Issue #2973 Return structured JSON errors from config API

Detect MultiError at the HTTP response layer and return a JSON array
of structured ValidationError objects with HTTP 422. Add nil guard in
writeMultiError and handle io.ReadAll errors on error response paths.

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(422).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.StatusUnprocessableEntity, 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 +258,19 @@ 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, readErr := io.ReadAll(res.Body)
+			if readErr != nil {
+				return nil, fmt.Errorf("failed to read error response body: %w", readErr)
+			}
+			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, readErr := io.ReadAll(res.Body)
+			if readErr != nil {
+				return nil, fmt.Errorf("failed to read error response body: %w", readErr)
+			}
+			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
 		}
@@ -125,3 +131,20 @@ 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 {
+		if e == nil {
+			continue
+		}
+		validationErrors = append(validationErrors, client.ValidationError{
+			Message: e.Error(),
+		})
+	}
+	w.Header().Set("Content-Type", "application/json")
+	w.WriteHeader(http.StatusUnprocessableEntity)
+	if err := json.NewEncoder(w).Encode(validationErrors); err != nil {
+		logging.Error("Failed to write error response: ", err)
+	}
+}