Subject: Re: [PATCH] git p4 fix for failure to decode p4 errors

From: Nikolay Shustov <[email-masked]>
Date: Mon, 31 Mar 2025 19:37:01 -0400

Hi Fahad,
Thank you for taking a look.
Yes, you can run this test locally, that should be enough.
The test is conditionalized on a) having p4 server installation with no 
Unicode support and b) running with Python 3 only.
If either of these do not match, it will skip the execution.

I tested it on my computer with the freshly installed p4 helix server 
and client; but it was on Kubuntu only, did not try it on Windows.
Perforce company allows limited use of the server and client for 
non-commercial purposes, so it was all legit.

Please let me know how it runs for you.

Cheers,
- Nikolay

On 3/31/25 05:01, Fahad Al-Rashed wrote:
> Hi Nikolay,
>
> The patch looks reasonable.
>
> What I can help with is test it on our Perforce installation when I go back to work next week.
>
> For the purpose of testing, is running t/t9837-git-p4-error-encoding.sh locally on my computer enough to test your patch?
>
> Best,
> Fahad
>
>> On 31 Mar 2025, at 4:21 AM, Nikolay Shustov <[email-masked]> wrote:
>>
>> <adding Fahad Alrashed, James Touton and Patrick Steinhardt, whom Git points to as the contributors to the latest p4-git logic changes>
>>
>> Hello,
>> May I ask you to review the below change to p4-git?
>>
>> Thank you in advance,
>> - Nikolay
>>
>> On 3/30/25 16:06, Nikolay Shustov wrote:
>>> Hi Phillip,
>>> Thank you for your time and your feedback.
>>> It is especially valuable to me as it is the very first PR of mine.
>>> I will try to contact the recent contributors of git-p4 changes for review.
>>>
>>> To clarify on the fix:
>>>
>>> The error I hit was while using "git p4 clone":
>>> It was throwing decoding exception at line 901 of git-p4, preventing import from Perforce depot to complete successfully.
>>> The root cause is the logic for "git p4 clone" anticipates some p4 operations may return errors, it is a normal part of import process.
>>> But that logic uses just .decode() on the byte array of the returned error message, which does not work well when it contains the characters with high bit set (which may be the case when Perforce configured without unicode support). git-p4 implementation has a decoding fallback logic for such cases in other places, but this specific place did not use any.
>>>
>>> Using the bullet list in description was not intended to enumerate the separate changes, but rather to highlight the details of the change.
>>> I will make sure I won't use it in the future to avoid the confusion.
>>>
>>> That small refactoring I did was not a sidecar but a way I chose to implement the changes:
>>> There was an existing function that was doing the job of decoding the received p4 metadata, using the existing git-p4 configuration settings.
>>> There also were a few existing variables that kept the state between the calls of that function (e.g. indicator not to show decoding fallback warning twice, configuration settings).
>>> However, with the way the function was implemented, it could not be reused as-is for the new case.
>>> I would had to add a new function that would have to use the same core transcoding implementation but behave differently.
>>> Adding behavior variances into the existing function felt suboptimal: it would complicate it quite a bit and I felt sorry about next one who will have to reverse engineer its behavior again. Duplicating the part of logic of the existing function also looked suboptimal: any further changes would have to be done in two places.
>>> So, seeing the need in keeping state between calls and separating a part of existing logic into separate functions, I went for moving the implementation into a new class and organizing things there with the class instance. In my opinion, the new code looks pretty self-descritpitve.
>>>
>>> Thank you,
>>> - Nikolay
>>>
>>> On 3/26/25 11:09, Phillip Wood wrote:
>>>> Hi Nikolay
>>>>
>>>> On 25/03/2025 23:09, Nikolay Shustov wrote:
>>>>> I think this fix is important.
>>>>> git-p4 is used in the companies where there is an intent to migrate from Perforce to Git and having the issue that this change fixes is a real roadblock.
>>>>> The better we can make git-p4, the more adoption Git would get in the commercial world.
