From 60fef69d30eff571a6c316d02a0c0e8e6b057f2a Mon Sep 17 00:00:00 2001
From: Jeff Hodges <jeff@somethingsimilar.com>
Date: Tue, 11 Jul 2017 18:48:47 -0700
Subject: [PATCH] sort the generic config.Params in the DSN

This sorts the config.Params values as they are placed in the DSN.

This makes it easier for other projects to test that they are munging their DSNs
correctly and do other similar tasks.
---
 AUTHORS     |  1 +
 dsn.go      | 10 ++++++++--
 dsn_test.go | 16 ++++++++++++++++
 3 files changed, 25 insertions(+), 2 deletions(-)

diff --git a/AUTHORS b/AUTHORS
index 10e2ebb94..5526e3e90 100644
--- a/AUTHORS
+++ b/AUTHORS
@@ -33,6 +33,7 @@ ICHINOSE Shogo <shogo82148 at gmail.com>
 INADA Naoki <songofacandy at gmail.com>
 Jacek Szwec <szwec.jacek at gmail.com>
 James Harr <james.harr at gmail.com>
+Jeff Hodges <jeff at somethingsimilar.com>
 Jian Zhen <zhenjl at gmail.com>
 Joshua Prunier <joshua.prunier at gmail.com>
 Julien Lefevre <julien.lefevr at gmail.com>
diff --git a/dsn.go b/dsn.go
index ca1f2bf14..ab2fdfc6a 100644
--- a/dsn.go
+++ b/dsn.go
@@ -15,6 +15,7 @@ import (
 	"fmt"
 	"net"
 	"net/url"
+	"sort"
 	"strconv"
 	"strings"
 	"time"
@@ -257,7 +258,12 @@ func (cfg *Config) FormatDSN() string {
 
 	// other params
 	if cfg.Params != nil {
-		for param, value := range cfg.Params {
+		var params []string
+		for param := range cfg.Params {
+			params = append(params, param)
+		}
+		sort.Strings(params)
+		for _, param := range params {
 			if hasParam {
 				buf.WriteByte('&')
 			} else {
@@ -267,7 +273,7 @@ func (cfg *Config) FormatDSN() string {
 
 			buf.WriteString(param)
 			buf.WriteByte('=')
-			buf.WriteString(url.QueryEscape(value))
+			buf.WriteString(url.QueryEscape(cfg.Params[param]))
 		}
 	}
 
diff --git a/dsn_test.go b/dsn_test.go
index 4fd76b813..d1957f8e8 100644
--- a/dsn_test.go
+++ b/dsn_test.go
@@ -220,6 +220,22 @@ func TestDSNUnsafeCollation(t *testing.T) {
 	}
 }
 
+func TestParamsAreSorted(t *testing.T) {
+	expected := "/dbname?interpolateParams=true&foobar=baz&quux=loo"
+	dsn := &Config{
+		DBName:            "dbname",
+		InterpolateParams: true,
+		Params: map[string]string{
+			"quux":   "loo",
+			"foobar": "baz",
+		},
+	}
+	actual := dsn.FormatDSN()
+	if actual != expected {
+		t.Errorf("generic Config.Params were not sorted: want %#v, got %#v", expected, actual)
+	}
+}
+
 func BenchmarkParseDSN(b *testing.B) {
 	b.ReportAllocs()