Use $Restrict

src/vmod_objesi.c

@@ -13,12 +13,7 @@ vmod_is_esi(VRT_CTX)
 
 	CHECK_OBJ_NOTNULL(ctx, VRT_CTX_MAGIC);
 
-	if ((ctx->method & VCL_MET_DELIVER) == 0) {
-		VRT_fail(ctx, "objesi.is_esi may only be called from "
-		    "vcl_deliver {}");
-		return (0);
-	}
-
+	assert(ctx->method == VCL_MET_DELIVER);
 	req = ctx->req;
 	CHECK_OBJ_NOTNULL(req, REQ_MAGIC);
 

src/vmod_objesi.vcc

@@ -28,7 +28,7 @@ $Function BOOL is_esi()
 
 Return true if ESI processing is active.
 
-May only be called from ``vcl_deliver {}``.
+$Restrict vcl_deliver
 
 SEE ALSO
 ========vcl\(7),varnishd\(1)