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git-mergetool: improve error code paths and messages #1827

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2 changes: 1 addition & 1 deletion contrib/completion/git-completion.bash
Original file line number Diff line number Diff line change
Expand Up @@ -2331,7 +2331,7 @@ _git_mergetool ()
return
;;
--*)
__gitcomp "--tool= --prompt --no-prompt --gui --no-gui"
__gitcomp "--tool= --tool-help --prompt --no-prompt --gui --no-gui"
return
;;
esac
Expand Down
8 changes: 2 additions & 6 deletions git-difftool--helper.sh
Original file line number Diff line number Diff line change
Expand Up @@ -61,9 +61,7 @@ launch_merge_tool () {
export BASE
eval $GIT_DIFFTOOL_EXTCMD '"$LOCAL"' '"$REMOTE"'
else
initialize_merge_tool "$merge_tool"
# ignore the error from the above --- run_merge_tool
# will diagnose unusable tool by itself
initialize_merge_tool "$merge_tool" || exit 1
run_merge_tool "$merge_tool"
fi
}
Expand All @@ -87,9 +85,7 @@ if test -n "$GIT_DIFFTOOL_DIRDIFF"
then
LOCAL="$1"
REMOTE="$2"
initialize_merge_tool "$merge_tool"
# ignore the error from the above --- run_merge_tool
# will diagnose unusable tool by itself
initialize_merge_tool "$merge_tool" || exit 1
run_merge_tool "$merge_tool" false

status=$?
Expand Down
12 changes: 9 additions & 3 deletions git-mergetool--lib.sh
Original file line number Diff line number Diff line change
Expand Up @@ -159,7 +159,7 @@ check_unchanged () {
}
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On the Git mailing list, Junio C Hamano wrote (reply to this):

"Philippe Blain via GitGitGadget" <[email protected]> writes:

>  valid_tool () {
> -	setup_tool "$1" && return 0
> +	setup_tool "$1" 2>/dev/null && return 0
>  	cmd=$(get_merge_tool_cmd "$1")
>  	test -n "$cmd"
>  }

As we are checking if a tool is valid, it is normal for setup_tool
to fail when we are checking is not valid (aka "fails to get set
up").  There is no need to show an error message for such a failure,
as the callers of valid_tool would do so if they wish.  OK.

>  setup_user_tool () {
>  	merge_tool_cmd=$(get_merge_tool_cmd "$tool")
> -	test -n "$merge_tool_cmd" || return 1
> +	if test -z "$merge_tool_cmd"
> +	then
> +		echo >&2 "error: ${TOOL_MODE}tool.$tool.cmd not set for tool '$tool'"
> +		return 1
> +	fi

There are only two callers of setup_user_tool, and one of them
squelches this message by sending it to /dev/null.  The error
message composed here does not use anything that is unique to the
function (in other words, $tool and ${TOOL_MODE} are available to
its callers).

I wonder if it is a better design to leave this one as-is, and
instead show the error message from the other caller of
setup_user_tool that does not squelch the message?  Are we planning
to add more callers of this function that want to show the same
message?

>  	diff_cmd () {
>  		( eval $merge_tool_cmd )
> @@ -255,7 +259,7 @@ setup_tool () {
>  
>  	# Now let the user override the default command for the tool.  If
>  	# they have not done so then this will return 1 which we ignore.
> -	setup_user_tool
> +	setup_user_tool 2>/dev/null

If we did that, then this change can be dropped.  Instead, a few
lines above this hunk, we can give the error message ourselves from
this setup_tool function.

>  	if ! list_tool_variants | grep -q "^$tool$"
>  	then
> diff --git a/t/t7610-mergetool.sh b/t/t7610-mergetool.sh
> index 22b3a85b3e9..82a88107850 100755
> --- a/t/t7610-mergetool.sh
> +++ b/t/t7610-mergetool.sh
> @@ -898,4 +898,12 @@ test_expect_success 'mergetool with guiDefault' '
>  	git commit -m "branch1 resolved with mergetool"
>  '
>  
> +test_expect_success 'mergetool with non-existent tool' '
> +	test_when_finished "git reset --hard" &&
> +	git checkout -b test$test_count branch1 &&
> +	test_must_fail git merge main &&
> +	yes "" | test_must_fail git mergetool --tool=absent >out 2>&1 &&
> +	test_grep -i "not set for tool" out
> +'

Why "-i"?  I do not offhand see the reason why we want to be loose
here.

The "${TOOL_MODE}tool" part may also want to be verified, perhaps,
which was related to the topic of the fix in [2/5]?

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On the Git mailing list, Philippe Blain wrote (reply to this):

Hi Junio,

Le 2024-11-12 à 20:48, Junio C Hamano a écrit :
> "Philippe Blain via GitGitGadget" <[email protected]> writes:
> 
>>  setup_user_tool () {
>>  	merge_tool_cmd=$(get_merge_tool_cmd "$tool")
>> -	test -n "$merge_tool_cmd" || return 1
>> +	if test -z "$merge_tool_cmd"
>> +	then
>> +		echo >&2 "error: ${TOOL_MODE}tool.$tool.cmd not set for tool '$tool'"
>> +		return 1
>> +	fi
> 
> There are only two callers of setup_user_tool, and one of them
> squelches this message by sending it to /dev/null.  The error
> message composed here does not use anything that is unique to the
> function (in other words, $tool and ${TOOL_MODE} are available to
> its callers).
> 
> I wonder if it is a better design to leave this one as-is, and
> instead show the error message from the other caller of
> setup_user_tool that does not squelch the message?  Are we planning
> to add more callers of this function that want to show the same
> message?

I don't think we are planning to add more callers, no.

> 
>>  	diff_cmd () {
>>  		( eval $merge_tool_cmd )
>> @@ -255,7 +259,7 @@ setup_tool () {
>>  
>>  	# Now let the user override the default command for the tool.  If
>>  	# they have not done so then this will return 1 which we ignore.
>> -	setup_user_tool
>> +	setup_user_tool 2>/dev/null
> 
> If we did that, then this change can be dropped.  Instead, a few
> lines above this hunk, we can give the error message ourselves from
> this setup_tool function.

I agree it could be done this way, I can change if it we wish.


>>  	if ! list_tool_variants | grep -q "^$tool$"
>>  	then
>> diff --git a/t/t7610-mergetool.sh b/t/t7610-mergetool.sh
>> index 22b3a85b3e9..82a88107850 100755
>> --- a/t/t7610-mergetool.sh
>> +++ b/t/t7610-mergetool.sh
>> @@ -898,4 +898,12 @@ test_expect_success 'mergetool with guiDefault' '
>>  	git commit -m "branch1 resolved with mergetool"
>>  '
>>  
>> +test_expect_success 'mergetool with non-existent tool' '
>> +	test_when_finished "git reset --hard" &&
>> +	git checkout -b test$test_count branch1 &&
>> +	test_must_fail git merge main &&
>> +	yes "" | test_must_fail git mergetool --tool=absent >out 2>&1 &&
>> +	test_grep -i "not set for tool" out
>> +'
> 
> Why "-i"?  I do not offhand see the reason why we want to be loose
> here.

Indeed this is a leftover from my bisection test in which I had to 
be a bit more loose. I'll remove that flag.
 
> The "${TOOL_MODE}tool" part may also want to be verified, perhaps,
> which was related to the topic of the fix in [2/5]?

Yes, I guess I could make the pattern stricter. I'll update that.


valid_tool () {
setup_tool "$1" && return 0
setup_tool "$1" 2>/dev/null && return 0
cmd=$(get_merge_tool_cmd "$1")
test -n "$cmd"
}
Expand Down Expand Up @@ -250,7 +250,12 @@ setup_tool () {
. "$MERGE_TOOLS_DIR/${tool%[0-9]}"
else
setup_user_tool
return $?
rc=$?
if test $rc -ne 0
then
echo >&2 "error: ${TOOL_MODE}tool.$tool.cmd not set for tool '$tool'"
fi
return $rc
fi

# Now let the user override the default command for the tool. If
Expand All @@ -259,6 +264,7 @@ setup_tool () {

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On the Git mailing list, Junio C Hamano wrote (reply to this):

"Philippe Blain via GitGitGadget" <[email protected]> writes:

> From: Philippe Blain <[email protected]>
>
> In setup_tool, we check if the given tool is a known variant of a tool,
> and quietly return with an error if not. This leads to the following
> invocation quietly failing:
>
> 	git mergetool --tool=vimdiff4
>
> Add an error message before returning in this case.

