moves Field Collection section earlier

Author: yaacovCR

spec/Section 6 -- Execution.md

@@ -336,6 +336,112 @@ serial):
   selection set.
 - Return an unordered map containing {data} and {errors}.
 
+### Field Collection
+
+Before execution, the selection set is converted to a grouped field set by
+calling {CollectFields()}. Each entry in the grouped field set is a list of
+fields that share a response key (the alias if defined, otherwise the field
+name). This ensures all fields with the same response key (including those in
+referenced fragments) are executed at the same time.
+
+As an example, collecting the fields of this selection set would collect two
+instances of the field `a` and one of field `b`:
+
+```graphql example
+{
+  a {
+    subfield1
+  }
+  ...ExampleFragment
+}
+
+fragment ExampleFragment on Query {
+  a {
+    subfield2
+  }
+  b
+}
+```
+
+The depth-first-search order of the field groups produced by {CollectFields()}
+is maintained through execution, ensuring that fields appear in the executed
+response in a stable and predictable order.
+
+CollectFields(objectType, selectionSet, variableValues, visitedFragments):
+
+- If {visitedFragments} is not provided, initialize it to the empty set.
+- Initialize {groupedFields} to an empty ordered map of lists.
+- For each {selection} in {selectionSet}:
+  - If {selection} provides the directive `@skip`, let {skipDirective} be that
+    directive.
+    - If {skipDirective}'s {if} argument is {true} or is a variable in
+      {variableValues} with the value {true}, continue with the next {selection}
+      in {selectionSet}.
+  - If {selection} provides the directive `@include`, let {includeDirective} be
+    that directive.
+    - If {includeDirective}'s {if} argument is not {true} and is not a variable
+      in {variableValues} with the value {true}, continue with the next
+      {selection} in {selectionSet}.
+  - If {selection} is a {Field}:
+    - Let {responseKey} be the response key of {selection} (the alias if
+      defined, otherwise the field name).
+    - Let {groupForResponseKey} be the list in {groupedFields} for
+      {responseKey}; if no such list exists, create it as an empty list.
+    - Append {selection} to the {groupForResponseKey}.
+  - If {selection} is a {FragmentSpread}:
+    - Let {fragmentSpreadName} be the name of {selection}.
+    - If {fragmentSpreadName} is in {visitedFragments}, continue with the next
+      {selection} in {selectionSet}.
+    - Add {fragmentSpreadName} to {visitedFragments}.
+    - Let {fragment} be the Fragment in the current Document whose name is
+      {fragmentSpreadName}.
+    - If no such {fragment} exists, continue with the next {selection} in
+      {selectionSet}.
+    - Let {fragmentType} be the type condition on {fragment}.
+    - If {DoesFragmentTypeApply(objectType, fragmentType)} is false, continue
+      with the next {selection} in {selectionSet}.
+    - Let {fragmentSelectionSet} be the top-level selection set of {fragment}.
+    - Let {fragmentGroupedFieldSet} be the result of calling
+      {CollectFields(objectType, fragmentSelectionSet, variableValues,
+      visitedFragments)}.
+    - For each {fragmentGroup} in {fragmentGroupedFieldSet}:
+      - Let {responseKey} be the response key shared by all fields in
+        {fragmentGroup}.
+      - Let {groupForResponseKey} be the list in {groupedFields} for
+        {responseKey}; if no such list exists, create it as an empty list.
+      - Append all items in {fragmentGroup} to {groupForResponseKey}.
+  - If {selection} is an {InlineFragment}:
+    - Let {fragmentType} be the type condition on {selection}.
+    - If {fragmentType} is not {null} and {DoesFragmentTypeApply(objectType,
+      fragmentType)} is false, continue with the next {selection} in
+      {selectionSet}.
+    - Let {fragmentSelectionSet} be the top-level selection set of {selection}.
+    - Let {fragmentGroupedFieldSet} be the result of calling
+      {CollectFields(objectType, fragmentSelectionSet, variableValues,
+      visitedFragments)}.
+    - For each {fragmentGroup} in {fragmentGroupedFieldSet}:
+      - Let {responseKey} be the response key shared by all fields in
+        {fragmentGroup}.
+      - Let {groupForResponseKey} be the list in {groupedFields} for
+        {responseKey}; if no such list exists, create it as an empty list.
+      - Append all items in {fragmentGroup} to {groupForResponseKey}.
+- Return {groupedFields}.
+
+DoesFragmentTypeApply(objectType, fragmentType):
+
+- If {fragmentType} is an Object Type:
+  - if {objectType} and {fragmentType} are the same type, return {true},
+    otherwise return {false}.
+- If {fragmentType} is an Interface Type:
+  - if {objectType} is an implementation of {fragmentType}, return {true}
+    otherwise return {false}.
+- If {fragmentType} is a Union:
+  - if {objectType} is a possible type of {fragmentType}, return {true}
+    otherwise return {false}.
+
+Note: The steps in {CollectFields()} evaluating the `@skip` and `@include`
+directives may be applied in either order since they apply commutatively.
+
 ## Executing a Grouped Field Set
 
