Re: [PATCH v2] unit-tests: do show relative file paths on non-Windows, too

> Phillip Wood <phillip.wood123@gmail.com> writes:
> 
>>> There is a larger clean-up opportunity to drop the need for making a
>>> copy, which probably is worth doing, so I folded the above into this
>>> version.
>>
>> Ooh, that's nice. This version looks good, I found the code comments
>> very helpful
> 
> Thanks.
> 
> Judging from https://github.com/git/git/actions/runs/7878254534/job/21496314393#step:5:142
> I do not seen to have broken Windows with this change, so let's
> fast-track and merge it down to 'master' before -rc1.

>> Best Wishes
>>
>> Phillip
>>
>>> ------- >8 ------------- >8 ------------- >8 ------------- >8 -------
>>> There are compilers other than Visual C that want to show absolute
>>> paths.  Generalize the helper introduced by a2c5e294 (unit-tests: do
>>> show relative file paths, 2023-09-25) so that it can also work with
>>> a path that uses slash as the directory separator, and becomes
>>> almost no-op once one-time preparation finds out that we are using a
>>> compiler that already gives relative paths.  Incidentally, this also
>>> should do the right thing on Windows with a compiler that shows
>>> relative paths but with backslash as the directory separator (if
>>> such a thing exists and is used to build git).
>>> Reported-by: Randall S. Becker <rsbecker@nexbridge.com>
>>> Helped-by: Phillip Wood <phillip.wood@dunelm.org.uk>
>>> Signed-off-by: Junio C Hamano <gitster@pobox.com>
>>> ---
>>>     * I found that the diff relative to the result of applying v1 was
>>>       easier to follow than the range-diff, so here it is.
>>>     diff --git c/t/unit-tests/test-lib.c w/t/unit-tests/test-lib.c
>>>     index 83c9eb8c59..66d6980ffb 100644
>>>     --- c/t/unit-tests/test-lib.c
>>>     +++ w/t/unit-tests/test-lib.c
>>>     @@ -64,34 +64,33 @@ static const char *make_relative(const char *location)
>>>      		 * prefix_len == 0 if the compiler gives paths relative
>>>      		 * to the root of the working tree.  Otherwise, we want
>>>      		 * to see that we did find the needle[] at a directory
>>>     -		 * boundary.
>>>     +		 * boundary.  Again we rely on that needle[] begins with
>>>     +		 * "t" followed by the directory separator.
>>>      		 */
>>>      		if (fspathcmp(needle, prefix + prefix_len) ||
>>>     -		    (prefix_len &&
>>>     -		     prefix[prefix_len - 1] != '/' &&
>>>     -		     prefix[prefix_len - 1] != '\\'))
>>>     +		    (prefix_len && prefix[prefix_len - 1] != needle[1]))
>>>      			die("unexpected suffix of '%s'", prefix);
>>>     -
>>>      	}
>>>          	/*
>>>     -	 * If our compiler gives relative paths and we do not need
>>>     -	 * to munge directory separator, we can return location as-is.
>>>     +	 * Does it not start with the expected prefix?
>>>     +	 * Return it as-is without making it worse.
>>>      	 */
>>>     -	if (!prefix_len && !need_bs_to_fs)
>>>     +	if (prefix_len && fspathncmp(location, prefix, prefix_len))
>>>      		return location;
>>>         -	/* Does it not start with the expected prefix? */
>>>     -	if (fspathncmp(location, prefix, prefix_len))
>>>     -		return location;
>>>     +	/*
>>>     +	 * If we do not need to munge directory separator, we can return
>>>     +	 * the substring at the tail of the location.
>>>     +	 */
>>>     +	if (!need_bs_to_fs)
>>>     +		return location + prefix_len;
>>>         -	strlcpy(buf, location + prefix_len, sizeof(buf));
>>>      	/* convert backslashes to forward slashes */
>>>     -	if (need_bs_to_fs) {
>>>     -		for (p = buf; *p; p++)
>>>     -			if (*p == '\\')
>>>     -				*p = '/';
>>>     -	}
>>>     +	strlcpy(buf, location + prefix_len, sizeof(buf));
>>>     +	for (p = buf; *p; p++)
>>>     +		if (*p == '\\')
>>>     +			*p = '/';
>>>      	return buf;
>>>      }
>>>        t/unit-tests/test-lib.c | 61
>>> +++++++++++++++++++++++++++++++----------
>>>    1 file changed, 47 insertions(+), 14 deletions(-)
>>> diff --git a/t/unit-tests/test-lib.c b/t/unit-tests/test-lib.c
>>> index 7bf9dfdb95..66d6980ffb 100644
>>> --- a/t/unit-tests/test-lib.c
>>> +++ b/t/unit-tests/test-lib.c
>>> @@ -21,12 +21,11 @@ static struct {
>>>    	.result = RESULT_NONE,
>>>    };
>>>    -#ifndef _MSC_VER
>>> -#define make_relative(location) location
>>> -#else
>>>    /*
>>>     * Visual C interpolates the absolute Windows path for `__FILE__`,
>>>     * but we want to see relative paths, as verified by t0080.
