Robust Header Check

appsTransport.go

@@ -73,8 +73,9 @@ func (t *AppsTransport) RoundTrip(req *http.Request) (*http.Response, error) {
 	}
 
 	req.Header.Set("Authorization", "Bearer "+ss)
-	req.Header.Set("Accept", acceptHeader)
+	addAcceptHeader(req)
 
 	resp, err := t.tr.RoundTrip(req)
 	return resp, err
+
 }

transport.go

@@ -5,16 +5,21 @@ import (
 	"fmt"
 	"io/ioutil"
 	"net/http"
+	"regexp"
 	"sync"
 	"time"
 )
 
 const (
 	// acceptHeader is the GitHub Integrations Preview Accept header.
-	acceptHeader = "application/vnd.github.machine-man-preview+json"
-	apiBaseURL   = "https://api.github.com"
+	acceptHeader     = "application/vnd.github.machine-man-preview+json"
+	defaultMediaType = "application/octet-stream"
+	apiBaseURL       = "https://api.github.com"
 )
 
+//Used to detect if a single asset request is being made. https://developer.github.com/v3/repos/releases/#get-a-single-release-asset
+var assetPathRegex = regexp.MustCompile("/repos/.+/.+/releases/assets/\\d+")
+
 // Transport provides a http.RoundTripper by wrapping an existing
 // http.RoundTripper and provides GitHub Apps authentication as an
 // installation.
@@ -90,7 +95,7 @@ func (t *Transport) RoundTrip(req *http.Request) (*http.Response, error) {
 	}
 
 	req.Header.Set("Authorization", "token "+token)
-	req.Header.Add("Accept", acceptHeader) // We add to "Accept" header to avoid overwriting existing req headers.
+	addAcceptHeader(req)
 	resp, err := t.tr.RoundTrip(req)
 	return resp, err
 }
@@ -134,3 +139,15 @@ func (t *Transport) refreshToken() error {
 
 	return nil
 }
+
+func addAcceptHeader(req *http.Request) {
+	//Check to see if we're making a single asset GET request
+	fmt.Println(req.URL.Path)
+	if req.Method == http.MethodGet && assetPathRegex.MatchString(req.URL.Path) {
+		if req.Header.Get("Accept") != defaultMediaType {
+			req.Header.Add("Accept", acceptHeader) // We add to "Accept" header to avoid overwriting existing req headers.
+		}
+	} else {
+		req.Header.Add("Accept", acceptHeader) // We add to "Accept" header to avoid overwriting existing req headers.
+	}
+}

transport_test.go

@@ -7,6 +7,7 @@ import (
 	"net/http"
 	"net/http/httptest"
 	"os"
+	"strings"
 	"testing"
 	"time"
 )
@@ -173,3 +174,51 @@ func TestNew_appendHeader(t *testing.T) {
 		t.Errorf("could not find %v in request's accept headers: %v", myheader, headers["Accept"])
 	}
 }
+
+func TestSingleAssetBinary_AddAcceptHeader(t *testing.T) {
+	req, err := http.NewRequest(http.MethodGet, "https://api.github.com/repos/bradleyfalzon/ghinstallation/releases/assets/1", http.NoBody)
+	if err != nil {
+		t.Fatalf("Failed to create test request: %s", err.Error())
+	}
+
+	req.Header.Set("Accept", defaultMediaType)
+
+	addAcceptHeader(req)
+
+	for headerName, headers := range req.Header {
+		if strings.ToLower(headerName) == "accept" {
+			for _, header := range headers {
+				if header == acceptHeader {
+					fmt.Printf("Header Name: %s, Header: %s", headerName, header)
+					t.Error("Set Accept header improperly for single asset call")
+				}
+			}
+		}
+	}
+}
+
+func TestNormal_AddAcceptHeader(t *testing.T) {
+	req, err := http.NewRequest(http.MethodGet, "https://api.github.com/repos", http.NoBody)
+	if err != nil {
+		t.Fatalf("Failed to create test request: %s", err.Error())
+	}
+
+	addAcceptHeader(req)
+
+	if req.Header.Get("Accept") != acceptHeader {
+		t.Error("Did not correctly set 'Accept' header")
+	}
+}
+
+func TestSingleAssetJSON_AddAcceptHeader(t *testing.T) {
+	req, err := http.NewRequest(http.MethodGet, "https://api.github.com/repos/bradleyfalzon/ghinstallation/releases/assets/1", http.NoBody)
+	if err != nil {
+		t.Fatalf("Failed to create test request: %s", err.Error())
+	}
+
+	addAcceptHeader(req)
+
+	if req.Header.Get("Accept") != acceptHeader {
+		t.Error("Did not correctly set 'Accept' header")
+	}
+}