fix(bind): handle maps with defined string key and value types

bind.go

@@ -234,14 +234,15 @@ func bindData(destination any, data map[string][]string, tag string, dataFiles m
 			val.Set(reflect.MakeMap(typ))
 		}
 		for k, v := range data {
+			key := reflect.ValueOf(k).Convert(typ.Key())
 			if isElemString {
-				val.SetMapIndex(reflect.ValueOf(k), reflect.ValueOf(v[0]))
+				val.SetMapIndex(key, reflect.ValueOf(v[0]).Convert(typ.Elem()))
 			} else if isElemInterface {
 				// To maintain backward compatibility, we always bind to the first string value
 				// and not the slice of strings when dealing with map[string]any{}
-				val.SetMapIndex(reflect.ValueOf(k), reflect.ValueOf(v[0]))
+				val.SetMapIndex(key, reflect.ValueOf(v[0]))
 			} else {
-				val.SetMapIndex(reflect.ValueOf(k), reflect.ValueOf(v))
+				val.SetMapIndex(key, reflect.ValueOf(v))
 			}
 		}
 		return nil

bind_named_map_test.go

@@ -0,0 +1,106 @@
+// SPDX-License-Identifier: MIT
+// SPDX-FileCopyrightText: © 2015 LabStack LLC and Echo contributors
+
+package echo_test
+
+import (
+	"net/http"
+	"net/http/httptest"
+	"reflect"
+	"strings"
+	"testing"
+
+	"github.com/labstack/echo/v5"
+)
+
+type mapBindingKey string
+type mapBindingValue string
+type mapBindingValues []string
+
+func TestBindNamedMapTypes(t *testing.T) {
+	for _, source := range []string{"query", "bind", "path", "header", "form", "multipart"} {
+		for _, tc := range []struct {
+			name   string
+			target func() any
+			want   any
+		}{
+			{"named_key", func() any { return new(map[mapBindingKey]string) }, map[mapBindingKey]string{"item": "first"}},
+			{"named_both", func() any { return new(map[mapBindingKey]mapBindingValue) }, map[mapBindingKey]mapBindingValue{"item": "first"}},
+			{"named_key_interface", func() any { return new(map[mapBindingKey]any) }, map[mapBindingKey]any{"item": "first"}},
+			{"named_value", func() any { return new(map[string]mapBindingValue) }, map[string]mapBindingValue{"item": "first"}},
+			{"named_slice", func() any { return new(map[string]mapBindingValues) }, map[string]mapBindingValues{"item": {"first", "second"}}},
+			{"plain_string", func() any { return new(map[string]string) }, map[string]string{"item": "first"}},
+			{"plain_slice", func() any { return new(map[string][]string) }, map[string][]string{"item": {"first", "second"}}},
+			{"plain_interface", func() any { return new(map[string]any) }, map[string]any{"item": "first"}},
+		} {
+			t.Run(source+"/"+tc.name, func(t *testing.T) {
+				defer func() {
+					if p := recover(); p != nil {
+						t.Errorf("public binding panicked: %v", p)
+					}
+				}()
+				e := echo.New()
+				target := tc.target()
+				e.Any("/:item", func(c *echo.Context) error {
+					var err error
+					switch source {
+					case "bind":
+						err = c.Bind(target)
+					case "query":
+						err = echo.BindQueryParams(c, target)
+					case "path":
+						err = echo.BindPathValues(c, target)
+					case "header":
+						err = echo.BindHeaders(c, target)
+					default:
+						err = echo.BindBody(c, target)
+					}
+					if err != nil {
+						return err
+					}
+					return c.NoContent(http.StatusNoContent)
+				})
+				req := httptest.NewRequest(http.MethodPost, "/first?item=first&item=second", nil)
+				if source == "bind" {
+					req.Method = http.MethodGet
+				}
+				if source == "header" {
+					req.Header.Set("Item", "first")
+					req.Header.Add("Item", "second")
+				}
+				if source == "form" {
+					req = httptest.NewRequest(http.MethodPost, "/first", strings.NewReader("item=first&item=second"))
+					req.Header.Set(echo.HeaderContentType, echo.MIMEApplicationForm)
+				}
+				if source == "multipart" {
+					req = httptest.NewRequest(http.MethodPost, "/first", strings.NewReader("--boundary\r\nContent-Disposition: form-data; name=\"item\"\r\n\r\nfirst\r\n--boundary\r\nContent-Disposition: form-data; name=\"item\"\r\n\r\nsecond\r\n--boundary--\r\n"))
+					req.Header.Set(echo.HeaderContentType, "multipart/form-data; boundary=boundary")
+				}
+				rec := httptest.NewRecorder()
+				e.ServeHTTP(rec, req)
+				if rec.Code != http.StatusNoContent {
+					t.Fatalf("status = %d, body = %s", rec.Code, rec.Body.String())
+				}
+				want := tc.want
+				if source == "path" {
+					switch tc.name {
+					case "named_slice":
+						want = map[string]mapBindingValues{"item": {"first"}}
+					case "plain_slice":
+						want = map[string][]string{"item": {"first"}}
+					}
+				}
+				if source == "header" {
+					v := reflect.ValueOf(want)
+					value := v.MapIndex(reflect.ValueOf("item").Convert(v.Type().Key()))
+					v.SetMapIndex(reflect.ValueOf("item").Convert(v.Type().Key()), reflect.Value{})
+					v.SetMapIndex(reflect.ValueOf("Item").Convert(v.Type().Key()), value)
+				}
+				got := reflect.ValueOf(target).Elem().Interface()
+				if !reflect.DeepEqual(want, got) {
+					t.Fatalf("got %#v, want %#v", got, want)
+				}
+			})
+		}
+	}
+}