[PATCH v1 1/1] lib: make find_message{,by_filename) report errors

Austin Clements amdragon at MIT.EDU
Mon Oct 3 10:43:08 PDT 2011


All of the code looks good to me (and improving error handling is
always a good thing).  Some style nits are inline below.

The changes to _resolve_message_id_to_thread_id and
_notmuch_database_link_message_to_parents seem like just plain better
error handling and unrelated to the find_message API changes.  Perhaps
these should be in a separate patch?

Quoth Ali Polatel on Oct 03 at  7:49 pm:
> Previously, the functions notmuch_database_find_message() and
> notmuch_database_find_message_by_filename() functions did not properly
> report error condition to the library user.
> 
> For more information, read the thread on the notmuch mailing list
> starting with my mail "id:871uv2unfd.fsf at gmail.com"
> 
> Make these functions accept a pointer to 'notmuch_message_t' as argument
> and return notmuch_status_t which may be used to check for any error
> condition.
> 
> restore: Modify for the new notmuch_database_find_message()
> new: Modify for the new notmuch_database_find_message_by_filename()
> ---
>  lib/database.cc   |   90 ++++++++++++++++++++++++++++++++++------------------
>  lib/message.cc    |    6 ++--
>  lib/notmuch.h     |   61 +++++++++++++++++++++++++----------
>  notmuch-new.c     |    4 ++-
>  notmuch-restore.c |   11 ++++--
>  5 files changed, 115 insertions(+), 57 deletions(-)
> 
> diff --git a/lib/database.cc b/lib/database.cc
> index 9299c8d..1705232 100644
> --- a/lib/database.cc
> +++ b/lib/database.cc
> @@ -360,13 +360,17 @@ _message_id_compressed (void *ctx, const char *message_id)
>      return compressed;
>  }
>  
> -notmuch_message_t *
> +notmuch_status_t
>  notmuch_database_find_message (notmuch_database_t *notmuch,
> -			       const char *message_id)
> +			       const char *message_id,
> +			       notmuch_message_t **message)

Perhaps this should be message_ret to clearly distinguish it as an
out-argument?

>  {
>      notmuch_private_status_t status;
>      unsigned int doc_id;
>  
> +    if (message == NULL)
> +	return NOTMUCH_STATUS_NULL_POINTER;
> +
>      if (strlen (message_id) > NOTMUCH_MESSAGE_ID_MAX)
>  	message_id = _message_id_compressed (notmuch, message_id);
>  
> @@ -375,14 +379,21 @@ notmuch_database_find_message (notmuch_database_t *notmuch,
>  						       message_id, &doc_id);
>  
>  	if (status == NOTMUCH_PRIVATE_STATUS_NO_DOCUMENT_FOUND)
> -	    return NULL;
> +	    *message = NULL;
> +	else {
> +	    *message = _notmuch_message_create (notmuch, notmuch, doc_id,
> +						NULL);
> +	    if (*message == NULL)
> +		return NOTMUCH_STATUS_OUT_OF_MEMORY;
> +	}
>  
> -	return _notmuch_message_create (notmuch, notmuch, doc_id, NULL);
> +	return NOTMUCH_STATUS_SUCCESS;
>      } catch (const Xapian::Error &error) {
>  	fprintf (stderr, "A Xapian exception occurred finding message: %s.\n",
>  		 error.get_msg().c_str());
>  	notmuch->exception_reported = TRUE;
> -	return NULL;
> +	*message = NULL;
> +	return NOTMUCH_STATUS_XAPIAN_EXCEPTION;
>      }
>  }
>  
> @@ -1311,7 +1322,8 @@ _get_metadata_thread_id_key (void *ctx, const char *message_id)
>  
>  /* Find the thread ID to which the message with 'message_id' belongs.
>   *
> - * Always returns a newly talloced string belonging to 'ctx'.
> + * Note: 'thread_id' must not be NULL!
> + * On success '*thread_id' is set to a newly talloced string belonging to 'ctx'.
>   *
>   * Note: If there is no message in the database with the given
>   * 'message_id' then a new thread_id will be allocated for this
> @@ -1319,25 +1331,29 @@ _get_metadata_thread_id_key (void *ctx, const char *message_id)
>   * thread ID can be looked up if the message is added to the database
>   * later).
>   */
> -static const char *
> +static notmuch_status_t
>  _resolve_message_id_to_thread_id (notmuch_database_t *notmuch,
>  				  void *ctx,
> -				  const char *message_id)
> +				  const char *message_id,
> +				  const char **thread_id)

thread_id_ret?

