Received: from malur.postgresql.org ([217.196.149.56])
	by arkaria.postgresql.org with esmtps
 (TLS1.3:ECDHE_RSA_AES_256_GCM_SHA384:256)
	(Exim 4.92)
	(envelope-from <pgsql-hackers-owner+archive@lists.postgresql.org>)
	id 1kcoXT-0002XH-3o
	for pgsql-hackers@arkaria.postgresql.org; Wed, 11 Nov 2020 11:43:47 +0000
Received: from localhost ([127.0.0.1] helo=malur.postgresql.org)
	by malur.postgresql.org with esmtp (Exim 4.92)
	(envelope-from <pgsql-hackers-owner+archive@lists.postgresql.org>)
	id 1kcoXS-00027O-1p
	for pgsql-hackers@arkaria.postgresql.org; Wed, 11 Nov 2020 11:43:46 +0000
Received: from magus.postgresql.org ([2a02:c0:301:0:ffff::29])
	by malur.postgresql.org with esmtps (TLS1.3:ECDHE_RSA_AES_256_GCM_SHA384:256)
	(Exim 4.92)
	(envelope-from <vik@postgresfriends.org>)
	id 1kcoXR-00027F-RA
	for pgsql-hackers@lists.postgresql.org; Wed, 11 Nov 2020 11:43:45 +0000
Received: from relay4-d.mail.gandi.net ([217.70.183.196])
	by magus.postgresql.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256)
	(Exim 4.92)
	(envelope-from <vik@postgresfriends.org>)
	id 1kcoXP-00014K-K7
	for pgsql-hackers@postgresql.org; Wed, 11 Nov 2020 11:43:45 +0000
X-Originating-IP: 79.88.149.14
Received: from [172.16.255.146] (14.149.88.79.rev.sfr.net [79.88.149.14])
	(Authenticated sender: vik@postgresfriends.org)
	by relay4-d.mail.gandi.net (Postfix) with ESMTPSA id 04B93E0002;
	Wed, 11 Nov 2020 11:43:40 +0000 (UTC)
Subject: Re: Clean up optional rules in grammar
To: Peter Eisentraut <peter.eisentraut@enterprisedb.com>,
 pgsql-hackers <pgsql-hackers@postgresql.org>
References: <e9eed669-e32d-6919-fed4-acc0daea857b@enterprisedb.com>
From: Vik Fearing <vik@postgresfriends.org>
Message-ID: <0e608c89-3b1d-1dbf-7c03-423f15dcbbed@postgresfriends.org>
Date: Wed, 11 Nov 2020 12:43:40 +0100
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101
 Thunderbird/68.10.0
MIME-Version: 1.0
In-Reply-To: <e9eed669-e32d-6919-fed4-acc0daea857b@enterprisedb.com>
Content-Type: text/plain; charset=utf-8
Content-Language: en-US
Content-Transfer-Encoding: 8bit
List-Id: <pgsql-hackers.lists.postgresql.org>
List-Help: <https://lists.postgresql.org/manage/>
List-Subscribe: <https://lists.postgresql.org/manage/>
List-Post: <mailto:pgsql-hackers@lists.postgresql.org>
List-Owner: <mailto:pgsql-hackers-owner@lists.postgresql.org>
List-Archive: <https://www.postgresql.org/list/pgsql-hackers>
Precedence: bulk

On 11/11/20 10:12 AM, Peter Eisentraut wrote:
> There are a number of rules like this in the grammar:
> 
> opt_foo: FOO
>         | /*EMPTY*/
> ;
> 
> And there are some like this:
> 
> opt_foo: FOO         {}
>         | /*EMPTY*/  {}
> ;
> 
> and some even like this:
> 
> %type <node> opt_foo
> 
> opt_foo: FOO         { $$ = NULL; }
>         | /*EMPTY*/  { $$ = NULL; }
> ;
> 
> (I mean here specifically those rules where FOO is a noise word and the
> actions are the same in each branch.)
> 
> It's obviously confusing to have multiple different styles to do the
> same thing.  And these extra rules (including the empty ones) also end
> up in the output, so they create more work down the line.
> 
> The attached patch cleans this up to make them all look like the first
> style.

No objections, but could we also take this opportunity to standardize
the comment itself?  Even in your patch there is a mix of spacing and
casing.

My preference is /* EMPTY */.  That is, uppercase with spaces, but
whatever gets chosen is fine with me.
-- 
Vik Fearing