string>* availableImages_) noexcept {
+        availableImages = availableImages_;
+        return *this;
+    };
+
     optional<float> zoom;
     optional<mbgl::Value> accumulated;
     GeometryTileFeature const * feature = nullptr;
@@ -57,6 +60,7 @@ public:
     // Contains formatted section object, std::unordered_map<std::string, Value>.
     const Value* formattedSection = nullptr;
     const FeatureState* featureState = nullptr;
+    const std::set<std::string>* availableImages = nullptr;
 };
 
 template <typename T>
@@ -155,7 +159,8 @@ enum class Kind : int32_t {
     Comparison,
     FormatExpression,
     FormatSectionOverride,
-    NumberFormat
+    NumberFormat,
+    ImageExpression
 };
 
 class Expression {
@@ -172,9 +177,14 @@ public:
 
     Kind getKind() const { return kind; };
     type::Type getType() const { return type; };
-    
+
     EvaluationResult evaluate(optional<float> zoom, const Feature& feature, optional<double> colorRampParameter) const;
+    EvaluationResult evaluate(optional<float> zoom,
+                              const Feature& feature,
+                              optional<double> colorRampParameter,
+                              const std::set<std::string>& availableImages) const;
     EvaluationResult evaluate(optional<mbgl::Value> accumulated, const Feature& feature) const;
+
     /**
      * Statically analyze the expression, attempting to enumerate possible outputs. Returns
      * an array of values plus the sentinel null optional value, used to indicate that the
diff --git a/include/mbgl/style/expression/formatted.hpp b/include/mbgl/style/expression/formatted.hpp
index bb3d609c91..09edad240f 100644
--- a/include/mbgl/style/expression/formatted.hpp
+++ b/include/mbgl/style/expression/formatted.hpp
@@ -36,7 +36,7 @@ struct FormattedSection {
 class Formatted {
 public:
     Formatted() = default;
-    
+
     Formatted(const char* plainU8String) {
         sections.emplace_back(std::string(plainU8String), nullopt, nullopt, nullopt);
     }
diff --git a/include/mbgl/style/expression/image.hpp b/include/mbgl/style/expression/image.hpp
new file mode 100644
index 0000000000..0bc4794a24
--- /dev/null
+++ b/include/mbgl/style/expression/image.hpp
@@ -0,0 +1,49 @@
+#pragma once
+
+#include <mbgl/style/conversion.hpp>
+#include <mbgl/util/color.hpp>
+#include <mbgl/util/optional.hpp>
+
+#include <string>
+#include <vector>
+
+namespace mbgl {
+namespace style {
+namespace expression {
+
+class Image {
+public:
+    Image() = default;
+    Image(const char* imageID);
+    Image(std::string imageID);
+    explicit Image(std::string imageID, bool available);
+    bool operator==(const Image&) const;
+    mbgl::Value toValue() const;
+    const std::string& id() const;
+    bool isAvailable() const;
+    bool empty() const;
+
+private:
+    std::string imageID;
+    bool available;
+};
+
+} // namespace expression
+
+namespace conversion {
+
+template <>
+struct Converter<expression::Image> {
+public:
+    optional<expression::Image> operator()(const Convertible& value, Error& error) const;
+};
+
+template <>
+struct ValueFactory<expression::Image> {
+    static Value make(const expression::Image& image) { return image.toValue(); }
+};
+
+} // namespace conversion
+
+} // namespace style
+} // namespace mbgl
diff --git a/include/mbgl/style/expression/image_expression.hpp b/include/mbgl/style/expression/image_expression.hpp
new file mode 100644
index 0000000000..cd3d375284
--- /dev/null
+++ b/include/mbgl/style/expression/image_expression.hpp
@@ -0,0 +1,33 @@
+#pragma once
+
+#include <mbgl/style/expression/expression.hpp>
+
+namespace mbgl {
+namespace style {
+namespace expression {
+
+class ParsingContext;
+
+class ImageExpression final : public Expression {
+public:
+    explicit ImageExpression(std::unique_ptr<Expression> imageID);
+
+    EvaluationResult evaluate(const EvaluationContext&) const override;
+    static ParseResult parse(const mbgl::style::conversion::Convertible&, ParsingContext&);
+
+    void eachChild(const std::function<void(const Expression&)>&) const override;
+
+    bool operator==(const Expression& e) const override;
+
+    std::vector<optional<Value>> possibleOutputs() const override { return {nullopt}; }
+
+    mbgl::Value serialize() const override;
+    std::string getOperator() const override { return "image"; }
+
+private:
+    std::shared_ptr<Expression> imageID;
+};
+
+} // namespace expression
+} // namespace style
+} // namespace mbgl
diff --git a/include/mbgl/style/expression/is_constant.hpp b/include/mbgl/style/expression/is_constant.hpp
index 2861407af0..a9c41e48b1 100644
--- a/include/mbgl/style/expression/is_constant.hpp
+++ b/include/mbgl/style/expression/is_constant.hpp
@@ -30,6 +30,8 @@ bool isGlobalPropertyConstant(const Expression& expression, const T& properties)
 bool isFeatureConstant(const Expression& expression);
 bool isZoomConstant(const Expression& e);
 
