Install aftermarket expression functions

platform/darwin/docs/guides/For Style Authors.md.ejs

@@ -343,7 +343,7 @@ In style specification | Method, function, or predicate type | Format string syn
 `properties`           | |`$mgl_featureProperties`
 `at`                   | `objectFrom:withIndex:` | `array[n]`
 `get`                  | `+[NSExpression expressionForKeyPath:]` | Key path
-`has`                  | `mgl_hasProperty:properties:` |
+`has`                  | `mgl_does:have:` | `mgl_does:have:(self, 'key')`
 `length`               | `count:` | `count({1, 2, 2, 3, 4, 7, 9})`
 `!`                    | `NSNotPredicateType` | `NOT (p0 OR … OR pn)`
 `!=`                   | `NSNotEqualToPredicateOperatorType` | `key != value`

platform/darwin/docs/guides/Predicates and Expressions.md

@@ -192,8 +192,9 @@ string syntax:
 
 Initializer parameter | Format string syntax | Description
 ----------------------|----------------------|------------
+`mgl_does:have:` | `mgl_does:have:(SELF, 'key')` or `mgl_does:have:(%@, 'key')` | Returns a Boolean value indicating whether the dictionary has a value for the key or whether the evaluated object (`SELF`) has a value for the feature attribute. Compared to the `mgl_has:` custom function, that function’s target is instead passed in as the first argument to this function. Both functions are equivalent to the syntax `key != NIL` or `%@[key] != NIL` but can be used outside of a predicate.
 `mgl_interpolate:withCurveType:parameters:stops:` | `mgl_interpolate:withCurveType:parameters:stops:(x, 'linear', nil, %@)` | Produces continuous, smooth results by interpolating between pairs of input and output values (“stops”). Compared to the `mgl_interpolateWithCurveType:parameters:stops:` custom function, the input expression (that function’s target) is instead passed in as the first argument to this function.
-`mgl_step:from:stops:` | `mgl_step:from:stops:(x, 11, %@)` |Produces discrete, stepped results by evaluating a piecewise-constant function defined by pairs of input and output values ("stops"). Compared to the `mgl_stepWithMinimum:stops:` custom function, the input expression (that function’s target) is instead passed in as the first argument to this function.
+`mgl_step:from:stops:` | `mgl_step:from:stops:(x, 11, %@)` | Produces discrete, stepped results by evaluating a piecewise-constant function defined by pairs of input and output values ("stops"). Compared to the `mgl_stepWithMinimum:stops:` custom function, the input expression (that function’s target) is instead passed in as the first argument to this function.
 `mgl_join:` | `mgl_join({'Old', 'MacDonald'})` | Returns the result of concatenating together all the elements of an array in order. Compared to the `stringByAppendingString:` custom function, this function takes only one argument, which is an aggregate expression containing the strings to concatenate.
 `mgl_coalesce:` | `mgl_coalesce({x, y, z})` | Returns the first non-`nil` value from an array of expressions.
 `MGL_LET` | `MGL_LET('age', uppercase('old'), 'name', uppercase('MacDonald'), mgl_join({$age, $name}))` | Any number of variable names interspersed with their assigned `NSExpression` values, followed by an `NSExpression` that may contain references to those variables. Compared to the `mgl_expressionWithContext:` custom function, this function takes the variable names and values inline before the expression that contains references to those variables.
@@ -221,6 +222,17 @@ The following custom functions are also available with the
       empty string, 0, `FALSE`, `NIL`, or NaN, otherwise `TRUE`.
    </td>
 </tr>
+<tr>
+   <td><code>mgl_has:</code></td>
+   <td>
+      An `NSExpression` that evaluates to an <code>NSDictionary</code> or the evaluated object (<code>SELF</code>).
+   </td>
+   <td>
+      An `NSExpression` that evaluates to an <code>NSString</code> representing the key to look up in the dictionary or the feature attribute to look up in the evaluated object (see <code>MGLFeature.attributes</code>).
+   </td>
+   <td>
+      `true` if the dictionary has a value for the key or if the evaluated object has a value for the feature attribute.
+   </td>
 <tr>
    <td><code>mgl_expressionWithContext:</code></td>
    <td>

platform/darwin/src/NSExpression+MGLAdditions.mm

@@ -61,7 +61,7 @@ + (void)installFunctions {
     INSTALL_METHOD(mgl_interpolate:withCurveType:parameters:stops:);
     INSTALL_METHOD(mgl_step:from:stops:);
     INSTALL_METHOD(mgl_coalesce:);
-    INSTALL_METHOD(mgl_hasProperty:properties:);
+    INSTALL_METHOD(mgl_does:have:);
 
     // Install functions that resemble control structures, taking arbitrary
     // numbers of arguments. Vararg aftermarket functions need to be declared
@@ -111,12 +111,11 @@ - (id)mgl_coalesce:(NSArray<NSExpression *> *)elements {
 }
 
 /**
- A placeholder for a method that evaluates has expression.
+ Returns a Boolean value indicating whether the object has a value for the given
+ key.
  */
-- (id)mgl_hasProperty:(id)element properties:(id)properties {
-    [NSException raise:NSInvalidArgumentException
-                format:@"Has expressions lack underlying Objective-C implementations."];
-    return nil;
+- (BOOL)mgl_does:(id)object have:(NSString *)key {
+    return [object valueForKey:key] != nil;
 }
 
