Default binder can use UnmarshalParams(params []string) error inter…

[aldas]

Default binder can use UnmarshalParams(params []string) error interface to bind multiple input values at one go.

Relates to #2602

This allows developers to build fancy unmarsallers like related PR had. that turns /?a=1,2,3&a=4,5,6 into IntArrayB([]int{1, 2, 3, 4, 5, 6})

type IntArrayB []int

func (i *IntArrayB) UnmarshalParams(params []string) error {
	var numbers = make([]int, 0, len(params))

	for _, param := range params {
		var values = strings.Split(param, ",")
		for _, v := range values {
			n, err := strconv.ParseInt(v, 10, 64)
			if err != nil {
				return fmt.Errorf("'%s' is not an integer", v)
			}
			numbers = append(numbers, int(n))
		}
	}

	*i = append(*i, numbers...)
	return nil
}

func TestBindUnmarshalParams(t *testing.T) {
	t.Run("ok, target is an alias to slice and is nil, append multiple inputs", func(t *testing.T) {
		e := New()
		req := httptest.NewRequest(http.MethodGet, "/?a=1,2,3&a=4,5,6", nil)
		rec := httptest.NewRecorder()
		c := e.NewContext(req, rec)
		result := struct {
			V IntArrayB `query:"a"`
		}{}
		err := c.Bind(&result)

		assert.NoError(t, err)
		assert.Equal(t, IntArrayB([]int{1, 2, 3, 4, 5, 6}), result.V)
	})
}

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 93.02%. Comparing base (a3b0ba2) to head (bdd4ac3).

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #2607      +/-   ##
==========================================
- Coverage   93.20%   93.02%   -0.18%     
==========================================
  Files          41       41              
  Lines        4693     4702       +9     
==========================================
  Hits         4374     4374              
- Misses        230      236       +6     
- Partials       89       92       +3     

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