Re: [RFC PATCH v2] t4210: detect REG_ILLSEQ dynamically

> 7187c7bbb8 (t4210: skip i18n tests that don't work on FreeBSD, 2019-11-27)
> adds a REG_ILLSEQ prerequisite to avoid failures from the tests added with
> 4e2443b181 (log tests: test regex backends in "--encode=<enc>" tests,
> 2019-06-28), but hardcodes it to be only enabled for FreeBSD.
>
> Instead of hardcoding the affected platform, add a test using test-tool to
> make sure it can be dynamically detected in other affected systems (like
> DragonFlyBSD or macOS), and while at it, enhance the tool so it can report
> better on the cause of failure and be silent when needed.
>
> To minimize changes, it is assumed the regcomp error is of the right type
> since we control the only caller, and is also assumed to affect both basic
> and extended syntax (only extended is tested, but both behave the same in
> all three affected platforms).
>
> The description of the first test which wasn't accurate has been corrected,
> and unlike the original fix from 7187c7bbb8, all added entries to test-lib
> are no longer needed and only the 2 affected engines will have their tests
> suppressed.
>
> Signed-off-by: Carlo Marcelo Arenas Belón <carenas@gmail.com>
> ---
> v2:
> - nicer variable names and hopefully easier to understand logic

>
>  t/helper/test-regex.c | 20 +++++++++++++++----
>  t/t4210-log-i18n.sh   | 45 ++++++++++++++++++++++++++++---------------
>  t/test-lib.sh         |  6 ------
>  3 files changed, 45 insertions(+), 26 deletions(-)
>
> diff --git a/t/helper/test-regex.c b/t/helper/test-regex.c
> index 10284cc56f..a4bd1f3a36 100644
> --- a/t/helper/test-regex.c
> +++ b/t/helper/test-regex.c
> @@ -41,16 +41,21 @@ int cmd__regex(int argc, const char **argv)
>  {
>  	const char *pat;
>  	const char *str;
> -	int flags = 0;
> +	int ret, silent = 0, flags = 0;
>  	regex_t r;
>  	regmatch_t m[1];
> +	char errbuf[64];
>  
>  	if (argc == 2 && !strcmp(argv[1], "--bug"))
>  		return test_regex_bug();
>  	else if (argc < 3)
>  		usage("test-tool regex --bug\n"
> -		      "test-tool regex <pattern> <string> [<options>]");
> +		      "test-tool regex [--silent] <pattern> <string> [<options>]");
>  
> +	if (!strcmp(argv[1], "--silent")) {
> +		silent = 1;
> +		argv++;
> +	}
>  	argv++;
>  	pat = *argv++;
>  	str = *argv++;
> @@ -67,8 +72,15 @@ int cmd__regex(int argc, const char **argv)
>  	}
>  	git_setup_gettext();
>  
> -	if (regcomp(&r, pat, flags))
> -		die("failed regcomp() for pattern '%s'", pat);
> +	ret = regcomp(&r, pat, flags);
> +	if (ret) {
> +		if (!silent) {
> +			regerror(ret, &r, errbuf, sizeof(errbuf));
> +			die("failed regcomp() for pattern '%s' (%s)",
> +				pat, errbuf);
> +		} else
> +			return 1;
> +	}
>  	if (regexec(&r, str, 1, m, 0))
>  		return 1;
>  
> diff --git a/t/t4210-log-i18n.sh b/t/t4210-log-i18n.sh
> index c3792081e6..8fccb83020 100755
> --- a/t/t4210-log-i18n.sh
> +++ b/t/t4210-log-i18n.sh
> @@ -10,6 +10,12 @@ latin1_e=$(printf '\351')
>  # invalid UTF-8
>  invalid_e=$(printf '\303\50)') # ")" at end to close opening "("
>  
