From 9883d058069228492a3072484d1d2108d9e347a2 Mon Sep 17 00:00:00 2001
From: Jerry <fumm@mxchip.com>
Date: Wed, 6 May 2020 10:25:23 +0800
Subject: [PATCH] fix bug that tag `form:",default=1"` are not effective in
 some cases, e.g: http://host/list?page_no=&page_size=

---
 binding/form_mapping.go      |  4 +++-
 binding/form_mapping_test.go | 16 ++++++++++++----
 2 files changed, 15 insertions(+), 5 deletions(-)

diff --git a/binding/form_mapping.go b/binding/form_mapping.go
index b81ad195..718eb054 100644
--- a/binding/form_mapping.go
+++ b/binding/form_mapping.go
@@ -163,8 +163,10 @@ func setByForm(value reflect.Value, field reflect.StructField, form map[string][
 			val = opt.defaultValue
 		}
 
-		if len(vs) > 0 {
+		if len(vs) > 0 && vs[0] != "" {
 			val = vs[0]
+		} else {
+			val = opt.defaultValue
 		}
 		return true, setWithProperType(val, value, field)
 	}
diff --git a/binding/form_mapping_test.go b/binding/form_mapping_test.go
index 2a560371..dfa9b6d5 100644
--- a/binding/form_mapping_test.go
+++ b/binding/form_mapping_test.go
@@ -62,14 +62,22 @@ func TestMappingBaseTypes(t *testing.T) {
 
 func TestMappingDefault(t *testing.T) {
 	var s struct {
-		Int   int    `form:",default=9"`
-		Slice []int  `form:",default=9"`
-		Array [1]int `form:",default=9"`
+		Int    int    `form:",default=9"`
+		PageNo int    `form:"page_no,default=9"`
+		String string `form:"string,default=9"`
+		Slice  []int  `form:",default=9"`
+		Array  [1]int `form:",default=9"`
 	}
-	err := mappingByPtr(&s, formSource{}, "form")
+	form := map[string][]string{
+		"page_no": []string{""},
+		"string":  []string{""},
+	}
+	err := mappingByPtr(&s, formSource(form), "form")
 	assert.NoError(t, err)
 
 	assert.Equal(t, 9, s.Int)
+	assert.Equal(t, 9, s.PageNo)
+	assert.Equal(t, "9", s.String)
 	assert.Equal(t, []int{9}, s.Slice)
 	assert.Equal(t, [1]int{9}, s.Array)
 }