Date: Thu, 8 Dec 2011 18:34:29 -0500
From: Austin Clements <amdragon@MIT.EDU>
To: Jani Nikula <jani@nikula.org>
Subject: Re: [PATCH v4 1/3] cli: introduce the concept of user defined hooks
Message-ID: <20111208233429.GA3190@mit.edu>
References: <cover.1323384304.git.jani@nikula.org>
	<1e4ddb5e3a6b980e47418f67e16709a42e63bc47.1323384304.git.jani@nikula.org>
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User-Agent: Mutt/1.5.21 (2010-09-15)
Cc: notmuch@notmuchmail.org
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Quoth Jani Nikula on Dec 09 at 12:48 am:
> Add mechanism for running user defined hooks. Hooks are executables or
> symlinks to executables stored under the new notmuch hooks directory,
> <database-path>/.notmuch/hooks.
> 
> No hooks are introduced here, but adding support for a hook is now a simple
> matter of calling the new notmuch_run_hook() function at an appropriate
> location with the hook name.
> 
> Signed-off-by: Jani Nikula <jani@nikula.org>
> ---
>  Makefile.local   |    1 +
>  hooks.c          |   93 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
>  notmuch-client.h |    3 ++
>  3 files changed, 97 insertions(+), 0 deletions(-)
>  create mode 100644 hooks.c
> 
> diff --git a/Makefile.local b/Makefile.local
> index 15e6d88..88365da 100644
> --- a/Makefile.local
> +++ b/Makefile.local
> @@ -298,6 +298,7 @@ notmuch_client_srcs =		\
>  	debugger.c		\
>  	gmime-filter-reply.c	\
>  	gmime-filter-headers.c	\
> +	hooks.c			\
>  	notmuch.c		\
>  	notmuch-config.c	\
>  	notmuch-count.c		\
> diff --git a/hooks.c b/hooks.c
> new file mode 100644
> index 0000000..44ee419
> --- /dev/null
> +++ b/hooks.c
> @@ -0,0 +1,93 @@
> +/* notmuch - Not much of an email program, (just index and search)
> + *
> + * This file is part of notmuch.
> + *
> + * Copyright © 2011 Jani Nikula
> + *
> + * This program is free software: you can redistribute it and/or modify
> + * it under the terms of the GNU General Public License as published by
> + * the Free Software Foundation, either version 3 of the License, or
> + * (at your option) any later version.
> + *
> + * This program is distributed in the hope that it will be useful,
> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
> + * GNU General Public License for more details.
> + *
> + * You should have received a copy of the GNU General Public License
> + * along with this program.  If not, see http://www.gnu.org/licenses/ .
> + *
> + * Author: Jani Nikula <jani@nikula.org>
> + */
> +
> +#include "notmuch-client.h"
> +#include <sys/wait.h>
> +
> +int
> +notmuch_run_hook (const char *db_path, const char *hook)
> +{
> +    char *hook_path;
> +    int status = 0;
> +    pid_t pid;
> +
> +    hook_path = talloc_asprintf (NULL, "%s/%s/%s/%s", db_path, ".notmuch",
> +				 "hooks", hook);
> +    if (hook_path == NULL) {
> +	fprintf (stderr, "Out of memory\n");
> +	return 1;
> +    }
> +
> +    /* Check access before fork() for speed and simplicity of error handling. */
> +    if (access (hook_path, X_OK) == -1) {
> +	/* Ignore ENOENT. It's okay not to have a hook, hook dir, or even
> +	 * notmuch dir. Dangling symbolic links also result in ENOENT, but
> +	 * we'll ignore that too for simplicity. */
> +	if (errno != ENOENT) {
> +	    fprintf (stderr, "Error: %s hook access failed: %s\n", hook,
> +		     strerror (errno));
> +	    status = 1;
> +	}

Is it the intent that a present but non-executable hook (errno ==
EACCES) will print the above error message and return with a failure?
I'm pretty sure this differs from the behavior of git hooks.

Other than this, this patch looks good to me.

> +	goto DONE;
> +    }
> +
> +    pid = fork();
> +    if (pid == -1) {
> +	fprintf (stderr, "Error: %s hook fork failed: %s\n", hook,
> +		 strerror (errno));
> +	status = 1;
> +	goto DONE;
> +    } else if (pid == 0) {
> +	execl (hook_path, hook_path, NULL);
> +	/* Same as above for ENOENT, but unlikely now. Indicate all other errors
> +	 * to parent through non-zero exit status. */
> +	if (errno != ENOENT) {
> +	    fprintf (stderr, "Error: %s hook execution failed: %s\n", hook,
> +		     strerror (errno));
> +	    status = 1;
> +	}
> +	exit (status);
> +    }
> +
> +    if (waitpid (pid, &status, 0) == -1) {
> +	fprintf (stderr, "Error: %s hook wait failed: %s\n", hook,
> +		 strerror (errno));
> +	status = 1;
> +	goto DONE;
> +    }
> +
> +    if (!WIFEXITED (status) || WEXITSTATUS (status)) {
> +	if (WIFEXITED (status)) {
> +	    fprintf (stderr, "Error: %s hook failed with status %d\n",
> +		     hook, WEXITSTATUS (status));
> +	} else if (WIFSIGNALED (status)) {
> +	    fprintf (stderr, "Error: %s hook terminated with signal %d\n",
> +		     hook, WTERMSIG (status));
> +	}
> +	status = 1;
> +    }
> +
> +  DONE:
> +    talloc_free (hook_path);
> +
> +    return status;
> +}
> diff --git a/notmuch-client.h b/notmuch-client.h
> index b50cb38..a91ad6c 100644
> --- a/notmuch-client.h
> +++ b/notmuch-client.h
> @@ -235,6 +235,9 @@ void
>  notmuch_config_set_maildir_synchronize_flags (notmuch_config_t *config,
>  					      notmuch_bool_t synchronize_flags);
>  
> +int
> +notmuch_run_hook (const char *db_path, const char *hook);
> +
>  notmuch_bool_t
>  debugger_is_active (void);