fix(06-12): bound named middleware by body cap, cache factories, fail boot on bad body config and mux conflicts

surf/router.go

@@ -3,6 +3,7 @@ package surf
 import (
 	"bytes"
 	"fmt"
+	"math"
 	"net/http"
 	"strings"
 	"time"
@@ -56,6 +57,7 @@ type Router struct {
 	corsCfg      CORSConfig
 	defaultBytes int64
 	uploadBytes  int64
+	built        map[string]pact.Middleware
 }
 
 var (
@@ -78,6 +80,7 @@ func New(origins []string) *Router {
 		named:     make(map[string]namedMiddleware),
 		factories: make(map[string]namedMiddlewareFactory),
 		seen:      make(map[string]string),
+		built:     make(map[string]pact.Middleware),
 		origins:   origins,
 	}
 }
@@ -345,20 +348,30 @@ func (r *Router) compile() (http.Handler, error) {
 		if err != nil {
 			return nil, err
 		}
-		mux.Handle(rt.method+" "+rt.path, h)
+		if err := handleRoute(mux, rt, h); err != nil {
+			return nil, err
+		}
 	}
 	return pathScopedCORS(r.corsCfg, mux), nil
 }
 
+// handleRoute registers a route, converting a ServeMux conflict panic into an error.
+func handleRoute(mux *http.ServeMux, rt route, h http.Handler) (err error) {
+	defer func() {
+		if rec := recover(); rec != nil {
+			err = fmt.Errorf("surf: route conflict for %s %s (plugin %q): %v", rt.method, rt.path, rt.pluginID, rec)
+		}
+	}()
+	mux.Handle(rt.method+" "+rt.path, h)
+	return nil
+}
+
 func (r *Router) wrap(rt route) (http.Handler, error) {
 	h := constrain(rt.handler, rt.constraints)
 	limit, err := routeBodyLimit(rt, r.defaultBytes)
 	if err != nil {
 		return nil, fmt.Errorf("surf: plugin %q: %w", rt.pluginID, err)
 	}
-	if limit > 0 {
-		h = bodyLimit(limit)(h)
-	}
 	h = orgSlot(h)
 	for i := len(rt.middleware) - 1; i >= 0; i-- {
 		name := rt.middleware[i]
@@ -391,6 +404,10 @@ func (r *Router) wrap(rt route) (http.Handler, error) {
 		}
 		return nil, fmt.Errorf("surf: plugin %q references unknown middleware %q", rt.pluginID, name)
 	}
+	// Body cap wraps every named/factory middleware but stays inside recovery.
+	if limit > 0 {
+		h = bodyLimit(limit)(h)
+	}
 	h = locale(h)
 	if rt.raw {
 		h = recoverBare(h)
@@ -426,7 +443,7 @@ func BuildRouter(app *backpack.App, plugins []party.Plugin) (*Router, error) {
 		return nil, err
 	}
 	if err := r.RegisterMiddlewareFactory("surf", "body.limit", func(param string) pact.Middleware {
-		// Limit is applied innermost in wrap(); the factory only occupies the name.
+		// Limit is applied outermost-inside-recovery in wrap(); the factory only occupies the name.
 		return func(next http.Handler) http.Handler { return next }
 	}); err != nil {
 		return nil, err
@@ -438,8 +455,15 @@ func BuildRouter(app *backpack.App, plugins []party.Plugin) (*Router, error) {
 		}
 		r.corsCfg = corsCfg
 		if app.Config != nil {
-			r.defaultBytes = int64(app.Config.Int("http.body_limits.default_bytes"))
-			r.uploadBytes = int64(app.Config.Int("http.body_limits.upload_bytes"))
+			d, err := requiredBytes(app, "http.body_limits.default_bytes")
+			if err != nil {
+				return nil, err
+			}
+			u, err := requiredBytes(app, "http.body_limits.upload_bytes")
+			if err != nil {
+				return nil, err
+			}
+			r.defaultBytes, r.uploadBytes = d, u
 		}
 	}
 	for _, p := range plugins {
@@ -494,6 +518,36 @@ func BuildRouter(app *backpack.App, plugins []party.Plugin) (*Router, error) {
 	return r, nil
 }
 
+func requiredBytes(app *backpack.App, key string) (int64, error) {
+	raw, ok := app.Config.Lookup(key)
+	if !ok {
+		return 0, fmt.Errorf("surf: config %s is required", key)
+	}
+	var n int64
+	switch v := raw.(type) {
+	case int:
+		n = int64(v)
+	case int64:
+		n = v
+	case uint64:
+		if v > math.MaxInt64 {
+			return 0, fmt.Errorf("surf: config %s out of range", key)
+		}
+		n = int64(v)
+	case float64:
+		if v != math.Trunc(v) || v > 9007199254740992 {
+			return 0, fmt.Errorf("surf: config %s must be a whole number", key)
+		}
+		n = int64(v)
+	default:
+		return 0, fmt.Errorf("surf: config %s must be numeric, got %T", key, raw)
+	}
+	if n < 1 {
+		return 0, fmt.Errorf("surf: config %s must be >= 1", key)
+	}
+	return n, nil
+}
+
 func corsOrigins(app *backpack.App) []string {
 	if app == nil || app.Config == nil {
 		return nil