HttpClient doesn' t transfer any data if `chunkedTransferEncoding = false` and `contentLength`isn't set

[escamoteur]

• Dart 2.7.0
• Flutter on Android

I needed to make an HTTP Post request without data chuncking.
On my first attempts I didn't set the contentLength because I didn't had to do it with chunked transfer so far.
The request was executed but with an empty body.
After setting the length it worked like here:

      final request = await client.postUrl(Uri.parse(endPointUrl));
      request.headers.chunkedTransferEncoding = false;
      request.headers.contentType = ContentType.json;
      request.headers.set('accept-encoding', 'gzip,deflate');
      var content = utf8.encode(asJson);
      request.contentLength = content.length;
      request.add(content = content);

      final response = await request.close();

As it took me quite some time to figure this out, I see this either as a bug, because the chunked version doesn't behave like the non chunked one without throwing any assert or exeception, or at least there should be a hint in the API docs of request.headers.chunkedTransferEncoding so that people know that they have to set a length.

[sortie]

Hi, this behavior is described in Section 4.3 of the HTTP/1.1 specification (RFC 2616):

The presence of a message-body in a request is signaled by the inclusion of a Content-Length or Transfer-Encoding header field in the request's message-headers. A message-body MUST NOT be included in a request if the specification of the request method (section 5.1.1) does not allow sending an entity-body in requests.

Based on this language, it seems sensible that Dart would not send a body in this case. You must either use a transfer encoding or set a content length.

The other part of this is what should happen one tries to send a body when no body is allowed (neither a transfer encoding nor a content length). It seems here that Dart silently ignores the attempt. It could potentially throw an exception. Alternatively some appropriate language could be added to the documentation, although we don't want to describe every aspect of the HTTP/1.1 specification.

Another case would be if the content-length was set, and too much data is attempted sent, or the sink is closed too early. What happens then?

[escamoteur]

I only wonder why this is allowed in chunked transfer? I guess an assert in case you select parameter values that don't make sense would be helpful.