BUG report: unicode normalization on APFS (Mac OS High Sierra)

BUG report: unicode normalization on APFS (Mac OS High Sierra)

[Elijah Newren]

On HFS (which appears to be the default Mac filesystem prior to High
Sierra), unicode names are "normalized" before recording.  Thus with a
script like:

    mkdir tmp
    cd tmp

    auml=$(printf "\303\244")
    aumlcdiar=$(printf "\141\314\210")
    >"$auml"

    echo "auml:          " $(echo -n "$auml" | xxd)
    echo "aumlcdiar:     " $(echo -n "$aumlcdiar" | xxd)
    echo "Dir contents:  " $(echo -n * | xxd)

    echo "Stat auml:     " "$(stat -f "%i   %Sm   %Su %N" "$auml")"
    echo "Stat aumlcdiar:" "$(stat -f "%i   %Sm   %Su %N" "$aumlcdiar")"

We see output like:

    auml:           00000000: c3a4 ..
    aumlcdiar:      00000000: 61cc 88 a..
    Dir contents:   00000000: 61cc 88 a..
    Stat auml:      857473   Apr 26 09:40:40 2018   newren ä
    Stat aumlcdiar: 857473   Apr 26 09:40:40 2018   newren ä

On APFS, which appears to be the new default filesystem in Mac OS High
Sierra, we instead see:

    auml:           00000000: c3a4 ..
    aumlcdiar:      00000000: 61cc 88 a..
    Dir contents:   00000000: c3a4 ..
    Stat auml:      8591766636   Apr 26 09:40:59 2018   newren ä
    Stat aumlcdiar: 8591766636   Apr 26 09:40:59 2018   newren ä

i.e. APFS appears to record the filename as specified by the user, but
continues to allow the user to access it via any name that normalizes
to the same thing.  This difference causes t0050-filesystem.sh to fail
the final two tests.  I could change the "UTF8_NFD_TO_NFC" flag
checking in test-lib.sh to instead test the exit code of stat to make
it pass these two tests, but I have no idea if there are problems
elsewhere that this would just be papering over.

I dislike Mac OS and avoid it, so I'd prefer to find someone else
motivated to fix this.  If no one is, I may eventually try to fix this
up...in a year or three from now.  But is someone else interested?
Would this serve as a good microproject for our microprojects list (or
are the internals hairy enough that this is too big of a project for
that list)?


Elijah

Re: BUG report: unicode normalization on APFS (Mac OS High Sierra)

[Torsten Bögershausen]

On 26.04.18 18:48, Elijah Newren wrote:
> On HFS (which appears to be the default Mac filesystem prior to High
> Sierra), unicode names are "normalized" before recording.  Thus with a
> script like:
> 
>     mkdir tmp
>     cd tmp
> 
>     auml=$(printf "\303\244")
>     aumlcdiar=$(printf "\141\314\210")
>     >"$auml"
> 
>     echo "auml:          " $(echo -n "$auml" | xxd)
>     echo "aumlcdiar:     " $(echo -n "$aumlcdiar" | xxd)
>     echo "Dir contents:  " $(echo -n * | xxd)
> 
>     echo "Stat auml:     " "$(stat -f "%i   %Sm   %Su %N" "$auml")"
>     echo "Stat aumlcdiar:" "$(stat -f "%i   %Sm   %Su %N" "$aumlcdiar")"
> 
> We see output like:
> 
>     auml:           00000000: c3a4 ..
>     aumlcdiar:      00000000: 61cc 88 a..
>     Dir contents:   00000000: 61cc 88 a..
>     Stat auml:      857473   Apr 26 09:40:40 2018   newren ä
>     Stat aumlcdiar: 857473   Apr 26 09:40:40 2018   newren ä
> 
> On APFS, which appears to be the new default filesystem in Mac OS High
> Sierra, we instead see:
> 
>     auml:           00000000: c3a4 ..
>     aumlcdiar:      00000000: 61cc 88 a..
>     Dir contents:   00000000: c3a4 ..
>     Stat auml:      8591766636   Apr 26 09:40:59 2018   newren ä
>     Stat aumlcdiar: 8591766636   Apr 26 09:40:59 2018   newren ä
> 
> i.e. APFS appears to record the filename as specified by the user, but
> continues to allow the user to access it via any name that normalizes
> to the same thing.  This difference causes t0050-filesystem.sh to fail
> the final two tests.  I could change the "UTF8_NFD_TO_NFC" flag
> checking in test-lib.sh to instead test the exit code of stat to make
> it pass these two tests, but I have no idea if there are problems
> elsewhere that this would just be papering over.
> 
> I dislike Mac OS and avoid it, so I'd prefer to find someone else
> motivated to fix this.  If no one is, I may eventually try to fix this
> up...in a year or three from now.  But is someone else interested?
> Would this serve as a good microproject for our microprojects list (or
> are the internals hairy enough that this is too big of a project for
> that list)?
> 
> 
> Elijah
> 

Hm,
thanks for the report.
I don't have a high sierra box, but I can probably get one.
t0050 -should- pass automagically, so I feel that I can do something.
Unless someone is faster of course.

