errors and validation formal definitions

Author: twof

spec/Section 5 -- Validation.md

@@ -426,6 +426,7 @@ FieldsInSetCanMerge(set):
 
 SameResponseShape(fieldA, fieldB):
 
+<<<<<<< HEAD
 - Let {typeA} be the return type of {fieldA}.
 - Let {typeB} be the return type of {fieldB}.
 - If {typeA} or {typeB} is Non-Null.
@@ -448,6 +449,34 @@ SameResponseShape(fieldA, fieldB):
 - Given each pair of members {subfieldA} and {subfieldB} in {fieldsForName}:
   - If {SameResponseShape(subfieldA, subfieldB)} is false, return false.
 - Return true.
+=======
+  * Let {typeA} be the return type of {fieldA}.
+  * Let {typeB} be the return type of {fieldB}.
+  * Let {fieldARequiredStatus} be the required status of {fieldA}
+  * Let {fieldBRequiredStatus} be the required status of {fieldB}
+  * Let {typeA} be the result of {ModifiedOutputType(typeA, fieldARequiredStatus)}
+  * Let {typeB} be the result of {ModifiedOutputType(typeB, fieldBRequiredStatus)}
+  * If {typeA} or {typeB} is Non-Null.
+    * If {typeA} or {typeB} is nullable, return false.
+    * Let {typeA} be the nullable type of {typeA}
+    * Let {typeB} be the nullable type of {typeB}
+  * If {typeA} or {typeB} is List.
+    * If {typeA} or {typeB} is not List, return false.
+    * Let {typeA} be the item type of {typeA}
+    * Let {typeB} be the item type of {typeB}
+    * Repeat from step 3.
+  * If {typeA} or {typeB} is Scalar or Enum.
+    * If {typeA} and {typeB} are the same type return true, otherwise return
+      false.
+  * Assert: {typeA} and {typeB} are both composite types.
+  * Let {mergedSet} be the result of adding the selection set of {fieldA} and
+    the selection set of {fieldB}.
+  * Let {fieldsForName} be the set of selections with a given response name in
+    {mergedSet} including visiting fragments and inline fragments.
+  * Given each pair of members {subfieldA} and {subfieldB} in {fieldsForName}:
+    * If {SameResponseShape(subfieldA, subfieldB)} is false, return false.
+  * Return true.
+>>>>>>> 9906241 (errors and validation formal definitions)
 
 **Explanatory Text**
 

spec/Section 6 -- Execution.md

@@ -797,9 +797,9 @@ field returned {null}, and the error must be added to the {"errors"} list in the
 response.
 
 If the result of resolving a field is {null} (either because the function to
-resolve the field returned {null} or because a field error was raised), and that
-field is of a `Non-Null` type, then a field error is raised. The error must be
-added to the {"errors"} list in the response.
+resolve the field returned {null} or because a field error was raised), and 
+the {ModifiedOutputType} of that field is of a `Non-Null` type, then a field 
+error is raised. The error must be added to the {"errors"} list in the response.
 
 If the field returns {null} because of a field error which has already been
 added to the {"errors"} list in the response, the {"errors"} list must not be
@@ -808,8 +808,8 @@ field.
 
 Since `Non-Null` type fields cannot be {null}, field errors are propagated to be
 handled by the parent field. If the parent field may be {null} then it resolves
-to {null}, otherwise if it is a `Non-Null` type, the field error is further
-propagated to its parent field.
+to {null}, otherwise if its {ModifiedOutputType} is a `Non-Null` type, the field 
+error is further propagated to its parent field.
 
 If a `List` type wraps a `Non-Null` type, and one of the elements of that list
 resolves to {null}, then the entire list must resolve to {null}. If the `List`