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

From: Johannes Schindelin <johannes.schindelin@gmx.de>
Date: Dec 10, 2019, 14:09 UTC
Message-ID: <nycvar.QRO.7.76.6.1912101457200.31080@tvgsbejvaqbjf.bet>
In-Reply-To: <xmqqo8wgsqnn.fsf@gitster-ct.c.googlers.com>

Hi,

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

Show 14 quoted lines

> 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.

Show 29 quoted lines

> >> 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