null content-type breaks request handling

[fiddlerwoaroof]

If the Content-Type header isn't passed, this code passes a content-type of NIL to HTTP-BODY:PARSE, preventing the request from being processed properly.

lack/src/request.lisp

Lines 105 to 108 in 8ddb653

	(let ((parsed (http-body:parse content-type content-length raw-body)))
	(when (and (consp parsed)
	(every #'consp parsed))
	(setf body-parameters parsed)))

This could be fixed either by adding a null check or defaulting content-type to text/plain when it's not passed.

[fukamachi]

Content-Type is thought to be required in Clack as it’s written in Lack’s README.

:content-type (Required, String)

Did you get this error with some Clack handler or situation?

[fiddlerwoaroof]

I'm writing a backend for this: http://www.todobackend.com/client/index.html?http://localhost:5000 and I've discovered that their DELETE requests don't set the Content-Type header:

Host: localhost:5000.
Connection: keep-alive.
Pragma: no-cache.
Cache-Control: no-cache.
Accept: application/json, text/javascript, */*; q=0.01.
User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_13_6) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/77.0.3865.19 Safari/537.36.
Sec-Fetch-Mode: cors.
Origin: http://www.todobackend.com.
Sec-Fetch-Site: cross-site.
Referer: http://www.todobackend.com/client/index.html?http://localhost:5000.
Accept-Encoding: gzip, deflate, br.
Accept-Language: en,fr;q=0.9,de;q=0.8,es;q=0.7,zh-TW;q=0.6,zh;q=0.5,ja;q=0.4,pt;q=0.3,pl;q=0.2,fr-FR;q=0.1,en-US;q=0.1,en-GB;q=0.1.

I'm just using a fairly simple ningle app: https://github.com/fiddlerwoaroof/cl-todo-backend/blob/master/routing.lisp#L33 using the Hunchentoot handler and something isn't being setup correctly.

[fukamachi]

I think the code only runs when Content-Length or Transfer-Encoding: chunked exist. Does the todobackend.com sends those headers without Content-Type with DELETE requests?
Sorry, I couldn't try your cl-todo-backend because of a data-lens package issue.

; caught ERROR:
;   READ error during COMPILE-FILE:
;
;     Symbol "MAKE-LIST-LENS" not found in the DATA-LENS.LENSES package.
;
;       Line: 4, Column: 49, File-Position: 134
;
;       Stream: #<SB-INT:FORM-TRACKING-STREAM for "file /Users/fukamachi/Programs/etc/cl-todo-backend/lack-cors-middleware.lisp" {1001E99823}>

[fiddlerwoaroof]

Ah, yeah, the relevant changes to data-lens haven't made it up to quicklisp

[fukamachi]

This was caused because the latest Http-Body assumes content-type is a string and passes to starts-with.

fukamachi/http-body@f7230c8#diff-a12cf9db7767789dad9bcd52d001cb46L14-R16