[ios, macos] NSPredicate expression filters. (#11587)

* [ios, macos] Add NSAndPredicateType predicate expression filter.

* [ios, macos] Add type to NSPredicate expressions.

* [ios, macos] Add Expression filter support.

* [ios, macos] Update NSPredicate expression based tests.

* [ios, macos] Refactor ExpressionFilters.

* [ios, macos] Add symmetric test to ExpressionFilters.

* [ios, macos] Update NSPredicate test to ExpressionFilters.

* [ios, macos] Re-introduce Filter tests.

* [ios, macos] Remove typed NSComparisonPredicate's comparable values.

* [ios, macos] Update style layers predicate tests.

* [ios, macos] Remove unused predicate conversion code.

* [ios, macos] Update documentation exaple's test.

* [ios, macos] Update Predicate and Expressions guide..

* [ios, macos] Remove mgl_ prefix from variable expressions.

* [ios, macos] Update predicates and expressions documentation.

* [ios, macos] Update changelogs.

5 files changed, 20 insertions, 296 deletions

diff --git a/platform/darwin/src/MGLVectorStyleLayer.h b/platform/darwin/src/MGLVectorStyleLayer.h
index b3c8fc2433..d9431215a1 100644
--- a/platform/darwin/src/MGLVectorStyleLayer.h
+++ b/platform/darwin/src/MGLVectorStyleLayer.h
@@ -47,7 +47,7 @@ MGL_EXPORT
  ```swift
  let layer = MGLLineStyleLayer(identifier: "contour", source: terrain)
  layer.sourceLayerIdentifier = "contours"
- layer.predicate = NSPredicate(format: "(index == 5 || index == 10) && ele >= 1500.0")
+ layer.predicate = NSPredicate(format: "(index == 5 || index == 10) && CAST(ele, 'NSNumber') >= 1500.0")
  mapView.style?.addLayer(layer)
  ```
  */
diff --git a/platform/darwin/src/NSComparisonPredicate+MGLAdditions.mm b/platform/darwin/src/NSComparisonPredicate+MGLAdditions.mm
index c39e987d85..380215ff32 100644
--- a/platform/darwin/src/NSComparisonPredicate+MGLAdditions.mm
+++ b/platform/darwin/src/NSComparisonPredicate+MGLAdditions.mm
@@ -1,231 +1,12 @@
 #import "NSComparisonPredicate+MGLAdditions.h"
 
+#import "MGLStyleValue_Private.h"
+
 #import "NSPredicate+MGLAdditions.h"
 #import "NSExpression+MGLPrivateAdditions.h"
 
 @implementation NSComparisonPredicate (MGLAdditions)
 