>  {
> +    notmuch_status_t status;
>      notmuch_message_t *message;
>      string thread_id_string;
> -    const char *thread_id;
>      char *metadata_key;
>      Xapian::WritableDatabase *db;
>  
> -    message = notmuch_database_find_message (notmuch, message_id);
> +    status = notmuch_database_find_message (notmuch, message_id, &message);
> +
> +    if (status)
> +	return status;
>  
>      if (message) {
> -	thread_id = talloc_steal (ctx, notmuch_message_get_thread_id (message));
> +	*thread_id = talloc_steal (ctx, notmuch_message_get_thread_id (message));
>  
>  	notmuch_message_destroy (message);
>  
> -	return thread_id;
> +	return NOTMUCH_STATUS_SUCCESS;
>      }
>  
>      /* Message has not been seen yet.
> @@ -1351,15 +1367,15 @@ _resolve_message_id_to_thread_id (notmuch_database_t *notmuch,
>      thread_id_string = notmuch->xapian_db->get_metadata (metadata_key);
>  
>      if (thread_id_string.empty()) {
> -	thread_id = _notmuch_database_generate_thread_id (notmuch);
> -	db->set_metadata (metadata_key, thread_id);
> +	*thread_id = talloc_strdup (ctx, _notmuch_database_generate_thread_id (notmuch));
> +	db->set_metadata (metadata_key, *thread_id);
>      } else {
> -	thread_id = thread_id_string.c_str();
> +	*thread_id = talloc_strdup(ctx, thread_id_string.c_str());

Missing space after talloc_strdup.

>      }
>  
>      talloc_free (metadata_key);
>  
> -    return talloc_strdup (ctx, thread_id);
> +    return NOTMUCH_STATUS_SUCCESS;
>  }
>  
>  static notmuch_status_t
> @@ -1446,9 +1462,12 @@ _notmuch_database_link_message_to_parents (notmuch_database_t *notmuch,
>  	_notmuch_message_add_term (message, "reference",
>  				   parent_message_id);
>  
> -	parent_thread_id = _resolve_message_id_to_thread_id (notmuch,
> -							     message,
> -							     parent_message_id);
> +	ret = _resolve_message_id_to_thread_id (notmuch,
> +						message,
> +						parent_message_id,
> +						&parent_thread_id);
> +	if (ret)
> +	    goto DONE;
>  
>  	if (*thread_id == NULL) {
>  	    *thread_id = talloc_strdup (message, parent_thread_id);
> @@ -1759,11 +1778,12 @@ notmuch_status_t
>  notmuch_database_remove_message (notmuch_database_t *notmuch,
>  				 const char *filename)
>  {
> -    notmuch_message_t *message =
> -	notmuch_database_find_message_by_filename (notmuch, filename);
> -    notmuch_status_t status = NOTMUCH_STATUS_SUCCESS;
> +    notmuch_status_t status;
> +    notmuch_message_t *message;
>  
> -    if (message) {
> +    status = notmuch_database_find_message_by_filename (notmuch, filename, &message);
> +
> +    if (status == NOTMUCH_STATUS_SUCCESS && message) {
>  	    status = _notmuch_message_remove_filename (message, filename);
>  	    if (status == NOTMUCH_STATUS_SUCCESS)
>  		_notmuch_message_delete (message);

This isn't a problem with your patch, but shouldn't this function be
notmuch_message_destroy'ing message?

> @@ -1774,24 +1794,27 @@ notmuch_database_remove_message (notmuch_database_t *notmuch,
>      return status;
>  }
>  
> -notmuch_message_t *
> +notmuch_status_t
>  notmuch_database_find_message_by_filename (notmuch_database_t *notmuch,
> -					   const char *filename)
> +					   const char *filename,
> +					   notmuch_message_t **message)

message_ret?