+// Returns true if expression does not depend on information provided by the runtime.
+bool isRuntimeConstant(const Expression& e);
 
 } // namespace expression
 } // namespace style
diff --git a/include/mbgl/style/expression/type.hpp b/include/mbgl/style/expression/type.hpp
index a5a1e76164..ab398741f0 100644
--- a/include/mbgl/style/expression/type.hpp
+++ b/include/mbgl/style/expression/type.hpp
@@ -14,65 +14,70 @@ template <class T>
 std::string toString(const T& t);
 
 struct NullType {
-    constexpr NullType() {};
+    constexpr NullType() = default;
     std::string getName() const { return "null"; }
     bool operator==(const NullType&) const { return true; }
 };
 
 struct NumberType {
-    constexpr NumberType() {};
+    constexpr NumberType() = default;
     std::string getName() const { return "number"; }
     bool operator==(const NumberType&) const { return true; }
 };
 
 struct BooleanType {
-    constexpr BooleanType() {};
+    constexpr BooleanType() = default;
     std::string getName() const { return "boolean"; }
     bool operator==(const BooleanType&) const { return true; }
 };
 
 struct StringType {
-    constexpr StringType() {};
+    constexpr StringType() = default;
     std::string getName() const { return "string"; }
     bool operator==(const StringType&) const { return true; }
 };
 
 struct ColorType {
-    constexpr ColorType() {};
+    constexpr ColorType() = default;
     std::string getName() const { return "color"; }
     bool operator==(const ColorType&) const { return true; }
 };
 
 struct ObjectType {
-    constexpr ObjectType() {};
+    constexpr ObjectType() = default;
     std::string getName() const { return "object"; }
     bool operator==(const ObjectType&) const { return true; }
 };
 
 struct ErrorType {
-    constexpr ErrorType() {};
+    constexpr ErrorType() = default;
     std::string getName() const { return "error"; }
     bool operator==(const ErrorType&) const { return true; }
 };
 
 struct ValueType {
-    constexpr ValueType() {};
+    constexpr ValueType() = default;
     std::string getName() const { return "value"; }
     bool operator==(const ValueType&) const { return true; }
 };
     
 struct CollatorType {
-    constexpr CollatorType() {}; // NOLINT
+    constexpr CollatorType() = default;
     std::string getName() const { return "collator"; }
     bool operator==(const CollatorType&) const { return true; }
 };
     
 struct FormattedType {
-    constexpr FormattedType() {}; // NOLINT
+    constexpr FormattedType() = default;
     std::string getName() const { return "formatted"; }
     bool operator==(const FormattedType&) const { return true; }
 };
 
+struct ImageType {
+    constexpr ImageType() = default;
+    std::string getName() const { return "resolvedImage"; }
+    bool operator==(const ImageType&) const { return true; }
+};
 
 constexpr NullType Null;
 constexpr NumberType Number;
@@ -84,21 +89,22 @@ constexpr ObjectType Object;
 constexpr CollatorType Collator;
 constexpr FormattedType Formatted;
 constexpr ErrorType Error;
+constexpr ImageType Image;
 
 struct Array;
 
-using Type = variant<
-    NullType,
-    NumberType,
-    BooleanType,
-    StringType,
-    ColorType,
-    ObjectType,
-    ValueType,
-    mapbox::util::recursive_wrapper<Array>,
-    CollatorType,
-    FormattedType,
-    ErrorType>;
+using Type = variant<NullType,
+                     NumberType,
+                     BooleanType,
+                     StringType,
+                     ColorType,
+                     ObjectType,
+                     ValueType,
+                     mapbox::util::recursive_wrapper<Array>,
+                     CollatorType,
+                     FormattedType,
+                     ErrorType,
+                     ImageType>;
 
 struct Array {
     explicit Array(Type itemType_) : itemType(std::move(itemType_)) {}
diff --git a/include/mbgl/style/expression/value.hpp b/include/mbgl/style/expression/value.hpp
index 91239d083f..902f5ae209 100644
--- a/include/mbgl/style/expression/value.hpp
+++ b/include/mbgl/style/expression/value.hpp
@@ -2,6 +2,7 @@
 
