[v2] Bug fix: ensure P4 "err" is displayed when exception is raised.

Commit Message

Fahad Alrashed May 8, 2024, 11:46 a.m. UTC

From: Fahad Alrashed <[e-mail]>

During "git p4 clone" if p4 process returns an error from the server,
it will store the message in the 'err' variable. Then it will send a
text command "die-now" to git-fast-import. However, git-fast-import
raises an exception: "fatal: Unsupported command: die-now" and err is
never displayed. This patch ensures that err is dispayed using
"finally:".

Signed-off-by: Fahad Alrashed <[e-mail]>
---
    In git p4, git fast-import fails from die-now command and err (from
    Perforce) is not shown
    
    When importing from Perforce using git p4 clone <depot location>,
    cloning works fine until Perforce command p4 raises an error. This error
    message is stored in err variable then git-fast-import is sent a die-now
    command to kill it. An exception is raised fatal: Unsupported command:
    die-now.
    
    This patch forces python to call die() with the err message returned
    from Perforce.
    
    This commit fixes the root cause of a bug that took me hours to find.
    I'm sure many faced the cryptic error and declared that git-p4 is not
    working for them.

Published-As: https://github.com/gitgitgadget/git/releases/tag/pr-git-1668%2Falrashedf%2Fmaster-v2
Fetch-It-Via: git fetch https://github.com/gitgitgadget/git pr-git-1668/alrashedf/master-v2
Pull-Request: https://github.com/git/git/pull/1668

Range-diff vs v1:

 1:  8dd2c730128 ! 1:  8d5b982bd08 Bug fix: ensure P4 "err" is displayed when exception is raised.
     @@ Metadata
       ## Commit message ##
          Bug fix: ensure P4 "err" is displayed when exception is raised.
      
     -    Bug fix: During "git p4 clone" if p4 process returns
     -    an error from the server, it will store it in variable
     -    "err". The it will send a text command "die-now" to
     -    git-fast-import. However, git-fast-import raises an
     -    exception: "fatal: Unsupported command: die-now"
     -    and err is never displayed. This patch ensures that
     -    err is dispayed using "finally:"
     +    During "git p4 clone" if p4 process returns an error from the server,
     +    it will store the message in the 'err' variable. Then it will send a
     +    text command "die-now" to git-fast-import. However, git-fast-import
     +    raises an exception: "fatal: Unsupported command: die-now" and err is
     +    never displayed. This patch ensures that err is dispayed using
     +    "finally:".
      
          Signed-off-by: Fahad Alrashed <[e-mail]>
      


 git-p4.py | 24 +++++++++++++-----------
 1 file changed, 13 insertions(+), 11 deletions(-)


base-commit: 235986be822c9f8689be2e9a0b7804d0b1b6d821

Comments

Junio C Hamano May 8, 2024, 4:53 p.m. UTC | #1

"Fahad Alrashed via GitGitGadget" <[e-mail]> writes:

> From: Fahad Alrashed <[e-mail]>
> Subject: Re: [PATCH v2] Bug fix: ensure P4 "err" is displayed when exception is raised.

Our convention is to use the name of the area as the prefix, e.g.,

	git-p4: show Perforce error to the user

in the title.  Documentation/SubmittingPatches has more guidance on
the title, like omitting the full-stop at the end, and on the
proposed log message in general.

> During "git p4 clone" if p4 process returns an error from the server,
> it will store the message in the 'err' variable. Then it will send a
> text command "die-now" to git-fast-import. However, git-fast-import
> raises an exception: "fatal: Unsupported command: die-now" and err is
> never displayed.

Nicely explained.

> This patch ensures that err is dispayed using
> "finally:".

Instead, we write it more like

	Ensure that err is shown to the end user.

The implementation (i.e., catching an error with try/finally) can be
seen from the patch text.  What is more important to capture in the
proposed log message is what _effect_ the commit wanted to make,
which is a good way to show _why_ we are making the change.

The intent of the original code being to always die at this point.
Even though it is necessary to enclose the earlier part up to
.wait() inside a try block to catch an exception, the two calls to
die() do not have to be inside finally block (in other words,
finally block could be just a no-op, and the die() calls can be done
after the whole try/finally block that kills the fast-import by
sending die-now and makes sure .wait() sees the process go), which
may have made the intent of the fix even more clear, which is "we
use the try/finally construct only to work around an exception
thrown by killing the fast-import process".

The patch posted as-is is not wrong per-se, though.

Thanks.

> diff --git a/git-p4.py b/git-p4.py
> index 28ab12c72b6..f1ab31d5403 100755
> --- a/git-p4.py
> +++ b/git-p4.py
> @@ -3253,17 +3253,19 @@ def streamP4FilesCb(self, marshalled):
>              if self.stream_have_file_info:
>                  if "depotFile" in self.stream_file:
>                      f = self.stream_file["depotFile"]
> -            # force a failure in fast-import, else an empty
> -            # commit will be made
> -            self.gitStream.write("\n")
> -            self.gitStream.write("die-now\n")
> -            self.gitStream.close()
> -            # ignore errors, but make sure it exits first
> -            self.importProcess.wait()
> -            if f:
> -                die("Error from p4 print for %s: %s" % (f, err))
> -            else:
> -                die("Error from p4 print: %s" % err)
> +            try:
> +                # force a failure in fast-import, else an empty
> +                # commit will be made
> +                self.gitStream.write("\n")
> +                self.gitStream.write("die-now\n")
> +                self.gitStream.close()
> +                # ignore errors, but make sure it exits first
> +                self.importProcess.wait()
> +            finally:
> +                if f:
> +                    die("Error from p4 print for %s: %s" % (f, err))
> +                else:
> +                    die("Error from p4 print: %s" % err)
>  
>          if 'depotFile' in marshalled and self.stream_have_file_info:
>              # start of a new file - output the old one first
>
> base-commit: 235986be822c9f8689be2e9a0b7804d0b1b6d821

Patch

diff --git a/git-p4.py b/git-p4.py
index 28ab12c72b6..f1ab31d5403 100755
--- a/git-p4.py
+++ b/git-p4.py
@@ -3253,17 +3253,19 @@  def streamP4FilesCb(self, marshalled):
             if self.stream_have_file_info:
                 if "depotFile" in self.stream_file:
                     f = self.stream_file["depotFile"]
-            # force a failure in fast-import, else an empty
-            # commit will be made
-            self.gitStream.write("\n")
-            self.gitStream.write("die-now\n")
-            self.gitStream.close()
-            # ignore errors, but make sure it exits first
-            self.importProcess.wait()
-            if f:
-                die("Error from p4 print for %s: %s" % (f, err))
-            else:
-                die("Error from p4 print: %s" % err)
+            try:
+                # force a failure in fast-import, else an empty
+                # commit will be made
+                self.gitStream.write("\n")
+                self.gitStream.write("die-now\n")
+                self.gitStream.close()
+                # ignore errors, but make sure it exits first
+                self.importProcess.wait()
+            finally:
+                if f:
+                    die("Error from p4 print for %s: %s" % (f, err))
+                else:
+                    die("Error from p4 print: %s" % err)
 
         if 'depotFile' in marshalled and self.stream_have_file_info:
             # start of a new file - output the old one first