feat(http): add form parser

http/param/param.go

@@ -2,6 +2,7 @@ package param
 
 import (
 	"encoding"
+	"errors"
 	"fmt"
 	"net/http"
 	"reflect"
@@ -11,6 +12,7 @@ import (
 
 const (
 	defaultTagName      = "param"
+	defaultMaxMemory    = 32 << 20 // 32 MB
 	queryTagValuePrefix = "query"
 	pathTagValuePrefix  = "path"
 	formTagValuePrefix  = "form"
@@ -248,8 +250,14 @@ func (p Parser) parseFormParam(r *http.Request, paramName string, v reflect.Valu
 	if r.Method != http.MethodPost && r.Method != http.MethodPut && r.Method != http.MethodPatch {
 		return fmt.Errorf("struct's field was tagged for parsing the form parameter (%s) but request method is not POST, PUT or PATCH", paramName)
 	}
-	if err := r.ParseForm(); err != nil {
-		return fmt.Errorf("parsing form data: %w", err)
+	if err := r.ParseMultipartForm(defaultMaxMemory); err != nil {
+		if !errors.Is(err, http.ErrNotMultipart) {
+			return fmt.Errorf("parsing multipart form: %w", err)
+		}
+		// Try to parse regular form if not multipart form.
+		if err := r.ParseForm(); err != nil {
+			return fmt.Errorf("parsing form: %w", err)
+		}
 	}
 	paramValue := p.FormParamFunc(r, paramName)
 	if paramValue != "" {

http/param/param_test.go

@@ -474,7 +474,7 @@ func TestParser_Parse_FormParam(t *testing.T) {
 		Nothing: "",
 	}
 	var parseError error
-	r.Post("/hello/objects", func(w http.ResponseWriter, r *http.Request) {
+	r.Post("/hello/objects", func(_ http.ResponseWriter, r *http.Request) {
 		parseError = p.Parse(r, &result)
 	})
 
@@ -484,7 +484,36 @@ func TestParser_Parse_FormParam(t *testing.T) {
 	req.Header.Set("Content-Type", "application/x-www-form-urlencoded")
 	r.ServeHTTP(httptest.NewRecorder(), req)
 
-	assert.NoError(t, parseError)
+	require.NoError(t, parseError)
+	assert.Equal(t, expected, result)
+}
+
+func TestParser_Parse_FormParam_NoParams(t *testing.T) {
+	p := DefaultParser()
+	result := structWithFormParams{
+		Subject: "should be replaced",
+		Amount:  ptr(123), // should be zeroed out
+		Nothing: "should be replaced",
+	}
+	expected := structWithFormParams{
+		Subject: "",
+		Amount:  nil,
+		Object:  nil,
+		Nothing: "",
+	}
+	var parseError error
+
+	r := chi.NewRouter()
+	r.Post("/hello/objects", func(_ http.ResponseWriter, r *http.Request) {
+		parseError = p.Parse(r, &result)
+	})
+
+	// Empty form body
+	req := httptest.NewRequest(http.MethodPost, "https://test.com/hello/objects", strings.NewReader(""))
+	req.Header.Set("Content-Type", "application/x-www-form-urlencoded")
+	r.ServeHTTP(httptest.NewRecorder(), req)
+
+	require.NoError(t, parseError)
 	assert.Equal(t, expected, result)
 }