Issue #2973 Return structured JSON errors from config API

When setting config via the API with invalid values, errors were
returned as concatenated plain text, making them unparseable by API
clients. Detect MultiError at the HTTP response layer and return a
JSON array of validation errors instead.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: sebrandon1

pkg/crc/api/api_http_test.go

@@ -1,6 +1,7 @@
 package api
 
 import (
+	"encoding/json"
 	"fmt"
 	"io"
 	"net/http"
@@ -10,6 +11,7 @@ import (
 	"strings"
 	"testing"
 
+	"github.com/crc-org/crc/v2/pkg/crc/api/client"
 	crcConfig "github.com/crc-org/crc/v2/pkg/crc/config"
 	"github.com/crc-org/crc/v2/pkg/crc/constants"
 	"github.com/crc-org/crc/v2/pkg/crc/machine/fakemachine"
@@ -301,6 +303,10 @@ var testCases = []testCase{
 		request:  get("config?cpus").withBody("xx"),
 		response: jSon(`{"Configs":{"cpus":4}}`),
 	},
+	{
+		request:  post("config").withBody(`{"properties":{"cpus":0}}`),
+		response: httpError(500).withBody("[{\"message\":\"Value '0' for configuration property 'cpus' is invalid, reason: requires CPUs \\u003e= 4\"}]\n"),
+	},
 
 	// logs
 	{
@@ -504,3 +510,30 @@ func TestRoutes(t *testing.T) {
 		}
 	}
 }
+
+func TestSetConfigMultipleErrors(t *testing.T) {
+	pullSecretPath := createDummyPullSecret(t)
+	defer os.Remove(pullSecretPath)
+	server := newMockServer(pullSecretPath)
+
+	// Send a request with multiple invalid config values
+	req := post("config").withBody(`{"properties":{"cpus":0,"memory":1}}`)
+	resp := sendRequest(server.Handler(), &req)
+
+	require.Equal(t, http.StatusInternalServerError, resp.StatusCode)
+
+	body, err := io.ReadAll(resp.Body)
+	require.NoError(t, err)
+
+	var validationErrors []client.ValidationError
+	require.NoError(t, json.Unmarshal(body, &validationErrors))
+	require.Len(t, validationErrors, 2)
+
+	// Map iteration order is non-deterministic, so check membership rather than order
+	messages := make([]string, len(validationErrors))
+	for i, ve := range validationErrors {
+		messages[i] = ve.Message
+	}
+	assert.Contains(t, messages, "Value '0' for configuration property 'cpus' is invalid, reason: requires CPUs >= 4")
+	assert.Contains(t, messages, "Value '1' for configuration property 'memory' is invalid, reason: requires memory in MiB >= 10752")
+}

pkg/crc/api/client/client.go

@@ -258,11 +258,13 @@ func (c *client) sendRequest(url string, method string, data io.Reader) ([]byte,
 	switch method {
 	case http.MethodPost:
 		if res.StatusCode != http.StatusOK && res.StatusCode != http.StatusCreated {
-			return nil, fmt.Errorf("Error occurred sending POST request to : %s : %d", url, res.StatusCode)
+			body, _ := io.ReadAll(res.Body)
+			return nil, &HTTPError{URL: url, Method: method, StatusCode: res.StatusCode, Body: string(body)}
 		}
 	case http.MethodDelete, http.MethodGet:
 		if res.StatusCode != http.StatusOK {
-			return nil, fmt.Errorf("Error occurred sending %s request to : %s : %d", method, url, res.StatusCode)
+			body, _ := io.ReadAll(res.Body)
+			return nil, &HTTPError{URL: url, Method: method, StatusCode: res.StatusCode, Body: string(body)}
 		}
 	}
 

pkg/crc/api/client/types.go

@@ -66,3 +66,8 @@ type TelemetryRequest struct {
 	Source string `json:"source"`
 	Status string `json:"status"`
 }
+
+// ValidationError represents a single validation error in a structured JSON error response.
+type ValidationError struct {
+	Message string `json:"message"`
+}

pkg/crc/api/helpers.go

@@ -7,6 +7,8 @@ import (
 	"net/url"
 	"sync"
 
+	"github.com/crc-org/crc/v2/pkg/crc/api/client"
+	"github.com/crc-org/crc/v2/pkg/crc/errors"
 	"github.com/crc-org/crc/v2/pkg/crc/logging"
 )
 
@@ -111,6 +113,10 @@ func (s *server) Handler() http.Handler {
 			url:         r.URL,
 		}
 		if err := handler(c); err != nil {
+			if multiErr, ok := err.(errors.MultiError); ok {
+				writeMultiError(w, multiErr)
+				return
+			}
 			http.Error(w, err.Error(), http.StatusInternalServerError)
 			return
 		}
@@ -124,3 +130,17 @@ func (s *server) Handler() http.Handler {
 		}
 	})
 }
+
+func writeMultiError(w http.ResponseWriter, multiErr errors.MultiError) {
+	validationErrors := make([]client.ValidationError, 0, len(multiErr.Errors))
+	for _, e := range multiErr.Errors {
+		validationErrors = append(validationErrors, client.ValidationError{
+			Message: e.Error(),
+		})
+	}
+	w.Header().Set("Content-Type", "application/json")
+	w.WriteHeader(http.StatusInternalServerError)
+	if err := json.NewEncoder(w).Encode(validationErrors); err != nil {
+		logging.Error("Failed to write error response: ", err)
+	}
+}