> +if test_have_prereq GETTEXT_LOCALE &&
> +	! LC_ALL=$is_IS_locale test-tool regex --silent $latin1_e $latin1_e EXTENDED
> +then
> +	have_reg_illseq=1
> +fi
> +
>  test_expect_success 'create commits in different encodings' '
>  	test_tick &&
>  	cat >msg <<-EOF &&
> @@ -61,33 +67,40 @@ do
>  	prereq=
>  	if test $engine = "perl"
>  	then
> -		prereq="PCRE"
> -	else
> -		prereq=""
> +		prereq=PCRE
>  	fi
>  	force_regex=
>  	if test $engine != "fixed"
>  	then
> -	    force_regex=.*
> +		force_regex=.*
> +	fi
> +
> +	if test -z "$have_reg_illseq" ||
> +		test $engine = "fixed" || test $engine = "perl"
> +	then
> +		test_expect_success !MINGW,GETTEXT_LOCALE,$prereq "-c grep.patternType=$engine log --grep searches in log output encoding (latin1 + locale)" "
> +			cat >expect <<-\EOF &&
> +			latin1
> +			utf8
> +			EOF
> +			LC_ALL=$is_IS_locale git -c grep.patternType=$engine log --encoding=ISO-8859-1 --format=%s --grep=\"$force_regex$latin1_e\" >actual &&
> +			test_cmp expect actual
> +		"
>  	fi
> -	test_expect_success !MINGW,!REGEX_ILLSEQ,GETTEXT_LOCALE,$prereq "-c grep.patternType=$engine log --grep does not find non-reencoded values (latin1 + locale)" "
> -		cat >expect <<-\EOF &&
> -		latin1
> -		utf8
> -		EOF
> -		LC_ALL=\"$is_IS_locale\" git -c grep.patternType=$engine log --encoding=ISO-8859-1 --format=%s --grep=\"$force_regex$latin1_e\" >actual &&
> -		test_cmp expect actual
> -	"
>  
>  	test_expect_success !MINGW,GETTEXT_LOCALE,$prereq "-c grep.patternType=$engine log --grep does not find non-reencoded values (latin1 + locale)" "
>  		LC_ALL=\"$is_IS_locale\" git -c grep.patternType=$engine log --encoding=ISO-8859-1 --format=%s --grep=\"$force_regex$utf8_e\" >actual &&
>  		test_must_be_empty actual
>  	"
>  
> -	test_expect_success !MINGW,!REGEX_ILLSEQ,GETTEXT_LOCALE,$prereq "-c grep.patternType=$engine log --grep does not die on invalid UTF-8 value (latin1 + locale + invalid needle)" "
> -		LC_ALL=\"$is_IS_locale\" git -c grep.patternType=$engine log --encoding=ISO-8859-1 --format=%s --grep=\"$force_regex$invalid_e\" >actual &&
> -		test_must_be_empty actual
> -	"
> +	if test -z "$have_reg_illseq" ||
> +		test $engine = "fixed" || test $engine = "perl"
> +	then
> +		test_expect_success !MINGW,GETTEXT_LOCALE,$prereq "-c grep.patternType=$engine log --grep does not die on invalid UTF-8 value (latin1 + locale + invalid needle)" "
> +			LC_ALL=$is_IS_locale git -c grep.patternType=$engine log --encoding=ISO-8859-1 --format=%s --grep=\"$force_regex$invalid_e\" >actual &&
> +			test_must_be_empty actual
> +		"
> +	fi
>  done
>  
>  test_done
> diff --git a/t/test-lib.sh b/t/test-lib.sh
> index 0ea1e5a05e..81473fea1d 100644
> --- a/t/test-lib.sh
> +++ b/t/test-lib.sh
> @@ -1454,12 +1454,6 @@ case $uname_s in
>  	test_set_prereq SED_STRIPS_CR
>  	test_set_prereq GREP_STRIPS_CR
>  	;;
> -FreeBSD)
> -	test_set_prereq REGEX_ILLSEQ
> -	test_set_prereq POSIXPERM
> -	test_set_prereq BSLASHPSPEC
> -	test_set_prereq EXECKEEPSPID
> -	;;
>  *)
>  	test_set_prereq POSIXPERM
>  	test_set_prereq BSLASHPSPEC