>>>> Unfortunately I don't think any of the regular git contributors use git-p4 so to find someone to review this patch I would look at who has contributed to git-p4 recently and cc them. Before you do that I have a couple of suggestions below
>>>>
>>>>> On 3/22/25 07:48, Nikolay Shustov wrote:
>>>>>> ping, pretty please? :-)
>>>>>>
>>>>>> On 3/19/25 23:20, Nikolay Shustov via GitGitGadget wrote:
>>>>>>> From: Nikolay Shustov <[email-masked]>
>>>>>>>
>>>>>>> Fixes the git p4 failure happening when Perforce command returns error
>>>>>>> containing byte stream of characters with high bit set. In such situations
>>>>>>> git p4 implementatino fails to decode this byte stream into utf-8 string.
>>>>>>>
>>>>>>> Design:
>>>>>>> Make use of existing decoding fallback strategy, described by
>>>>>>> git-p4.metadataDecodingStrategy and git-p4.metadataFallbackEncoding
>>>>>>> settings in the logic that decodes the Perforce command error bytes.
>>>> Our usual style for commit messages is to explain what the problem is and how it is fixed by the changes in the patch. Rather than saying "fixes the git p4 failure" I would start by explaining what that failure is and how it is caused. It would also be helpful to explain what the settings that you refer to do so that someone who is familiar with python but not with git-p4 can understand and potentially review the changes.
>>>>
>>>>>>> Details:
>>>>>>> - Moved p4 metadata transcoding logic from
>>>>>>>     metadata_stream_to_writable_bytes(..) into a new MetadataTranscoder class.
>>>>>>> - Enhcanced the implementation to use git-p4.metadataDecodingStrategy and
>>>>>>>     git-p4.metadataFallbackEncoding settings for p4 errors decoding.
>>>>>>> - Added test.
>>>> Thanks for taking the time to add a new test, it is much appreciated. When there is a bullet list in a commit message it is often a sign that the commit is doing more than one thing at once. In this case it appears there is a bug fix mixed in with some refactoring. I would split the refactoring out into a preparatory patch so that reviews can clearly see which changes are due to creating the MetadataTranscoder class and which are the changes that fix the bug. The new test should be added in the commit that fixes the bug.
>>>>
>>>> Best Wishes
>>>>
>>>> Phillip
>>>>
>>>>>>> Signed-off-by: Nikolay Shustov <[email-masked]>
>>>>>>> ---
>>>>>>>       git p4 fix for failure to decode p4 errors
>>>>>>>
>>>>>>> Published-As: https://github.com/gitgitgadget/git/releases/tag/pr- git-1926%2Fnshustov%2Fgit-p4-error-decoding-v1
>>>>>>> Fetch-It-Via: git fetch https://github.com/gitgitgadget/git pr- git-1926/nshustov/git-p4-error-decoding-v1
>>>>>>> Pull-Request: https://github.com/git/git/pull/1926
>>>>>>>
>>>>>>>    git-p4.py                        | 135 ++++++++++++++++++-------------
>>>>>>>    t/meson.build                    |   1 +
>>>>>>>    t/t9837-git-p4-error-encoding.sh |  53 ++++++++++++
>>>>>>>    t/t9837/git-p4-error-python3.py  |  15 ++++
>>>>>>>    4 files changed, 149 insertions(+), 55 deletions(-)
>>>>>>>    create mode 100755 t/t9837-git-p4-error-encoding.sh
>>>>>>>    create mode 100644 t/t9837/git-p4-error-python3.py
>>>>>>>
>>>>>>> diff --git a/git-p4.py b/git-p4.py
>>>>>>> index c0ca7becaf4..72a4c55f99e 100755
>>>>>>> --- a/git-p4.py
>>>>>>> +++ b/git-p4.py
>>>>>>> @@ -234,67 +234,91 @@ else:
>>>>>>>        class MetadataDecodingException(Exception):
>>>>>>> -    def __init__(self, input_string):
>>>>>>> +    def __init__(self, input_string, error=None):
>>>>>>>            self.input_string = input_string
>>>>>>> +        self.error = error
>>>>>>>          def __str__(self):
>>>>>>> -        return """Decoding perforce metadata failed!
>>>>>>> +        message = """Decoding perforce metadata failed!
