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From: "SZEDER Gábor" <szeder.dev@gmail.com>
To: Matthew DeVore <matvore@google.com>
Cc: git@vger.kernel.org, Jeff King <peff@peff.net>,
	Jonathan Tan <jonathantanmy@google.com>,
	Junio C Hamano <gitster@pobox.com>,
	Jonathan Nieder <jrn@google.com>,
	Eric Sunshine <sunshine@sunshineco.com>
Subject: Re: [PATCH v3 1/5] CodingGuidelines: add shell piping guidelines
Date: Thu, 27 Sep 2018 23:18:26 +0200	[thread overview]
Message-ID: <20180927211826.GL27036@localhost> (raw)
In-Reply-To: <CAMfpvhJ-chi7OMRKjjk79r0uqCqW67Vj9J=tT7Kz-XUmw41H5A@mail.gmail.com>

On Tue, Sep 25, 2018 at 02:58:08PM -0700, Matthew DeVore wrote:
> Here is the new commit with updated message (I will wait for a day or
> two before I send a reroll):
> 
>     Documentation: add shell guidelines
> 
>     Add the following guideline to Documentation/CodingGuidelines:
> 
>             &&, ||, and | should appear at the end of lines, not the
>             beginning, and the \ line continuation character should be
>             omitted
> 
>     And the following to t/README (since it is specific to writing tests):
> 
>             pipes and $(git ...) should be avoided when they swallow exit
>             codes of Git processes
> 
>     Signed-off-by: Matthew DeVore <matvore@google.com>
> 
> diff --git a/Documentation/CodingGuidelines b/Documentation/CodingGuidelines
> index 48aa4edfb..3d2cfea9b 100644
> --- a/Documentation/CodingGuidelines
> +++ b/Documentation/CodingGuidelines
> @@ -118,6 +118,24 @@ For shell scripts specifically (not exhaustive):
>                  do this
>          fi
> 
> + - If a command sequence joined with && or || or | spans multiple
> +   lines, put each command on a separate line and put && and || and |
> +   operators at the end of each line, rather than the start. This
> +   means you don't need to use \ to join lines, since the above
> +   operators imply the sequence isn't finished.
> +
> +        (incorrect)
> +        grep blob verify_pack_result \
> +        | awk -f print_1.awk \
> +        | sort >actual &&
> +        ...
> +
> +        (correct)
> +        grep blob verify_pack_result |
> +        awk -f print_1.awk |
> +        sort >actual &&
> +        ...
> +
>   - We prefer "test" over "[ ... ]".
> 
>   - We do not write the noiseword "function" in front of shell
> @@ -163,7 +181,6 @@ For shell scripts specifically (not exhaustive):
> 
>     does not have such a problem.
> 
> -
>  For C programs:
> 
>   - We use tabs to indent, and interpret tabs as taking up to
> diff --git a/t/README b/t/README
> index 9028b47d9..3e28b72c4 100644
> --- a/t/README
> +++ b/t/README
> @@ -461,6 +461,32 @@ Don't:
>     platform commands; just use '! cmd'.  We are not in the business
>     of verifying that the world given to us sanely works.
> 
> + - Use Git upstream in the non-final position in a piped chain, as in:

Note the starting upper case 'U'.

> +
> +     git -C repo ls-files |
> +     xargs -n 1 basename |
> +     grep foo
> +
> +   which will discard git's exit code and may mask a crash. In the
> +   above example, all exit codes are ignored except grep's.
> +
> +   Instead, write the output of that command to a temporary
> +   file with ">" or assign it to a variable with "x=$(git ...)" rather
> +   than pipe it.
> +
> + - Use command substitution in a way that discards git's exit code.

'U' again.

> +   When assigning to a variable, the exit code is not discarded, e.g.:
> +
> +     x=$(git cat-file -p $sha) &&
> +     ...
> +
> +   is OK because a crash in "git cat-file" will cause the "&&" chain
> +   to fail, but:
> +
> +     test_cmp expect $(git cat-file -p $sha)
> +
> +   is not OK and a crash in git could go undetected.

Well, this is not OK indeed, because it doesn't make any sense in the
first place :)  'test_cmp' requires two paths as argumens, but the
output of 'git cat-file -p' is the whole _content_ of the given object.

>   - use perl without spelling it as "$PERL_PATH". This is to help our

Note the starting lower case 'u'.

This is because these are the continuation of the "Don't:" some lines
earlier, so your new points should start with a lower case 'u' as
well.


Sidenote: I think we should consider reformatting this whole section
as:

  - Don't do this.
  - Don't do that.

because it grew so much that when I look at the last points, then that
starting "Don't:" has already scrolled out of my screen.

>     friends on Windows where the platform Perl often adds CR before
>     the end of line, and they bundle Git with a version of Perl that
> 
> 
> >
> >
> > These last two points, however, are specific to test scripts,
> > therefore I think they would be better placed in 't/README', where the
> > rest of the test-specific guidelines are.
> >
> > >  For C programs:
> > >
> > > --
> > > 2.19.0.444.g18242da7ef-goog
> > >

  reply	other threads:[~2018-09-27 21:18 UTC|newest]

