feat(scalars): distinct input/output codegen types

.changeset/input-output-codegen-types.md

@@ -0,0 +1,22 @@
+---
+'graphql-scalars': major
+---
+
+Emit distinct input/output codegen types for scalars whose parsed and returned types differ
+
+Scalars whose parsed **input** type is narrower than the accepted resolver-return **output** type
+now declare `codegenScalarType` as `{ input, output }`, so graphql-code-generator emits the two
+positions separately instead of collapsing them into one union:
+
+- `DateTime` / `Date` / `Time` / `Timestamp` — `input` is `Date`; `output` accepts a `Date` or an
+  ISO string (plus a unix `number` for `DateTime`/`Timestamp`)
+- `Byte` — `input` is `Buffer`; `output` accepts `Buffer | string`
+- `URL` — `input` is `URL`; `output` accepts `URL | string`
+- `BigInt` — `input` is `bigint | number`; `output` accepts `bigint | number | string`
+- `Port` / `Latitude` / `Longitude` — `input` is `number`; `output` accepts `string | number`
+
+(`DateTimeISO` and `Long` inherit their base configs.)
+
+Requires a version of `@graphql-codegen/typescript` whose `visitor-plugin-common` understands the
+object form of `codegenScalarType` (graphql-code-generator#10893). Older versions read the extension
+as a single string and will not handle the object form.

.changeset/tighten-scalar-codegen-types.md

@@ -0,0 +1,19 @@
+---
+'graphql-scalars': minor
+---
+
+Tighten scalar TypeScript and codegen types (#2554)
+
+Every scalar now declares precise `GraphQLScalarType<TParsed, TSerialized>` generics, and
+`codegenScalarType` consistently carries the resolver-return (output) type, so generated resolver
+types reflect what each scalar actually parses and accepts:
+
+- Enum scalars (CountryCode, Currency, CountryName) emit a string-literal union instead of `string`.
+- USCurrency emits `number` — resolvers both return and receive cents as a number — instead of
+  `string`.
+- DateTime and BigInt widen to cover every value `serialize` accepts.
+- Timestamp's jsonSchema type is corrected to `integer` to match its numeric wire value.
+
+These are type-level changes only, with no change to runtime behavior. Consumers relying on the
+previously looser types may see new — and correct — compile errors where a value was typed too
+broadly before.

src/scalars/BigInt.ts

@@ -101,7 +101,7 @@ export const GraphQLBigIntConfig: GraphQLScalarTypeConfig<
     return bigint;
   },
   extensions: {
-    codegenScalarType: 'bigint',
+    codegenScalarType: { input: 'bigint | number', output: 'bigint | number | string' },
     jsonSchema: {
       type: 'integer',
       format: 'int64',

src/scalars/Byte.ts

@@ -79,34 +79,33 @@ function parseObject(ast: ObjectValueNode) {
   });
 }
 
-export const GraphQLByteConfig: GraphQLScalarTypeConfig<Buffer | string | BufferJson, Buffer> =
-  /*#__PURE__*/ {
-    name: 'Byte',
-    description: 'The `Byte` scalar type represents byte value as a Buffer',
-    serialize: validate,
-    parseValue: validate,
-    parseLiteral(ast: ASTNode) {
-      switch (ast.kind) {
-        case Kind.STRING:
-          return validate(ast.value, ast);
-        case Kind.OBJECT:
-          return parseObject(ast);
-        default:
-          throw createGraphQLError(
-            `Can only parse base64 or hex encoded strings as Byte, but got a: ${ast.kind}`,
-            {
-              nodes: [ast],
-            },
-          );
-      }
-    },
-    extensions: {
-      codegenScalarType: 'Buffer | string',
-      jsonSchema: {
-        type: 'string',
-        format: 'byte',
-      },
+export const GraphQLByteConfig: GraphQLScalarTypeConfig<Buffer, Buffer> = /*#__PURE__*/ {
+  name: 'Byte',
+  description: 'The `Byte` scalar type represents byte value as a Buffer',
+  serialize: validate,
+  parseValue: validate,
+  parseLiteral(ast: ASTNode) {
+    switch (ast.kind) {
+      case Kind.STRING:
+        return validate(ast.value, ast);
+      case Kind.OBJECT:
+        return parseObject(ast);
+      default:
+        throw createGraphQLError(
+          `Can only parse base64 or hex encoded strings as Byte, but got a: ${ast.kind}`,
+          {
+            nodes: [ast],
+          },
+        );
+    }
+  },
+  extensions: {
+    codegenScalarType: { input: 'Buffer', output: 'Buffer | string' },
+    jsonSchema: {
+      type: 'string',
+      format: 'byte',
     },
-  };
+  },
+};
 
 export const GraphQLByte = /*#__PURE__*/ new GraphQLScalarType(GraphQLByteConfig);