Is it possible that  you run
debug=t verbose=t ./t0050-filesystem.sh 
and send the output to me ?

Re: BUG report: unicode normalization on APFS (Mac OS High Sierra)

[Elijah Newren]

On Thu, Apr 26, 2018 at 10:13 AM, Torsten Bögershausen <tboegi@web.de> wrote:
> Hm,
> thanks for the report.
> I don't have a high sierra box, but I can probably get one.
> t0050 -should- pass automagically, so I feel that I can do something.
> Unless someone is faster of course.

Sweet, thanks for taking a look.

> Is it possible that  you run
> debug=t verbose=t ./t0050-filesystem.sh
> and send the output to me ?

Sure.  First, though, note that I can make it pass (or at least "not
ok...TODO known breakage") with the following patch (may be
whitespace-damaged by gmail):

diff --git a/t/test-lib.sh b/t/test-lib.sh
index 483c8d6d7..770b91f8c 100644
--- a/t/test-lib.sh
+++ b/t/test-lib.sh
@@ -1106,12 +1106,7 @@ test_lazy_prereq UTF8_NFD_TO_NFC '
        auml=$(printf "\303\244")
        aumlcdiar=$(printf "\141\314\210")
        >"$auml" &&
-       case "$(echo *)" in
-       "$aumlcdiar")
-               true ;;
-       *)
-               false ;;
-       esac
+       stat "$aumlcdiar" >/dev/null 2>/dev/null
 '

 test_lazy_prereq AUTOIDENT '


I'm just worried there are bugs elsewhere in dealing with filesystems
like this that would need to be fixed and that this papers over them.

Anyway, the output you requested, at least for the last two failing tests, is:


expecting success:
git mv "$aumlcdiar" "$auml" &&
git commit -m rename

fatal: destination exists, source=ä, destination=ä
not ok 9 - rename (silent unicode normalization)

#
# git mv "$aumlcdiar" "$auml" &&
# git commit -m rename
#

expecting success:
git reset --hard initial &&
git merge topic

HEAD is now at 1b3caf6 initial
Updating 1b3caf6..2db1bf9
error: The following untracked working tree files would be overwritten by merge:
ä
Please move or remove them before you merge.
Aborting
not ok 10 - merge (silent unicode normalization)

#
# git reset --hard initial &&
# git merge topic
#

# still have 1 known breakage(s)
# failed 2 among remaining 9 test(s)

Re: BUG report: unicode normalization on APFS (Mac OS High Sierra)

[Totsten Bögershausen]

On 2018-04-26 19:23, Elijah Newren wrote:
> On Thu, Apr 26, 2018 at 10:13 AM, Torsten Bögershausen <tboegi@web.de> wrote:
>> Hm,
>> thanks for the report.
>> I don't have a high sierra box, but I can probably get one.
>> t0050 -should- pass automagically, so I feel that I can do something.
>> Unless someone is faster of course.
> 
> Sweet, thanks for taking a look.
> 
>> Is it possible that  you run
>> debug=t verbose=t ./t0050-filesystem.sh
>> and send the output to me ?
> 
> Sure.  First, though, note that I can make it pass (or at least "not
> ok...TODO known breakage") with the following patch (may be
> whitespace-damaged by gmail):
> 
> diff --git a/t/test-lib.sh b/t/test-lib.sh
> index 483c8d6d7..770b91f8c 100644
> --- a/t/test-lib.sh
> +++ b/t/test-lib.sh
> @@ -1106,12 +1106,7 @@ test_lazy_prereq UTF8_NFD_TO_NFC '
>          auml=$(printf "\303\244")
>          aumlcdiar=$(printf "\141\314\210")
>          >"$auml" &&
> -       case "$(echo *)" in
> -       "$aumlcdiar")
> -               true ;;
> -       *)
> -               false ;;
> -       esac
> +       stat "$aumlcdiar" >/dev/null 2>/dev/null

Nicely analyzed and improved.

