fix: use 415 status for bad input content type

api.go

@@ -3,6 +3,7 @@ package huma
 import (
 	"context"
 	"encoding/json"
+	"errors"
 	"fmt"
 	"io"
 	"mime/multipart"
@@ -19,6 +20,8 @@ import (
 
 var rxSchema = regexp.MustCompile(`#/components/schemas/([^"]+)`)
 
+var ErrUnknownContentType = errors.New("unknown content type")
+
 // Resolver runs a `Resolve` function after a request has been parsed, enabling
 // you to run custom validation or other code that can modify the request and /
 // or return errors.
@@ -229,7 +232,7 @@ func (a *api) Unmarshal(contentType string, data []byte, v any) error {
 	}
 	f, ok := a.formats[ct]
 	if !ok {
-		return fmt.Errorf("unknown content type: %s", contentType)
+		return fmt.Errorf("%w: %s", ErrUnknownContentType, contentType)
 	}
 	return f.Unmarshal(data, v)
 }

huma.go

@@ -10,6 +10,7 @@ package huma
 import (
 	"bytes"
 	"context"
+	"errors"
 	"fmt"
 	"io"
 	"net"
@@ -824,8 +825,10 @@ func Register[I, O any](api API, op Operation, handler func(context.Context, *I)
 					// expected struct type to call the handler.
 					var parsed any
 					if err := api.Unmarshal(ctx.Header("Content-Type"), body, &parsed); err != nil {
-						// TODO: handle not acceptable
 						errStatus = http.StatusBadRequest
+						if errors.Is(err, ErrUnknownContentType) {
+							errStatus = http.StatusUnsupportedMediaType
+						}
 						res.Errors = append(res.Errors, &ErrorDetail{
 							Location: "body",
 							Message:  err.Error(),

huma_test.go

@@ -292,6 +292,31 @@ func TestFeatures(t *testing.T) {
 				assert.Equal(t, http.StatusBadRequest, resp.Code)
 			},
 		},
+		{
+			Name: "request-body-unsupported-media-type",
+			Register: func(t *testing.T, api huma.API) {
+				huma.Register(api, huma.Operation{
+					Method: http.MethodPut,
+					Path:   "/body",
+				}, func(ctx context.Context, input *struct {
+					RawBody []byte
+					Body    struct {
+						Name string `json:"name"`
+					}
+				}) (*struct{}, error) {
+					assert.Equal(t, `{"name":"foo"}`, string(input.RawBody))
+					assert.Equal(t, "foo", input.Body.Name)
+					return nil, nil
+				})
+			},
+			Method:  http.MethodPut,
+			URL:     "/body",
+			Headers: map[string]string{"Content-Type": "application/foo"},
+			Body:    `abcd`,
+			Assert: func(t *testing.T, resp *httptest.ResponseRecorder) {
+				assert.Equal(t, http.StatusUnsupportedMediaType, resp.Code)
+			},
+		},
 		{
 			Name: "request-body-file-upload",
 			Register: func(t *testing.T, api huma.API) {