[ios, macos] Add format expression convenience methods support. (#14094)

Added the ios/macos format expression bindings.

The equivalent is mgl_attributed: or mgl_attributed({}) when making an expression using the expressionForFormat selector.

A new constructor called mgl_expressionForAttributedExpressions:(NSArray<NSExpression*>*)attributedExpressions was added to NSExpression+MGLAdditions category.

Updated the symbol style layer text test to use the bindings.

Updated the Predicates and Expressions.md and For Style Authors.md.ejs template with the bindings.

10 files changed, 299 insertions, 22 deletions

diff --git a/platform/darwin/docs/guides/For Style Authors.md.ejs b/platform/darwin/docs/guides/For Style Authors.md.ejs
index ead3b81ce6..cf0f79f419 100644
--- a/platform/darwin/docs/guides/For Style Authors.md.ejs
+++ b/platform/darwin/docs/guides/For Style Authors.md.ejs
@@ -403,6 +403,7 @@ In style specification | Method, function, or predicate type | Format string syn
 `zoom`                 | `NSExpression.zoomLevelVariableExpression` | `$zoomLevel`
 `heatmap-density`      | `NSExpression.heatmapDensityVariableExpression` | `$heatmapDensity`
 `line-progress`        | `NSExpression.lineProgressVariableExpression` | `$lineProgress`
+`format`               | `+[NSExpression mgl_expressionForAttributedExpressions:]` or `mgl_attributed:`  | `mgl_attributed({x, y, z})`
 
 For operators that have no corresponding `NSExpression` symbol, use the
 `MGL_FUNCTION()` format string syntax.
diff --git a/platform/darwin/docs/guides/Predicates and Expressions.md b/platform/darwin/docs/guides/Predicates and Expressions.md
index 0bb26b3bfd..5f5d9a22a8 100644
--- a/platform/darwin/docs/guides/Predicates and Expressions.md
+++ b/platform/darwin/docs/guides/Predicates and Expressions.md
@@ -534,6 +534,22 @@ This function corresponds to the
 [`coalesce`](https://www.mapbox.com/mapbox-gl-js/style-spec/#expressions-coalesce)
 operator in the Mapbox Style Specification.
 
+### `mgl_attributed:`
+
+<dl>
+<dt>Selector:</dt>
+<dd><code>mgl_attributed:</code></dd>
+<dt>Format string syntax:</dt>
+<dd><code>mgl_attributed({x, y, z})</code></dd>
+</dl>
+
+Concatenates and returns the array of `MGLAttributedExpression` objects, for use 
+with the `MGLSymbolStyleLayer.text` property.
+
+This function corresponds to the
+[`format`](https://www.mapbox.com/mapbox-gl-js/style-spec/#expressions-types-format)
+operator in the Mapbox Style Specification.
+
 ### `MGL_LET`
 