>>>>>>>    The failing string was:
>>>>>>>    ---
>>>>>>>    {}
>>>>>>>    ---
>>>>>>>    Consider setting the git-p4.metadataDecodingStrategy config option to
>>>>>>>    'fallback', to allow metadata to be decoded using a fallback encoding,
>>>>>>> -defaulting to cp1252.""".format(self.input_string)
>>>>>>> +defaulting to cp1252."""
>>>>>>> +        if verbose and self.error is not None:
>>>>>>> +            message += """
>>>>>>> +---
>>>>>>> +Error:
>>>>>>> +---
>>>>>>> +{}"""
>>>>>>> +        return message.format(self.input_string, self.error)
>>>>>>>      -encoding_fallback_warning_issued = False
>>>>>>> -encoding_escape_warning_issued = False
>>>>>>> -def metadata_stream_to_writable_bytes(s):
>>>>>>> -    encodingStrategy = gitConfig('git-p4.metadataDecodingStrategy') or defaultMetadataDecodingStrategy
>>>>>>> -    fallbackEncoding = gitConfig('git-p4.metadataFallbackEncoding') or defaultFallbackMetadataEncoding
>>>>>>> -    if not isinstance(s, bytes):
>>>>>>> -        return s.encode('utf_8')
>>>>>>> -    if encodingStrategy == 'passthrough':
>>>>>>> -        return s
>>>>>>> -    try:
>>>>>>> -        s.decode('utf_8')
>>>>>>> -        return s
>>>>>>> -    except UnicodeDecodeError:
>>>>>>> -        if encodingStrategy == 'fallback' and fallbackEncoding:
>>>>>>> -            global encoding_fallback_warning_issued
>>>>>>> -            global encoding_escape_warning_issued
>>>>>>> -            try:
>>>>>>> -                if not encoding_fallback_warning_issued:
>>>>>>> -                    print("\nCould not decode value as utf-8; using configured fallback encoding %s: %s" % (fallbackEncoding, s))
>>>>>>> -                    print("\n(this warning is only displayed once during an import)")
>>>>>>> -                    encoding_fallback_warning_issued = True
>>>>>>> -                return s.decode(fallbackEncoding).encode('utf_8')
>>>>>>> -            except Exception as exc:
>>>>>>> -                if not encoding_escape_warning_issued:
>>>>>>> -                    print("\nCould not decode value with configured fallback encoding %s; escaping bytes over 127: %s" % (fallbackEncoding, s))
>>>>>>> -                    print("\n(this warning is only displayed once during an import)")
>>>>>>> -                    encoding_escape_warning_issued = True
>>>>>>> -                escaped_bytes = b''
>>>>>>> -                # bytes and strings work very differently in python2 vs python3...
>>>>>>> -                if str is bytes:
>>>>>>> -                    for byte in s:
>>>>>>> -                        byte_number = struct.unpack('>B', byte)[0]
>>>>>>> -                        if byte_number > 127:
>>>>>>> -                            escaped_bytes += b'%'
>>>>>>> -                            escaped_bytes += hex(byte_number) [2:].upper()
>>>>>>> -                        else:
>>>>>>> -                            escaped_bytes += byte
>>>>>>> -                else:
>>>>>>> -                    for byte_number in s:
>>>>>>> -                        if byte_number > 127:
>>>>>>> -                            escaped_bytes += b'%'
>>>>>>> -                            escaped_bytes += hex(byte_number).upper().encode()[2:]
>>>>>>> -                        else:
>>>>>>> -                            escaped_bytes += bytes([byte_number])
>>>>>>> -                return escaped_bytes
>>>>>>> +class MetadataTranscoder:
>>>>>>> +    def __init__(self, default_metadata_decoding_strategy, default_fallback_metadata_encoding):
>>>>>>> +        self.decoding_fallback_warning_issued = False
>>>>>>> +        self.decoding_escape_warning_issued = False
>>>>>>> +        self.decodingStrategy = gitConfig('git- p4.metadataDecodingStrategy') or default_metadata_decoding_strategy
>>>>>>> +        self.fallbackEncoding = gitConfig('git- p4.metadataFallbackEncoding') or default_fallback_metadata_encoding
>>>>>>> +
>>>>>>> +    def decode_metadata(self, s, error_from_fallback=True):
>>>>>>> +        try:
>>>>>>> +            return [s.decode('utf_8'), 'utf_8']
>>>>>>> +        except UnicodeDecodeError as decode_exception:
>>>>>>> +            error = decode_exception
>>>>>>> +            if self.decodingStrategy == 'fallback' and self.fallbackEncoding:
>>>>>>> +                try:
