dotnet/aspnetcore · error · Error

No method defined.

Error message

No method defined.

What it means

FetchHttpClient.send throws early if the HttpRequest it receives has no method field. The method (GET/POST/etc.) is required for fetch() to make a request; a falsy value indicates the request object was constructed incorrectly upstream.

Solutions

  1. Ensure every HttpRequest you construct includes a method field (e.g. "POST", "GET").
  2. If wrapping HttpClient.send, default method to "GET" before delegating.
  3. Add a unit assertion that request.method is non-empty before calling send.

Example fix

// before
await httpClient.send({ url: "https://hub/negotiate" });

// after
await httpClient.send({ method: "POST", url: "https://hub/negotiate" });
Defensive patterns

Strategy: validation

Validate before calling

function assertRequest(req: signalR.HttpRequest): void {
  if (!req.method) throw new Error("HttpRequest.method is required");
  if (!req.url) throw new Error("HttpRequest.url is required");
}
// call before httpClient.send(req)

Type guard

function isValidHttpRequest(req: unknown): req is signalR.HttpRequest {
  return typeof req === "object" && req !== null
    && typeof (req as any).method === "string" && (req as any).method.length > 0
    && typeof (req as any).url === "string" && (req as any).url.length > 0;
}

Try / catch

try { await httpClient.send(req); }
catch (e) {
  if (e instanceof Error && e.message === "No method defined.") {
    req.method = "POST";
    return httpClient.send(req);
  }
  throw e;
}

Prevention

When it happens

Trigger: Calling httpClient.send({...}) with an object missing the method property. Reached indirectly when HttpConnection or the negotiate/long-polling code builds a request from a malformed IHttpConnectionOptions, or when a user-supplied HttpClient returns a request without a method.

Common situations: Custom HttpClient wrapper that forwards a partial request. Spread/merge of options that drops the method key. Bug in user code that builds an HttpRequest literal and omits method.

Related errors

AI-assisted analysis of dotnet/aspnetcore@3600ca084e (2026-08-11). Data as JSON: /api/errors/a9648fc68eb2fec4. Report an issue: GitHub.

Appendix: source

Thrown at src/SignalR/clients/ts/signalr/src/FetchHttpClient.ts:66

            // @ts-ignore: TS doesn't know about these names
            const requireFunc = typeof __webpack_require__ === "function" ? __non_webpack_require__ : require;

            // Node needs EventListener methods on AbortController which our custom polyfill doesn't provide
            this._abortControllerType = requireFunc("abort-controller");
        } else {
            this._abortControllerType = AbortController;
        }
    }

    /** @inheritDoc */
    public async send(request: HttpRequest): Promise<HttpResponse> {
        // Check that abort was not signaled before calling send
        if (request.abortSignal && request.abortSignal.aborted) {
            throw new AbortError();
        }

        if (!request.method) {
            throw new Error("No method defined.");
        }
        if (!request.url) {
            throw new Error("No url defined.");
        }

        const abortController = new this._abortControllerType();

        let error: any;
        // Hook our abortSignal into the abort controller
        if (request.abortSignal) {
            request.abortSignal.onabort = () => {
                abortController.abort();
                error = new AbortError();
            };
        }

        // If a timeout has been passed in, setup a timeout to call abort
        // Type needs to be any to fit window.setTimeout and NodeJS.setTimeout

View on GitHub (pinned to 3600ca084e)