 To execute a grouped field set, the object value being evaluated and the object
@@ -471,112 +577,6 @@ A correct executor must generate the following result for that selection set:
 }
 ```
 
-### Field Collection
-
-Before execution, the selection set is converted to a grouped field set by
-calling {CollectFields()}. Each entry in the grouped field set is a list of
-fields that share a response key (the alias if defined, otherwise the field
-name). This ensures all fields with the same response key (including those in
-referenced fragments) are executed at the same time.
-
-As an example, collecting the fields of this selection set would collect two
-instances of the field `a` and one of field `b`:
-
-```graphql example
-{
-  a {
-    subfield1
-  }
-  ...ExampleFragment
-}
-
-fragment ExampleFragment on Query {
-  a {
-    subfield2
-  }
-  b
-}
-```
-
-The depth-first-search order of the field groups produced by {CollectFields()}
-is maintained through execution, ensuring that fields appear in the executed
-response in a stable and predictable order.
-
-CollectFields(objectType, selectionSet, variableValues, visitedFragments):
-
-- If {visitedFragments} is not provided, initialize it to the empty set.
-- Initialize {groupedFields} to an empty ordered map of lists.
-- For each {selection} in {selectionSet}:
-  - If {selection} provides the directive `@skip`, let {skipDirective} be that
-    directive.
-    - If {skipDirective}'s {if} argument is {true} or is a variable in
-      {variableValues} with the value {true}, continue with the next {selection}
-      in {selectionSet}.
-  - If {selection} provides the directive `@include`, let {includeDirective} be
-    that directive.
-    - If {includeDirective}'s {if} argument is not {true} and is not a variable
-      in {variableValues} with the value {true}, continue with the next
-      {selection} in {selectionSet}.
-  - If {selection} is a {Field}:
-    - Let {responseKey} be the response key of {selection} (the alias if
-      defined, otherwise the field name).
-    - Let {groupForResponseKey} be the list in {groupedFields} for
-      {responseKey}; if no such list exists, create it as an empty list.
-    - Append {selection} to the {groupForResponseKey}.
-  - If {selection} is a {FragmentSpread}:
-    - Let {fragmentSpreadName} be the name of {selection}.
-    - If {fragmentSpreadName} is in {visitedFragments}, continue with the next
-      {selection} in {selectionSet}.
-    - Add {fragmentSpreadName} to {visitedFragments}.
-    - Let {fragment} be the Fragment in the current Document whose name is
-      {fragmentSpreadName}.
-    - If no such {fragment} exists, continue with the next {selection} in
-      {selectionSet}.
-    - Let {fragmentType} be the type condition on {fragment}.
-    - If {DoesFragmentTypeApply(objectType, fragmentType)} is false, continue
-      with the next {selection} in {selectionSet}.
-    - Let {fragmentSelectionSet} be the top-level selection set of {fragment}.
-    - Let {fragmentGroupedFieldSet} be the result of calling
-      {CollectFields(objectType, fragmentSelectionSet, variableValues,
-      visitedFragments)}.
-    - For each {fragmentGroup} in {fragmentGroupedFieldSet}:
-      - Let {responseKey} be the response key shared by all fields in
-        {fragmentGroup}.
-      - Let {groupForResponseKey} be the list in {groupedFields} for
-        {responseKey}; if no such list exists, create it as an empty list.
-      - Append all items in {fragmentGroup} to {groupForResponseKey}.
-  - If {selection} is an {InlineFragment}:
-    - Let {fragmentType} be the type condition on {selection}.
-    - If {fragmentType} is not {null} and {DoesFragmentTypeApply(objectType,
-      fragmentType)} is false, continue with the next {selection} in
-      {selectionSet}.
-    - Let {fragmentSelectionSet} be the top-level selection set of {selection}.
-    - Let {fragmentGroupedFieldSet} be the result of calling
-      {CollectFields(objectType, fragmentSelectionSet, variableValues,
-      visitedFragments)}.
-    - For each {fragmentGroup} in {fragmentGroupedFieldSet}:
-      - Let {responseKey} be the response key shared by all fields in
-        {fragmentGroup}.
-      - Let {groupForResponseKey} be the list in {groupedFields} for
-        {responseKey}; if no such list exists, create it as an empty list.
-      - Append all items in {fragmentGroup} to {groupForResponseKey}.
-- Return {groupedFields}.
-
-DoesFragmentTypeApply(objectType, fragmentType):
-
-- If {fragmentType} is an Object Type:
-  - if {objectType} and {fragmentType} are the same type, return {true},
-    otherwise return {false}.
-- If {fragmentType} is an Interface Type:
-  - if {objectType} is an implementation of {fragmentType}, return {true}
-    otherwise return {false}.
-- If {fragmentType} is a Union:
-  - if {objectType} is a possible type of {fragmentType}, return {true}
-    otherwise return {false}.
-
-Note: The steps in {CollectFields()} evaluating the `@skip` and `@include`
-directives may be applied in either order since they apply commutatively.
-
 ## Executing Fields
 
 Each field requested in the grouped field set that is defined on the selected