fix: return 500 for unhandled handler errors

internal/common/errors.go

@@ -2,6 +2,7 @@ package common
 
 import (
 	"errors"
+	"log"
 
 	"github.com/gofiber/fiber/v3"
 )
@@ -34,7 +35,12 @@ func CustomErrorHandler(ctx fiber.Ctx, err error) error {
 		case ProblemJSONError:
 			problemJSON = &e
 		default:
-			problemJSON = &ProblemJSONError{Status: fiber.StatusNotFound, Title: fiber.ErrNotFound.Message, Detail: e.Error()}
+			log.Printf("Unhandled request error: %v", err)
+
+			problemJSON = &ProblemJSONError{
+				Status: fiber.StatusInternalServerError,
+				Title:  fiber.ErrInternalServerError.Message,
+			}
 		}
 	}
 

main_test.go

@@ -1,11 +1,14 @@
 package main
 
 import (
+	"bytes"
 	"encoding/json"
+	"errors"
 	"fmt"
 	"io"
 	"log"
 	"net/http"
+	"net/http/httptest"
 	"net/url"
 	"os"
 	"strings"
@@ -129,6 +132,38 @@ func TestApi(t *testing.T) {
 	runTestCases(t, tests)
 }
 
+func TestUnhandledErrors(t *testing.T) {
+	for _, panics := range []bool{false, true} {
+		t.Run(fmt.Sprintf("panic=%t", panics), func(t *testing.T) {
+			var logs bytes.Buffer
+			previousOutput := log.Writer()
+			log.SetOutput(&logs)
+			t.Cleanup(func() { log.SetOutput(previousOutput) })
+
+			app := Setup()
+			app.Get("/error", func(ctx fiber.Ctx) error {
+				if panics {
+					panic("secret internal state")
+				}
+				return errors.New("secret internal state")
+			})
+
+			res, err := app.Test(httptest.NewRequest(http.MethodGet, "/error", nil))
+			if !assert.NoError(t, err) {
+				return
+			}
+			defer res.Body.Close()
+
+			body, err := io.ReadAll(res.Body)
+			assert.NoError(t, err)
+			assert.Equal(t, http.StatusInternalServerError, res.StatusCode)
+			assert.Equal(t, "application/problem+json", res.Header.Get("Content-Type"))
+			assert.JSONEq(t, `{"title":"Internal Server Error","status":500}`, string(body))
+			assert.Contains(t, logs.String(), "secret internal state")
+		})
+	}
+}
+
 func TestValidateEndpoint(t *testing.T) {
 	validYml := loadTestdata(t, "valid.publiccode.yml")
 	invalidYml := loadTestdata(t, "invalid.publiccode.yml")

publiccode-validator-api.oas.yaml

@@ -41,6 +41,16 @@ paths:
                 v: "1.0.0"
                 commit: "abc1234"
 
+        "500":
+          description: Unexpected server error
+          content:
+            application/problem+json:
+              schema:
+                $ref: "#/components/schemas/ProblemJSON"
+              example:
+                title: Internal Server Error
+                status: 500
+
   /validate:
     post:
       operationId: validatePubliccode
@@ -137,6 +147,16 @@ paths:
                 title: Not Found
                 status: 404
 
+        "500":
+          description: Unexpected server error
+          content:
+            application/problem+json:
+              schema:
+                $ref: "#/components/schemas/ProblemJSON"
+              example:
+                title: Internal Server Error
+                status: 500
+
 components:
   schemas:
     Status: