Handle JSON null when reading object/array-typed properties

JSONSchemaObject>>readUsing: and JSONSchemaArray>>readUsing: went
straight to a structural parse (parseMapKeysDo:/parseListDo:, expecting
{ or [ respectively) with no concept of null, even though any property
can legitimately be JSON null regardless of its declared type - Stripe's
responses do this constantly (address, discount, items, and most other
optional fields are null unless set). Added a shared
JSONSchema>>peekNullThenReadUsing:ifNotNull: (uses parseConstantDo:, which
does not consume the stream on a non-match, to peek for null/true/false
before committing to the structural read) and wired both readUsing:
methods through it. A literal true/false where an object/array was
expected now raises a clear JSONTypeError instead of an opaque
NeoJSONParseError ('{ expected'/'[ expected').

Found the same way as the rest of today's fixes: driving OpenApiClient
against the real Stripe spec + a live stripe-mock instance. The full
Customer and Subscription response bodies - both deeply nested, both
full of null fields - now read back correctly end to end.

Author: noha

source/JSONSchema-Core-Tests/JSONSchemaTests.class.st

@@ -57,6 +57,31 @@ JSONSchemaTests >> testSchemaReadArrayMultipleItems [
 	self assert: object foo third equals: (DateAndTime year: 2019 month: 10 day: 9 hour: 13 minute: 15 second: 8 offset: 1 hour).	
 ]
 
+{ #category : 'tests' }
+JSONSchemaTests >> testSchemaReadArrayPropertyThatIsNull [
+	"A schema saying a property is an array does not forbid the actual
+	value being JSON null - readString: must not crash trying to parse
+	null as a list."
+	| schema object |
+	schema := {
+		#foo -> (JSONSchemaArray new items: JSONSchema string).
+	} asJSONSchema.
+	object := schema readString: '{"foo":null}'.
+	self assert: object foo equals: nil
+]
+
+{ #category : 'tests' }
+JSONSchemaTests >> testSchemaReadArrayPropertyThatIsWrongType [
+	"A literal true/false where an array was expected is invalid JSON for
+	this schema and should raise a clear type error, not an obscure parser
+	error from trying to read it as a list."
+	| schema |
+	schema := {
+		#foo -> (JSONSchemaArray new items: JSONSchema string).
+	} asJSONSchema.
+	self should: [ schema readString: '{"foo":true}' ] raise: JSONTypeError
+]
+
 { #category : 'tests' }
 JSONSchemaTests >> testSchemaReadNested [
 
@@ -75,6 +100,17 @@ JSONSchemaTests >> testSchemaReadNested [
 
 ]
 
+{ #category : 'tests' }
+JSONSchemaTests >> testSchemaReadNestedObjectPropertyThatIsNull [
+	"Same as above for an object-typed property."
+	| schema object |
+	schema := {
+		#bar -> { #one -> JSONSchema string }
+	} asJSONSchema.
+	object := schema readString: '{"bar":null}'.
+	self assert: object bar equals: nil
+]
+
 { #category : 'tests' }
 JSONSchemaTests >> testSchemaWriteArray [
 

source/JSONSchema-Core/JSONSchema.class.st

@@ -164,6 +164,24 @@ JSONSchema >> neoJsonOn: jsonWriter [
 
 ]
 
+{ #category : 'private' }
+JSONSchema >> peekNullThenReadUsing: aReader ifNotNull: aBlock [
+	"Both object- and array-typed schemas hand off straight to a structural
+	parse (parseMapKeysDo:/parseListDo:), which expects { or [ and has no
+	concept of null - but any OpenAPI/JSON-Schema property can legitimately
+	be null regardless of its declared type. Peek for a null/true/false
+	literal first (parseConstantDo: does not consume the stream if there is
+	no match) before committing to the structural read."
+	| matched value |
+	matched := false.
+	value := nil.
+	aReader parseConstantDo: [ :v | matched := true. value := v ].
+	(matched and: [ value isNil ]) ifTrue: [ ^ nil ].
+	matched ifTrue: [ 
+		^ JSONTypeError signal: self class typeName, ' cannot be ', value printString ].
+	^ aBlock value
+]
+
 { #category : 'instance creation' }
 JSONSchema >> readFrom: aStream [
 	^ self readUsing: (NeoJSONReader on: aStream)

source/JSONSchema-Core/JSONSchemaArray.class.st

@@ -61,15 +61,16 @@ JSONSchemaArray >> read: aString object: object [
 
 { #category : 'private' }
 JSONSchemaArray >> readUsing: aReader [
-	| index |
-	index := 0.
-	^ Array streamContents: [:stream |
+	^ self peekNullThenReadUsing: aReader ifNotNull: [
+		| index |
+		index := 0.
+		Array streamContents: [:stream |
 			aReader parseListDo: [ 
 				stream nextPut: (items isCollection 
 					ifTrue: [ 
 						index := index + 1.
 						(items at: index) readUsing: aReader ]
-					ifFalse: [ items readUsing: aReader ])]]
+					ifFalse: [ items readUsing: aReader ])]] ]
 ]
 
 { #category : 'accessing' }

source/JSONSchema-Core/JSONSchemaObject.class.st

@@ -149,27 +149,24 @@ JSONSchemaObject >> read: string object: object [
 ]
 
 { #category : 'as yet unclassified' }
-JSONSchemaObject >> readKey: key reader: reader [
-	properties ifNotNil: [  
-		properties 
-			at: key
-			ifPresent: [ :propertySchema |
-				"schema for property is existing using it to read the value"
-				^ propertySchema readUsing: reader ] ].
-		
-	(additionalProperties isNil | (additionalProperties = true)) 
-		ifTrue: [ 
-			"if additionProperties is absent or true any additional property
-			is allowed"
-			^ reader parseValue ].
-	
-	(additionalProperties = false) 
-		ifTrue: [
-			"addtional properties are disallowed" 											
-			JSONTypeError signal: 'additional properties are not allowed' ].
-				
-	"if additionalProperty is present and not a boolean it is a
-	schema defining the type of the addtional properties"
+JSONSchemaObject >> readKey: key reader: reader [ 
+	properties ifNotNil: [  		
+		properties 			
+			at: key			
+			ifPresent: [ :propertySchema |				
+				"schema for property is existing using it to read the value"				
+				^ propertySchema readUsing: reader ] ].			
+	(additionalProperties isNil | (additionalProperties = true)) 		
+		ifTrue: [ 			
+			"if additionProperties is absent or true any additional property			
+			is allowed"			
+			^ reader parseValue ].		
+	(additionalProperties = false) 		
+		ifTrue: [			
+			"addtional properties are disallowed" 														
+			JSONTypeError signal: 'additional properties are not allowed' ].					
+	"if additionalProperty is present and not a boolean it is a	
+	schema defining the type of the addtional properties"	
 	^ additionalProperties readUsing: reader
 ]
 
@@ -194,9 +191,8 @@ JSONSchemaObject >> readString: aString [
 
 { #category : 'private' }
 JSONSchemaObject >> readUsing: reader [
-	^ self 
-		readUsing: reader
-		object: self newInstance 
+	^ self peekNullThenReadUsing: reader ifNotNull: [
+		self readUsing: reader object: self newInstance ]
 ]
 
 { #category : 'private' }