NAME

       hh_server - Hack language typechecker daemon

SYNOPSIS

       hh_server [--check [--json]] DIRECTORY

DESCRIPTION

       hh_server(1)  is  the actual typechecker that enforces the Hack type system. It is typically accessed via
       hh_client(1); see the documentation for that tool for more information on the Hack type system and how to
       interface with hh_server(1).

       Directly invoking hh_server(1) is of minimal use, since hh_client(1) will start and stop  it  as  needed.
       The only widely useful manual invocation is --check mode.

       With  no options, hh_server(1) will start up, do an initial typecheck of DIRECTORY, and continue running,
       waiting for connections from hh_client(1).  Again, this is not  the  normal  way  the  server  should  be
       invoked  --  just running hh_client(1) and ignoring the existence of this server binary is sufficient for
       common use.

OPTIONS

       --check
              Start up, check the DIRECTORY, print type errors in a human-readable format, and then  exit.  This
              "batch  mode"  might  be  useful  in  cases where a single check is needed and so starting a long-
              running daemon is not appropriate, such as in a pre-commit hook. The output is intended for  human
              consumption, not tools; for tool consumption, see --json below.

       --json If  --check  is  specified,  generate  machine-readable  JSON output instead of the human-readable
              output generated by default.

       --check TARGET
              Start up and check DIRECTORY in the same manner as --check mode. Then, re-check TARGET and attempt
              to add type annotations to locations in those files that are missing. The analysis process is slow
              and imperfect, but often useful. This process can change the code in ways that  fail  at  runtime;
              see  http://docs.hhvm.com/hack/tools/introduction  for detailed information on how to combine this
              mode with hackificator(1) and hack_remove_soft_types(1) to do a full and safe conversion from  PHP
              to Hack.

EXIT STATUS

       If  --check  is specified, exits with 0 if there are no type errors, nonzero otherwise. Other exit values
       are undefined.

ENVIRONMENT and FILES

       Uses the same  scheme  for  constructing  a  path  to  a  socket  for  client/server  communication  that
       hh_client(1) uses. See its documentation for a description.

EXAMPLE

       It might be useful to have a pre-commit hook to make sure that type errors don't sneak into trunk. A hook
       might  want  to  directly  invoke hh_server(1) so that it doesn't need a running daemon. That can be done
       with something like

              hh_server --check /var/www

       and, if that fails, printing its output and rejecting the commit. For tool usage, something like

              hh_server --check --json /var/www

       might be more appropriate; the JSON output can be passed up to a code review tool and displayed there.

       This is only for cases where having a long-running daemon is inappropriate. For normal development usage,
       invoking hh_client(1) and allowing it to use the server itself will be much  faster  to  check  code  and
       return type errors.

BUGS

       The  Hack  language  is  part  of the HHVM project. Known bugs can be found at that tracker, and new ones
       should be reported there as well: https://github.com/facebook/hhvm/issues

SEE ALSO

       hh_client(1), hackificator(1), hack_remove_soft_types(1).
       http://docs.hhvm.com/hack/typechecker/setup
       http://www.hacklang.org/

                                                                                                    HH_SERVER(1)