Subject: Re: [PATCH 2/2] test-lib: exhaustively insert non-alnum ASCII into the TRASH_DIRECTORY name

From: SZEDER Gábor <[email-masked]>
Date: Mon, 10 Apr 2017 03:47:12 +0200

> Change the test library to insert non-alphanumeric ASCII characters
> into the TRASH_DIRECTORY name, that's the directory the test library
> creates, chdirs to and runs each individual test from.
> 
> Unless test_fails_on_unusual_directory_names=1 is declared before
> importing test-lib.sh (and if perl isn't available on the system), the
> trash directory will contain every non-alphanumeric character in
> ASCII, in order.

At the very least there must be an easier way to disable this, e.g. a
command line option.

This change is sure effective in smoking out bugs, but it's a major
annoyance during development when it comes to debugging a test.  At
first I could not even cd into the trash directory, because TAB
completing the directory name with all those non-printable characters
didn't work (this may be a bug in the bash-completion package).  And
simply copy-pasting the dirname didn't work either, because 'ls'
displayed it as

  trash directory.t9902-completion.??????????????????????????????? !"#$%&'()*+,-:;<=>?@[\]^_`{|}~?

After some headscratching, Sunday night may be my excuse, I figured
out that 'cd tr*' works...  only to be greeted with the ugliest-ever
three-line(!) shell prompt.

Therefore I would say that this should not even be enabled by default
in test-lib.sh, so at least running a test directly from the command
line as ./t1234-foo.sh would considerately give us an easily
accessible trash directory even without any command line options.  We
could enable it for 'make test' by default via GIT_TEST_OPTS in
t/Makefile, though.

> This includes all the control characters, !, [], {} etc. the "."
> character isn't included because it's already in the directory name,
> and nor is "/" for obvious reasons, although that would actually work,
> we'd just create a subdirectory, which would make the tests harder to
> inspect when they fail.i

1. Heh.  How an additional subdirectory would make the tests harder to
   inspect is nothing compared to the effect of all the other
   characters.

2. s/i$//

> This change is inspired by the "submodule: prevent backslash expantion
> in submodule names" patch[1]. If we'd had backslashes in the
> TRASH_DIRECTORY all along that bug would have been fixed a long time
> ago. This will flag such issues by marking tests that currently fail
> with "test_fails_on_unusual_directory_names=1", ensure that new tests
> aren't added unless a discussion is had about why the code can't
> handle unusual pathnames, and prevent future regressions.
> 
> 1. <[email-masked]>
> ---
>  t/README      | 12 ++++++++++++
>  t/test-lib.sh |  4 ++++
>  2 files changed, 16 insertions(+)
> 
> diff --git a/t/README b/t/README
> index ab386c3681..314dd40221 100644
> --- a/t/README
> +++ b/t/README
> @@ -345,6 +345,18 @@ assignment to variable 'test_description', like this:
>  	This test registers the following structure in the cache
>  	and tries to run git-ls-files with option --frotz.'
>  
> +By default the tests will be run from a directory with a highly
> +unusual filename that includes control characters, a newline, various
> +punctuation etc., this is done to smoke out any bugs related to path
> +handling. If for whatever reason the tests can't deal with such
> +unusual path names, set:
> +
> +    test_fails_on_unusual_directory_names=1
> +
> +Before sourcing 'test-lib.sh' as described below. This option is
> +mainly intended to grandfather in existing broken tests & code, and
> +should usually not be used in new code, instead your tests or code
> +probably need fixing.
> 
>  Source 'test-lib.sh'
>  --------------------
> diff --git a/t/test-lib.sh b/t/test-lib.sh
> index 13b5696822..089ff5ac7d 100644
> --- a/t/test-lib.sh
> +++ b/t/test-lib.sh
> @@ -914,6 +914,10 @@ fi
>  
>  # Test repository
>  TRASH_DIRECTORY="trash directory.$(basename "$0" .sh)"
> +if test -z "$test_fails_on_unusual_directory_names" -a "$(perl -e 'print 1+1' 2>/dev/null)" = "2"
> +then
> +   TRASH_DIRECTORY="$TRASH_DIRECTORY.$(perl -e 'print join q[], grep { /[^[:alnum:]]/ and !m<[./]> } map chr, 0x01..0x7f')"
> +fi
>  test -n "$root" && TRASH_DIRECTORY="$root/$TRASH_DIRECTORY"
>  case "$TRASH_DIRECTORY" in
>  /*) ;; # absolute path is good
> -- 
> 2.11.0