content_by_lua_block ignored if fastcgi_pass statement is used

Hello,

Lua is not invoked when fastcgi_pass is used.

location / {
  content_by_lua_block {
    ngx.log(ngx.ERR, "HELLO")
    ngx.exit(ngx.HTTP_FORBIDDEN)
    }
  fastcgi_pass  unix:/dev/shm/master/fcgiwrap.socket;
}

Commenting the 'fastcgi_pass' line and it all works as expected (I see "HELLO" in the logs). But with fastcgi_pass statement the lua-block is not evaluated at all. In fact it's possible to have illegal LUA statements inside the lua_block and nginx wont even complain about them being illegal.

I came to this while trying to process some FORM POST data before passing them on via fastcgi_pass.

Start by reproducing the shown location configuration with content_by_lua_block and fastcgi_pass, then trace the module entry points handling those directives. Confirm whether the Lua block is skipped during FastCGI processing; done means valid Lua is evaluated and can log or reject the request before FastCGI handling.