-- (mbgl::style::Filter)mgl_filter {
-    NSExpression *leftExpression = self.leftExpression;
-    NSExpression *rightExpression = self.rightExpression;
-    NSExpressionType leftType = leftExpression.expressionType;
-    NSExpressionType rightType = rightExpression.expressionType;
-    BOOL isReversed = ((leftType == NSConstantValueExpressionType || leftType == NSAggregateExpressionType)
-                       && rightType == NSKeyPathExpressionType);
-    switch (self.predicateOperatorType) {
-        case NSEqualToPredicateOperatorType: {
-            mbgl::style::EqualsFilter eqFilter;
-            eqFilter.key = self.mgl_keyPath.UTF8String;
-            eqFilter.value = self.mgl_constantValue;
-            
-            // Convert $type == to TypeEqualsFilter.
-            if (eqFilter.key == "$type") {
-                mbgl::style::TypeEqualsFilter typeEqFilter;
-                typeEqFilter.value = self.mgl_featureType;
-                return typeEqFilter;
-            }
-            
-            // Convert $id == to IdentifierEqualsFilter.
-            if (eqFilter.key == "$id") {
-                // Convert $id == nil to NotHasIdentifierFilter.
-                if (eqFilter.value.is<mbgl::NullValue>()) {
-                    return mbgl::style::NotHasIdentifierFilter();
-                }
-                
-                mbgl::style::IdentifierEqualsFilter idEqFilter;
-                idEqFilter.value = self.mgl_featureIdentifier;
-                return idEqFilter;
-            }
-
-            // Convert == nil to NotHasFilter.
-            if (eqFilter.value.is<mbgl::NullValue>()) {
-                mbgl::style::NotHasFilter notHasFilter;
-                notHasFilter.key = eqFilter.key;
-                return notHasFilter;
-            }
-
-            return eqFilter;
-        }
-        case NSNotEqualToPredicateOperatorType: {
-            mbgl::style::NotEqualsFilter neFilter;
-            neFilter.key = self.mgl_keyPath.UTF8String;
-            neFilter.value = self.mgl_constantValue;
-            
-            // Convert $type != to TypeNotEqualsFilter.
-            if (neFilter.key == "$type") {
-                mbgl::style::TypeNotEqualsFilter typeNeFilter;
-                typeNeFilter.value = self.mgl_featureType;
-                return typeNeFilter;
-            }
-            
-            // Convert $id != to IdentifierNotEqualsFilter.
-            if (neFilter.key == "$id") {
-                // Convert $id != nil to HasIdentifierFilter.
-                if (neFilter.value.is<mbgl::NullValue>()) {
-                    return mbgl::style::HasIdentifierFilter();
-                }
-                
-                mbgl::style::IdentifierNotEqualsFilter idNeFilter;
-                idNeFilter.value = self.mgl_featureIdentifier;
-                return idNeFilter;
-            }
-
-            // Convert != nil to HasFilter.
-            if (neFilter.value.is<mbgl::NullValue>()) {
-                mbgl::style::HasFilter hasFilter;
-                hasFilter.key = neFilter.key;
-                return hasFilter;
-            }
-
-            return neFilter;
-        }
-        case NSGreaterThanPredicateOperatorType: {
-            if (isReversed) {
-                mbgl::style::LessThanFilter ltFilter;
-                ltFilter.key = self.mgl_keyPath.UTF8String;
-                ltFilter.value = self.mgl_constantValue;
-                return ltFilter;
-            } else {
-                mbgl::style::GreaterThanFilter gtFilter;
-                gtFilter.key = self.mgl_keyPath.UTF8String;
-                gtFilter.value = self.mgl_constantValue;
-                return gtFilter;
-            }
-        }
-        case NSGreaterThanOrEqualToPredicateOperatorType: {
-            if (isReversed) {
-                mbgl::style::LessThanEqualsFilter lteFilter;
-                lteFilter.key = self.mgl_keyPath.UTF8String;
-                lteFilter.value = self.mgl_constantValue;
-                return lteFilter;
-            } else {
-                mbgl::style::GreaterThanEqualsFilter gteFilter;
-                gteFilter.key = self.mgl_keyPath.UTF8String;
-                gteFilter.value = self.mgl_constantValue;
-                return gteFilter;
-            }
-        }
-        case NSLessThanPredicateOperatorType: {
-            if (isReversed) {
-                mbgl::style::GreaterThanFilter gtFilter;
-                gtFilter.key = self.mgl_keyPath.UTF8String;
-                gtFilter.value = self.mgl_constantValue;
-                return gtFilter;
-            } else {
-                mbgl::style::LessThanFilter ltFilter;
-                ltFilter.key = self.mgl_keyPath.UTF8String;
-                ltFilter.value = self.mgl_constantValue;
-                return ltFilter;
-            }
-        }
-        case NSLessThanOrEqualToPredicateOperatorType: {
-            if (isReversed) {
-                mbgl::style::GreaterThanEqualsFilter gteFilter;
-                gteFilter.key = self.mgl_keyPath.UTF8String;
-                gteFilter.value = self.mgl_constantValue;
-                return gteFilter;
-            } else {
-                mbgl::style::LessThanEqualsFilter lteFilter;
-                lteFilter.key = self.mgl_keyPath.UTF8String;