 <dl>
diff --git a/platform/darwin/scripts/generate-style-code.js b/platform/darwin/scripts/generate-style-code.js
index 704b0a29f4..a8bdec7865 100755
--- a/platform/darwin/scripts/generate-style-code.js
+++ b/platform/darwin/scripts/generate-style-code.js
@@ -107,7 +107,7 @@ global.objCTestValue = function (property, layerType, arraysAsStructs, indent) {
             // converts Formatted back to string.
             return layerType === 'string' ?
                 `@"'${_.startCase(propertyName)}'"` :
-                `@"MGL_FUNCTION('format', '${_.startCase(propertyName)}', %@)", @{}`;
+                `@"${_.startCase(propertyName)}"`;
         case 'string':
             return `@"'${_.startCase(propertyName)}'"`;
         case 'enum':
diff --git a/platform/darwin/src/MGLAttributedExpression.h b/platform/darwin/src/MGLAttributedExpression.h
new file mode 100644
index 0000000000..aa5d51c66e
--- /dev/null
+++ b/platform/darwin/src/MGLAttributedExpression.h
@@ -0,0 +1,44 @@
+#import "MGLFoundation.h"
+
+NS_ASSUME_NONNULL_BEGIN
+
+typedef NSString * MGLAttributedExpressionKey NS_EXTENSIBLE_STRING_ENUM;
+
+FOUNDATION_EXTERN MGL_EXPORT MGLAttributedExpressionKey const MGLFontNamesAttribute;
+FOUNDATION_EXTERN MGL_EXPORT MGLAttributedExpressionKey const MGLFontSizeAttribute;
+
+/**
+ An `MGLAttributedExpression` object associates text formatting attibutes (such as font size or
+ font names) to an `NSExpression`.
+ */
+MGL_EXPORT
+@interface MGLAttributedExpression : NSObject
+
+/**
+ The expression content of the receiver as `NSExpression`.
+ */
+@property (strong, nonatomic) NSExpression *expression;
+
+/**
+ The formatting attributes.
+ */
+@property (strong, nonatomic, readonly) NSDictionary<MGLAttributedExpressionKey, id> *attributes;
+
+/**
+ Returns an `MGLAttributedExpression` object initialized with an expression and no attribute information.
+ */
+- (instancetype)initWithExpression:(NSExpression *)expression;
+
+/** 
+ Returns an `MGLAttributedExpression` object initialized with an expression and text format attributes.
+ */
+- (instancetype)initWithExpression:(NSExpression *)expression attributes:(nullable NSDictionary <MGLAttributedExpressionKey, id> *)attrs;
+
+/**
+ Creates an `MGLAttributedExpression` object initialized with an expression and the format attributes for font names and font size.
+ */
++ (instancetype)attributedExpression:(NSExpression *)expression fontNames:(nullable NSArray<NSString*> *)fontNames fontSize:(nullable NSNumber *)fontSize;
+
+@end
+
+NS_ASSUME_NONNULL_END
diff --git a/platform/darwin/src/MGLAttributedExpression.m b/platform/darwin/src/MGLAttributedExpression.m
new file mode 100644
index 0000000000..715f74e42f
--- /dev/null
+++ b/platform/darwin/src/MGLAttributedExpression.m
@@ -0,0 +1,59 @@
+#import "MGLAttributedExpression.h"
+#import "MGLLoggingConfiguration_Private.h"
+
+const MGLAttributedExpressionKey MGLFontNamesAttribute = @"text-font";
+const MGLAttributedExpressionKey MGLFontSizeAttribute = @"font-scale";
+
+@implementation MGLAttributedExpression
+
+- (instancetype)initWithExpression:(NSExpression *)expression {
+    self = [self initWithExpression:expression attributes:nil];
+    return self;
+}
+
++ (instancetype)attributedExpression:(NSExpression *)expression fontNames:(nullable NSArray<NSString *> *)fontNames fontSize:(nullable NSNumber *)fontSize {
+    MGLAttributedExpression *attributedExpression;
+    
+    NSMutableDictionary *attrs = [NSMutableDictionary dictionary];
+    
+    if (fontNames && fontNames.count > 0) {
+        attrs[MGLFontNamesAttribute] = fontNames;
+    }
+    
+    if (fontSize) {
+        attrs[MGLFontSizeAttribute] = fontSize;
+    }
+    
+    attributedExpression = [[self alloc] initWithExpression:expression attributes:attrs];
+    return attributedExpression;
+}
+
+- (instancetype)initWithExpression:(NSExpression *)expression attributes:(NSDictionary<MGLAttributedExpressionKey,id> *)attrs {
+    if (self = [super init])
+    {
+        MGLLogInfo(@"Starting %@ initialization.", NSStringFromClass([self class]));
+        _expression = expression;
+        _attributes = attrs;
+        
+        MGLLogInfo(@"Finalizing %@ initialization.", NSStringFromClass([self class]));
+    }
+    return self;
+}
+
+- (BOOL)isEqual:(id)object {
+    BOOL result = NO;
+    
+    if ([object isKindOfClass:[self class]]) {
+        MGLAttributedExpression *otherObject = object;
+        result = [self.expression isEqual:otherObject.expression] &&
+        [_attributes isEqual:otherObject.attributes];
+    }
+    
+    return result;
+}
+
+- (NSString *)description {
+    return [NSString stringWithFormat:@"MGLAttributedExpression<Expression: %@ Attributes: %@>", self.expression, self.attributes];
+}
+
+@end
diff --git a/platform/darwin/src/NSExpression+MGLAdditions.h b/platform/darwin/src/NSExpression+MGLAdditions.h
index 1e6fd6fc46..a19ec1af2e 100644
--- a/platform/darwin/src/NSExpression+MGLAdditions.h
+++ b/platform/darwin/src/NSExpression+MGLAdditions.h
@@ -7,6 +7,8 @@
 
 #import "MGLTypes.h"
 