Makes sense, but ...

> Signed-off-by: Philippe Blain <[email protected]>
> ---
>  git-mergetool--lib.sh | 1 +
>  1 file changed, 1 insertion(+)
>
> diff --git a/git-mergetool--lib.sh b/git-mergetool--lib.sh
> index f4786afc63f..9a00fabba27 100644
> --- a/git-mergetool--lib.sh
> +++ b/git-mergetool--lib.sh
> @@ -263,6 +263,7 @@ setup_tool () {
>  
>  	if ! list_tool_variants | grep -q "^$tool$"
>  	then
> +		echo "error: unknown ${tool%[0-9]} variant '$tool'" >&2

... I do not understand why you strip a single digit from the end.

    git mergetool --tool=nvimdiff4

says 'nvimdiff4' is not known as a variant of 'nvimdiff', but
wouldn't it still be a variant of 'vimdiff'?  Of course,

    git mergetool --tool=nvimdiff48

gets a vastly different error message ;-)

Saying

	echo >&2 "error: unknown variant '$tool'"

may be sufficient, perhaps?  I dunno.


>  		return 1
>  	fi

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On the Git mailing list, Philippe Blain wrote (reply to this):

Le 2024-11-12 à 21:01, Junio C Hamano a écrit :
> "Philippe Blain via GitGitGadget" <[email protected]> writes:
> 
>> From: Philippe Blain <[email protected]>
>>
>> In setup_tool, we check if the given tool is a known variant of a tool,
>> and quietly return with an error if not. This leads to the following
>> invocation quietly failing:
>>
>> 	git mergetool --tool=vimdiff4
>>
>> Add an error message before returning in this case.
> 
> Makes sense, but ...
> 
>> Signed-off-by: Philippe Blain <[email protected]>
>> ---
>>  git-mergetool--lib.sh | 1 +
>>  1 file changed, 1 insertion(+)
>>
>> diff --git a/git-mergetool--lib.sh b/git-mergetool--lib.sh
>> index f4786afc63f..9a00fabba27 100644
>> --- a/git-mergetool--lib.sh
>> +++ b/git-mergetool--lib.sh
>> @@ -263,6 +263,7 @@ setup_tool () {
>>  
>>  	if ! list_tool_variants | grep -q "^$tool$"
>>  	then
>> +		echo "error: unknown ${tool%[0-9]} variant '$tool'" >&2
> 
> ... I do not understand why you strip a single digit from the end.
> 
>     git mergetool --tool=nvimdiff4
> 
> says 'nvimdiff4' is not known as a variant of 'nvimdiff', but
> wouldn't it still be a variant of 'vimdiff'?  Of course,
> 
>     git mergetool --tool=nvimdiff48
> 
> gets a vastly different error message ;-)
> 
> Saying
> 
> 	echo >&2 "error: unknown variant '$tool'"
> 
> may be sufficient, perhaps?  I dunno.

the stripping of the last digit is just because I copied from 
the 'if' a few lines above, where we source "$MERGE_TOOLS_DIR/${tool%[0-9]}".
In MERGE_TOOLS_DIR we have 'nvimdiff' and 'gvimdiff' that simply source vimdiff,
so this works. But I agree that we can simplify the error message, I'll do that.

if ! list_tool_variants | grep -q "^$tool$"
then
echo "error: unknown tool variant '$tool'" >&2
return 1
fi

Expand Down Expand Up @@ -474,7 +480,7 @@ get_merge_tool_path () {
merge_tool="$1"
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On the Git mailing list, Junio C Hamano wrote (reply to this):

"Philippe Blain via GitGitGadget" <[email protected]> writes:

> From: Philippe Blain <[email protected]>
>
> In git-mergetool--lib.sh::get_merge_tool_path, we check if the chosen
> tool is valid via valid_tool and exit with an error message if not. This
> error message mentions "Unknown merge tool", even if the command the
> user tried was 'git difftool --tool=unknown'. Use the global 'TOOL_MODE'
> variable for a more correct error message.