-                lteFilter.value = self.mgl_constantValue;
-                return lteFilter;
-            }
-        }
-        case NSInPredicateOperatorType: {
-            if (isReversed) {
-                if (leftType == NSConstantValueExpressionType && [leftExpression.constantValue isKindOfClass:[NSString class]]) {
-                    [NSException raise:NSInvalidArgumentException
-                                format:@"CONTAINS not supported for string comparison."];
-                }
-                [NSException raise:NSInvalidArgumentException
-                            format:@"Predicate cannot compare values IN attribute."];
-            }
-            
-            // Convert $type IN to TypeInFilter.
-            if ([leftExpression.keyPath isEqualToString:@"$type"]) {
-                mbgl::style::TypeInFilter typeInFilter;
-                typeInFilter.values = rightExpression.mgl_aggregateFeatureType;
-                return typeInFilter;
-            }
-            
-            // Convert $id IN to IdentifierInFilter.
-            if ([leftExpression.keyPath isEqualToString:@"$id"]) {
-                mbgl::style::IdentifierInFilter idInFilter;
-                idInFilter.values = rightExpression.mgl_aggregateFeatureIdentifier;
-                return idInFilter;
-            }
-            
-            mbgl::style::InFilter inFilter;
-            inFilter.key = leftExpression.keyPath.UTF8String;
-            inFilter.values = rightExpression.mgl_aggregateMBGLValue;
-            return inFilter;
-        }
-        case NSContainsPredicateOperatorType: {
-            if (!isReversed) {
-                if (rightType == NSConstantValueExpressionType && [rightExpression.constantValue isKindOfClass:[NSString class]]) {
-                    [NSException raise:NSInvalidArgumentException
-                                format:@"IN not supported for string comparison."];
-                }
-                [NSException raise:NSInvalidArgumentException
-                            format:@"Predicate cannot compare attribute CONTAINS values."];
-            }
-            
-            // Convert CONTAINS $type to TypeInFilter.
-            if ([rightExpression.keyPath isEqualToString:@"$type"]) {
-                mbgl::style::TypeInFilter typeInFilter;
-                typeInFilter.values = leftExpression.mgl_aggregateFeatureType;
-                return typeInFilter;
-            }
-            
-            // Convert CONTAINS $id to IdentifierInFilter.
-            if ([rightExpression.keyPath isEqualToString:@"$id"]) {
-                mbgl::style::IdentifierInFilter idInFilter;
-                idInFilter.values = leftExpression.mgl_aggregateFeatureIdentifier;
-                return idInFilter;
-            }
-            
-            mbgl::style::InFilter inFilter;
-            inFilter.key = rightExpression.keyPath.UTF8String;
-            inFilter.values = leftExpression.mgl_aggregateMBGLValue;
-            return inFilter;
-        }
-        case NSBetweenPredicateOperatorType: {
-            if (isReversed) {
-                [NSException raise:NSInvalidArgumentException
-                            format:@"Predicate cannot compare bounds BETWEEN attribute."];
-            }
-            if (![rightExpression.constantValue isKindOfClass:[NSArray class]]) {
-                [NSException raise:NSInvalidArgumentException
-                            format:@"Right side of BETWEEN predicate must be an array."]; // not NSSet
-            }
-            auto values = rightExpression.mgl_aggregateMBGLValue;
-            if (values.size() != 2) {
-                [NSException raise:NSInvalidArgumentException
-                            format:@"Right side of BETWEEN predicate must have two items."];
-            }
-            mbgl::style::AllFilter allFilter;
-            mbgl::style::GreaterThanEqualsFilter gteFilter;
-            gteFilter.key = leftExpression.keyPath.UTF8String;
-            gteFilter.value = values[0];
-            allFilter.filters.push_back(gteFilter);
-            mbgl::style::LessThanEqualsFilter lteFilter;
-            lteFilter.key = leftExpression.keyPath.UTF8String;
-            lteFilter.value = values[1];
-            allFilter.filters.push_back(lteFilter);
-            return allFilter;
-        }
-        case NSMatchesPredicateOperatorType:
-        case NSLikePredicateOperatorType:
-        case NSBeginsWithPredicateOperatorType:
-        case NSEndsWithPredicateOperatorType:
-        case NSCustomSelectorPredicateOperatorType:
-            [NSException raise:NSInvalidArgumentException
-                        format:@"NSPredicateOperatorType:%lu is not supported.", (unsigned long)self.predicateOperatorType];
-    }
-
-    return {};
-}
-
 - (NSString *)mgl_keyPath {
     NSExpression *leftExpression = self.leftExpression;
     NSExpression *rightExpression = self.rightExpression;
diff --git a/platform/darwin/src/NSCompoundPredicate+MGLAdditions.mm b/platform/darwin/src/NSCompoundPredicate+MGLAdditions.mm
index 19568b8033..5a98b763ea 100644
--- a/platform/darwin/src/NSCompoundPredicate+MGLAdditions.mm
+++ b/platform/darwin/src/NSCompoundPredicate+MGLAdditions.mm
@@ -1,8 +1,12 @@
 #import "NSCompoundPredicate+MGLAdditions.h"
 
