fix(typescript): use bracket notation for non-identifier property names in file upload requests

generators/typescript/sdk/client-class-generator/src/request-parameter/FileUploadRequestParameter.ts

@@ -1,5 +1,5 @@
 import { ExampleEndpointCall, HttpHeader, InlinedRequestBodyProperty, QueryParameter } from "@fern-fern/ir-sdk/api";
-import { GetReferenceOpts } from "@fern-typescript/commons";
+import { GetReferenceOpts, isValidIdentifier } from "@fern-typescript/commons";
 import { GeneratedRequestWrapper, SdkContext } from "@fern-typescript/contexts";
 import { ts } from "ts-morph";
 
@@ -111,9 +111,13 @@ export class FileUploadRequestParameter extends AbstractRequestParameter {
     }
 
     private getReferenceToProperty(propertyName: string): ts.Expression {
-        return ts.factory.createPropertyAccessExpression(
-            ts.factory.createIdentifier(this.getRequestParameterName()),
-            propertyName
-        );
+        const requestIdentifier = ts.factory.createIdentifier(this.getRequestParameterName());
+        if (!isValidIdentifier(propertyName)) {
+            return ts.factory.createElementAccessExpression(
+                requestIdentifier,
+                ts.factory.createStringLiteral(propertyName)
+            );
+        }
+        return ts.factory.createPropertyAccessExpression(requestIdentifier, propertyName);
     }
 }

generators/typescript/sdk/versions.yml

@@ -1,4 +1,14 @@
 # yaml-language-server: $schema=../../../fern-versions-yml.schema.json
+- version: 3.38.4
+  changelogEntry:
+    - summary: |
+        Fix file upload request parameters to use bracket notation for property names that are not valid JavaScript identifiers (e.g., header names with hyphens like `X-Custom-Header`).
+        Previously, the generator produced invalid JavaScript like `request.X - Custom - Header` which was interpreted as subtraction operations.
+        Now it correctly generates `request["X-Custom-Header"]`.
+      type: fix
+  createdAt: "2025-12-10"
+  irVersion: 62
+
 - version: 3.38.3
   changelogEntry:
     - summary: |

generators/typescript/utils/commons/src/codegen-utils/getPropertyKey.ts

@@ -1,5 +1,13 @@
 import esutils from "esutils";
 
+/**
+ * Checks if a string is a valid JavaScript/TypeScript identifier name.
+ * This can be used to determine whether to use dot notation (obj.prop) or bracket notation (obj["prop"]).
+ */
+export function isValidIdentifier(name: string): boolean {
+    return esutils.keyword.isIdentifierNameES6(name);
+}
+
 export function getPropertyKey(key: string): string {
     // [key: string]: any; => [key: string]: any;
     if (key.startsWith("[") && key.endsWith("]")) {

generators/typescript/utils/commons/src/index.ts

@@ -9,7 +9,7 @@ export {
     getParameterNameForRootExamplePathParameter,
     getParameterNameForRootPathParameter
 } from "./codegen-utils/getParameterNameForPathParameter";
-export { getPropertyKey } from "./codegen-utils/getPropertyKey";
+export { getPropertyKey, isValidIdentifier } from "./codegen-utils/getPropertyKey";
 export { getSchemaOptions } from "./codegen-utils/getSchemaOptions";
 export { getSdkParameterPropertyName } from "./codegen-utils/getSdkParameterPropertyName";
 export { getTextOfTsKeyword } from "./codegen-utils/getTextOfTsKeyword";