api/render: implemented BadRequest

api/render/render.go

@@ -113,3 +113,30 @@ func Error(w http.ResponseWriter, err error) {
 		log.Error(w, err)
 	}
 }
+
+// BadRequest renders the JSON representation of err into w and sets its
+// status code to http.StatusBadRequest.
+func BadRequest(w http.ResponseWriter, err error) {
+	codedError(w, http.StatusBadRequest, err)
+}
+
+func codedError(w http.ResponseWriter, code int, err error) {
+	var wrapper = struct {
+		Status  int    `json:"status"`
+		Message string `json:"message"`
+	}{
+		Status:  code,
+		Message: err.Error(),
+	}
+
+	data, err := json.Marshal(wrapper)
+	if err != nil {
+		log.Error(w, err)
+
+		return
+	}
+
+	w.Header().Set("Content-Type", "application/json")
+	w.WriteHeader(code)
+	w.Write(data)
+}

api/render/render_test.go

@@ -3,8 +3,11 @@ package render
 import (
 	"net/http"
 	"net/http/httptest"
+	"strconv"
 	"testing"
 
+	"github.com/stretchr/testify/assert"
+
 	"github.com/smallstep/certificates/logging"
 )
 
@@ -51,3 +54,35 @@ func TestJSON(t *testing.T) {
 		})
 	}
 }
+
+func TestErrors(t *testing.T) {
+	cases := []struct {
+		fn   func(http.ResponseWriter, error) // helper
+		err  error                            // error being render
+		code int                              // expected status code
+		body string                           // expected body
+	}{
+		// --- BadRequest
+		0: {
+			fn:   BadRequest,
+			err:  assert.AnError,
+			code: http.StatusBadRequest,
+			body: `{"status":400,"message":"assert.AnError general error for testing"}`,
+		},
+	}
+
+	for caseIndex := range cases {
+		kase := cases[caseIndex]
+
+		t.Run(strconv.Itoa(caseIndex), func(t *testing.T) {
+			rec := httptest.NewRecorder()
+			kase.fn(rec, kase.err)
+
+			ret := rec.Result()
+
+			assert.Equal(t, "application/json", ret.Header.Get("Content-Type"))
+			assert.Equal(t, kase.code, ret.StatusCode)
+			assert.Equal(t, kase.body, rec.Body.String())
+		})
+	}
+}