+@class MGLAttributedExpression;
+
 NS_ASSUME_NONNULL_BEGIN
 
 typedef NSString *MGLExpressionInterpolationMode NS_TYPED_ENUM;
@@ -150,6 +152,14 @@ FOUNDATION_EXTERN MGL_EXPORT const MGLExpressionInterpolationMode MGLExpressionI
  */
 + (instancetype)mgl_expressionForMatchingExpression:(nonnull NSExpression *)inputExpression inDictionary:(nonnull NSDictionary<NSExpression *, NSExpression *> *)matchedExpressions defaultExpression:(nonnull NSExpression *)defaultExpression NS_SWIFT_NAME(init(forMGLMatchingKey:in:default:));
 
+/**
+ Returns an attributed function expression specifying an `MGLAttributedExpression` constant
+ expression array.
+ 
+ @param attributedExpressions The `MGLAttributedExpression` constant expression array.
+ */
++ (instancetype)mgl_expressionForAttributedExpressions:(nonnull NSArray<NSExpression *> *)attributedExpressions NS_SWIFT_NAME(init(forAttributedExpressions:));
+
 #pragma mark Concatenating String Expressions
 
 /**
diff --git a/platform/darwin/src/NSExpression+MGLAdditions.mm b/platform/darwin/src/NSExpression+MGLAdditions.mm
index 6aaba4dd90..c4e2908888 100644
--- a/platform/darwin/src/NSExpression+MGLAdditions.mm
+++ b/platform/darwin/src/NSExpression+MGLAdditions.mm
@@ -11,6 +11,7 @@
 #import "NSPredicate+MGLAdditions.h"
 #import "NSValue+MGLStyleAttributeAdditions.h"
 #import "MGLVectorTileSource_Private.h"
+#import "MGLAttributedExpression.h"
 
 #import <objc/runtime.h>
 
@@ -75,6 +76,7 @@ const MGLExpressionInterpolationMode MGLExpressionInterpolationModeCubicBezier =
     INSTALL_METHOD(mgl_atan:);
     INSTALL_METHOD(mgl_tan:);
     INSTALL_METHOD(mgl_log2:);
+    INSTALL_METHOD(mgl_attributed:);
     
     // Install functions that resemble control structures, taking arbitrary
     // numbers of arguments. Vararg aftermarket functions need to be declared
@@ -96,6 +98,12 @@ const MGLExpressionInterpolationMode MGLExpressionInterpolationModeCubicBezier =
     return [components componentsJoinedByString:@""];
 }
 
+- (NSString *)mgl_attributed:(NSArray<MGLAttributedExpression *> *)attributedExpressions {
+    [NSException raise:NSInvalidArgumentException
+                format:@"Text format expressions lack underlying Objective-C implementations."];
+    return nil;
+}
+
 /**
  Rounds the given number to the nearest integer. If the number is halfway
  between two integers, this method rounds it away from zero.
@@ -229,7 +237,6 @@ const MGLExpressionInterpolationMode MGLExpressionInterpolationModeCubicBezier =
     return nil;
 }
 
-
 /**
  A placeholder for a catch-all method that evaluates an arbitrary number of
  arguments as an expression according to the Mapbox Style Specification’s
@@ -591,6 +598,10 @@ const MGLExpressionInterpolationMode MGLExpressionInterpolationModeCubicBezier =
                                      arguments:optionsArray];
 }
 
++ (instancetype)mgl_expressionForAttributedExpressions:(nonnull NSArray<NSExpression *> *)attributedExpressions {
+    return [NSExpression expressionForFunction:@"mgl_attributed:" arguments:attributedExpressions];
+}
+
 - (instancetype)mgl_expressionByAppendingExpression:(nonnull NSExpression *)expression {
     NSExpression *subexpression = [NSExpression expressionForAggregate:@[self, expression]];
     return [NSExpression expressionForFunction:@"mgl_join:" arguments:@[subexpression]];
@@ -860,6 +871,22 @@ NSArray *MGLSubexpressionsWithJSONObjects(NSArray *objects) {
         