The "stat" statement is technically correct.
I think that a more git-style fix would be
[] ---
+       test -r "$aumlcdiar"

instead of the stat.

I looked into the 2 known breakages.
In short: they test use cases which are not sooo important for a user in 
practice, but do a good test if the code is broken.
IOW: I can't see a need for immediate action.

As you already did all the analyzes:
Do you want to send a patch ?

Re: BUG report: unicode normalization on APFS (Mac OS High Sierra)

[Elijah Newren]

Hi,

On Fri, Apr 27, 2018 at 2:45 PM, Totsten Bögershausen <tboegi@web.de> wrote:
> On 2018-04-26 19:23, Elijah Newren wrote:

>> Sure.  First, though, note that I can make it pass (or at least "not
>> ok...TODO known breakage") with the following patch (may be
>> whitespace-damaged by gmail):
>>
>> diff --git a/t/test-lib.sh b/t/test-lib.sh
>> index 483c8d6d7..770b91f8c 100644
>> --- a/t/test-lib.sh
>> +++ b/t/test-lib.sh
>> @@ -1106,12 +1106,7 @@ test_lazy_prereq UTF8_NFD_TO_NFC '
>>          auml=$(printf "\303\244")
>>          aumlcdiar=$(printf "\141\314\210")
>>          >"$auml" &&
>> -       case "$(echo *)" in
>> -       "$aumlcdiar")
>> -               true ;;
>> -       *)
>> -               false ;;
>> -       esac
>> +       stat "$aumlcdiar" >/dev/null 2>/dev/null
>
>
> Nicely analyzed and improved.
>
> The "stat" statement is technically correct.
> I think that a more git-style fix would be
> [] ---
> +       test -r "$aumlcdiar"
>
> instead of the stat.
>
> I looked into the 2 known breakages.
> In short: they test use cases which are not sooo important for a user in
> practice, but do a good test if the code is broken.
> IOW: I can't see a need for immediate action.
>
> As you already did all the analyzes:
> Do you want to send a patch ?

You know, despite seeing the "test_expect_failure" and "TODO...known
breakage" with these tests and even mentioning them, it somehow didn't
sink in and I was still thinking that there might be some kind of
unicode normalization handling in the codebase somewhere (similar to
the case insensitivy handling that I've seen in a place or two) that
now needed to be extended.  I should have realized that
test_expect_failure meant there wasn't, and thus all we needed to do
was to mark it as continuing to fail with the new filesystem,  Should
have realized, but didn't.  Oops.

Anyway, it looks like you've already submitted a patch and marked it
as having been reported by me, which is just fine.  Thanks!

Elijah

[PATCH v1 1/1] test: Correct detection of UTF8_NFD_TO_NFC for APFS

[tboegi]

From: Torsten Bögershausen <tboegi@web.de>

On HFS (which is the default Mac filesystem prior to High Sierra),
unicode names are "decomposed" before recording.
On APFS, which appears to be the new default filesystem in Mac OS High
Sierra, filenames are recorded as specified by the user.

APFS continues to allow the user to access it via any name
that normalizes to the same thing.

This difference causes t0050-filesystem.sh to fail two tests.

Improve the test for a NFD/NFC in test-lib.sh:
Test if the same file can be reached in pre- and decomposed unicode.

Reported-By: Elijah Newren <newren@gmail.com>
Signed-off-by: Torsten Bögershausen <tboegi@web.de>
---
 t/test-lib.sh | 7 +------
 1 file changed, 1 insertion(+), 6 deletions(-)

diff --git a/t/test-lib.sh b/t/test-lib.sh
index ea2bbaaa7a..e206250d1b 100644
--- a/t/test-lib.sh
+++ b/t/test-lib.sh
@@ -1106,12 +1106,7 @@ test_lazy_prereq UTF8_NFD_TO_NFC '
 	auml=$(printf "\303\244")
 	aumlcdiar=$(printf "\141\314\210")
 	>"$auml" &&
-	case "$(echo *)" in
-	"$aumlcdiar")
-		true ;;
-	*)
-		false ;;
-	esac
+	test -r "$aumlcdiar"
 '
 
 test_lazy_prereq AUTOIDENT '
-- 
2.16.0.rc0.8.g5497051b43

Re: [PATCH v1 1/1] test: Correct detection of UTF8_NFD_TO_NFC for APFS

[Junio C Hamano]

tboegi@web.de writes:

