Catch invalid/missing URLs in server config JSON

url.Parse() accepts garbage like "" or "foo bar" without returning an
error. The resulting URLs don't work and cause errors later on, when
it's hard to tell where they came from. I'm working around this by
checking the parsed URL object for a non-empty Scheme component.
Added a utility function ParseURL that does this.
(See issue couchbase/sync_gateway#147)

pools.go

@@ -186,7 +186,7 @@ func (b basicAuth) GetCredentials() (string, string) {
 }
 
 func basicAuthFromURL(us string) (ah AuthHandler) {
-	u, err := url.Parse(us)
+	u, err := ParseURL(us)
 	if err != nil {
 		return
 	}
@@ -200,7 +200,7 @@ func basicAuthFromURL(us string) (ah AuthHandler) {
 // ConnectWithAuth connects to a couchbase cluster with the given
 // authentication handler.
 func ConnectWithAuth(baseU string, ah AuthHandler) (c Client, err error) {
-	c.BaseURL, err = url.Parse(baseU)
+	c.BaseURL, err = ParseURL(baseU)
 	if err != nil {
 		return
 	}

util.go

@@ -1,6 +1,10 @@
 package couchbase
 
-import "strings"
+import (
+	"fmt"
+	"net/url"
+	"strings"
+)
 
 // Return the hostname with the given suffix removed.
 func CleanupHost(h, commonSuffix string) string {
@@ -32,3 +36,14 @@ func FindCommonSuffix(input []string) string {
 	}
 	return rv
 }
+
+// Some sanity-checking around URL.Parse, which is woefully trusting of bogus URL strings
+// like "" or "foo bar".
+func ParseURL(urlStr string) (url *url.URL, err error) {
+	url, err = url.Parse(urlStr)
+	if url != nil && url.Scheme == "" {
+		url = nil
+		err = fmt.Errorf("Invalid URL <%s>", urlStr)
+	}
+	return
+}

views.go

@@ -36,7 +36,7 @@ func (b *Bucket) randomBaseURL() (*url.URL, error) {
 		return nil, errors.New("no couch rest URLs")
 	}
 	node := b.Nodes[rand.Intn(len(b.Nodes))]
-	u, err := url.Parse(node.CouchAPIBase)
+	u, err := ParseURL(node.CouchAPIBase)
 	if err == nil && b.pool != nil {
 		u.User = b.pool.client.BaseURL.User
 	}

views_test.go

@@ -1,7 +1,6 @@
 package couchbase
 
 import (
-	"net/url"
 	"testing"
 )
 
@@ -61,7 +60,7 @@ func TestViewURL(t *testing.T) {
 			continue
 		}
 
-		u, err := url.Parse(us)
+		u, err := ParseURL(us)
 		if err != nil {
 			t.Errorf("Failed on %v", test)
 			continue