             return [NSExpression expressionForFunction:@"MGL_MATCH"
                                              arguments:optionsArray];
+        } else if ([op isEqualToString:@"format"]) {
+            NSMutableArray *attributedExpressions = [NSMutableArray array];
+            
+            for (NSUInteger index = 0; index < argumentObjects.count; index+=2) {
+                NSExpression *expression = [NSExpression expressionWithMGLJSONObject:argumentObjects[index]];
+                NSMutableDictionary *attrs = [NSMutableDictionary dictionary];
+                if ((index + 1) < argumentObjects.count) {
+                    attrs = argumentObjects[index + 1];
+                }
+                
+                MGLAttributedExpression *attributedExpression = [[MGLAttributedExpression alloc] initWithExpression:expression attributes:attrs];
+
+                [attributedExpressions addObject:[NSExpression expressionForConstantValue:attributedExpression]];
+            }
+            return [NSExpression expressionForFunction:@"mgl_attributed:" arguments:attributedExpressions];
+            
         } else if ([op isEqualToString:@"coalesce"]) {
             NSMutableArray *expressions = [NSMutableArray array];
             for (id operand in argumentObjects) {
@@ -971,6 +998,23 @@ NSArray *MGLSubexpressionsWithJSONObjects(NSArray *objects) {
                     return @[@"literal", @[@(mglValue[0]), @(mglValue[1]), @(mglValue[2]), @(mglValue[3])]];
                 }
             }
+            if ([constantValue isKindOfClass:[MGLAttributedExpression class]]) {
+                MGLAttributedExpression *attributedExpression = (MGLAttributedExpression *)constantValue;
+                id jsonObject = attributedExpression.expression.mgl_jsonExpressionObject;
+                NSMutableArray *attributes = [NSMutableArray array];
+                if ([jsonObject isKindOfClass:[NSArray class]]) {
+                    [attributes addObjectsFromArray:jsonObject];
+                } else {
+                    [attributes addObject:jsonObject];
+                }
+                if (attributedExpression.attributes) {
+                    [attributes addObject:attributedExpression.attributes];
+                } else {
+                    [attributes addObject:@{}];
+                }
+ 
+                return attributes;
+            }
             return self.constantValue;
         }
             
@@ -1115,6 +1159,9 @@ NSArray *MGLSubexpressionsWithJSONObjects(NSArray *objects) {
                 }
                 [NSException raise:NSInvalidArgumentException
                             format:@"Casting expression to %@ not yet implemented.", type];
+            } else if ([function isEqualToString:@"mgl_attributed:"]) {
+                return [self mgl_jsonFormatExpressionObject];
+                
             } else if ([function isEqualToString:@"MGL_FUNCTION"] ||
                        [function isEqualToString:@"MGL_FUNCTION:"]) {
                 NSExpression *firstOp = self.arguments.firstObject;
@@ -1363,6 +1410,25 @@ NSArray *MGLSubexpressionsWithJSONObjects(NSArray *objects) {
     return expressionObject;
 }
 
+- (id)mgl_jsonFormatExpressionObject {
+    NSArray<NSExpression *> *attributedExpressions;
+    NSExpression *formatArray = self.arguments.firstObject;
+    
+    if ([formatArray respondsToSelector:@selector(constantValue)] && [formatArray.constantValue isKindOfClass:[NSArray class]]) {
+        attributedExpressions = (NSArray *)formatArray.constantValue;
+    } else {
+        attributedExpressions = self.arguments;
+    }
+    
+    NSMutableArray *expressionObject = [NSMutableArray arrayWithObjects:@"format", nil];
+    
+    for (NSUInteger index = 0; index < attributedExpressions.count; index++) {
+        [expressionObject addObjectsFromArray:attributedExpressions[index].mgl_jsonExpressionObject];
+    }
+    
+    return expressionObject;
+}
+
 #pragma mark Localization
 
 /**
diff --git a/platform/darwin/test/MGLExpressionTests.mm b/platform/darwin/test/MGLExpressionTests.mm
index bcc30e49fd..8b8a79f184 100644
--- a/platform/darwin/test/MGLExpressionTests.mm
+++ b/platform/darwin/test/MGLExpressionTests.mm
@@ -12,6 +12,7 @@
 #else
 #import "NSColor+MGLAdditions.h"
 #endif
+#import "MGLAttributedExpression.h"
 
 #define MGLAssertEqualValues(actual, expected, ...) \
     XCTAssertTrue(actual.is<__typeof__(expected)>()); \
@@ -990,6 +991,87 @@ using namespace std::string_literals;
     }
 }
 
