feat(matcher): seal Context from matcher API via onlyRequestContext (#111)

Author: tigerwill90

context.go

@@ -415,6 +415,23 @@ func (c *Context) getQueries() url.Values {
 	return c.cachedQueries
 }
 
+// onlyRequestContext wraps *Context so matchers can only reach the [RequestContext] interface and cannot
+// misuse the full Context API.
+type onlyRequestContext struct {
+	c *Context
+}
+
+func (s onlyRequestContext) Request() *http.Request         { return s.c.Request() }
+func (s onlyRequestContext) RemoteIP() *net.IPAddr          { return s.c.RemoteIP() }
+func (s onlyRequestContext) ClientIP() (*net.IPAddr, error) { return s.c.ClientIP() }
+func (s onlyRequestContext) Method() string                 { return s.c.Method() }
+func (s onlyRequestContext) Path() string                   { return s.c.Path() }
+func (s onlyRequestContext) EscapedPath() string            { return s.c.EscapedPath() }
+func (s onlyRequestContext) Host() string                   { return s.c.Host() }
+func (s onlyRequestContext) QueryParams() url.Values        { return s.c.QueryParams() }
+func (s onlyRequestContext) QueryParam(name string) string  { return s.c.QueryParam(name) }
+func (s onlyRequestContext) Header(key string) string       { return s.c.Header(key) }
+
 // WrapF is an adapter for wrapping [http.HandlerFunc] and returns a [HandlerFunc] function.
 // The route parameters are being accessed by the wrapped handler through the context.
 func WrapF(f http.HandlerFunc) HandlerFunc {

route.go

@@ -135,7 +135,7 @@ func (r *Route) String() string {
 
 // match reports whether the request satisfies this route's method constraint (if any)
 // and all attached matchers.
-func (r *Route) match(method string, c RequestContext) bool {
+func (r *Route) match(method string, c *Context) bool {
 	// Fast path: routes with exactly one method and no matchers cache that
 	// method in methodFast.
 	if r.methodFast == method {
@@ -149,7 +149,7 @@ func (r *Route) match(method string, c RequestContext) bool {
 // inlinable.
 //
 //go:noinline
-func (r *Route) matchSlow(method string, c RequestContext) bool {
+func (r *Route) matchSlow(method string, c *Context) bool {
 	methods := r.methods
 	switch len(methods) {
 	case 0:
@@ -165,8 +165,9 @@ func (r *Route) matchSlow(method string, c RequestContext) bool {
 			return false
 		}
 	}
+	sealed := onlyRequestContext{c}
 	for _, m := range r.matchers {
-		if !m.Match(c) {
+		if !m.Match(sealed) {
 			return false
 		}
 	}