seanmonstar/warp · warning

valid method

Error message

valid method

What it means

`warp::test::request().method("...")` parses the given string into an `http::Method` and panics with "valid method" if it is not a valid HTTP method token (src/test.rs:186). This is documented as a deliberate panic in the test builder: invalid method names are test-authoring bugs, not runtime conditions. The panic occurs while constructing the test request, before the filter is exercised.

Solutions

1. Use a valid uppercase method string: "GET", "POST", "PUT", "DELETE", "PATCH", "HEAD", "OPTIONS"
2. Pre-validate with `"MYMETHOD".parse::<http::Method>()` in test helpers before passing it to `.method()`
3. Trim the string and ensure it matches the HTTP token grammar (no spaces, separators, or non-ASCII)
4. For custom methods, verify the token is RFC 7230 compliant (ALPHA / DIGIT / "!#$%&'*+-.^_`|~")

Example fix

// before
warp::test::request().method("GET ").path("/health");
// after
warp::test::request().method("GET").path("/health");

fn assert_http_token(m: &str) {
    assert!(m.parse::<http::Method>().is_ok(), "'{}' is not a valid HTTP method", m);
}

fn is_valid_method(m: &str) -> bool { m.parse::<http::Method>().is_ok() }

When it happens

Trigger: Calling `.method("GET ")` (trailing space), `.method("get?")` or any string containing characters outside the HTTP token grammar; empty strings; non-ASCII method names.

Common situations: Copy-pasted method names with whitespace or quotes; typos like "GT" (that one parses fine as a custom method, but "GET;" doesn't); generating methods dynamically from data files with stray characters.

Understand the failure class

Background: "Invalid ... format", "must be in format X", "does not look like a ..." — invalid argument format errors across CLI tools and libraries — this error's family across 17 libraries.

Related errors

• test request path invalid
• illegal Method
• websocket handshake thread panicked
• polled after complete
• polled after complete

AI-assisted analysis of seanmonstar/warp@ff34d7213e (2026-09-09). Data as JSON: /api/errors/fe88fbd667eccf0d. Report an issue: GitHub.

Appendix: source

Thrown at src/test.rs:186

impl RequestBuilder {
    /// Sets the method of this builder.
    ///
    /// The default if not set is `GET`.
    ///
    /// # Example
    ///
    /// ```
    /// let req = warp::test::request()
    ///     .method("POST");
    /// ```
    ///
    /// # Panic
    ///
    /// This panics if the passed string is not able to be parsed as a valid
    /// `Method`.
    pub fn method(mut self, method: &str) -> Self {
        *self.req.method_mut() = method.parse().expect("valid method");
        self
    }

    /// Sets the request path of this builder.
    ///
    /// The default is not set is `/`.
    ///
    /// # Example
    ///
    /// ```
    /// let req = warp::test::request()
    ///     .path("/todos/33");
    /// ```
    ///
    /// # Panic
    ///
    /// This panics if the passed string is not able to be parsed as a valid
    /// `Uri`.

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