feat(form): add array collection format in form binding (#3986)

* feat(form): add array collection format in form binding

* feat(form): add array collection format in form binding

* test(form): fix test code for array collection format in form binding

binding/form_mapping.go

@@ -182,6 +182,38 @@ func trySetCustom(val string, value reflect.Value) (isSet bool, err error) {
 	return false, nil
 }
 
+func trySplit(vs []string, field reflect.StructField) (newVs []string, err error) {
+	cfTag := field.Tag.Get("collection_format")
+	if cfTag == "" || cfTag == "multi" {
+		return vs, nil
+	}
+
+	var sep string
+	switch cfTag {
+	case "csv":
+		sep = ","
+	case "ssv":
+		sep = " "
+	case "tsv":
+		sep = "\t"
+	case "pipes":
+		sep = "|"
+	default:
+		return vs, fmt.Errorf("%s is not supported in the collection_format. (csv, ssv, pipes)", cfTag)
+	}
+
+	totalLength := 0
+	for _, v := range vs {
+		totalLength += strings.Count(v, sep) + 1
+	}
+	newVs = make([]string, 0, totalLength)
+	for _, v := range vs {
+		newVs = append(newVs, strings.Split(v, sep)...)
+	}
+
+	return newVs, nil
+}
+
 func setByForm(value reflect.Value, field reflect.StructField, form map[string][]string, tagValue string, opt setOptions) (isSet bool, err error) {
 	vs, ok := form[tagValue]
 	if !ok && !opt.isDefaultExists {
@@ -198,6 +230,10 @@ func setByForm(value reflect.Value, field reflect.StructField, form map[string][
 			return ok, err
 		}
 
+		if vs, err = trySplit(vs, field); err != nil {
+			return false, err
+		}
+
 		return true, setSlice(vs, value, field)
 	case reflect.Array:
 		if !ok {
@@ -208,6 +244,10 @@ func setByForm(value reflect.Value, field reflect.StructField, form map[string][
 			return ok, err
 		}
 
+		if vs, err = trySplit(vs, field); err != nil {
+			return false, err
+		}
+
 		if len(vs) != value.Len() {
 			return false, fmt.Errorf("%q is not valid value for %s", vs, value.Type().String())
 		}

binding/form_mapping_test.go

@@ -264,6 +264,45 @@ func TestMappingArray(t *testing.T) {
 	require.Error(t, err)
 }
 
+func TestMappingCollectionFormat(t *testing.T) {
+	var s struct {
+		SliceMulti []int  `form:"slice_multi" collection_format:"multi"`
+		SliceCsv   []int  `form:"slice_csv" collection_format:"csv"`
+		SliceSsv   []int  `form:"slice_ssv" collection_format:"ssv"`
+		SliceTsv   []int  `form:"slice_tsv" collection_format:"tsv"`
+		SlicePipes []int  `form:"slice_pipes" collection_format:"pipes"`
+		ArrayMulti [2]int `form:"array_multi" collection_format:"multi"`
+		ArrayCsv   [2]int `form:"array_csv" collection_format:"csv"`
+		ArraySsv   [2]int `form:"array_ssv" collection_format:"ssv"`
+		ArrayTsv   [2]int `form:"array_tsv" collection_format:"tsv"`
+		ArrayPipes [2]int `form:"array_pipes" collection_format:"pipes"`
+	}
+	err := mappingByPtr(&s, formSource{
+		"slice_multi": {"1", "2"},
+		"slice_csv":   {"1,2"},
+		"slice_ssv":   {"1 2"},
+		"slice_tsv":   {"1	2"},
+		"slice_pipes": {"1|2"},
+		"array_multi": {"1", "2"},
+		"array_csv":   {"1,2"},
+		"array_ssv":   {"1 2"},
+		"array_tsv":   {"1	2"},
+		"array_pipes": {"1|2"},
+	}, "form")
+	require.NoError(t, err)
+
+	assert.Equal(t, []int{1, 2}, s.SliceMulti)
+	assert.Equal(t, []int{1, 2}, s.SliceCsv)
+	assert.Equal(t, []int{1, 2}, s.SliceSsv)
+	assert.Equal(t, []int{1, 2}, s.SliceTsv)
+	assert.Equal(t, []int{1, 2}, s.SlicePipes)
+	assert.Equal(t, [2]int{1, 2}, s.ArrayMulti)
+	assert.Equal(t, [2]int{1, 2}, s.ArrayCsv)
+	assert.Equal(t, [2]int{1, 2}, s.ArraySsv)
+	assert.Equal(t, [2]int{1, 2}, s.ArrayTsv)
+	assert.Equal(t, [2]int{1, 2}, s.ArrayPipes)
+}
+
 func TestMappingStructField(t *testing.T) {
 	var s struct {
 		J struct {

docs/doc.md

@@ -26,6 +26,7 @@
   - [Custom Validators](#custom-validators)
   - [Only Bind Query String](#only-bind-query-string)
   - [Bind Query String or Post Data](#bind-query-string-or-post-data)
+  - [Collection format for arrays](#collection-format-for-arrays)
   - [Bind Uri](#bind-uri)
   - [Bind custom unmarshaler](#bind-custom-unmarshaler)
   - [Bind Header](#bind-header)
@@ -861,6 +862,59 @@ Test it with:
 curl -X GET "localhost:8085/testing?name=appleboy&address=xyz&birthday=1992-03-15&createTime=1562400033000000123&unixTime=1562400033"
 ```
 
+#### Collection format for arrays
+
+| Format          | Description                                               | Example                 |
+| --------------- | --------------------------------------------------------- | ----------------------- |
+| multi (default) | Multiple parameter instances rather than multiple values. | key=foo&key=bar&key=baz |
+| csv             | Comma-separated values.                                   | foo,bar,baz             |
+| ssv             | Space-separated values.                                   | foo bar baz             |
+| tsv             | Tab-separated values.                                     | "foo\tbar\tbaz"         |
+| pipes           | Pipe-separated values.                                    | foo\|bar\|baz           |
+
+```go
+package main
+
+import (
+	"log"
+	"time"
+	"github.com/gin-gonic/gin"
+)
+
+type Person struct {
+	Name       string    `form:"name"`
+	Addresses  []string  `form:"addresses" collection_format:"csv"`
+	Birthday   time.Time `form:"birthday" time_format:"2006-01-02" time_utc:"1"`
+	CreateTime time.Time `form:"createTime" time_format:"unixNano"`
+	UnixTime   time.Time `form:"unixTime" time_format:"unix"`
+}
+
+func main() {
+	route := gin.Default()
+	route.GET("/testing", startPage)
+	route.Run(":8085")
+}
+func startPage(c *gin.Context) {
+	var person Person
+	// If `GET`, only `Form` binding engine (`query`) used.
+	// If `POST`, first checks the `content-type` for `JSON` or `XML`, then uses `Form` (`form-data`).
+	// See more at https://github.com/gin-gonic/gin/blob/master/binding/binding.go#L48
+        if c.ShouldBind(&person) == nil {
+                log.Println(person.Name)
+                log.Println(person.Addresses)
+                log.Println(person.Birthday)
+                log.Println(person.CreateTime)
+                log.Println(person.UnixTime)
+        }
+	c.String(200, "Success")
+}
+```
+
+Test it with:
+```sh
+$ curl -X GET "localhost:8085/testing?name=appleboy&addresses=foo,bar&birthday=1992-03-15&createTime=1562400033000000123&unixTime=1562400033"
+```
+
 ### Bind Uri
 
 See the [detail information](https://github.com/gin-gonic/gin/issues/846).