>  {
>      void *local;
>      const char *prefix = _find_prefix ("file-direntry");
>      char *direntry, *term;
>      Xapian::PostingIterator i, end;
> -    notmuch_message_t *message = NULL;
>      notmuch_status_t status;
>  
> +    if (message == NULL)
> +	return NOTMUCH_STATUS_NULL_POINTER;
> +
>      local = talloc_new (notmuch);
>  
>      try {
>  	status = _notmuch_database_filename_to_direntry (local, notmuch,
>  							 filename, &direntry);
>  	if (status)
> -	    return NULL;
> +	    goto DONE;
>  
>  	term = talloc_asprintf (local, "%s%s", prefix, direntry);
>  
> @@ -1800,19 +1823,24 @@ notmuch_database_find_message_by_filename (notmuch_database_t *notmuch,
>  	if (i != end) {
>  	    notmuch_private_status_t private_status;
>  
> -	    message = _notmuch_message_create (notmuch, notmuch,
> -					       *i, &private_status);
> +	    *message = _notmuch_message_create (notmuch, notmuch,
> +						*i, &private_status);
> +	    if (*message == NULL)
> +		status = NOTMUCH_STATUS_OUT_OF_MEMORY;
>  	}
>      } catch (const Xapian::Error &error) {
>  	fprintf (stderr, "Error: A Xapian exception occurred finding message by filename: %s\n",
>  		 error.get_msg().c_str());
>  	notmuch->exception_reported = TRUE;
> -	message = NULL;
> +	status = NOTMUCH_STATUS_OUT_OF_MEMORY;
>      }
>  
> +  DONE:
>      talloc_free (local);
>  
> -    return message;
> +    if (status)
> +	*message = NULL;
> +    return status;
>  }
>  
>  notmuch_string_list_t *
> diff --git a/lib/message.cc b/lib/message.cc
> index 531d304..2a85744 100644
> --- a/lib/message.cc
> +++ b/lib/message.cc
> @@ -216,11 +216,11 @@ _notmuch_message_create_for_message_id (notmuch_database_t *notmuch,
>      unsigned int doc_id;
>      char *term;
>  
> -    *status_ret = NOTMUCH_PRIVATE_STATUS_SUCCESS;
> -
> -    message = notmuch_database_find_message (notmuch, message_id);
> +    *status_ret = (notmuch_private_status_t) notmuch_database_find_message (notmuch, message_id, &message);

Long line, should probably be wrapped.

>      if (message)
>  	return talloc_steal (notmuch, message);
> +    else if (*status_ret)
> +	return NULL;
>  
>      term = talloc_asprintf (NULL, "%s%s",
>  			    _find_prefix ("id"), message_id);
> diff --git a/lib/notmuch.h b/lib/notmuch.h
> index 6d7a99f..08b4ce2 100644
> --- a/lib/notmuch.h
> +++ b/lib/notmuch.h
> @@ -347,35 +347,60 @@ notmuch_database_remove_message (notmuch_database_t *database,
>  
>  /* Find a message with the given message_id.
>   *
> - * If the database contains a message with the given message_id, then
> - * a new notmuch_message_t object is returned. The caller should call
> - * notmuch_message_destroy when done with the message.
> + * If message with the given message_id is found then, on successful return

"If a message"

> + * (NOTMUCH_STATUS_SUCCESS) '*message' will be initialized to a message object.
> + * The user should call notmuch_message_destroy when done with the message.

Probably s/user/caller/, since "the user" is the person sitting at the
keyboard.  (notmuch.h isn't very good about this, but it does use
"caller" more often than "user").

> - * This function returns NULL in the following situations:
> + * On any failure or when the message is not found, this function initializes
> + * '*message' to NULL. This means, when NOTMUCH_STATUS_SUCCESS is returned, the
> + * user is supposed to check '*message' for NULL to find out whether the
> + * message with the given message_id was found.
>   *
> - *	* No message is found with the given message_id
> - *	* An out-of-memory situation occurs
> - *	* A Xapian exception occurs
> + * Note: The argument 'message' must not be NULL!

Since it's clearly specified what happens if 'message' is NULL, this
note isn't necessary.