+- (void)testFormatExpressionObject {
+    {
+        MGLAttributedExpression *attribute1 = [MGLAttributedExpression attributedExpression:[NSExpression expressionForConstantValue:@"foo"]
+                                                                                  fontNames:nil
+                                                                                   fontSize:@(1.2)];
+        MGLAttributedExpression *attribute2 = [MGLAttributedExpression attributedExpression:[NSExpression expressionForConstantValue:@"biz"]
+                                                                                  fontNames:nil
+                                                                                   fontSize:@(1.0)];
+        MGLAttributedExpression *attribute3 = [MGLAttributedExpression attributedExpression:[NSExpression expressionForConstantValue:@"bar"]
+                                                                                  fontNames:nil
+                                                                                   fontSize:@(0.8)];
+        MGLAttributedExpression *attribute4 = [MGLAttributedExpression attributedExpression:[NSExpression expressionForConstantValue:@"\r"]
+                                                                                  fontNames:@[]
+                                                                                   fontSize:nil];
+        NSExpression *expression = [NSExpression expressionWithFormat:@"mgl_attributed:(%@, %@, %@, %@)",
+                                    MGLConstantExpression(attribute1),
+                                    MGLConstantExpression(attribute4),
+                                    MGLConstantExpression(attribute2),
+                                    MGLConstantExpression(attribute3)];
+        NSArray *jsonExpression = @[@"format", @"foo", @{@"font-scale": @1.2}, @"\r", @{}, @"biz", @{@"font-scale": @1.0}, @"bar", @{@"font-scale": @0.8}];
+        XCTAssertEqualObjects(expression.mgl_jsonExpressionObject, jsonExpression);
+        XCTAssertEqualObjects([NSExpression expressionWithMGLJSONObject:jsonExpression], expression);
+    }
+    {
+        MGLAttributedExpression *attribute1 = [MGLAttributedExpression attributedExpression:[NSExpression expressionForConstantValue:@"foo"]
+                                                                                  fontNames:nil
+                                                                                   fontSize:@(1.2)];
+        MGLAttributedExpression *attribute2 = [MGLAttributedExpression attributedExpression:[NSExpression expressionForConstantValue:@"biz"]
+                                                                                  fontNames:nil
+                                                                                   fontSize:@(1.0)];
+        MGLAttributedExpression *attribute3 = [MGLAttributedExpression attributedExpression:[NSExpression expressionForConstantValue:@"bar"]
+                                                                                  fontNames:nil
+                                                                                   fontSize:@(0.8)];
+        MGLAttributedExpression *attribute4 = [MGLAttributedExpression attributedExpression:[NSExpression expressionForConstantValue:@"\n"]
+                                                                                  fontNames:@[]
+                                                                                   fontSize:nil];
+        NSExpression *expression = [NSExpression expressionWithFormat:@"mgl_attributed:(%@, %@, %@, %@)",
+                                    MGLConstantExpression(attribute1),
+                                    MGLConstantExpression(attribute4),
+                                    MGLConstantExpression(attribute2),
+                                    MGLConstantExpression(attribute3)];
+        NSArray *jsonExpression = @[@"format", @"foo", @{@"font-scale": @1.2}, @"\n", @{}, @"biz", @{@"font-scale": @1.0}, @"bar", @{@"font-scale": @0.8}];
+        XCTAssertEqualObjects(expression.mgl_jsonExpressionObject, jsonExpression);
+        XCTAssertEqualObjects([NSExpression expressionWithMGLJSONObject:jsonExpression], expression);
+    }
+    {
+        MGLAttributedExpression *attribute1 = [MGLAttributedExpression attributedExpression:[NSExpression expressionForConstantValue:@"foo"]
+                                                                                  fontNames:nil
+                                                                                   fontSize:@(1.2)];
+        NSExpression *expression = [NSExpression expressionWithFormat:@"mgl_attributed:(%@)", MGLConstantExpression(attribute1)];
+        
