refactor: standardize API error handling (#1635)

backend/internal/httpserver/handler.go

@@ -0,0 +1,46 @@
+package httpserver
+
+import (
+	"context"
+	"errors"
+	"fmt"
+	"net/http"
+	"runtime/debug"
+
+	"github.com/gin-gonic/gin"
+)
+
+// HandlerFunc is an application HTTP handler that returns failures to the shared error middleware
+type HandlerFunc func(*gin.Context) error
+
+// Handle adapts an error-returning application handler to Gin
+func Handle(handler HandlerFunc) gin.HandlerFunc {
+	return func(c *gin.Context) {
+		defer func() {
+			recovered := recover()
+			if recovered == nil {
+				return
+			}
+
+			// Preserve net/http's intentional request-abort behavior without logging it as an application panic
+			if err, ok := recovered.(error); ok && errors.Is(err, http.ErrAbortHandler) {
+				panic(recovered)
+			}
+
+			// Keep recovered errors out of the unwrap chain so every panic is reported as an internal failure
+			err := fmt.Errorf("panic in HTTP handler (%T): %v\n%s", recovered, recovered, debug.Stack())
+			_ = c.Error(err)
+			c.Abort()
+		}()
+
+		if err := handler(c); err != nil {
+			if errors.Is(err, context.Canceled) {
+				c.Abort()
+				return
+			}
+
+			_ = c.Error(err)
+			c.Abort()
+		}
+	}
+}