I've been thinking of this issue and I want to manifest my proposal for
changing the way exit works with Rivet.
First of all I think the command exit, being a Tcl core command must be
kept in some form and not just deleted. We rather should give it a
meaning. The first idea that came up to me was to let exit behave like
::rivet::abort_page, giving it a structured error code the way we did
with ::rivet::redirect. The exit command synopsis is easy
NAME
exit - End the application
SYNOPSIS
exit ?returnCode?
we may add a ::rivet::exit command that is meant to shadow the core
command accepting the same error code parameter, which interrupts the
script execution and passes control to the AbortScript (if defined).
Through the command ::rivet::abort_code the exit return code can be
retrieved and the call to exit detected. It doesn't add a special value
to the command set, it might look like syntactic sugar for a special
form of ::rivet::abort_page, the way 'redirect' builds a dictionary with
a key 'error_code' set as 'redirect' and then a key 'location' with the
URL it redirects to. It just tries to give a meaning to the command exit
that would fit into Rivet and Apache
The new form of exit should store in the thread status a dictionary like
error_code -> exit
return_code -> ?returnCode?
I stick to the idea that in some cases (development, debugging etc)
could be useful to have a way to terminate a process. In order to stress
the whole concept that exit is not something to be used carelessly in
that way we could introduce a new global configuration parameter
ExitTerminatesProcess (by default set to Off, naturally) as a way to
highlight the proper usage of this option.
Since abort_page returns a Tcl error which is trapped to fire
AbortScript the catch command could prevent this to happen. I think that
at least in the case of the error raised by 'exit' (but I would favor a
general usage of it) we should give the programmer the option of a
abort-page aware catch command that should fall back to the core catch
command if the error is anything not generated by either 'redirect'
'abort_page' or 'exit'
-- Massimo
On 09/12/2015 12:23 AM, Massimo Manghi wrote:
[...]
We may compromise between the case of removing it altogether and having
an immediate process exit. For example we might integrate it with the
abort_page command or take inspiration from the recently introduced
::rivet::redir command. The new form for exit might interrupt instantly
the script execution and signal a deferred process/thread exit after the
request processing finished. But even in these scheme 'exit' should be
advertised for what would be in Rivet: a solution to be used only in
extreme cases
-- Massimo
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