fix up response headers (#788)

* fix up response headers

* stops defaulting to application/json. this was something awful, go stdlib has
a func to detect content type. sadly, it doesn't contain json, but we can do a
pretty good job by checking for an opening '{'... there are other fish in the
sea, and now we handle them nicely instead of saying it's a json [when it's
not]. a test confirms this, there should be no breakage for any routes
returning a json blob that were relying on us defaulting to this format
(granted that they start with a '{').
* buffers output now to a buffer for all protocol types (default is no longer
left out in the cold). use a little response writer so that we can still let
users write headers from their functions. this is useful for content type
detection instead of having to do it in multiple places.
* plumbs the little content type bit into fn-test-util just so we can test it,
we don't want to put this in the fdk since it's redundant.

I am totally in favor of getting rid of content type from the top level json
blurb. it's redundant, at best, and can have confusing behaviors if a user
uses both the headers and the content_type field (we override with the latter,
now). it's client protocol specific to http to a certain degree, other
protocols may use this concept but have their own way to set it (like http
does in headers..). I realize that it mostly exists because it's somewhat gross
to have to index a list from the headers in certain languages more than
others, but with the ^ behavior, is it really worth it?

closes #782

* reset idle timeouts back

* move json prefix to stack / next to use

images/fn-test-utils/fn-test-utils.go

@@ -29,6 +29,9 @@ type AppRequest struct {
 	ResponseCode int `json:"responseCode,omitempty"`
 	// if specified, this is our response content-type
 	ResponseContentType string `json:"responseContentType,omitempty"`
+	// if specified, this is our response content-type.
+	// jason doesn't sit with the other kids at school.
+	JasonContentType string `json:"jasonContentType,omitempty"`
 	// if specified, this is echoed back to client
 	EchoContent string `json:"echoContent,omitempty"`
 	// verbose mode
@@ -85,22 +88,29 @@ func getTotalLeaks() int {
 
 func AppHandler(ctx context.Context, in io.Reader, out io.Writer) {
 	req, resp := processRequest(ctx, in)
-	finalizeRequest(out, req, resp)
+	var outto fdkresponse
+	outto.Writer = out
+	finalizeRequest(&outto, req, resp)
 }
 
-func finalizeRequest(out io.Writer, req *AppRequest, resp *AppResponse) {
+func finalizeRequest(out *fdkresponse, req *AppRequest, resp *AppResponse) {
 	// custom response code
 	if req.ResponseCode != 0 {
-		fdk.WriteStatus(out, req.ResponseCode)
+		out.Status = req.ResponseCode
 	} else {
-		fdk.WriteStatus(out, 200)
+		out.Status = 200
 	}
 
 	// custom content type
 	if req.ResponseContentType != "" {
-		fdk.SetHeader(out, "Content-Type", req.ResponseContentType)
-	} else {
-		fdk.SetHeader(out, "Content-Type", "application/json")
+		out.Header.Set("Content-Type", req.ResponseContentType)
+	}
+	// NOTE: don't add 'application/json' explicitly here as an else,
+	// we will test that go's auto-detection logic does not fade since
+	// some people are relying on it now
+
+	if req.JasonContentType != "" {
+		out.JasonContentType = req.JasonContentType
 	}
 
 	json.NewEncoder(out).Encode(resp)
@@ -236,11 +246,10 @@ func testDoJSON(ctx context.Context, in io.Reader, out io.Writer) {
 func testDoJSONOnce(ctx context.Context, in io.Reader, out io.Writer, buf *bytes.Buffer, hdr http.Header) error {
 	buf.Reset()
 	fdkutils.ResetHeaders(hdr)
-	resp := fdkutils.Response{
-		Writer: buf,
-		Status: 200,
-		Header: hdr,
-	}
+	var resp fdkresponse
+	resp.Writer = buf
+	resp.Status = 200
+	resp.Header = hdr
 
 	responseSize := 0
 
@@ -268,7 +277,7 @@ func testDoJSONOnce(ctx context.Context, in io.Reader, out io.Writer, buf *bytes
 		responseSize = appReq.ResponseSize
 	}
 
-	jsonResponse := fdkutils.GetJSONResp(buf, &resp, &jsonRequest)
+	jsonResponse := getJSONResp(buf, &resp, &jsonRequest)
 
 	if responseSize > 0 {
 		b, err := json.Marshal(jsonResponse)
@@ -287,14 +296,33 @@ func testDoJSONOnce(ctx context.Context, in io.Reader, out io.Writer, buf *bytes
 	return nil
 }
 
+// since we need to test little jason's content type since he's special. but we
+// don't want to add redundant and confusing fields to the fdk...
+type fdkresponse struct {
+	fdkutils.Response
+
+	JasonContentType string // dumb
+}
+
+// copy of fdk.GetJSONResp but with sugar for stupid jason's little fields
+func getJSONResp(buf *bytes.Buffer, fnResp *fdkresponse, req *fdkutils.JsonIn) *fdkutils.JsonOut {
+	return &fdkutils.JsonOut{
+		Body:        buf.String(),
+		ContentType: fnResp.JasonContentType,
+		Protocol: fdkutils.CallResponseHTTP{
+			StatusCode: fnResp.Status,
+			Headers:    fnResp.Header,
+		},
+	}
+}
+
 func testDoHTTPOnce(ctx context.Context, in io.Reader, out io.Writer, buf *bytes.Buffer, hdr http.Header) error {
 	buf.Reset()
 	fdkutils.ResetHeaders(hdr)
-	resp := fdkutils.Response{
-		Writer: buf,
-		Status: 200,
-		Header: hdr,
-	}
+	var resp fdkresponse
+	resp.Writer = buf
+	resp.Status = 200
+	resp.Header = hdr
 
 	responseSize := 0
 
@@ -323,7 +351,7 @@ func testDoHTTPOnce(ctx context.Context, in io.Reader, out io.Writer, buf *bytes
 		responseSize = appReq.ResponseSize
 	}
 
-	hResp := fdkutils.GetHTTPResp(buf, &resp, req)
+	hResp := fdkutils.GetHTTPResp(buf, &resp.Response, req)
 
 	if responseSize > 0 {