fix(dataproxy): no trailing slash if proxypath is empty

The JoinUrlFragments function adds a trailing slash if to the proxy url
if the proxy path is an empty string. This fix removes that trailing
slash. Fixes #3847

pkg/util/url.go

@@ -27,6 +27,11 @@ func (r *UrlQueryReader) Get(name string, def string) string {
 func JoinUrlFragments(a, b string) string {
 	aslash := strings.HasSuffix(a, "/")
 	bslash := strings.HasPrefix(b, "/")
+
+	if len(b) == 0 {
+		return a
+	}
+
 	switch {
 	case aslash && bslash:
 		return a + b[1:]

pkg/util/url_test.go

@@ -0,0 +1,46 @@
+package util
+
+import (
+	"testing"
+
+	. "github.com/smartystreets/goconvey/convey"
+)
+
+func TestUrl(t *testing.T) {
+
+	Convey("When joining two urls where right hand side is empty", t, func() {
+		result := JoinUrlFragments("http://localhost:8080", "")
+
+		So(result, ShouldEqual, "http://localhost:8080")
+	})
+
+	Convey("When joining two urls where right hand side is empty and lefthand side has a trailing slash", t, func() {
+		result := JoinUrlFragments("http://localhost:8080/", "")
+
+		So(result, ShouldEqual, "http://localhost:8080/")
+	})
+
+	Convey("When joining two urls where neither has a trailing slash", t, func() {
+		result := JoinUrlFragments("http://localhost:8080", "api")
+
+		So(result, ShouldEqual, "http://localhost:8080/api")
+	})
+
+	Convey("When joining two urls where lefthand side has a trailing slash", t, func() {
+		result := JoinUrlFragments("http://localhost:8080/", "api")
+
+		So(result, ShouldEqual, "http://localhost:8080/api")
+	})
+
+	Convey("When joining two urls where righthand side has preceding slash", t, func() {
+		result := JoinUrlFragments("http://localhost:8080", "/api")
+
+		So(result, ShouldEqual, "http://localhost:8080/api")
+	})
+
+	Convey("When joining two urls where righthand side has trailing slash", t, func() {
+		result := JoinUrlFragments("http://localhost:8080", "api/")
+
+		So(result, ShouldEqual, "http://localhost:8080/api/")
+	})
+}