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From: Matthew DeVore <matvore@google.com>
To: Junio C Hamano <gitster@pobox.com>
Cc: sunshine@sunshineco.com, git@vger.kernel.org,
	Jeff King <peff@peff.net>,
	Jonathan Tan <jonathantanmy@google.com>,
	Jonathan Nieder <jrn@google.com>
Subject: Re: [PATCH v2 1/6] CodingGuidelines: add shell piping guidelines
Date: Wed, 19 Sep 2018 13:06:27 -0700	[thread overview]
Message-ID: <CAMfpvhLYjmb4kF8tObAiROtcDHfpah0J=Y1KhUHZnvFoyK6sgA@mail.gmail.com> (raw)
In-Reply-To: <xmqqo9ct4lap.fsf@gitster-ct.c.googlers.com>

On Wed, Sep 19, 2018 at 5:36 AM Eric Sunshine <sunshine@sunshineco.com> wrote:
>
> On Tue, Sep 18, 2018 at 10:11 PM Matthew DeVore <matvore@google.com> wrote:
> > Yes, it's probably better to add a point about that. Here is the new
> > documentation after applying your suggestions:
> >
> >  - If a piped sequence which spans multiple lines, put each statement
>
> s/which//
Done.

On Wed, Sep 19, 2018 at 7:24 AM Junio C Hamano <gitster@pobox.com> wrote:
> The formatting advice to place '|' at the end applies equally to
> '&&' and '||' because these three syntactic elements share exactly
> the same trait: the shell knows you haven't finished speaking when
> it sees them at the end of the line and keeps listening, and humans
> would know that too, so there is no need for explicitly continuing
> the line with backslash.
>
I've reworded the text to indicate the advice applies to && and || as well.

> Organizationally speaking, I wonder if the above about formatting
> would better appear separate from the latter two points that are
> about semantics.
>
I moved the formatting point to right under the point about formatting
if statements, which does seem like a more natural progression.

Here is the new patch to summarize the changes (warning: tabs are mangled):

--------------------------------------------------------------------------------

    CodingGuidelines: add shell piping guidelines

    Add two guidelines:

     - pipe characters should appear at the end of lines, and not cause
       indentation
     - pipes should be avoided when they swallow exit codes that can
       potentially fail

diff --git a/Documentation/CodingGuidelines b/Documentation/CodingGuidelines
index 48aa4edfb..6d265327c 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
@@ -163,6 +181,15 @@ For shell scripts specifically (not exhaustive):

    does not have such a problem.

+ - In a piped chain such as "grep blob objects | sort", the exit codes
+   returned by processes besides the last are ignored. This means that
+   if git crashes at the beginning or middle of a chain, it may go
+   undetected. Prefer writing the output of that command to a
+   temporary file with '>' rather than pipe it.
+
+ - The $(git ...) construct also discards git's exit code, so if the
+   goal is to test that particular command, redirect its output to a
+   temporary file rather than wrap it with $( ).

 For C programs:

  reply	other threads:[~2018-09-19 20:06 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 [this message]
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
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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