> From: Torsten Bögershausen <tboegi@web.de>
>
> On HFS (which is the default Mac filesystem prior to High Sierra),
> unicode names are "decomposed" before recording.
> On APFS, which appears to be the new default filesystem in Mac OS High
> Sierra, filenames are recorded as specified by the user.
>
> APFS continues to allow the user to access it via any name
> that normalizes to the same thing.
>
> This difference causes t0050-filesystem.sh to fail two tests.
>
> Improve the test for a NFD/NFC in test-lib.sh:
> Test if the same file can be reached in pre- and decomposed unicode.
>
> Reported-By: Elijah Newren <newren@gmail.com>
> Signed-off-by: Torsten Bögershausen <tboegi@web.de>
> ---
>  t/test-lib.sh | 7 +------
>  1 file changed, 1 insertion(+), 6 deletions(-)

Thanks.  

Wouldn't it logically make more sense to check for the target being
an existing file with "-f"?  It is not an essential part of the test
for the target to be "readable", but "can be stat(2)ed with the
other UTF-8 representation" is.

> diff --git a/t/test-lib.sh b/t/test-lib.sh
> index ea2bbaaa7a..e206250d1b 100644
> --- a/t/test-lib.sh
> +++ b/t/test-lib.sh
> @@ -1106,12 +1106,7 @@ test_lazy_prereq UTF8_NFD_TO_NFC '
>  	auml=$(printf "\303\244")
>  	aumlcdiar=$(printf "\141\314\210")
>  	>"$auml" &&
> -	case "$(echo *)" in
> -	"$aumlcdiar")
> -		true ;;
> -	*)
> -		false ;;
> -	esac
> +	test -r "$aumlcdiar"
>  '
>  
>  test_lazy_prereq AUTOIDENT '

Re: [PATCH v1 1/1] test: Correct detection of UTF8_NFD_TO_NFC for APFS

[Torsten Bögershausen]

On 30.04.18 09:56, Junio C Hamano wrote:
> tboegi@web.de writes:
> 
>> From: Torsten Bögershausen <tboegi@web.de>
>>
>> On HFS (which is the default Mac filesystem prior to High Sierra),
>> unicode names are "decomposed" before recording.
>> On APFS, which appears to be the new default filesystem in Mac OS High
>> Sierra, filenames are recorded as specified by the user.
>>
>> APFS continues to allow the user to access it via any name
>> that normalizes to the same thing.
>>
>> This difference causes t0050-filesystem.sh to fail two tests.
>>
>> Improve the test for a NFD/NFC in test-lib.sh:
>> Test if the same file can be reached in pre- and decomposed unicode.
>>
>> Reported-By: Elijah Newren <newren@gmail.com>
>> Signed-off-by: Torsten Bögershausen <tboegi@web.de>
>> ---
>>  t/test-lib.sh | 7 +------
>>  1 file changed, 1 insertion(+), 6 deletions(-)
> 
> Thanks.  
> 
> Wouldn't it logically make more sense to check for the target being
> an existing file with "-f"?  It is not an essential part of the test
> for the target to be "readable", but "can be stat(2)ed with the
> other UTF-8 representation" is.

That make sense.
Would you like to amend the patch ?

Re: [PATCH v1 1/1] test: Correct detection of UTF8_NFD_TO_NFC for APFS

[Elijah Newren]

Hi,

On Sun, Apr 29, 2018 at 11:35 PM,  <tboegi@web.de> wrote:
> From: Torsten Bögershausen <tboegi@web.de>
>
> On HFS (which is the default Mac filesystem prior to High Sierra),
> unicode names are "decomposed" before recording.
> On APFS, which appears to be the new default filesystem in Mac OS High
> Sierra, filenames are recorded as specified by the user.
>
> APFS continues to allow the user to access it via any name
> that normalizes to the same thing.
>
> This difference causes t0050-filesystem.sh to fail two tests.
>
> Improve the test for a NFD/NFC in test-lib.sh:
> Test if the same file can be reached in pre- and decomposed unicode.
>
> Reported-By: Elijah Newren <newren@gmail.com>
> Signed-off-by: Torsten Bögershausen <tboegi@web.de>
> ---
>  t/test-lib.sh | 7 +------
>  1 file changed, 1 insertion(+), 6 deletions(-)
>
> diff --git a/t/test-lib.sh b/t/test-lib.sh
> index ea2bbaaa7a..e206250d1b 100644
> --- a/t/test-lib.sh
> +++ b/t/test-lib.sh
> @@ -1106,12 +1106,7 @@ test_lazy_prereq UTF8_NFD_TO_NFC '

I'm not sure what "NFD" and "NFC" stand for, but I suspect the test
prerequisite name may be specific to how HFS handled things.  If so,
should it be renamed from UTF8_NFD_TO_NFC to something else, such as
UTF8_NORMALIZATION?