> + *
> + * Return value:
> + *
> + * NOTMUCH_STATUS_SUCCESS: Successful return, check '*message'.
> + *
> + * NOTMUCH_STATUS_NULL_POINTER: The given 'message' argument is NULL
> + *
> + * NOTMUCH_STATUS_OUT_OF_MEMORY: Out of memory, creating message object
> + *
> + * NOTMUCH_STATUS_XAPIAN_EXCEPTION: A Xapian exception occurred
>   */
> -notmuch_message_t *
> +notmuch_status_t
>  notmuch_database_find_message (notmuch_database_t *database,
> -			       const char *message_id);
> +			       const char *message_id,
> +			       notmuch_message_t **message);
>  
>  /* Find a message with the given filename.
>   *
> - * If the database contains a message with the given filename, then a
> - * new notmuch_message_t object is returned.  The caller should call 
> - * notmuch_message_destroy when done with the message.
> + * If the database contains a message with the given filename then, on
> + * successful return (NOTMUCH_STATUS_SUCCESS) '*message' will be initialized to
> + * a message object. The user should call notmuch_message_destroy when done
> + * with the message.

Same comment about "user" as above.

>   *
> - * This function returns NULL in the following situations:
> + * On any failure or when the message is not found, this function initializes
> + * '*message' to NULL. This means, when NOTMUCH_STATUS_SUCCESS is returned, the
> + * user is supposed to check '*message' for NULL to find out whether the
> + * message with the given filename is found.
>   *
> - *	* No message is found with the given filename
> - *	* An out-of-memory situation occurs
> - *	* A Xapian exception occurs
> + * Note: The argument 'message' must not be NULL!

Same comment about this note as above.

> + *
> + * Return value:
> + *
> + * NOTMUCH_STATUS_SUCCESS: Successful return, check '*message'
> + *
> + * NOTMUCH_STATUS_NULL_POINTER: The given 'message' argument is NULL
> + *
> + * NOTMUCH_STATUS_OUT_OF_MEMORY: Out of memory, creating the message object
> + *
> + * NOTMUCH_STATUS_XAPIAN_EXCEPTION: A Xapian exception occurred
>   */
> -notmuch_message_t *
> +notmuch_status_t
>  notmuch_database_find_message_by_filename (notmuch_database_t *notmuch,
> -					   const char *filename);
> +					   const char *filename,
> +					   notmuch_message_t **message);
>  
>  /* Return a list of all tags found in the database.
>   *
> diff --git a/notmuch-new.c b/notmuch-new.c
> index e79593c..96a1e31 100644
> --- a/notmuch-new.c
> +++ b/notmuch-new.c
> @@ -743,7 +743,9 @@ remove_filename (notmuch_database_t *notmuch,
>      status = notmuch_database_begin_atomic (notmuch);
>      if (status)
>  	return status;
> -    message = notmuch_database_find_message_by_filename (notmuch, path);
> +    status = notmuch_database_find_message_by_filename (notmuch, path, &message);
> +    if (status || message == NULL)
> +	return status;
>      status = notmuch_database_remove_message (notmuch, path);
>      if (status == NOTMUCH_STATUS_DUPLICATE_MESSAGE_ID) {
>  	add_files_state->renamed_messages++;
> diff --git a/notmuch-restore.c b/notmuch-restore.c
> index f095f64..e4a5355 100644
> --- a/notmuch-restore.c
> +++ b/notmuch-restore.c
> @@ -87,10 +87,13 @@ notmuch_restore_command (unused (void *ctx), int argc, char *argv[])
>  	file_tags = xstrndup (line + match[2].rm_so,
>  			      match[2].rm_eo - match[2].rm_so);
>  
> -	message = notmuch_database_find_message (notmuch, message_id);
> -	if (message == NULL) {
> -	    fprintf (stderr, "Warning: Cannot apply tags to missing message: %s\n",
> -		     message_id);
> +	status = notmuch_database_find_message (notmuch, message_id, &message);
> +	if (status || message == NULL) {
> +	    fprintf (stderr, "Warning: Cannot apply tags to %smessage: %s\n",
> +		     message ? "" : "missing ", message_id);
> +	    if (status)
> +		fprintf (stderr, "%s\n",
> +			 notmuch_status_to_string(status));
>  	    goto NEXT_LINE;
>  	}
>  

-- 
Austin Clements                                      MIT/'06/PhD/CSAIL
amdragon at mit.edu                           http://web.mit.edu/amdragon
       Somewhere in the dream we call reality you will find me,
              searching for the reality we call dreams.


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