Exit early on invalid URLs

When creating a new client, invalid URLs are skipped and the problem is
only seen when e.g. the health checks set in. This commit changes the
code so that invalid URLs are found early in the cycle, when setting
them with `SetURL`.

Close olivere#1339

canonicalize.go

@@ -4,7 +4,10 @@
 
 package elastic
 
-import "net/url"
+import (
+	"net/url"
+	"strings"
+)
 
 // canonicalize takes a list of URLs and returns its canonicalized form, i.e.
 // remove anything but scheme, userinfo, host, path, and port.
@@ -14,15 +17,17 @@ import "net/url"
 // Example:
 // http://127.0.0.1:9200/?query=1 -> http://127.0.0.1:9200
 // http://127.0.0.1:9200/db1/ -> http://127.0.0.1:9200/db1
+// http://127.0.0.1:9200/db1/// -> http://127.0.0.1:9200/db1
 func canonicalize(rawurls ...string) []string {
 	var canonicalized []string
 	for _, rawurl := range rawurls {
 		u, err := url.Parse(rawurl)
 		if err == nil {
 			if u.Scheme == "http" || u.Scheme == "https" {
-				// Trim trailing slashes
-				for len(u.Path) > 0 && u.Path[len(u.Path)-1] == '/' {
-					u.Path = u.Path[0 : len(u.Path)-1]
+				// Trim trailing slashes. Notice that strings.TrimSuffix will only remove the last slash,
+				// not all slashes from the suffix, so we'll loop over the path to remove all slashes.
+				for strings.HasSuffix(u.Path, "/") {
+					u.Path = u.Path[:len(u.Path)-1]
 				}
 				u.Fragment = ""
 				u.RawQuery = ""

client.go

@@ -506,6 +506,12 @@ func SetURL(urls ...string) ClientOptionFunc {
 		default:
 			c.urls = urls
 		}
+		// Check URLs
+		for _, urlStr := range c.urls {
+			if _, err := url.Parse(urlStr); err != nil {
+				return err
+			}
+		}
 		return nil
 	}
 }

client_test.go

@@ -133,6 +133,19 @@ func TestClientWithMultipleURLs(t *testing.T) {
 	}
 }
 
+func TestClientWithInvalidURLs(t *testing.T) {
+	client, err := NewClient(SetURL(" http://foo.com", "http://[fe80::%31%25en0]:8080/"))
+	if err == nil {
+		t.Fatal("expected error, got nil")
+	}
+	if want, have := `parse " http://foo.com": first path segment in URL cannot contain colon`, err.Error(); want != have {
+		t.Fatalf("expected error %q, have %q", want, have)
+	}
+	if client != nil {
+		t.Fatal("expected client == nil")
+	}
+}
+
 func TestClientWithBasicAuth(t *testing.T) {
 	client, err := NewClient(SetBasicAuth("user", "secret"))
 	if err != nil {