>         auml=$(printf "\303\244")
>         aumlcdiar=$(printf "\141\314\210")
>         >"$auml" &&
> -       case "$(echo *)" in
> -       "$aumlcdiar")
> -               true ;;
> -       *)
> -               false ;;
> -       esac
> +       test -r "$aumlcdiar"
>  '
>
>  test_lazy_prereq AUTOIDENT '
> --
> 2.16.0.rc0.8.g5497051b43

Re: [PATCH v1 1/1] test: Correct detection of UTF8_NFD_TO_NFC for APFS

[Torsten Bögershausen]

On 30.04.18 17:33, Elijah Newren wrote:
> Hi,
> 
> On Sun, Apr 29, 2018 at 11:35 PM,  <tboegi@web.de> wrote:
>> From: Torsten Bögershausen <tboegi@web.de>
>>
>> On HFS (which is the default Mac filesystem prior to High Sierra),
>> unicode names are "decomposed" before recording.
>> On APFS, which appears to be the new default filesystem in Mac OS High
>> Sierra, filenames are recorded as specified by the user.
>>
>> APFS continues to allow the user to access it via any name
>> that normalizes to the same thing.
>>
>> This difference causes t0050-filesystem.sh to fail two tests.
>>
>> Improve the test for a NFD/NFC in test-lib.sh:
>> Test if the same file can be reached in pre- and decomposed unicode.
>>
>> Reported-By: Elijah Newren <newren@gmail.com>
>> Signed-off-by: Torsten Bögershausen <tboegi@web.de>
>> ---
>>  t/test-lib.sh | 7 +------
>>  1 file changed, 1 insertion(+), 6 deletions(-)
>>
>> diff --git a/t/test-lib.sh b/t/test-lib.sh
>> index ea2bbaaa7a..e206250d1b 100644
>> --- a/t/test-lib.sh
>> +++ b/t/test-lib.sh
>> @@ -1106,12 +1106,7 @@ test_lazy_prereq UTF8_NFD_TO_NFC '
> 
> I'm not sure what "NFD" and "NFC" stand for, but I suspect the test
> prerequisite name may be specific to how HFS handled things.  If so,
> should it be renamed from UTF8_NFD_TO_NFC to something else, such as
> UTF8_NORMALIZATION?

NFD and NFC both come from the unicode standard, and are just taken
"as is" into the Git world:
https://en.wikipedia.org/wiki/Unicode_equivalence

If you are otherwise happy with the patch, would it be possible
to run it on your system ?
(I don't have a High Sierra box, but I am confident that the test work
 for you).

The other comments may be addressed later, may be.
In any case, they should go into a different commit.
 

Re: [PATCH v1 1/1] test: Correct detection of UTF8_NFD_TO_NFC for APFS

[Elijah Newren]

On Mon, Apr 30, 2018 at 8:41 AM, Torsten Bögershausen <tboegi@web.de> wrote:
> On 30.04.18 17:33, Elijah Newren wrote:
>
>> On Sun, Apr 29, 2018 at 11:35 PM,  <tboegi@web.de> wrote:
>>> From: Torsten Bögershausen <tboegi@web.de>
>>>

>>> @@ -1106,12 +1106,7 @@ test_lazy_prereq UTF8_NFD_TO_NFC '
>>
>> I'm not sure what "NFD" and "NFC" stand for, but I suspect the test
>> prerequisite name may be specific to how HFS handled things.  If so,
>> should it be renamed from UTF8_NFD_TO_NFC to something else, such as
>> UTF8_NORMALIZATION?
>
> NFD and NFC both come from the unicode standard, and are just taken
> "as is" into the Git world:
> https://en.wikipedia.org/wiki/Unicode_equivalence
>
> If you are otherwise happy with the patch, would it be possible
> to run it on your system ?
> (I don't have a High Sierra box, but I am confident that the test work
>  for you).

Sure, feel free to add a

Tested-by: Elijah Newren <newren@gmail.com>

if you like.  (Works with both 'test -r', as in your patch, and 'test
-f', as suggested by Junio.)