Re: git-p4 crashes on non UTF-8 output from p4

From: Torsten Bögershausen <tboegi@web.de>
Date: Apr 11, 2021, 09:37 UTC
Message-ID: <20210411093746.ymqofe2uawclwu5i@tb-raspi4>
In-Reply-To: <CAKu1iLX1AyTCSGxDVgiR1cr4=4ODD-gn8jHAinhp7OhDChAf1A@mail.gmail.com>

On Sun, Apr 11, 2021 at 12:16:25AM -0700, Tzadik Vanderhoof wrote:

> Here is the pull request:

Thanks for the work. Some comments inline.

>
> From 8d234af842223dceae76ce0affd3bbb3f17bb6d9 Mon Sep 17 00:00:00 2001
> From: Tzadik Vanderhoof <tzadik.vanderhoof@gmail.com>
> Date: Sat, 10 Apr 2021 22:41:39 -0700

The subject should be one short line, highlighting what this is all about, followed by a blank line and a longer description about the problem and the solution. The original description was good, see below.

> Subject: [PATCH] add git-p4.fallbackEncoding config variable, to prevent
>  git-p4 from crashing on non UTF-8 changeset descriptions

In that sense I make a first trial here, subject for improvements:

Subject: [PATCH] Add git-p4.fallbackEncoding config variable

When git-p4 reads the output from a p4 command, it assumes it will be 100% UTF-8. If even one character in the output of one p4 command is not UTF-8, git-p4 crashes e.g. with:

File "C:/Program Files/Git/bin/git-p4.py", line 774, in p4CmdList
    value = value.decode() UnicodeDecodeError: 'utf-8' codec can't
decode byte Ox93 in position 42: invalid start byte

Allow to try another encoding (eg cp1252) and/or use the Unicode replacement character to prevent the whole program from crashing on such a "minor" problem.

This is especially a problem on the "git p4 clone" command with @all, where git-p4 needs to read thousands of changeset descriptions, one of which may have a stray smart quote, causing the whole clone operation to fail.

Introduce "git-p4.fallbackEncoding" to handle non UTF-8 encodings, if needed.

Show 18 quoted lines

>
> ---
>  Documentation/git-p4.txt | 10 ++++++++++
>  git-p4.py                | 11 ++++++++++-
>  2 files changed, 20 insertions(+), 1 deletion(-)
>
> diff --git a/Documentation/git-p4.txt b/Documentation/git-p4.txt
> index f89e68b..71f3487 100644
> --- a/Documentation/git-p4.txt
> +++ b/Documentation/git-p4.txt
> @@ -638,6 +638,16 @@ git-p4.pathEncoding::
>   to transcode the paths to UTF-8. As an example, Perforce on Windows
>   often uses "cp1252" to encode path names.
>
> +git-p4.fallbackEncoding::
> +    Perforce changeset descriptions can be in a mixture of encodings. Git-p4
> +    first tries to interpret each description as UTF-8. If that fails, this
> +    config allows another encoding to be tried.  The default is "cp1252".  You

I know that cp1252 is attractive to be used, especially for Windows installations that
use Latin-based "characters".
But: If we introduce a new config-variable into Git, the default tends to be
"if not set to anything, behave as the old Git".

> +    can set it to another encoding, for example, "iso-8859-5". If instead of

ISO-8859-5 may be more portable on the different i18 implementations than the lower-case spelling.

> +    an encoding, you specify "replace", UTF-8 will be used, with invalid UTF-8
> +    characters replaced by the Unicode replacement character. If you specify
> +    "none", there is no fallback, and any non UTF-8 character will cause
> +    git-p4 to immediately fail.

As said, before, many people may expect Git to fail, so that the default should be none to avoid surprises. When a "non-UTF-8-clean" repo is handled, they want to know it.

Show 22 quoted lines

> +
>  git-p4.largeFileSystem::
>   Specify the system that is used for large (binary) files. Please note
>   that large file systems do not support the 'git p4 submit' command.
> diff --git a/git-p4.py b/git-p4.py
> index 09c9e93..18d02b4 100755
> --- a/git-p4.py
> +++ b/git-p4.py
> @@ -771,7 +771,16 @@ def p4CmdList(cmd, stdin=None, stdin_mode='w+b',
> cb=None, skip_info=False,
>                  for key, value in entry.items():
>                      key = key.decode()
>                      if isinstance(value, bytes) and not (key in
> ('data', 'path', 'clientFile') or key.startswith('depotFile')):
> -                        value = value.decode()
> +                        try:
> +                            value = value.decode()
> +                        except:
> +                            fallbackEncoding =
> gitConfig("git-p4.fallbackEncoding").lower() or 'cp1252'
> +                            if fallbackEncoding == 'none':
> +                                raise

Would it make sense to tell the user about the new config value here?
 raise Exception("Non UTF-8 detected. See git-p4.fallbackEncoding"
Or somewhat in that style ?

Show 8 quoted lines

> +                            elif fallbackEncoding == 'replace':
> +                                value = value.decode(errors='replace')
> +                            else:
> +                                value = value.decode(encoding=fallbackEncoding)
>                      decoded_entry[key] = value
>                  # Parse out data if it's an error response
>                  if decoded_entry.get('code') == 'error' and 'data' in
> decoded_entry:

Did I miss the Signed-off-by here?

Please have a look here: https://git-scm.com/docs/SubmittingPatches

(or look at Documentation/SubmittingPatches in your git source code)

And finally: Thanks for the contribution. Is there any chance to add test-cases, to make sure that this feature is well-tested now and in the future ?

Show 43 quoted lines

> --
> 2.31.1.windows.1
>
> On Fri, Apr 9, 2021 at 8:38 AM Torsten Bögershausen <tboegi@web.de> wrote:
> >
> > On Thu, Apr 08, 2021 at 12:28:25PM -0700, Tzadik Vanderhoof wrote:
> > > When git-p4 reads the output from a p4 command, it assumes it will be
> > > 100% UTF-8. If even one character in the output of one p4 command is
> > > not UTF-8, git-p4 crashes with:
> > >
> > > File "C:/Program Files/Git/bin/git-p4.py", line 774, in p4CmdList
> > >     value = value.decode() UnicodeDecodeError: 'utf-8' codec can't
> > > decode byte Ox93 in position 42: invalid start byte
> > >
> > > I'd like to make a pull request to have it try another encoding (eg
> > > cp1252) and/or use the Unicode replacement character, to prevent the
> > > whole program from crashing on such a minor problem.
> > >
> > > This is especially a problem on the "git p4 clone" command with @all,
> > > where git-p4 needs to read thousands of changeset descriptions, one of
> > > which may have a stray smart quote, causing the whole clone operation
> > > to fail.
> > >
> > > Sound ok?
> >
> > Welcome to the Git community.
> > To start with: I am not a git-p4 expert as such, but seeing that a program is crashing
> > is never a good thing.
> > All efforts to prevent the crash are a step forward.
> >
> > As you mention cp1252 (which is more used under Windows), there are probably lots of
> > system out there which use ISO-8859-15 (or ISO-8859-1) we may have the first whish:
> >
> > Make the encoding/fallback configurable.
> > Let people choose if they want a crash (if things are broken),
> > fallback to cp1252 or one of the other ISO-ISO-8859-x encodings.
> >
> > In that sense: we look forward to a pull-request.
>
>
>
> --
> Tzadik