>>>>>>> +                    if not self.decoding_fallback_warning_issued:
>>>>>>> +                        print("\nCould not decode value as utf-8; using configured fallback encoding %s: %s" % (self.fallbackEncoding, s))
>>>>>>> +                        print("\n(this warning is only displayed once during an import)")
>>>>>>> + self.decoding_fallback_warning_issued = True
>>>>>>> +                    return [s.decode(self.fallbackEncoding), self.fallbackEncoding]
>>>>>>> +                except Exception as decode_exception:
>>>>>>> +                    if not error_from_fallback:
>>>>>>> +                        return [s, None]
>>>>>>> +                    error = decode_exception
>>>>>>> +            raise MetadataDecodingException(s, error)
>>>>>>> +
>>>>>>> +    def metadata_stream_to_writable_bytes(self, s):
>>>>>>> +        if not isinstance(s, bytes):
>>>>>>> +            return s.encode('utf_8')
>>>>>>> +        if self.decodingStrategy == 'passthrough':
>>>>>>> +            return s
>>>>>>> +
>>>>>>> +        [text, encoding] = self.decode_metadata(s, False)
>>>>>>> +        if encoding == 'utf_8':
>>>>>>> +            # s is of utf-8 already
>>>>>>> +            return s
>>>>>>> +
>>>>>>> +        if encoding is None:
>>>>>>> +            # could not decode s, even with fallback encoding
>>>>>>> +            if not self.decoding_escape_warning_issued:
>>>>>>> +                print("\nCould not decode value with configured fallback encoding %s; escaping bytes over 127: %s" % (self.fallbackEncoding, s))
>>>>>>> +                print("\n(this warning is only displayed once during an import)")
>>>>>>> +                self.decoding_escape_warning_issued = True
>>>>>>> +            escaped_bytes = b''
>>>>>>> +            # bytes and strings work very differently in python2 vs python3...
>>>>>>> +            if str is bytes:
>>>>>>> +                for byte in s:
>>>>>>> +                    byte_number = struct.unpack('>B', byte)[0]
>>>>>>> +                    if byte_number > 127:
>>>>>>> +                        escaped_bytes += b'%'
>>>>>>> +                        escaped_bytes += hex(byte_number)[2:].upper()
>>>>>>> +                    else:
>>>>>>> +                        escaped_bytes += byte
>>>>>>> +            else:
>>>>>>> +                for byte_number in s:
>>>>>>> +                    if byte_number > 127:
>>>>>>> +                        escaped_bytes += b'%'
>>>>>>> +                        escaped_bytes += hex(byte_number).upper().encode()[2:]
>>>>>>> +                    else:
>>>>>>> +                        escaped_bytes += bytes([byte_number])
>>>>>>> +            return escaped_bytes
>>>>>>>    -        raise MetadataDecodingException(s)
>>>>>>> +        # were able to decode but not to utf-8
>>>>>>> +        return text.encode('utf_8')
>>>>>>>        def decode_path(path):
>>>>>>> @@ -898,14 +922,14 @@ def p4CmdList(cmd, stdin=None, stdin_mode='w+b', cb=None, skip_info=False,
>>>>>>>                        decoded_entry[key] = value
>>>>>>>                    # Parse out data if it's an error response
>>>>>>>                    if decoded_entry.get('code') == 'error' and 'data' in decoded_entry:
>>>>>>> -                    decoded_entry['data'] = decoded_entry['data'].decode()
>>>>>>> +                    decoded_entry['data'] = metadataTranscoder.decode_metadata(decoded_entry['data'])
>>>>>>>                    entry = decoded_entry
>>>>>>>                if skip_info:
>>>>>>>                    if 'code' in entry and entry['code'] == 'info':
>>>>>>>                        continue
>>>>>>>                for key in p4KeysContainingNonUtf8Chars():
>>>>>>>                    if key in entry:
>>>>>>> -                    entry[key] = metadata_stream_to_writable_bytes(entry[key])
>>>>>>> +                    entry[key] = metadataTranscoder.metadata_stream_to_writable_bytes(entry[key])
>>>>>>>                if cb is not None:
>>>>>>>                    cb(entry)
>>>>>>>                else:
>>>>>>> @@ -1718,7 +1742,7 @@ class P4UserMap:
>>>>>>>                # python2 or python3. To support
>>>>>>>                # git-p4.metadataDecodingStrategy=fallback, self.users dict values
>>>>>>>                # are always bytes, ready to be written to git.
