[ios, macos] Add lookup and feature operators. (#11528)

* [ios, macos] Add Expressions 'at' operator.

* [ios, macos] Implement 'has' operator.

* [ios, macos] Implement expressions feature operators.

* [ios, macos] Refactor expressions variable name and 'mgl_has' implementation.

* [ios, macos] Refactor expresssion variable names.

* [ios, macos] Update 'mgl_has' to support non-self operands.

3 files changed, 106 insertions, 0 deletions

diff --git a/platform/darwin/src/NSExpression+MGLAdditions.mm b/platform/darwin/src/NSExpression+MGLAdditions.mm
index 9797709b7b..a193b85caa 100644
--- a/platform/darwin/src/NSExpression+MGLAdditions.mm
+++ b/platform/darwin/src/NSExpression+MGLAdditions.mm
@@ -277,6 +277,12 @@
     return expressionObject;
 }
 
+- (id)mgl_has:(id)element {
+    [NSException raise:NSInvalidArgumentException
+                format:@"Has expressions lack underlying Objective-C implementations."];
+    return nil;
+}
+
 @end
 
 @implementation NSExpression (MGLExpressionAdditions)
@@ -287,6 +293,12 @@
     return self;
 }
 
+- (id)mgl_has:(id)element {
+    [NSException raise:NSInvalidArgumentException
+                format:@"Has expressions lack underlying Objective-C implementations."];
+    return nil;
+}
+
 @end
 
 @implementation NSExpression (MGLAdditions)
@@ -406,6 +418,16 @@ NSArray *MGLSubexpressionsWithJSONObjects(NSArray *objects) {
             NSExpression *operand = subexpressions.firstObject;
             subexpressions = [subexpressions subarrayWithRange:NSMakeRange(1, subexpressions.count - 1)];
             return [NSExpression expressionForFunction:operand selectorName:@"stringByAppendingString:" arguments:subexpressions];
+        }  else if ([op isEqualToString:@"at"]) {
+            NSArray *subexpressions = MGLSubexpressionsWithJSONObjects(argumentObjects);
+            NSExpression *index = subexpressions.firstObject;
+            NSExpression *operand = subexpressions[1];
+            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 expressionWithFormat:@"FUNCTION(%@, 'mgl_has:', %@)", operand, property];
         } else if ([op isEqualToString:@"interpolate"]) {
             NSArray *interpolationOptions = argumentObjects.firstObject;
             NSString *curveType = interpolationOptions.firstObject;
@@ -456,6 +478,12 @@ NSArray *MGLSubexpressionsWithJSONObjects(NSArray *objects) {
             return [NSExpression expressionForVariable:@"zoomLevel"];
         } else if ([op isEqualToString:@"heatmap-density"]) {
             return [NSExpression expressionForVariable:@"heatmapDensity"];
+        } else if ([op isEqualToString:@"geometry-type"]) {
+            return [NSExpression expressionForVariable:@"mgl_geometryType"];
+        } else if ([op isEqualToString:@"id"]) {
+            return [NSExpression expressionForVariable:@"mgl_featureIdentifier"];
+        }  else if ([op isEqualToString:@"properties"]) {
+            return [NSExpression expressionForVariable:@"mgl_featureProperties"];
         } else if ([op isEqualToString:@"let"]) {
             NSExpression *operand = [NSExpression mgl_expressionWithJSONObject:argumentObjects.lastObject];
             NSArray *bindingObjects = [argumentObjects subarrayWithRange:NSMakeRange(0, argumentObjects.count - 1)];
@@ -544,6 +572,15 @@ NSArray *MGLSubexpressionsWithJSONObjects(NSArray *objects) {
             if ([self.variable isEqualToString:@"zoomLevel"]) {
                 return @[@"zoom"];
             }
+            if ([self.variable isEqualToString:@"mgl_geometryType"]) {
+                return @[@"geometry-type"];
+            }
+            if ([self.variable isEqualToString:@"mgl_featureIdentifier"]) {
+                return @[@"id"];
+            }
+            if ([self.variable isEqualToString:@"mgl_featureProperties"]) {
+                return @[@"properties"];
+            }
             return @[@"var", self.variable];
         }
         
