Re: [PATCH v2 8/8] test-lib: clear watchman watches at test completion

From: Johannes Schindelin <Johannes.Schindelin@gmx.de>
To: Junio C Hamano <gitster@pobox.com>
Cc: Derrick Stolee <stolee@gmail.com>,
	Derrick Stolee via GitGitGadget <gitgitgadget@gmail.com>,
	git@vger.kernel.org, szeder.dev@gmail.com, ukshah2@illinois.edu,
	Kevin.Willford@microsoft.com,
	Derrick Stolee <dstolee@microsoft.com>
Subject: Re: [PATCH v2 8/8] test-lib: clear watchman watches at test completion
Date: Tue, 10 Dec 2019 15:09:02 +0100 (CET)	[thread overview]
Message-ID: <nycvar.QRO.7.76.6.1912101457200.31080@tvgsbejvaqbjf.bet> (raw)
In-Reply-To: <xmqqo8wgsqnn.fsf@gitster-ct.c.googlers.com>

Hi,

On Mon, 9 Dec 2019, Junio C Hamano wrote:

> Derrick Stolee <stolee@gmail.com> writes:
>
> > Hm. That is a good point. Can we assume that our version of grep has
> > a "-F" or "--fixed-strings" option? ([1] seems to say that "-F" would
> > work.)
>
> $ git grep "grep -F" -- \*.sh
>
> is your friend ;-)
>
> And never use https://www.gnu.org/ manual as a yardstick---you will
> end up using GNUism that is not unavailable elsewhere pretty easily.
>
> > [1] https://www.gnu.org/savannah-checkouts/gnu/grep/manual/grep.html#index-grep-programs

I often look at GNU grep's man page first and then verify via
https://man.openbsd.org/grep and
https://pubs.opengroup.org/onlinepubs/009695399/utilities/grep.html
that the option can be considered portable.

> >> What are these stripping of ", and " about?  Could you tell readers
> >> how a typical output from the program we are reading from looks like
> >> perhaps in the log message or in-code comment around here?
> >
> > Watchman outputs its list of paths in JSON format. Luckily, it formats
> > the output so the path lines are on separate lines, each quoted.
> >
> > For example:
> >
> > {
> > 	"version": "4.9.0",
> > 	"roots": [
> > 		"<path1>",
> > 		"<path2>",
> > 		"<path3>"
> > 	]
> > }
>
> Yeek; how is a dq in path represented?  by doubling?  by
> backslash-quoting (if so how is a backslash in path represented)?
> By something else?
>
> It's OK at least for now to declare that our test repository does
> not contain any funny paths, but in the longer run does the above
> mean that we somehow need to be able to grok JSON reliably in our
> tests?  It may not be such a bad thing especially for longer term,
> as there are other parts of the system that may benefit from having
> JSON capable output readers in our tests (e.g. trace2 code can do
> JSON, right?)..

From
https://www.ecma-international.org/publications/files/ECMA-ST/ECMA-404.pdf
(section "9 String"):

A string is a sequence of Unicode code points wrapped with quotation marks
(U+0022). All code points may be  placed  within  the  quotation  marks
except  for  the code  points that  must  be  escaped:  quotation  mark
(U+0022), reverse solidus (U+005C), and the control characters U+0000 to
U+001F. There are two-character escape sequence representations of some
characters.

	\"	represents the quotation mark character (U+0022).
	\\	represents the reverse solidus character(U+005C).
	\/	represents the solidus character (U+002F).
	\b	represents the backspace character(U+0008).
	\f	represents the form feed character (U+000C).
	\n	represents the line feed character (U+000A).
	\r	represents the carriage return character (U+000D).
	\t	represents the character tabulation character (U+0009).

(Side note: It is amazing what things you learn unexpectedly, e.g. when
researching information about the JSON format, you learn that about the
word "solidus", that it refers to the slash, and that it was once also
know as the "shilling mark"...)

I am not sure why the forward slash needs to be escaped, but I guess that
this is voluntary rather than mandatory.

Ciao,
Dscho