[Redbean] Feature / OnError(status, message) hook (#1103)

tool/net/definitions.lua

@@ -550,6 +550,17 @@ SPECIAL PATHS
 ---
 function OnHttpRequest() end
 
+--- Hooks catch errors
+---
+--- If this functiopn is defined in the global scope by your `/.init.lua`
+--- then any errors occuring in the OnHttpRequest() hook will be catched.
+--- You'll be able then to do whatever you need with the error status and
+--- error message.
+---
+---@param status uint16
+---@param message string
+function OnError(status, message) end
+
 --- Hooks client connection creation.
 ---
 --- If this function is defined it'll be called from the main process

tool/net/help.txt

@@ -576,6 +576,12 @@ HOOKS
           *). See functions like Route which asks redbean to do its default
           thing from the handler.
 
+  OnError(status:int, message:string)
+          If this function is defined and if any errors occurs in
+          OnHttpRequest() then this method will be called instead of displaying
+          the default error page. Useful if you need to display the error page
+          using your specific code or send it to any tier service.
+
   OnClientConnection(ip:int, port:int, serverip:int, serverport:int) → bool
           If this function is defined it'll be called from the main process
           each time redbean accepts a new client connection. If it returns

tool/net/redbean.c

@@ -456,6 +456,7 @@ static bool isexitingworker;
 static bool hasonworkerstart;
 static bool leakcrashreports;
 static bool hasonhttprequest;
+static bool hasonerror;
 static bool ishandlingrequest;
 static bool listeningonport443;
 static bool hasonprocesscreate;
@@ -2532,7 +2533,7 @@ img { vertical-align: middle; }\r\n\
   return p;
 }
 
-static char *ServeErrorImpl(unsigned code, const char *reason,
+static char *ServeErrorImplDefault(unsigned code, const char *reason,
                             const char *details) {
   size_t n;
   char *p, *s;
@@ -2570,6 +2571,28 @@ static char *ServeErrorImpl(unsigned code, const char *reason,
   }
 }
 
+static char *GetLuaResponse(void) {
+  return cpm.luaheaderp ? cpm.luaheaderp : SetStatus(200, "OK");
+}
+
+static char *ServeErrorImpl(unsigned code, const char *reason,
+                            const char *details) {
+  lua_State *L = GL;
+  if (hasonerror) {
+    lua_getglobal(L, "OnError");
+    lua_pushinteger(L, code);
+    lua_pushstring(L, reason);
+    if (LuaCallWithTrace(L, 2, 0, NULL) == LUA_OK) {
+      return CommitOutput(GetLuaResponse());
+    } else {
+      return ServeErrorImplDefault(code, reason, details);
+    }
+  } else {
+    return ServeErrorImplDefault(code, reason, details);
+  }
+
+}
+
 static char *ServeErrorWithPath(unsigned code, const char *reason,
                                 const char *path, size_t pathlen) {
   ERRORF("(srvr) server error: %d %s %`'.*s", code, reason, pathlen, path);
@@ -3227,10 +3250,6 @@ static char *ServeIndex(const char *path, size_t pathlen) {
   return p;
 }
 
-static char *GetLuaResponse(void) {
-  return cpm.luaheaderp ? cpm.luaheaderp : SetStatus(200, "OK");
-}
-
 static bool ShouldServeCrashReportDetails(void) {
   uint32_t ip;
   uint16_t port;
@@ -5569,6 +5588,7 @@ static void LuaInit(void) {
   }
   if (LuaRunAsset("/.init.lua", true)) {
     hasonhttprequest = IsHookDefined("OnHttpRequest");
+    hasonerror = IsHookDefined("OnError");
     hasonclientconnection = IsHookDefined("OnClientConnection");
     hasonprocesscreate = IsHookDefined("OnProcessCreate");
     hasonprocessdestroy = IsHookDefined("OnProcessDestroy");