@@ -639,6 +676,8 @@ NSArray *MGLSubexpressionsWithJSONObjects(NSArray *objects) {
             } else if ([function isEqualToString:@"stringByAppendingString:"]) {
                 NSArray *arguments = self.arguments.mgl_jsonExpressionObject;
                 return [@[@"concat", self.operand.mgl_jsonExpressionObject] arrayByAddingObjectsFromArray:arguments];
+            } else if ([function isEqualToString:@"objectFrom:withIndex:"]) {
+                return @[@"at", self.arguments[1].mgl_jsonExpressionObject, self.arguments[0].mgl_jsonExpressionObject];
             } else if ([function isEqualToString:@"boolValue"]) {
                 return @[@"to-boolean", self.operand.mgl_jsonExpressionObject];
             } else if ([function isEqualToString:@"mgl_numberWithFallbackValues:"] ||
@@ -651,6 +690,12 @@ NSArray *MGLSubexpressionsWithJSONObjects(NSArray *objects) {
                 return @[@"to-string", self.operand.mgl_jsonExpressionObject];
             } else if ([function isEqualToString:@"noindex:"]) {
                 return self.arguments.firstObject.mgl_jsonExpressionObject;
+            } else if ([function isEqualToString:@"mgl_has:"]) {
+                NSMutableArray *expressionObject = [NSMutableArray arrayWithObjects:@"has", self.arguments[0].mgl_jsonExpressionObject, nil];
+                if (self.operand.expressionType != NSEvaluatedObjectExpressionType) {
+                    [expressionObject addObject:self.operand.mgl_jsonExpressionObject];
+                }
+                return expressionObject;
             } else if ([function isEqualToString:@"mgl_interpolateWithCurveType:parameters:stops:"]) {
                 if (self.arguments.count < 3) {
                     [NSException raise:NSInvalidArgumentException format:
diff --git a/platform/darwin/src/NSExpression+MGLPrivateAdditions.h b/platform/darwin/src/NSExpression+MGLPrivateAdditions.h
index b16e2625a0..f726dd3e71 100644
--- a/platform/darwin/src/NSExpression+MGLPrivateAdditions.h
+++ b/platform/darwin/src/NSExpression+MGLPrivateAdditions.h
@@ -62,6 +62,8 @@ NS_ASSUME_NONNULL_BEGIN
 
 @property (nonatomic, readonly) id mgl_jsonExpressionObject;
 
+- (id)mgl_has:(id)element;
+
 @end
 
 @interface MGLColor (MGLExpressionAdditions)
@@ -74,6 +76,8 @@ NS_ASSUME_NONNULL_BEGIN
 
 - (NSExpression *)mgl_expressionWithContext:(NSDictionary<NSString *, NSExpression *> *)context;
 
+- (id)mgl_has:(id)element;
+
 @end
 
 extern NSArray *MGLSubexpressionsWithJSONObjects(NSArray *objects);
diff --git a/platform/darwin/test/MGLExpressionTests.mm b/platform/darwin/test/MGLExpressionTests.mm
index ea5a1cd41c..d189b41cd7 100644
--- a/platform/darwin/test/MGLExpressionTests.mm
+++ b/platform/darwin/test/MGLExpressionTests.mm
@@ -171,6 +171,24 @@ using namespace std::string_literals;
         XCTAssertEqualObjects([expression expressionValueWithObject:nil context:context], @1);
     }
     {
+        NSExpression *expression = [NSExpression expressionForVariable:@"mgl_geometryType"];
+        XCTAssertEqualObjects(expression.mgl_jsonExpressionObject, @[@"geometry-type"]);
+        XCTAssertEqualObjects([NSExpression expressionWithFormat:@"$mgl_geometryType"].mgl_jsonExpressionObject, @[@"geometry-type"]);
+        XCTAssertEqualObjects([NSExpression mgl_expressionWithJSONObject:@[@"geometry-type"]], expression);
+    }
+    {
+        NSExpression *expression = [NSExpression expressionForVariable:@"mgl_featureIdentifier"];
+        XCTAssertEqualObjects(expression.mgl_jsonExpressionObject, @[@"id"]);
+        XCTAssertEqualObjects([NSExpression expressionWithFormat:@"$mgl_featureIdentifier"].mgl_jsonExpressionObject, @[@"id"]);
+        XCTAssertEqualObjects([NSExpression mgl_expressionWithJSONObject:@[@"id"]], expression);
+    }
+    {
+        NSExpression *expression = [NSExpression expressionForVariable:@"mgl_featureProperties"];
+        XCTAssertEqualObjects(expression.mgl_jsonExpressionObject, @[@"properties"]);
+        XCTAssertEqualObjects([NSExpression expressionWithFormat:@"$mgl_featureProperties"].mgl_jsonExpressionObject, @[@"properties"]);
+        XCTAssertEqualObjects([NSExpression mgl_expressionWithJSONObject:@[@"properties"]], expression);
+    }
+    {
         NSExpression *expression = [NSExpression expressionForVariable:@"loremIpsum"];
         NSArray *jsonExpression = @[@"var", @"loremIpsum"];
         XCTAssertEqualObjects(expression.mgl_jsonExpressionObject, jsonExpression);
@@ -629,4 +647,43 @@ using namespace std::string_literals;
     
