kataras/iris · error

no trailing path parameter found

Error message

no trailing path parameter found

What it means

This error is raised by parsePathParam in the MVC controller method-to-route parser when the path template uses a wildcard '{param:string ...}' marker but no trailing parameter type was actually registered before it. In practice it means the method signature/path combination implies a trailing wildcard parameter that does not exist.

Source

Thrown at mvc/controller_method_parser.go:245

		// By found but input arguments are not there, so act like /by path without restricts.
		path = addPathWord(path, w)
		return path, funcArgPos, nil
	}

	var (
		paramKey  = genParamKey(funcArgPos) // argfirst, argsecond...
		m         = p.macros.GetMaster()    // default (String by-default)
		trailings = p.macros.GetTrailings()
	)

	// string, int...
	goType := typ.In(funcArgPos).Kind()
	nextWord := p.lexer.peekNext()

	if nextWord == tokenWildcard {
		p.lexer.skip() // skip the Wildcard word.
		if len(trailings) == 0 {
			return "", 0, errors.New("no trailing path parameter found")
		}
		m = trailings[0]
	} else {
		// validMacros := p.macros.LookupForGoType(goType)

		// instead of mapping with a reflect.Kind which has its limitation,
		// we map the param types with a go type as a string,
		// so custom structs such as "user" can be mapped to a macro with indent || alias == "user".
		m = p.macros.Get(strings.ToLower(goType.String()))

		if m == nil {
			if typ.NumIn() > funcArgPos {
				// has more input arguments but we are not in the correct
				// index now, maybe the first argument was an `iris/context.Context`
				// so retry with the "funcArgPos" incremented.
				//
				// the "funcArgPos" will be updated to the caller as well
				// because we return it among the path and the error.

View on GitHub (pinned to 7bedaf55a0)

Solutions

1. Remove the stray wildcard token from the controller method's path template.
2. Ensure the method has a trailing string parameter matching the wildcard, e.g. func (c *Controller) Get(path string).
3. Register the route with the standard router (app.Handle) instead of MVC if exotic wildcard syntax is needed.

Example fix

// before
func (c *FileController) GetBy(path string, rest string) {} // path: /files/{p:string ...} with mismatched param

// after
func (c *FileController) GetByWildcard(path string) {} // single trailing param: /files/{path:string ...}

// ensure every wildcard in an MVC path has exactly one trailing string param
// /files/{path:string ...} requires: func (c *Ctl) GetBy(path string)

When it happens

Trigger: An MVC controller method is registered whose path ends with the wildcard token but whose parameter list does not define a matching trailing parameter (trailings slice is empty), so when the lexer peeks the wildcard token there is no trailing param to map.

Common situations: Hand-writing path templates with '...' or wildcard syntax on MVC controller methods; typos like '{param:string ...}' without the macro registering a trailing entry; refactoring method signatures and leaving stale wildcard syntax in the path.

Related errors

• %s: parameter type "%s" should be registered to the very end
• errors joined from param parser: strings.Join(p.errors, "\n"
• parameter is not alphabetical
• parameter is not a file
• parameter is not a valid weekday

AI-assisted analysis of kataras/iris@7bedaf55a0 (2026-08-30). Data as JSON: /api/errors/d80727b8406de352. Report an issue: GitHub.