[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.

1 files changed, 59 insertions, 0 deletions

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