>>> + * There are other compilers that do the same, and are not for
>>> + * Windows.
>>>     */
>>>    #include "dir.h"
>>>    @@ -34,32 +33,66 @@ static const char *make_relative(const char
>>> *location)
>>>    {
>>>    	static char prefix[] = __FILE__, buf[PATH_MAX], *p;
>>>    	static size_t prefix_len;
>>> +	static int need_bs_to_fs = -1;
>>>    -	if (!prefix_len) {
>>> +	/* one-time preparation */
>>> +	if (need_bs_to_fs < 0) {
>>>    		size_t len = strlen(prefix);
>>> -		const char *needle = "\\t\\unit-tests\\test-lib.c";
>>> +		char needle[] = "t\\unit-tests\\test-lib.c";
>>>    		size_t needle_len = strlen(needle);
>>>    -		if (len < needle_len || strcmp(needle, prefix + len -
>>> needle_len))
>>> -			die("unexpected suffix of '%s'", prefix);
>>> +		if (len < needle_len)
>>> +			die("unexpected prefix '%s'", prefix);
>>> +
>>> +		/*
>>> +		 * The path could be relative (t/unit-tests/test-lib.c)
>>> +		 * or full (/home/user/git/t/unit-tests/test-lib.c).
>>> +		 * Check the slash between "t" and "unit-tests".
>>> +		 */
>>> +		prefix_len = len - needle_len;
>>> +		if (prefix[prefix_len + 1] == '/') {
>>> +			/* Oh, we're not Windows */
>>> +			for (size_t i = 0; i < needle_len; i++)
>>> +				if (needle[i] == '\\')
>>> +					needle[i] = '/';
>>> +			need_bs_to_fs = 0;
>>> +		} else {
>>> +			need_bs_to_fs = 1;
>>> +		}
>>>    -		/* let it end in a directory separator */
>>> -		prefix_len = len - needle_len + 1;
>>> +		/*
>>> +		 * prefix_len == 0 if the compiler gives paths relative
>>> +		 * to the root of the working tree.  Otherwise, we want
>>> +		 * to see that we did find the needle[] at a directory
>>> +		 * boundary.  Again we rely on that needle[] begins with
>>> +		 * "t" followed by the directory separator.
>>> +		 */
>>> +		if (fspathcmp(needle, prefix + prefix_len) ||
>>> +		    (prefix_len && prefix[prefix_len - 1] != needle[1]))
>>> +			die("unexpected suffix of '%s'", prefix);
>>>    	}
>>>    -	/* Does it not start with the expected prefix? */
>>> -	if (fspathncmp(location, prefix, prefix_len))
>>> +	/*
>>> +	 * Does it not start with the expected prefix?
>>> +	 * Return it as-is without making it worse.
>>> +	 */
>>> +	if (prefix_len && fspathncmp(location, prefix, prefix_len))
>>>    		return location;
>>>    -	strlcpy(buf, location + prefix_len, sizeof(buf));
>>> +	/*
>>> +	 * If we do not need to munge directory separator, we can return
>>> +	 * the substring at the tail of the location.
>>> +	 */
>>> +	if (!need_bs_to_fs)
>>> +		return location + prefix_len;
>>> +
>>>    	/* convert backslashes to forward slashes */
>>> +	strlcpy(buf, location + prefix_len, sizeof(buf));
>>>    	for (p = buf; *p; p++)
>>>    		if (*p == '\\')
>>>    			*p = '/';
>>> -
>>>    	return buf;
>>>    }
>>> -#endif
>>>      static void msg_with_prefix(const char *prefix, const char
>>> *format, va_list ap)
>>>    {