hh_server (1) - Linux Man Pages
hh_server: Hack language typechecker daemon
SYNOPSIShh_server [--check [--json]] DIRECTORY
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).
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.
Start up, check the
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
is specified, generate machine-readable JSON output instead of the
human-readable output generated by default.
- --check TARGET
Start up and check
in the same manner as
mode. Then, re-check
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
for detailed information on how to combine this mode with
to do a full and safe conversion from PHP to Hack.
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.
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.