 #include <mbgl/style/expression/collator.hpp>
 #include <mbgl/style/expression/formatted.hpp>
+#include <mbgl/style/expression/image.hpp>
 #include <mbgl/style/expression/type.hpp>
 #include <mbgl/style/position.hpp>
 #include <mbgl/style/types.hpp>
@@ -19,16 +20,16 @@ namespace expression {
 
 struct Value;
 
-using ValueBase = variant<
-    NullValue,
-    bool,
-    double,
-    std::string,
-    Color,
-    Collator,
-    Formatted,
-    mapbox::util::recursive_wrapper<std::vector<Value>>,
-    mapbox::util::recursive_wrapper<std::unordered_map<std::string, Value>>>;
+using ValueBase = variant<NullValue,
+                          bool,
+                          double,
+                          std::string,
+                          Color,
+                          Collator,
+                          Formatted,
+                          Image,
+                          mapbox::util::recursive_wrapper<std::vector<Value>>,
+                          mapbox::util::recursive_wrapper<std::unordered_map<std::string, Value>>>;
 struct Value : ValueBase {
     using ValueBase::ValueBase;
     
diff --git a/include/mbgl/style/layers/background_layer.hpp b/include/mbgl/style/layers/background_layer.hpp
index ebdce35d0f..bc9d5222fd 100644
--- a/include/mbgl/style/layers/background_layer.hpp
+++ b/include/mbgl/style/layers/background_layer.hpp
@@ -40,9 +40,9 @@ public:
     void setBackgroundOpacityTransition(const TransitionOptions&);
     TransitionOptions getBackgroundOpacityTransition() const;
 
-    static PropertyValue<std::string> getDefaultBackgroundPattern();
-    const PropertyValue<std::string>& getBackgroundPattern() const;
-    void setBackgroundPattern(const PropertyValue<std::string>&);
+    static PropertyValue<expression::Image> getDefaultBackgroundPattern();
+    const PropertyValue<expression::Image>& getBackgroundPattern() const;
+    void setBackgroundPattern(const PropertyValue<expression::Image>&);
     void setBackgroundPatternTransition(const TransitionOptions&);
     TransitionOptions getBackgroundPatternTransition() const;
 
diff --git a/include/mbgl/style/layers/fill_extrusion_layer.hpp b/include/mbgl/style/layers/fill_extrusion_layer.hpp
index 76c2359617..2996cd0066 100644
--- a/include/mbgl/style/layers/fill_extrusion_layer.hpp
+++ b/include/mbgl/style/layers/fill_extrusion_layer.hpp
@@ -52,9 +52,9 @@ public:
     void setFillExtrusionOpacityTransition(const TransitionOptions&);
     TransitionOptions getFillExtrusionOpacityTransition() const;
 
-    static PropertyValue<std::string> getDefaultFillExtrusionPattern();
-    const PropertyValue<std::string>& getFillExtrusionPattern() const;
-    void setFillExtrusionPattern(const PropertyValue<std::string>&);
+    static PropertyValue<expression::Image> getDefaultFillExtrusionPattern();
+    const PropertyValue<expression::Image>& getFillExtrusionPattern() const;
+    void setFillExtrusionPattern(const PropertyValue<expression::Image>&);
     void setFillExtrusionPatternTransition(const TransitionOptions&);
     TransitionOptions getFillExtrusionPatternTransition() const;
 
diff --git a/include/mbgl/style/layers/fill_layer.hpp b/include/mbgl/style/layers/fill_layer.hpp
index 9ec33d7e96..90e51c85a3 100644
--- a/include/mbgl/style/layers/fill_layer.hpp
+++ b/include/mbgl/style/layers/fill_layer.hpp
@@ -52,9 +52,9 @@ public:
     void setFillOutlineColorTransition(const TransitionOptions&);
     TransitionOptions getFillOutlineColorTransition() const;
 
-    static PropertyValue<std::string> getDefaultFillPattern();
-    const PropertyValue<std::string>& getFillPattern() const;
-    void setFillPattern(const PropertyValue<std::string>&);
+    static PropertyValue<expression::Image> getDefaultFillPattern();
+    const PropertyValue<expression::Image>& getFillPattern() const;
+    void setFillPattern(const PropertyValue<expression::Image>&);
     void setFillPatternTransition(const TransitionOptions&);
     TransitionOptions getFillPatternTransition() const;
 
diff --git a/include/mbgl/style/layers/line_layer.hpp b/include/mbgl/style/layers/line_layer.hpp
index 4f2cf53708..33312795d0 100644
--- a/include/mbgl/style/layers/line_layer.hpp
+++ b/include/mbgl/style/layers/line_layer.hpp
@@ -91,9 +91,9 @@ public:
     void setLineOpacityTransition(const TransitionOptions&);
     TransitionOptions getLineOpacityTransition() const;
 
