Multiple cache-control headers are not handled

[tjarvstrand]

Describe the bug
While debugging some code I came across a situation where the server returned a response with multiple cache-control header values. This is valid according to RFC2616 but it will currently cause stash_dio to throw an exception ('"cache-control" header has more than one value, please use Headers[name]')

To Reproduce
Make a request to an endpoint returning several cache-control header values

Expected behavior
The values are concatenated, interspersed with commas

Version
Flutter 2.2.0 • channel stable • https://github.com/flutter/flutter.git
Framework • revision b22742018b (5 weeks ago) • 2021-05-14 19:12:57 -0700
Engine • revision a9d88a4d18
Tools • Dart 2.13.0

Additional context
Relevant section of RFC2616
Stack overflow question

[tjarvstrand]

This interceptor seems to function as a workaround:

static final _cacheControlWrapper = InterceptorsWrapper(
    onResponse: (response, handler) {
      final cacheControl = response.headers["cache-control"];
      if (cacheControl != null && cacheControl.length > 1) {
        response.headers.set("cache-control", cacheControl.join(","));
      }
      handler.next(response);
    },
  );

[ivoleitao]

Thanks for the report @tjarvstrand I will take a look at this during the weekend

[ivoleitao]

Fixed, it was easy to simulate although your complete description helped a lot. I've added a unit test for this and actually used a similar solution as the one you employed on the workaround as per RFC spec two separate cache-control headers are the same as one with the values separated by commas. It's now available on the latest version of stash_dio ^3.0.2

[tjarvstrand]

Great! Thanks!