Thread overview: 66+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-09-15  0:02 [PATCH v1 0/2] Cleanup tests for test_cmp argument ordering and "|" placement Matthew DeVore
2018-09-15  0:02 ` [PATCH v1 1/2] t/*: fix pipe placement and remove \'s Matthew DeVore
2018-09-17 16:31   ` Jonathan Nieder
2018-09-17 21:47     ` Matthew DeVore
2018-09-15  0:02 ` [PATCH v1 2/2] t/*: fix ordering of expected/observed arguments Matthew DeVore
2018-09-17 12:56   ` Matthew DeVore
2018-09-15 15:55 ` [PATCH v1 0/2] Cleanup tests for test_cmp argument ordering and "|" placement Junio C Hamano
2018-09-17 22:24 ` [PATCH v2 0/6] Clean up tests for test_cmp arg ordering and pipe placement Matthew DeVore
2018-09-17 22:24   ` [PATCH v2 4/6] tests: Add linter check for pipe placement style Matthew DeVore
2018-09-18  0:34     ` Eric Sunshine
2018-09-19 17:39       ` Matthew DeVore
     [not found] ` <cover.1537223021.git.matvore@google.com>
2018-09-17 22:24   ` [PATCH v2 1/6] CodingGuidelines: add shell piping guidelines Matthew DeVore
2018-09-18  0:16     ` Eric Sunshine
2018-09-19  2:11       ` Matthew DeVore
2018-09-19 12:36         ` Eric Sunshine
2018-09-19 14:24         ` Junio C Hamano
2018-09-19 20:06           ` Matthew DeVore
2018-09-17 22:24   ` [PATCH v2 2/6] tests: standardize pipe placement Matthew DeVore
2018-09-17 22:24   ` [PATCH v2 3/6] t/*: fix ordering of expected/observed arguments Matthew DeVore
2018-09-17 22:24   ` [PATCH v2 4/6] tests: add linter check for pipe placement style Matthew DeVore
2018-09-17 22:24   ` [PATCH v2 5/6] tests: split up pipes Matthew DeVore
2018-09-18  1:30     ` Eric Sunshine
2018-09-19  2:33       ` Matthew DeVore
2018-09-17 22:24   ` [PATCH v2 6/6] t9109-git-svn-props.sh: split up several pipes Matthew DeVore
2018-09-18  1:56     ` Eric Sunshine
2018-09-19  2:56       ` Matthew DeVore
2018-09-19 12:50         ` Eric Sunshine
2018-09-19 18:43           ` Matthew DeVore
2018-09-21  1:43 ` [PATCH v3 0/5] Clean up tests for test_cmp arg ordering and pipe placement Matthew DeVore
2018-09-21  1:43   ` [PATCH v3 1/5] CodingGuidelines: add shell piping guidelines Matthew DeVore
2018-09-21  2:06     ` Eric Sunshine
2018-09-21 21:03       ` Matthew DeVore
2018-09-24 21:03     ` SZEDER Gábor
2018-09-25 21:58       ` Matthew DeVore
2018-09-27 21:18         ` SZEDER Gábor [this message]
2018-10-01 23:07           ` Matthew DeVore
2018-09-21  1:43   ` [PATCH v3 2/5] tests: standardize pipe placement Matthew DeVore
2018-09-21  1:43   ` [PATCH v3 3/5] t/*: fix ordering of expected/observed arguments Matthew DeVore
2018-09-21  1:43   ` [PATCH v3 4/5] tests: don't swallow Git errors upstream of pipes Matthew DeVore
2018-09-21  1:43   ` [PATCH v3 5/5] t9109: " Matthew DeVore
2018-10-03 16:25 ` [PATCH v4 0/7] Clean up tests for test_cmp arg ordering and pipe placement Matthew DeVore
2018-10-03 16:25   ` [PATCH v4 1/7] t/README: reformat Do, Don't, Keep in mind lists Matthew DeVore
2018-10-05  6:15     ` Junio C Hamano
2018-10-05 14:57       ` Matthew DeVore
2018-10-03 16:26   ` [PATCH v4 2/7] Documentation: add shell guidelines Matthew DeVore
2018-10-05 16:48     ` Junio C Hamano
2018-10-05 18:21       ` Matthew DeVore
2018-10-03 16:26   ` [PATCH v4 3/7] tests: standardize pipe placement Matthew DeVore
2018-10-03 16:26   ` [PATCH v4 4/7] t/*: fix ordering of expected/observed arguments Matthew DeVore
2018-10-03 16:26   ` [PATCH v4 5/7] tests: don't swallow Git errors upstream of pipes Matthew DeVore
2018-10-05 16:48     ` Junio C Hamano
2018-10-05 17:54       ` Matthew DeVore
2018-10-05 18:12         ` Matthew DeVore
2018-10-03 16:26   ` [PATCH v4 6/7] t9109: " Matthew DeVore
2018-10-03 16:26   ` [PATCH v4 7/7] tests: order arguments to git-rev-list properly Matthew DeVore
2018-10-03 16:33     ` Matthew DeVore
2018-10-05  8:16       ` Junio C Hamano
2018-10-05 21:54 ` [PATCH v5 0/7] subject: Clean up tests for test_cmp arg ordering and pipe placement Matthew DeVore
2018-10-05 21:54   ` [PATCH v5 1/7] t/README: reformat Do, Don't, Keep in mind lists Matthew DeVore
2018-10-05 21:54   ` [PATCH v5 2/7] Documentation: add shell guidelines Matthew DeVore
2018-10-05 21:54   ` [PATCH v5 3/7] tests: standardize pipe placement Matthew DeVore
2018-10-05 21:54   ` [PATCH v5 4/7] t/*: fix ordering of expected/observed arguments Matthew DeVore
2018-10-05 21:54   ` [PATCH v5 5/7] tests: don't swallow Git errors upstream of pipes Matthew DeVore
2018-10-05 21:54   ` [PATCH v5 6/7] t9109: " Matthew DeVore
2018-10-05 21:54   ` [PATCH v5 7/7] tests: order arguments to git-rev-list properly Matthew DeVore
2018-10-06 23:53   ` [PATCH v5 0/7] subject: Clean up tests for test_cmp arg ordering and pipe placement Junio C Hamano

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