From 66b585c16f371634ec6805b0f2fbf4a8b6037ae0 Mon Sep 17 00:00:00 2001
From: Phil Pluckthun <phil@kitten.sh>
Date: Mon, 22 Apr 2024 11:38:51 +0100
Subject: [PATCH] fix: Ensure TS excess property error can be triggered by
 `graphql.scalar` (#243)

---
 .changeset/nervous-rice-invent.md |  5 +++
 src/__tests__/api.test-d.ts       | 52 +++++++++++++++++++++++++++++++
 src/api.ts                        | 36 ++++++++++++++++-----
 src/variables.ts                  | 24 +++-----------
 4 files changed, 91 insertions(+), 26 deletions(-)
 create mode 100644 .changeset/nervous-rice-invent.md

diff --git a/.changeset/nervous-rice-invent.md b/.changeset/nervous-rice-invent.md
new file mode 100644
index 00000000..33c966ee
--- /dev/null
+++ b/.changeset/nervous-rice-invent.md
@@ -0,0 +1,5 @@
+---
+"gql.tada": patch
+---
+
+Ensure that `graphql.scalar()` accepts value arguments as-is, so excess properties trigger an error.
diff --git a/src/__tests__/api.test-d.ts b/src/__tests__/api.test-d.ts
index e22597b6..c33bfe1f 100644
--- a/src/__tests__/api.test-d.ts
+++ b/src/__tests__/api.test-d.ts
@@ -146,6 +146,29 @@ describe('graphql()', () => {
           };
     }>();
   });
+
+  it('should preserve object literal types for variables', () => {
+    const mutation = graphql(`
+      mutation ($input: TodoPayload!) {
+        updateTodo(input: $input) {
+          id
+        }
+      }
+    `);
+
+    expectTypeOf<VariablesOf<typeof mutation>>().toEqualTypeOf<{
+      input: {
+        title: string;
+        description: string;
+        complete?: boolean | null | undefined;
+      };
+    }>();
+
+    const vars = (input: VariablesOf<typeof mutation>) => input;
+
+    // @ts-expect-error
+    vars({ excess: true, input: { title: 'title', description: 'description' } });
+  });
 });
 
 describe('graphql() with custom scalars', () => {
@@ -310,6 +333,16 @@ describe('graphql.scalar()', () => {
     expectTypeOf<actual>().toEqualTypeOf<expected>();
   });
 
+  it('should return the type of a given input object', () => {
+    type actual = ReturnType<typeof graphql.scalar<'TodoPayload'>>;
+
+    expectTypeOf<actual>().toEqualTypeOf<{
+      complete?: boolean | undefined | null;
+      title: string;
+      description: string;
+    }>();
+  });
+
   it('should return the type of a given enum', () => {
     type actual = ReturnType<typeof graphql.scalar<'String'>>;
     expectTypeOf<actual>().toEqualTypeOf<string>();
@@ -335,6 +368,25 @@ describe('graphql.scalar()', () => {
     // @ts-expect-error
     const actual = graphql.scalar('what', null);
   });
+
+  it('should accept exact input objects', () => {
+    const actual = graphql.scalar('TodoPayload', {
+      title: 'title',
+      description: 'description',
+    });
+
+    expectTypeOf<typeof actual>().toEqualTypeOf<{
+      title: string;
+      description: string;
+    }>();
+
+    graphql.scalar('TodoPayload', {
+      title: 'title',
+      description: 'description',
+      // @ts-expect-error
+      excess: true,
+    });
+  });
 });
 