 /**
@@ -594,10 +593,9 @@ + (instancetype)mgl_expressionWithJSONObject:(id)object {
             return [NSExpression expressionForFunction:@"objectFrom:withIndex:" arguments:@[operand, index]];
         } else if ([op isEqualToString:@"has"]) {
             NSArray *subexpressions = MGLSubexpressionsWithJSONObjects(argumentObjects);
-            NSExpression *operand = argumentObjects.count > 1 ? subexpressions[1] : [NSExpression expressionWithFormat:@"self"];
-            NSExpression *property = subexpressions.firstObject;
-
-            return [NSExpression expressionForFunction:@"mgl_hasProperty:properties:" arguments:@[property, operand]];
+            NSExpression *operand = argumentObjects.count > 1 ? subexpressions[1] : [NSExpression expressionForEvaluatedObject];
+            NSExpression *key = subexpressions.firstObject;
+            return [NSExpression expressionForFunction:@"mgl_does:have:" arguments:@[operand, key]];
         } else if ([op isEqualToString:@"interpolate"]) {
             NSArray *interpolationOptions = argumentObjects.firstObject;
             NSString *curveType = interpolationOptions.firstObject;
@@ -848,7 +846,7 @@ - (id)mgl_jsonExpressionObject {
                 return @[@"to-string", self.operand.mgl_jsonExpressionObject];
             } else if ([function isEqualToString:@"noindex:"]) {
                 return self.arguments.firstObject.mgl_jsonExpressionObject;
-            } else if ([function isEqualToString:@"mgl_hasProperty:properties:"] ||
+            } else if ([function isEqualToString:@"mgl_does:have:"] ||
                        [function isEqualToString:@"mgl_has:"]) {
                 return self.mgl_jsonHasExpressionObject;
             } else if ([function isEqualToString:@"mgl_interpolate:withCurveType:parameters:stops:"]
@@ -1075,16 +1073,15 @@ - (id)mgl_jsonCoalesceExpressionObject {
 }
 
 - (id)mgl_jsonHasExpressionObject {
-    BOOL isAftermarketFunction = [self.function isEqualToString:@"mgl_hasProperty:properties:"];
-    NSExpression *operand = isAftermarketFunction ? self.arguments[1] : self.operand;
+    BOOL isAftermarketFunction = [self.function isEqualToString:@"mgl_does:have:"];
+    NSExpression *operand = isAftermarketFunction ? self.arguments[0] : self.operand;
+    NSExpression *key = self.arguments[isAftermarketFunction ? 1 : 0];
 
-    NSMutableArray *expressionObject = [NSMutableArray arrayWithObjects:@"has", self.arguments[0].mgl_jsonExpressionObject, nil];
+    NSMutableArray *expressionObject = [NSMutableArray arrayWithObjects:@"has", key.mgl_jsonExpressionObject, nil];
     if (operand.expressionType != NSEvaluatedObjectExpressionType) {
         [expressionObject addObject:operand.mgl_jsonExpressionObject];
     }
     return expressionObject;
-
-    return expressionObject;
 }
 
 @end

platform/darwin/test/MGLExpressionTests.mm

@@ -720,24 +720,27 @@ - (void)testLookupExpressionObject {
         XCTAssertEqualObjects([NSExpression mgl_expressionWithJSONObject:jsonExpression], expression);
     }
     {
-        NSExpression *expression = [NSExpression expressionForFunction:@"mgl_hasProperty:properties:" arguments:@[[NSExpression expressionForConstantValue:@"x"],
-                                                                                                                 [NSExpression expressionForEvaluatedObject]]];
+        NSExpression *expression = [NSExpression expressionForFunction:@"mgl_does:have:"
+                                                             arguments:@[[NSExpression expressionForEvaluatedObject],
+                                                                         [NSExpression expressionForConstantValue:@"x"]]];
         NSExpression *compatibilityExpression = [NSExpression expressionWithFormat:@"FUNCTION(self, 'mgl_has:', 'x')"];
         NSArray *jsonExpression = @[@"has", @"x"];
         XCTAssertEqualObjects(expression.mgl_jsonExpressionObject, jsonExpression);
         XCTAssertEqualObjects(compatibilityExpression.mgl_jsonExpressionObject, jsonExpression);
         XCTAssertEqualObjects([NSExpression mgl_expressionWithJSONObject:jsonExpression], expression);
     }
     {
-        NSExpression *expression = [NSExpression expressionForFunction:@"mgl_hasProperty:properties:" arguments:@[[NSExpression expressionForConstantValue:@"x"],
-                                                                                                                  [NSExpression expressionForConstantValue:@{@"x": MGLConstantExpression(@0)}]]];
+        NSExpression *expression = [NSExpression expressionForFunction:@"mgl_does:have:"
+                                                             arguments:@[MGLConstantExpression(@{@"x": MGLConstantExpression(@0)}),
+                                                                         MGLConstantExpression(@"x")]];
         NSArray *jsonExpression = @[@"has", @"x",  @[@"literal", @{@"x": @0}]];
         XCTAssertEqualObjects(expression.mgl_jsonExpressionObject, jsonExpression);
         XCTAssertEqualObjects([NSExpression mgl_expressionWithJSONObject:jsonExpression], expression);
     }
     {
-        NSExpression *expression = [NSExpression expressionForFunction:@"mgl_hasProperty:properties:" arguments:@[[NSExpression expressionForConstantValue:@"x"],
-                                                                                                                  [NSExpression expressionForVariable:@"mgl_featureProperties"]]];
+        NSExpression *expression = [NSExpression expressionForFunction:@"mgl_does:have:"
+                                                             arguments:@[[NSExpression expressionForVariable:@"mgl_featureProperties"],
+                                                                         [NSExpression expressionForConstantValue:@"x"]]];
         NSArray *jsonExpression = @[@"has", @"x", @[@"properties"]];
         XCTAssertEqualObjects(expression.mgl_jsonExpressionObject, jsonExpression);
         XCTAssertEqualObjects([NSExpression mgl_expressionWithJSONObject:jsonExpression], expression);