fix(fmodata): tighten defect guard and header merge

Author: eluce2

packages/fmodata/src/client/update-builder.ts

@@ -176,13 +176,15 @@ export class ExecutableUpdateBuilder<
         this.table && shouldUseIds ? transformFieldNamesToIds(validatedData, this.table) : validatedData;
 
       // Step 3: Make PATCH request via DI
+      const requestHeaders = new Headers(callerHeaders);
+      for (const [key, value] of Object.entries(headers)) {
+        requestHeaders.set(key, value);
+      }
+
       const response = yield* requestFromService(url, {
         ...requestOptions,
         method: "PATCH",
-        headers: {
-          ...(callerHeaders || {}),
-          ...headers,
-        },
+        headers: requestHeaders,
         body: JSON.stringify(transformedData),
       });
 

packages/fmodata/src/effect.ts

@@ -11,7 +11,7 @@
 import type { FFetchOptions } from "@fetchkit/ffetch";
 import { Effect, Schedule } from "effect";
 import type { FMODataErrorType } from "./errors";
-import { BuilderInvariantError, isTransientError } from "./errors";
+import { BuilderInvariantError, isFMODataError, isTransientError } from "./errors";
 import type {
   FMODataLayer,
   HttpClient as HttpClientService,
@@ -63,10 +63,7 @@ export function runAsResult<T>(effect: Effect.Effect<T, FMODataErrorType>): Prom
     ),
   ).catch((defect) => ({
     data: undefined,
-    error:
-      defect instanceof Error
-        ? (defect as FMODataErrorType)
-        : (new BuilderInvariantError("runAsResult", String(defect)) as FMODataErrorType),
+    error: isFMODataError(defect) ? defect : new BuilderInvariantError("runAsResult", String(defect)),
   }));
 }