 describe('graphql.scalar() with custom scalars', () => {
diff --git a/src/api.ts b/src/api.ts
index 53706372..da2fda59 100644
--- a/src/api.ts
+++ b/src/api.ts
@@ -176,17 +176,39 @@ interface GraphQLTadaAPI<Schema extends SchemaLike, Config extends AbstractConfi
    * const myEnumValue = graphql.scalar('myEnum', 'value');
    * ```
    */
-  scalar<
-    const Name extends string,
-    const Value extends getScalarType<Name, Schema, null | undefined>,
-  >(
+  scalar<const Name extends string, Value>(
     name: Name,
-    value: Value
+    value: getScalarType<Name, Schema> extends Value
+      ? Value & getScalarType<Name, Schema>
+      : getScalarType<Name, Schema>
   ): Value;
-
+  scalar<const Name extends string, Value>(
+    name: Name,
+    value: getScalarType<Name, Schema> extends Value
+      ? never extends Value
+        ? never
+        : (Value & getScalarType<Name, Schema>) | null
+      : getScalarType<Name, Schema> | null
+  ): Value | null;
+  scalar<const Name extends string, Value>(
+    name: Name,
+    value: getScalarType<Name, Schema> extends Value
+      ? never extends Value
+        ? never
+        : (Value & getScalarType<Name, Schema>) | undefined
+      : getScalarType<Name, Schema> | undefined
+  ): Value | undefined;
+  scalar<const Name extends string, Value>(
+    name: Name,
+    value: getScalarType<Name, Schema> extends Value
+      ? never extends Value
+        ? never
+        : (Value & getScalarType<Name, Schema>) | null | undefined
+      : getScalarType<Name, Schema> | null | undefined
+  ): Value | null | undefined;
   scalar<const Name extends string>(
     name: Name,
-    value?: getScalarType<Name, Schema>
+    value: getScalarType<Name, Schema> | undefined
   ): getScalarType<Name, Schema>;
 
   /** Function to replace a GraphQL document with a persisted document.
diff --git a/src/variables.ts b/src/variables.ts
index 684c8a3d..ea5c2a87 100644
--- a/src/variables.ts
+++ b/src/variables.ts
@@ -37,8 +37,8 @@ type unwrapTypeRec<TypeRef, Introspection extends SchemaLike, IsOptional> = Type
       : null | Array<unwrapTypeRec<TypeRef['ofType'], Introspection, true>>
     : TypeRef extends { name: any }
       ? IsOptional extends false
-        ? _getScalarType<TypeRef['name'], Introspection>
-        : null | _getScalarType<TypeRef['name'], Introspection>
+        ? getScalarType<TypeRef['name'], Introspection>
+        : null | getScalarType<TypeRef['name'], Introspection>
       : unknown;
 
 type unwrapTypeRefRec<Type, Introspection extends SchemaLike, IsOptional> = Type extends {
@@ -52,8 +52,8 @@ type unwrapTypeRefRec<Type, Introspection extends SchemaLike, IsOptional> = Type
       : null | Array<unwrapTypeRefRec<Type['type'], Introspection, true>>
     : Type extends { kind: Kind.NAMED_TYPE; name: any }
       ? IsOptional extends false
-        ? _getScalarType<Type['name']['value'], Introspection>
-        : null | _getScalarType<Type['name']['value'], Introspection>
+        ? getScalarType<Type['name']['value'], Introspection>
+        : null | getScalarType<Type['name']['value'], Introspection>
       : unknown;
 
 type _getVariablesRec<
@@ -90,7 +90,7 @@ type getVariablesType<
   Introspection extends SchemaLike,
 > = _getVariablesRec<Document['definitions'][0]['variableDefinitions'], Introspection>;
 
-type _getScalarType<
+type getScalarType<
   TypeName,
   Introspection extends SchemaLike,
 > = TypeName extends keyof Introspection['types']
@@ -99,20 +99,6 @@ type _getScalarType<
     : Introspection['types'][TypeName] extends { type: any }
       ? Introspection['types'][TypeName]['type']
       : Introspection['types'][TypeName]['enumValues']
-  : unknown;
-
-type getScalarType<
-  TypeName,
-  Introspection extends SchemaLike,
-  OrType = never,
-> = TypeName extends keyof Introspection['types']
-  ? Introspection['types'][TypeName] extends { kind: 'INPUT_OBJECT'; inputFields: any }
-    ? getInputObjectTypeRec<Introspection['types'][TypeName]['inputFields'], Introspection> | OrType
-    : Introspection['types'][TypeName] extends { type: any }
-      ? Introspection['types'][TypeName]['type'] | OrType
-      : Introspection['types'][TypeName] extends { enumValues: any }
-        ? Introspection['types'][TypeName]['enumValues'] | OrType
-        : never
   : never;
 
 export type { getVariablesType, getScalarType };