 }
 
+- (void)testLookupExpressionObject {
+    {
+        NSExpression *array = [NSExpression expressionForAggregate:@[MGLConstantExpression(@9),
+                                                                         MGLConstantExpression(@8),
+                                                                         MGLConstantExpression(@7)]];
+        NSExpression *expression = [NSExpression expressionForFunction:@"objectFrom:withIndex:" arguments:@[array, MGLConstantExpression(@1)]];
+        NSArray *jsonExpression = @[@"at", @1, @[ @"literal", @[@9, @8, @7]]];
+        XCTAssertEqualObjects(expression.mgl_jsonExpressionObject, jsonExpression);
+        XCTAssertEqualObjects([NSExpression mgl_expressionWithJSONObject:jsonExpression], expression);
+    }
+    {
+        NSExpression *array = [NSExpression expressionForAggregate:@[MGLConstantExpression(@9),
+                                                                       MGLConstantExpression(@8),
+                                                                       MGLConstantExpression(@7)]];
+        NSExpression *expression = [NSExpression expressionForFunction:@"objectFrom:withIndex:" arguments:@[array, [NSExpression expressionForKeyPath:@"x"]]];
+        NSArray *jsonExpression = @[@"at", @[@"get", @"x"], @[ @"literal", @[@9, @8, @7]]];
+        XCTAssertEqualObjects(expression.mgl_jsonExpressionObject, jsonExpression);
+        XCTAssertEqualObjects([NSExpression mgl_expressionWithJSONObject:jsonExpression], expression);
+    }
+    {
+        NSExpression *expression = [NSExpression expressionWithFormat:@"FUNCTION(self, 'mgl_has:', 'x')"];
+        NSArray *jsonExpression = @[@"has", @"x"];
+        XCTAssertEqualObjects(expression.mgl_jsonExpressionObject, jsonExpression);
+        XCTAssertEqualObjects([NSExpression mgl_expressionWithJSONObject:jsonExpression], expression);
+    }
+    {
+        NSExpression *expression = [NSExpression expressionWithFormat:@"FUNCTION(%@, 'mgl_has:', 'x')", [NSExpression expressionForConstantValue:@{@"x": MGLConstantExpression(@0)}]];
+        NSArray *jsonExpression = @[@"has", @"x",  @[@"literal", @{@"x": @0}]];
+        XCTAssertEqualObjects(expression.mgl_jsonExpressionObject, jsonExpression);
+        XCTAssertEqualObjects([NSExpression mgl_expressionWithJSONObject:jsonExpression], expression);
+    }
+    {
+        NSExpression *expression = [NSExpression expressionWithFormat:@"FUNCTION($mgl_featureProperties, 'mgl_has:', 'x')"];
+        NSArray *jsonExpression = @[@"has", @"x", @[@"properties"]];
+        XCTAssertEqualObjects(expression.mgl_jsonExpressionObject, jsonExpression);
+        XCTAssertEqualObjects([NSExpression mgl_expressionWithJSONObject:jsonExpression], expression);
+    }
+}
+
 @end