>>>>>>> -            emailbytes = metadata_stream_to_writable_bytes(output["Email"])
>>>>>>> +            emailbytes = metadataTranscoder.metadata_stream_to_writable_bytes(output["Email"])
>>>>>>>                self.users[output["User"]] = output["FullName"] + b" <" + emailbytes + b">"
>>>>>>>                self.emails[output["Email"]] = output["User"]
>>>>>>>    @@ -1730,12 +1754,12 @@ class P4UserMap:
>>>>>>>                    fullname = mapUser[0][1]
>>>>>>>                    email = mapUser[0][2]
>>>>>>>                    fulluser = fullname + " <" + email + ">"
>>>>>>> -                self.users[user] = metadata_stream_to_writable_bytes(fulluser)
>>>>>>> +                self.users[user] = metadataTranscoder.metadata_stream_to_writable_bytes(fulluser)
>>>>>>>                    self.emails[email] = user
>>>>>>>              s = b''
>>>>>>>            for (key, val) in self.users.items():
>>>>>>> -            keybytes = metadata_stream_to_writable_bytes(key)
>>>>>>> +            keybytes = metadataTranscoder.metadata_stream_to_writable_bytes(key)
>>>>>>>                s += b"%s\t%s\n" % (keybytes.expandtabs(1), val.expandtabs(1))
>>>>>>>              open(self.getUserCacheFilename(), 'wb').write(s)
>>>>>>> @@ -3349,7 +3373,7 @@ class P4Sync(Command, P4UserMap):
>>>>>>>            if userid in self.users:
>>>>>>>                return self.users[userid]
>>>>>>>            else:
>>>>>>> -            userid_bytes = metadata_stream_to_writable_bytes(userid)
>>>>>>> +            userid_bytes = metadataTranscoder.metadata_stream_to_writable_bytes(userid)
>>>>>>>                return b"%s <a@b>" % userid_bytes
>>>>>>>          def streamTag(self, gitStream, labelName, labelDetails, commit, epoch):
>>>>>>> @@ -4561,6 +4585,7 @@ commands = {
>>>>>>>        "unshelve": P4Unshelve,
>>>>>>>    }
>>>>>>>    +metadataTranscoder = MetadataTranscoder(defaultMetadataDecodingStrategy, defaultFallbackMetadataEncoding)
>>>>>>>      def main():
>>>>>>>        if len(sys.argv[1:]) == 0:
>>>>>>> diff --git a/t/meson.build b/t/meson.build
>>>>>>> index a59da26be3f..656424fdff3 100644
>>>>>>> --- a/t/meson.build
>>>>>>> +++ b/t/meson.build
>>>>>>> @@ -1090,6 +1090,7 @@ integration_tests = [
>>>>>>>      't9834-git-p4-file-dir-bug.sh',
>>>>>>>      't9835-git-p4-metadata-encoding-python2.sh',
>>>>>>>      't9836-git-p4-metadata-encoding-python3.sh',
>>>>>>> +  't9837-git-p4-error-encoding.sh',
>>>>>>>      't9850-shell.sh',
>>>>>>>      't9901-git-web--browse.sh',
>>>>>>>      't9902-completion.sh',
>>>>>>> diff --git a/t/t9837-git-p4-error-encoding.sh b/t/t9837-git-p4-error- encoding.sh
>>>>>>> new file mode 100755
>>>>>>> index 00000000000..1ea774afb1b
>>>>>>> --- /dev/null
>>>>>>> +++ b/t/t9837-git-p4-error-encoding.sh
>>>>>>> @@ -0,0 +1,53 @@
>>>>>>> +#!/bin/sh
>>>>>>> +
>>>>>>> +test_description='git p4 error encoding
>>>>>>> +
>>>>>>> +This test checks that the import process handles inconsistent text
>>>>>>> +encoding in p4 error messages without failing'
>>>>>>> +
>>>>>>> +. ./lib-git-p4.sh
>>>>>>> +
>>>>>>> +###############################
>>>>>>> +## SECTION REPEATED IN t9835 ##
>>>>>>> +###############################
>>>>>>> +
>>>>>>> +# These tests require Perforce with non-unicode setup.