+#import "MGLStyleValue_Private.h"
+
 #import "NSPredicate+MGLAdditions.h"
 #import "NSExpression+MGLPrivateAdditions.h"
 
+#include <mbgl/style/conversion/property_value.hpp>
+
 @implementation NSCompoundPredicate (MGLAdditions)
 
 - (std::vector<mbgl::style::Filter>)mgl_subfilters
@@ -14,62 +18,6 @@
     return filters;
 }
 
-- (mbgl::style::Filter)mgl_filter
-{
-    switch (self.compoundPredicateType) {
-        case NSNotPredicateType: {
-            NSAssert(self.subpredicates.count <= 1, @"NOT predicate cannot have multiple subpredicates.");
-            NSPredicate *subpredicate = self.subpredicates.firstObject;
-            mbgl::style::Filter subfilter = subpredicate.mgl_filter;
-
-            // Convert NOT(!= nil) to NotHasFilter.
-            if (subfilter.is<mbgl::style::HasFilter>()) {
-                auto hasFilter = subfilter.get<mbgl::style::HasFilter>();
-                return mbgl::style::NotHasFilter { .key = hasFilter.key };
-            }
-
-            // Convert NOT(== nil) to HasFilter.
-            if (subfilter.is<mbgl::style::NotHasFilter>()) {
-                auto hasFilter = subfilter.get<mbgl::style::NotHasFilter>();
-                return mbgl::style::HasFilter { .key = hasFilter.key };
-            }
-
-            // Convert NOT(IN) or NOT(CONTAINS) to NotInFilter.
-            if (subfilter.is<mbgl::style::InFilter>()) {
-                auto inFilter = subfilter.get<mbgl::style::InFilter>();
-                mbgl::style::NotInFilter notInFilter;
-                notInFilter.key = inFilter.key;
-                notInFilter.values = inFilter.values;
-                return notInFilter;
-            }
-
-            // Convert NOT(), NOT(AND), NOT(NOT), NOT(==), etc. into NoneFilter.
-            mbgl::style::NoneFilter noneFilter;
-            if (subfilter.is<mbgl::style::AnyFilter>()) {
-                // Flatten NOT(OR).
-                noneFilter.filters = subfilter.get<mbgl::style::AnyFilter>().filters;
-            } else if (subpredicate) {
-                noneFilter.filters = { subfilter };
-            }
-            return noneFilter;
-        }
-        case NSAndPredicateType: {
-            mbgl::style::AllFilter filter;
-            filter.filters = self.mgl_subfilters;
-            return filter;
-        }
-        case NSOrPredicateType: {
-            mbgl::style::AnyFilter filter;
-            filter.filters = self.mgl_subfilters;
-            return filter;
-        }
-    }
-
-    [NSException raise:@"Compound predicate type not handled"
-                format:@""];
-    return {};
-}
-
 @end
 
 @implementation NSCompoundPredicate (MGLExpressionAdditions)
diff --git a/platform/darwin/src/NSExpression+MGLAdditions.mm b/platform/darwin/src/NSExpression+MGLAdditions.mm
index 3c42b80a13..c175868dae 100644
--- a/platform/darwin/src/NSExpression+MGLAdditions.mm
+++ b/platform/darwin/src/NSExpression+MGLAdditions.mm
@@ -562,7 +562,7 @@ NSArray *MGLSubexpressionsWithJSONObjects(NSArray *objects) {
             argumentObjects = [argumentObjects subarrayWithRange:NSMakeRange(1, argumentObjects.count - 1)];
             NSArray *subexpressions = MGLSubexpressionsWithJSONObjects(argumentObjects);
             return [NSExpression expressionForFunction:operand selectorName:@"mgl_numberWithFallbackValues:" arguments:subexpressions];
-        } else if ([op isEqualToString:@"to-string"]) {
+        } else if ([op isEqualToString:@"to-string"] || [op isEqualToString:@"string"]) {
             NSExpression *operand = [NSExpression expressionWithMGLJSONObject:argumentObjects.firstObject];
             return [NSExpression expressionWithFormat:@"CAST(%@, 'NSString')", operand];
         } else if ([op isEqualToString:@"get"]) {
diff --git a/platform/darwin/src/NSPredicate+MGLAdditions.mm b/platform/darwin/src/NSPredicate+MGLAdditions.mm
index ed48c794aa..bbd324bb63 100644
--- a/platform/darwin/src/NSPredicate+MGLAdditions.mm
+++ b/platform/darwin/src/NSPredicate+MGLAdditions.mm
@@ -3,6 +3,8 @@
 #import "MGLValueEvaluator.h"
 #import "MGLStyleValue_Private.h"
 
+#include <mbgl/style/conversion/filter.hpp>
+
 class FilterEvaluator {
 public:
 
@@ -206,25 +208,18 @@ public:
 
 - (mbgl::style::Filter)mgl_filter
 {
-    if ([self isEqual:[NSPredicate predicateWithValue:YES]])
-    {
-        return mbgl::style::AllFilter();
-    }
-
-    if ([self isEqual:[NSPredicate predicateWithValue:NO]])
-    {
-        return mbgl::style::AnyFilter();
-    }
-
-    if ([self.predicateFormat hasPrefix:@"BLOCKPREDICATE("])
-    {
+    mbgl::style::conversion::Error valueError;
+    NSArray *jsonObject = self.mgl_jsonExpressionObject;
+    auto value = mbgl::style::conversion::convert<mbgl::style::Filter>(mbgl::style::conversion::makeConvertible(jsonObject), valueError);
+    
+    if (!value) {
         [NSException raise:NSInvalidArgumentException
-                    format:@"Block-based predicates are not supported."];
+                    format:@"Invalid filter value: %@", @(valueError.message.c_str())];
+        return {};
     }
-
-    [NSException raise:NSInvalidArgumentException
-                format:@"Unrecognized predicate type."];
-    return {};
+    mbgl::style::Filter filter = std::move(*value);
+    
+    return filter;
 }
 
 + (instancetype)mgl_predicateWithFilter:(mbgl::style::Filter)filter