fix: Fix __typename fields on abstract selections not being exact (#11)

* Add failing test for __typename on abstract types * Handle __typename fields in possible fragment iterator * Add optional field handling to new __typename field * Remove getFieldsSelectionRec and reconcile code paths * Refactor getTypenameOfType * Rename utility * Fix isOptionalRec boolean result being inverted * Add changeset
0no-co · Jan 16, 2024 · 7986c54 · 7986c54
1 parent 50b43ba
commit 7986c54
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diff --git a/.changeset/mean-geckos-dream.md b/.changeset/mean-geckos-dream.md
@@ -0,0 +1,5 @@
+---
+'gql.tada': patch
+---
+
+Fix `__typename` literal string not being exact and instead a union of possible types, when the `__typename` field is put onto an abstract type’s selection set.
diff --git a/src/__tests__/selection.test-d.ts b/src/__tests__/selection.test-d.ts
@@ -301,6 +301,32 @@ test('infers unions and interfaces correctly', () => {
   expectTypeOf<expected>().toEqualTypeOf<actual>();
 });
 
+test('infers __typename on union unambiguously', () => {
+  type query = parseDocument</* GraphQL */ `
+    query {
+      test {
+        __typename
+        ... on BigTodo { wallOfText }
+      }
+    }
+  `>;
+
+  type actual = getDocumentType<query, schema>;
+  type expected = {
+    test:
+      | {
+          __typename: 'SmallTodo';
+        }
+      | {
+          __typename: 'BigTodo';
+          wallOfText: string | null;
+        }
+      | null;
+  };
+
+  expectTypeOf<expected>().toEqualTypeOf<actual>();
+});
+
 test('infers queries from GitHub introspection schema', () => {
   type schema = mapIntrospection<
     typeof import('./fixtures/githubIntrospection').githubIntrospection

diff --git a/src/selection.ts b/src/selection.ts
@@ -65,10 +65,10 @@ type isOptionalRec<Directives extends readonly unknown[] | undefined> =
   Directives extends readonly [infer Directive, ...infer Rest]
     ? Directive extends { kind: Kind.DIRECTIVE; name: any }
       ? Directive['name']['value'] extends 'include' | 'skip' | 'defer'
-        ? false
+        ? true
         : isOptionalRec<Rest>
       : isOptionalRec<Rest>
-    : true;
+    : false;
 
 type getFieldAlias<Node extends FieldNode> = Node['alias'] extends undefined
   ? Node['name']['value']
@@ -114,52 +114,17 @@ type getSpreadSubtype<
 type getTypenameOfType<Type extends ObjectLikeType> = Type extends {
   possibleTypes: any;
 }
-  ? Type['possibleTypes']
+  ? Type['name'] | Type['possibleTypes']
   : Type['name'];
 
 type getSelection<
   Selections extends readonly any[],
   Type extends ObjectLikeType,
   Introspection extends IntrospectionLikeType,
   Fragments extends { [name: string]: any },
-> = obj<
-  getFieldsSelectionRec<Selections, Type, Introspection, Fragments> &
-    getFragmentsSelection<Selections, Type, Introspection, Fragments>
->;
+> = obj<getPossibleTypesSelection<Selections, Type, Introspection, Fragments>>;
 
-type getFieldsSelectionRec<
-  Selections extends readonly unknown[],
-  Type extends ObjectLikeType,
-  Introspection extends IntrospectionLikeType,
-  Fragments extends { [name: string]: any },
-> = Selections extends readonly [infer Selection, ...infer Rest]
-  ? (Selection extends FieldNode
-      ? isOptionalRec<Selection['directives']> extends true
-        ? {
-            [Prop in getFieldAlias<Selection>]: Selection['name']['value'] extends '__typename'
-              ? getTypenameOfType<Type>
-              : unwrapType<
-                  Type['fields'][Selection['name']['value']]['type'],
-                  Selection['selectionSet'],
-                  Introspection,
-                  Fragments
-                >;
-          }
-        : {
-            [Prop in getFieldAlias<Selection>]?: Selection['name']['value'] extends '__typename'
-              ? getTypenameOfType<Type>
-              : unwrapType<
-                  Type['fields'][Selection['name']['value']]['type'],
-                  Selection['selectionSet'],
-                  Introspection,
-                  Fragments
-                >;
-          }
-      : {}) &
-      getFieldsSelectionRec<Rest, Type, Introspection, Fragments>
-  : {};
-
-type _getFragmentsSelectionRec<
+type _getPossibleTypeSelectionRec<
   Selections extends readonly unknown[],
   PossibleType extends string,
   Type extends ObjectLikeType,
@@ -169,26 +134,48 @@ type _getFragmentsSelectionRec<
   ? (Node extends FragmentSpreadNode | InlineFragmentNode
       ? getSpreadSubtype<Node, Type, Introspection, Fragments> extends infer Subtype extends
           ObjectLikeType
-        ? PossibleType extends Subtype['name'] | getTypenameOfType<Subtype>
+        ? PossibleType extends getTypenameOfType<Subtype>
           ?
-              | (isOptionalRec<Node['directives']> extends true ? never : {})
+              | (isOptionalRec<Node['directives']> extends true ? {} : never)
               | getFragmentSelection<Node, Subtype, Introspection, Fragments>
           : {}
         : Node extends FragmentSpreadNode
           ? makeUndefinedFragmentRef<Node['name']['value']>
           : {}
-      : {}) &
-      _getFragmentsSelectionRec<Rest, PossibleType, Type, Introspection, Fragments>
+      : Node extends FieldNode
+        ? isOptionalRec<Node['directives']> extends true
+          ? {
+              [Prop in getFieldAlias<Node>]?: Node['name']['value'] extends '__typename'
+                ? PossibleType
+                : unwrapType<
+                    Type['fields'][Node['name']['value']]['type'],
+                    Node['selectionSet'],
+                    Introspection,
+                    Fragments
+                  >;
+            }
+          : {
+              [Prop in getFieldAlias<Node>]: Node['name']['value'] extends '__typename'
+                ? PossibleType
+                : unwrapType<
+                    Type['fields'][Node['name']['value']]['type'],
+                    Node['selectionSet'],
+                    Introspection,
+                    Fragments
+                  >;
+            }
+        : {}) &
+      _getPossibleTypeSelectionRec<Rest, PossibleType, Type, Introspection, Fragments>
   : {};
 
-type getFragmentsSelection<
+type getPossibleTypesSelection<
   Selections extends readonly unknown[],
   Type extends ObjectLikeType,
   Introspection extends IntrospectionLikeType,
   Fragments extends { [name: string]: any },
 > = Type extends { kind: 'UNION' | 'INTERFACE'; possibleTypes: any }
   ? objValues<{
-      [PossibleType in Type['possibleTypes']]: _getFragmentsSelectionRec<
+      [PossibleType in Type['possibleTypes']]: _getPossibleTypeSelectionRec<
         Selections,
         PossibleType,
         Type,
@@ -197,7 +184,7 @@ type getFragmentsSelection<
       >;
     }>
   : Type extends { kind: 'OBJECT'; name: any }
-    ? _getFragmentsSelectionRec<Selections, Type['name'], Type, Introspection, Fragments>
+    ? _getPossibleTypeSelectionRec<Selections, Type['name'], Type, Introspection, Fragments>
     : {};
 
 type getOperationSelectionType<