>>>>>>> +out=$(2>&1 P4CHARSET=utf8 p4 client -o)
>>>>>>> +if test $? -eq 0
>>>>>>> +then
>>>>>>> +    skip_all="skipping git p4 error encoding tests; Perforce is setup with unicode"
>>>>>>> +    test_done
>>>>>>> +fi
>>>>>>> +
>>>>>>> +# These tests are specific to Python 3. Write a custom script that executes
>>>>>>> +# git-p4 directly with the Python 3 interpreter to ensure that we use that
>>>>>>> +# version even if Git was compiled with Python 2.
>>>>>>> +python_target_binary=$(which python3)
>>>>>>> +if test -n "$python_target_binary"
>>>>>>> +then
>>>>>>> +    mkdir temp_python
>>>>>>> +    PATH="$(pwd)/temp_python:$PATH"
>>>>>>> +    export PATH
>>>>>>> +
>>>>>>> +    write_script temp_python/git-p4-python3 <<-EOF
>>>>>>> +    exec "$python_target_binary" "$(git --exec-path)/git-p4" "\$@"
>>>>>>> +    EOF
>>>>>>> +fi
>>>>>>> +
>>>>>>> +git p4-python3 >err
>>>>>>> +if ! grep 'valid commands' err
>>>>>>> +then
>>>>>>> +    skip_all="skipping python3 git p4 tests; python3 not available"
>>>>>>> +    test_done
>>>>>>> +fi
>>>>>>> +
>>>>>>> +test_expect_success 'start p4d' '
>>>>>>> +    start_p4d
>>>>>>> +'
>>>>>>> +
>>>>>>> +test_expect_success 'see if Perforce error with characters not convertable to utf-8 will be processed correctly' '
>>>>>>> +    test_when_finished cleanup_git &&
>>>>>>> +    $python_target_binary "$TEST_DIRECTORY"/t9837/git-p4-error- python3.py "$TEST_DIRECTORY"
>>>>>>> +'
>>>>>>> +
>>>>>>> +test_done
>>>>>>> diff --git a/t/t9837/git-p4-error-python3.py b/t/t9837/git-p4-error- python3.py
>>>>>>> new file mode 100644
>>>>>>> index 00000000000..fb65aee386e
>>>>>>> --- /dev/null
>>>>>>> +++ b/t/t9837/git-p4-error-python3.py
>>>>>>> @@ -0,0 +1,15 @@
>>>>>>> +import os
>>>>>>> +import sys
>>>>>>> +from  importlib.machinery import SourceFileLoader
>>>>>>> +
>>>>>>> +def main():
>>>>>>> +    if len(sys.argv[1:]) != 1:
>>>>>>> +        print("Expected test directory name")
>>>>>>> +
>>>>>>> +    gitp4_path = sys.argv[1] + "/../git-p4.py"
>>>>>>> +    gitp4 = SourceFileLoader("gitp4", gitp4_path).load_module()
>>>>>>> +    gitp4.p4CmdList(["edit", b'\xFEfile'])
>>>>>>> +
>>>>>>> +if __name__ == '__main__':
>>>>>>> +    main()
>>>>>>> +
>>>>>>>
>>>>>>> base-commit: 683c54c999c301c2cd6f715c411407c413b1d84e