+        NSExpression *compatibilityExpression = [NSExpression expressionForFunction:@"mgl_attributed:" arguments:@[MGLConstantExpression(attribute1)]];
+        NSArray *jsonExpression = @[@"format", @"foo", @{@"font-scale": @1.2}];
+        XCTAssertEqualObjects(compatibilityExpression.mgl_jsonExpressionObject, expression.mgl_jsonExpressionObject);
+        XCTAssertEqualObjects(compatibilityExpression, expression);
+        XCTAssertEqualObjects(expression.mgl_jsonExpressionObject, jsonExpression);
+        XCTAssertEqualObjects([NSExpression expressionWithMGLJSONObject:jsonExpression], expression);
+    }
+    {
+        MGLAttributedExpression *attribute1 = [MGLAttributedExpression attributedExpression:[NSExpression expressionForConstantValue:@"foo"]
+                                                                                  fontNames:nil
+                                                                                   fontSize:@(1.2)];
+        MGLAttributedExpression *attribute2 = [MGLAttributedExpression attributedExpression:[NSExpression expressionForConstantValue:@"biz"]
+                                                                                  fontNames:nil
+                                                                                   fontSize:@(1.0)];
+        MGLAttributedExpression *attribute3 = [MGLAttributedExpression attributedExpression:[NSExpression expressionForConstantValue:@"bar"]
+                                                                                  fontNames:nil
+                                                                                   fontSize:@(0.8)];
+        MGLAttributedExpression *attribute4 = [MGLAttributedExpression attributedExpression:[NSExpression expressionForConstantValue:@"\n"]
+                                                                                  fontNames:@[]
+                                                                                   fontSize:nil];
+        NSExpression *expression = [NSExpression mgl_expressionForAttributedExpressions:@[MGLConstantExpression(attribute1),
+                                                                                          MGLConstantExpression(attribute4),
+                                                                                          MGLConstantExpression(attribute2),
+                                                                                          MGLConstantExpression(attribute3)]];
+        NSArray *jsonExpression = @[@"format", @"foo", @{@"font-scale": @1.2}, @"\n", @{}, @"biz", @{@"font-scale": @1.0}, @"bar", @{@"font-scale": @0.8}];
+        XCTAssertEqualObjects(expression.mgl_jsonExpressionObject, jsonExpression);
+        XCTAssertEqualObjects([NSExpression expressionWithMGLJSONObject:jsonExpression], expression);
+    }
+}
+
 - (void)testGenericExpressionObject {
     {
         NSExpression *expression = [NSExpression expressionWithFormat:@"MGL_FUNCTION('random', 1, 2, 3, 4, 5)"];
@@ -1002,23 +1084,6 @@ using namespace std::string_literals;
         XCTAssertThrowsSpecificNamed([expression expressionValueWithObject:nil context:nil], NSException, NSInvalidArgumentException);
     }
     {
-        NSExpression *expression = [NSExpression expressionWithFormat:@"MGL_FUNCTION('format', 'foo', %@, '\r', %@, 'biz', %@, 'bar', %@)", @{@"font-scale": @1.2}, @{}, @{@"font-scale": @1.0}, @{@"font-scale": @0.8}];
-        NSArray *jsonExpression = @[@"format", @"foo", @{@"font-scale": @1.2}, @"\r", @{}, @"biz", @{@"font-scale": @1.0}, @"bar", @{@"font-scale": @0.8}];
-
-        XCTAssertEqualObjects(expression.mgl_jsonExpressionObject, jsonExpression);
-        
-        NSExpression *encodedExpression = [NSExpression expressionWithMGLJSONObject:jsonExpression];
-
-        // Expressions encoded from a json create a different constant abstract type
-        // thus even tho knowing that the constant values are the same, the base
-        // class is not. This compares the resulting array which is type agnostic encoding.
-        for (NSUInteger index = 0; index < jsonExpression.count; index++) {
-            NSExpression *left = encodedExpression.mgl_jsonExpressionObject[index];
-            NSExpression *right = expression.mgl_jsonExpressionObject[index];
-            XCTAssertEqualObjects(left.mgl_jsonExpressionObject, right.mgl_jsonExpressionObject);
-        }
-    }
-    {
         NSArray *arguments = @[
             MGLConstantExpression(@"one"), MGLConstantExpression(@1),
             [NSExpression expressionForVariable:@"one"],
diff --git a/platform/darwin/test/MGLStyleLayerTests.mm.ejs b/platform/darwin/test/MGLStyleLayerTests.mm.ejs
index ba878b8bbe..4a38070007 100644
--- a/platform/darwin/test/MGLStyleLayerTests.mm.ejs
+++ b/platform/darwin/test/MGLStyleLayerTests.mm.ejs
@@ -8,6 +8,9 @@
 
