Add basic infrastructure for layout validation

AsyncDisplayKit/Layout/ASLayoutValidation.h

@@ -0,0 +1,73 @@
+/*
+ *  Copyright (c) 2014-present, Facebook, Inc.
+ *  All rights reserved.
+ *
+ *  This source code is licensed under the BSD-style license found in the
+ *  LICENSE file in the root directory of this source tree. An additional grant
+ *  of patent rights can be found in the PATENTS file in the same directory.
+ *
+ */
+
+#import <Foundation/Foundation.h>
+
+NS_ASSUME_NONNULL_BEGIN
+
+@class ASLayout;
+
+#pragma mark - ASLayoutableValidator
+
+@protocol ASLayoutableValidator <NSObject>
+- (void)validateLayout:(ASLayout *)layout;
+@end
+
+typedef void (^ASLayoutableBlockValidatorBlock)(id layout);
+
+@interface ASLayoutableBlockValidator : NSObject<ASLayoutableValidator>
+@property (nonatomic, copy) ASLayoutableBlockValidatorBlock block;
+- (instancetype)initWithBlock:(ASLayoutableBlockValidatorBlock)block NS_DESIGNATED_INITIALIZER;
+- (instancetype)init NS_UNAVAILABLE;
+@end
+
+/*
+ * ASLayoutables that have sizeRange or layoutPosition set needs to be wrapped into a ASStaticLayoutSpec. This
+ * validator checks if sublayouts has sizeRange or layoutPosition set and is wrapped in a ASStaticLayoutSpec
+ */
+@interface ASLayoutableStaticValidator : NSObject<ASLayoutableValidator>
+
+@end
+
+/*
+ * ASLayoutables that have spacingBefore, spacingAfter, flexGrow, flexShrink, flexBasis, alignSelf, ascender or descender
+ * set needs to be wrapped into a ASStackLayout. This validator checks if sublayouts has set one of this properties and
+ * asserts if it's not wrapped in a ASStackLayout if so.
+ */
+@interface ASLayoutableStackValidator : NSObject<ASLayoutableValidator>
+
+@end
+
+@interface ASLayoutablePreferredSizeValidator : NSObject<ASLayoutableValidator>
+
+@end
+
+
+#pragma mark - ASLayoutableValidation
+
+@interface ASLayoutableValidation : NSObject
+
+/// Currently registered validators
+@property (copy, nonatomic, readonly) NSMutableArray<id<ASLayoutableValidator>> *validators;
+
+/// Start from given layout and validates each layout in the layout tree with registered validators
+- (void)validateLayout:(ASLayout *)layout;
+
+/// Register a layout validator
+- (void)registerValidator:(id<ASLayoutableValidator>)validator;
+
+/// Register a layout validator with a block. Method returns the registered ASLayoutableValidator object that can be used to store somewhere and unregister
+- (id<ASLayoutableValidator>)registerValidatorWithBlock:(ASLayoutableBlockValidatorBlock)block;
+
+/// Unregister a validtor
+- (void)unregisterValidator:(id<ASLayoutableValidator>)validator;
+@end
+
+NS_ASSUME_NONNULL_END