-    static PropertyValue<std::string> getDefaultLinePattern();
-    const PropertyValue<std::string>& getLinePattern() const;
-    void setLinePattern(const PropertyValue<std::string>&);
+    static PropertyValue<expression::Image> getDefaultLinePattern();
+    const PropertyValue<expression::Image>& getLinePattern() const;
+    void setLinePattern(const PropertyValue<expression::Image>&);
     void setLinePatternTransition(const TransitionOptions&);
     TransitionOptions getLinePatternTransition() const;
 
diff --git a/include/mbgl/style/layers/symbol_layer.hpp b/include/mbgl/style/layers/symbol_layer.hpp
index 92e214919a..0ef212a3b9 100644
--- a/include/mbgl/style/layers/symbol_layer.hpp
+++ b/include/mbgl/style/layers/symbol_layer.hpp
@@ -42,9 +42,9 @@ public:
     const PropertyValue<bool>& getIconIgnorePlacement() const;
     void setIconIgnorePlacement(const PropertyValue<bool>&);
 
-    static PropertyValue<std::string> getDefaultIconImage();
-    const PropertyValue<std::string>& getIconImage() const;
-    void setIconImage(const PropertyValue<std::string>&);
+    static PropertyValue<expression::Image> getDefaultIconImage();
+    const PropertyValue<expression::Image>& getIconImage() const;
+    void setIconImage(const PropertyValue<expression::Image>&);
 
     static PropertyValue<bool> getDefaultIconKeepUpright();
     const PropertyValue<bool>& getIconKeepUpright() const;
diff --git a/include/mbgl/style/property_expression.hpp b/include/mbgl/style/property_expression.hpp
index f68285fb1b..7dcd818dde 100644
--- a/include/mbgl/style/property_expression.hpp
+++ b/include/mbgl/style/property_expression.hpp
@@ -16,7 +16,7 @@ public:
 
     bool isZoomConstant() const noexcept;
     bool isFeatureConstant() const noexcept;
-    bool canEvaluateWith(const expression::EvaluationContext&) const noexcept;
+    bool isRuntimeConstant() const noexcept;
     float interpolationFactor(const Range<float>&, const float) const noexcept;
     Range<float> getCoveringStops(const float, const float) const noexcept;
     const expression::Expression& getExpression() const noexcept;
@@ -28,6 +28,7 @@ protected:
     variant<std::nullptr_t, const expression::Interpolate*, const expression::Step*> zoomCurve;
     bool isZoomConstant_;
     bool isFeatureConstant_;
+    bool isRuntimeConstant_;
 };
 
 template <class T>
@@ -40,7 +41,6 @@ public:
     }
 
     T evaluate(const expression::EvaluationContext& context, T finalDefaultValue = T()) const {
-        assert(canEvaluateWith(context));
         const expression::EvaluationResult result = expression->evaluate(context);
         if (result) {
             const optional<T> typed = expression::fromExpressionValue<T>(*result);
@@ -50,18 +50,38 @@ public:
     }
 
     T evaluate(float zoom) const {
+        assert(!isZoomConstant());
+        assert(isFeatureConstant());
         return evaluate(expression::EvaluationContext(zoom));
     }
 
     T evaluate(const GeometryTileFeature& feature, T finalDefaultValue) const {
+        assert(isZoomConstant());
+        assert(!isFeatureConstant());
         return evaluate(expression::EvaluationContext(&feature), finalDefaultValue);
     }
 
+    T evaluate(const GeometryTileFeature& feature,
+               const std::set<std::string>& availableImages,
+               T finalDefaultValue) const {
+        return evaluate(expression::EvaluationContext(&feature).withAvailableImages(&availableImages),
+                        finalDefaultValue);
+    }
+
     T evaluate(float zoom, const GeometryTileFeature& feature, T finalDefaultValue) const {
         return evaluate(expression::EvaluationContext(zoom, &feature), finalDefaultValue);
     }
 
+    T evaluate(float zoom,
+               const GeometryTileFeature& feature,
+               const std::set<std::string>& availableImages,
+               T finalDefaultValue) const {
+        return evaluate(expression::EvaluationContext(zoom, &feature).withAvailableImages(&availableImages),
+                        finalDefaultValue);
+    }
+
     T evaluate(float zoom, const GeometryTileFeature& feature, const FeatureState& state, T finalDefaultValue) const {
+        assert(!isFeatureConstant());
         return evaluate(expression::EvaluationContext(zoom, &feature, &state), finalDefaultValue);
     }