 #import "MGLStyleLayerTests.h"
 #import "../../darwin/src/NSDate+MGLAdditions.h"
+<% if (type === 'symbol') { -%>
+#include "../../darwin/src/MGLAttributedExpression.h"
+<% } -%>
 
 #import "MGLStyleLayer_Private.h"
 
@@ -80,7 +83,13 @@
         XCTAssertEqualObjects(layer.<%- objCName(property) %>, constantExpression,
                               @"<%- objCName(property) %> should round-trip constant value expressions.");
 
+<% if (property.type !== 'formatted') { -%>
         constantExpression = [NSExpression expressionWithFormat:<%- objCTestValue(property, type, false, 3) %>];
+<% } else { -%>
+        MGLAttributedExpression *attributedConstantExpression = [[MGLAttributedExpression alloc] initWithExpression:[NSExpression expressionWithFormat:<%- objCTestValue(property, 'string', true, 3) %>]
+                                                                                                 attributes:@{}];
+        constantExpression = [NSExpression mgl_expressionForAttributedExpressions:@[[NSExpression expressionForConstantValue:attributedConstantExpression]]];
+<% } -%>
         NSExpression *functionExpression = [NSExpression expressionWithFormat:@"mgl_step:from:stops:($zoomLevel, %@, %@)", constantExpression, @{@18: constantExpression}];
         layer.<%- objCName(property) %> = functionExpression;
 
@@ -180,7 +189,9 @@
                        @"Setting <%- objCName(property) %> to a constant string with tokens should convert to an expression.");
 
 <% if (property.type === 'formatted') { -%>
-        NSExpression* tokenExpression = [NSExpression expressionWithFormat:@"MGL_FUNCTION('format', CAST(token, 'NSString'), %@)", @{}];
+        MGLAttributedExpression *tokenAttibutedExpression = [[MGLAttributedExpression alloc] initWithExpression:[NSExpression expressionWithFormat:@"CAST(token, 'NSString')"]
+                                                                                                     attributes:@{}];
+        NSExpression* tokenExpression = [NSExpression mgl_expressionForAttributedExpressions:@[[NSExpression expressionForConstantValue:tokenAttibutedExpression]]];
 <% } else { -%>
         NSExpression* tokenExpression = [NSExpression expressionWithFormat:@"CAST(token, \"NSString\")"];
 <% } -%>
diff --git a/platform/darwin/test/MGLSymbolStyleLayerTests.mm b/platform/darwin/test/MGLSymbolStyleLayerTests.mm
index f02c5d496e..2f4206a96b 100644
--- a/platform/darwin/test/MGLSymbolStyleLayerTests.mm
+++ b/platform/darwin/test/MGLSymbolStyleLayerTests.mm
@@ -3,6 +3,7 @@
 
 #import "MGLStyleLayerTests.h"
 #import "../../darwin/src/NSDate+MGLAdditions.h"
+#include "../../darwin/src/MGLAttributedExpression.h"
 
 #import "MGLStyleLayer_Private.h"
 
@@ -1104,7 +1105,9 @@
         XCTAssertEqualObjects(layer.text, constantExpression,
                               @"text should round-trip constant value expressions.");
 
-        constantExpression = [NSExpression expressionWithFormat:@"MGL_FUNCTION('format', 'Text Field', %@)", @{}];
+        MGLAttributedExpression *attributedConstantExpression = [[MGLAttributedExpression alloc] initWithExpression:[NSExpression expressionWithFormat:@"'Text Field'"]
+                                                                                                 attributes:@{}];
+        constantExpression = [NSExpression mgl_expressionForAttributedExpressions:@[[NSExpression expressionForConstantValue:attributedConstantExpression]]];
         NSExpression *functionExpression = [NSExpression expressionWithFormat:@"mgl_step:from:stops:($zoomLevel, %@, %@)", constantExpression, @{@18: constantExpression}];
         layer.text = functionExpression;
 
@@ -1140,7 +1143,9 @@
         XCTAssertEqual(rawLayer->getTextField(), propertyValue,
                        @"Setting text to a constant string with tokens should convert to an expression.");
 
-        NSExpression* tokenExpression = [NSExpression expressionWithFormat:@"MGL_FUNCTION('format', CAST(token, 'NSString'), %@)", @{}];
+        MGLAttributedExpression *tokenAttibutedExpression = [[MGLAttributedExpression alloc] initWithExpression:[NSExpression expressionWithFormat:@"CAST(token, 'NSString')"]
+                                                                                                     attributes:@{}];
+        NSExpression* tokenExpression = [NSExpression mgl_expressionForAttributedExpressions:@[[NSExpression expressionForConstantValue:tokenAttibutedExpression]]];
         XCTAssertEqualObjects(layer.text, tokenExpression,
                               @"Setting text to a constant string with tokens should convert to an expression.");
     }