Makes sense.  Is this something we can easily test to catch future
regression, or is it too trivial to matter?

I wouldn't mind if the answer were "the latter" ;-)

Thanks.

> Signed-off-by: Philippe Blain <[email protected]>
> ---
>  git-mergetool--lib.sh | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/git-mergetool--lib.sh b/git-mergetool--lib.sh
> index 1ff26170ffc..269a60ea44c 100644
> --- a/git-mergetool--lib.sh
> +++ b/git-mergetool--lib.sh
> @@ -474,7 +474,7 @@ get_merge_tool_path () {
>  	merge_tool="$1"
>  	if ! valid_tool "$merge_tool"
>  	then
> -		echo >&2 "Unknown merge tool $merge_tool"
> +		echo >&2 "Unknown $TOOL_MODE tool $merge_tool"
>  		exit 1
>  	fi
>  	if diff_mode

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On the Git mailing list, Philippe Blain wrote (reply to this):

Hi Junio (sorry for a late response),

Le 2024-11-12 à 20:27, Junio C Hamano a écrit :
> "Philippe Blain via GitGitGadget" <[email protected]> writes:
> 
>> From: Philippe Blain <[email protected]>
>>
>> In git-mergetool--lib.sh::get_merge_tool_path, we check if the chosen
>> tool is valid via valid_tool and exit with an error message if not. This
>> error message mentions "Unknown merge tool", even if the command the
>> user tried was 'git difftool --tool=unknown'. Use the global 'TOOL_MODE'
>> variable for a more correct error message.
> 
> Makes sense.  Is this something we can easily test to catch future
> regression, or is it too trivial to matter?
> 
> I wouldn't mind if the answer were "the latter" ;-)

With the changes in the next commit of the series, this particular error
becomes hard to trigger, as setup_user_tool will return with an error
before the error message change in this patch is reached. So I would way
it is not worth to add a test for this particular code path since it seems like
it becomes unreachable in the next commit (but I could be wrong). So mostly
"the latter" is my answer.

Thanks,
Philippe.

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On the Git mailing list, Philippe Blain wrote (reply to this):

Le 2024-11-22 à 13:57, Philippe Blain a écrit :
> Hi Junio (sorry for a late response),
> 
> Le 2024-11-12 à 20:27, Junio C Hamano a écrit :
>> "Philippe Blain via GitGitGadget" <[email protected]> writes:
>>
>>> From: Philippe Blain <[email protected]>
>>>
>>> In git-mergetool--lib.sh::get_merge_tool_path, we check if the chosen
>>> tool is valid via valid_tool and exit with an error message if not. This
>>> error message mentions "Unknown merge tool", even if the command the
>>> user tried was 'git difftool --tool=unknown'. Use the global 'TOOL_MODE'
>>> variable for a more correct error message.
>>
>> Makes sense.  Is this something we can easily test to catch future
>> regression, or is it too trivial to matter?
>>
>> I wouldn't mind if the answer were "the latter" ;-)
> 
> With the changes in the next commit of the series,

correction: with the changes in 3/5 and 5/5,

> this particular error
> becomes hard to trigger, as setup_user_tool will return with an error
> before the error message change in this patch is reached. So I would way
> it is not worth to add a test for this particular code path since it seems like
> it becomes unreachable in the next commit (but I could be wrong). So mostly
> "the latter" is my answer.

if ! valid_tool "$merge_tool"
then
echo >&2 "Unknown merge tool $merge_tool"
echo >&2 "Unknown $TOOL_MODE tool $merge_tool"
exit 1
fi
if diff_mode
Expand Down
8 changes: 8 additions & 0 deletions t/t7610-mergetool.sh
Original file line number Diff line number Diff line change
Expand Up @@ -898,4 +898,12 @@ test_expect_success 'mergetool with guiDefault' '
git commit -m "branch1 resolved with mergetool"
'

test_expect_success 'mergetool with non-existent tool' '
test_when_finished "git reset --hard" &&
git checkout -b test$test_count branch1 &&
test_must_fail git merge main &&
yes "" | test_must_fail git mergetool --tool=absent >out 2>&1 &&
test_grep "mergetool.absent.cmd not set for tool" out
'

test_done
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