Subject: Re: [PATCH v2 3/5] completion: add and use __git_compute_first_level_config_vars_for_section

From: Patrick Steinhardt <[email-masked]>
Date: Thu, 8 Feb 2024 08:42:14 +0100

On Mon, Jan 29, 2024 at 01:27:59PM +0000, Philippe Blain via GitGitGadget wrote:
> From: Philippe Blain <[email-masked]>
> 
> The function __git_complete_config_variable_name in the Bash completion
> script hardcodes several config variable names. These variables are
> those in config section where user-defined names can appear, such as
> "branch.<name>". These sections are treated first by the case statement,
> and the two last "catch all" cases are used for other sections, making
> use of the __git_compute_config_vars and __git_compute_config_sections
> function, which omit listing any variables containing wildcards or
> placeholders. Having hardcoded config variables introduces the risk of
> the completion code becoming out of sync with the actual config
> variables accepted by Git.
> 
> To avoid these hardcoded config variables, introduce a new function,
> __git_compute_first_level_config_vars_for_section, making use of the
> existing __git_config_vars variable. This function takes as argument a
> config section name and computes the matching "first level" config
> variables for that section, i.e. those _not_ containing any placeholder,
> like 'branch.autoSetupMerge, 'remote.pushDefault', etc.  Use this
> function and the variables it defines in the 'branch.*', 'remote.*' and
> 'submodule.*' switches of the case statement instead of hardcoding the
> corresponding config variables.  Note that we use indirect expansion
> instead of associative arrays because those are not supported in Bash 3,
> on which macOS is stuck for licensing reasons.
> 
> Add a test to make sure the new function works correctly by verfying it
> lists all 'submodule' config variables. This has the downside that this
> test must be updated when new 'submodule' configuration are added, but
> this should be a small burden since it happens infrequently.
> 
> Signed-off-by: Philippe Blain <[email-masked]>
> ---
>  contrib/completion/git-completion.bash | 24 +++++++++++++++++++++---
>  t/t9902-completion.sh                  | 11 +++++++++++
>  2 files changed, 32 insertions(+), 3 deletions(-)
> 
> diff --git a/contrib/completion/git-completion.bash b/contrib/completion/git-completion.bash
> index 8af9bc3f4e1..2934ceb7637 100644
> --- a/contrib/completion/git-completion.bash
> +++ b/contrib/completion/git-completion.bash
> @@ -2596,6 +2596,15 @@ __git_compute_config_vars ()
>  	__git_config_vars="$(git help --config-for-completion)"
>  }
>  
> +__git_compute_first_level_config_vars_for_section ()
> +{
> +	section="$1"

Section needs to be `local`, right?

> +	__git_compute_config_vars
> +	local this_section="__git_first_level_config_vars_for_section_${section}"
> +	test -n "${!this_section}" ||
> +	printf -v "__git_first_level_config_vars_for_section_${section}" %s "$(echo "$__git_config_vars" | grep -E "^${section}\.[a-z]" | awk -F. '{print $2}')"
> +}

I've been wondering a bit why we store the result in a global variable.
The value certainly isn't reused in the completion scripts here. It took
me quite some time to realize though that it's going to end up in the
user's shell environment even after completion finishes so that it can
be reused the next time we invoke the completion function.

While this does feel a tad weird to me to be stateful like this across
completion calls, we use the same pattern for `__git_config_vars` and
`__git_config_sections`. So I guess it should be fine given that there
is precedent.

>  __git_config_sections=
>  __git_compute_config_sections ()
>  {
> @@ -2749,8 +2758,11 @@ __git_complete_config_variable_name ()
>  	branch.*)
>  		local pfx="${cur_%.*}."
>  		cur_="${cur_#*.}"
> +		local section="${pfx%.}"
>  		__gitcomp_direct "$(__git_heads "$pfx" "$cur_" ".")"
> -		__gitcomp_nl_append $'autoSetupMerge\nautoSetupRebase\n' "$pfx" "$cur_" "${sfx:- }"
> +		__git_compute_first_level_config_vars_for_section "${section}"
> +		local this_section="__git_first_level_config_vars_for_section_${section}"
> +		__gitcomp_nl_append "${!this_section}" "$pfx" "$cur_" "${sfx:- }"
>  		return
>  		;;
>  	guitool.*.*)
> @@ -2799,8 +2811,11 @@ __git_complete_config_variable_name ()
>  	remote.*)
>  		local pfx="${cur_%.*}."
>  		cur_="${cur_#*.}"
> +		local section="${pfx%.}"
>  		__gitcomp_nl "$(__git_remotes)" "$pfx" "$cur_" "."
> -		__gitcomp_nl_append "pushDefault" "$pfx" "$cur_" "${sfx:- }"
> +		__git_compute_first_level_config_vars_for_section "${section}"
> +		local this_section="__git_first_level_config_vars_for_section_${section}"
> +		__gitcomp_nl_append "${!this_section}" "$pfx" "$cur_" "${sfx:- }"
>  		return
>  		;;
>  	submodule.*.*)
> @@ -2812,8 +2827,11 @@ __git_complete_config_variable_name ()
>  	submodule.*)
>  		local pfx="${cur_%.*}."
>  		cur_="${cur_#*.}"
> +		local section="${pfx%.}"
>  		__gitcomp_nl "$(__git config -f "$(__git rev-parse --show-toplevel)/.gitmodules" --get-regexp 'submodule.*.path' | awk -F. '{print $2}')" "$pfx" "$cur_" "."
> -		__gitcomp_nl_append $'alternateErrorStrategy\nfetchJobs\nactive\nalternateLocation\nrecurse\npropagateBranches' "$pfx" "$cur_" "${sfx:- }"
> +		__git_compute_first_level_config_vars_for_section "${section}"
> +		local this_section="__git_first_level_config_vars_for_section_${section}"
> +		__gitcomp_nl_append "${!this_section}" "$pfx" "$cur_" "${sfx:- }"
>  		return
>  		;;
>  	url.*.*)
> diff --git a/t/t9902-completion.sh b/t/t9902-completion.sh
> index 35eb534fdda..f28d8f531b7 100755
> --- a/t/t9902-completion.sh
> +++ b/t/t9902-completion.sh
> @@ -2583,6 +2583,17 @@ test_expect_success 'git config - variable name include' '
>  	EOF
>  '
>  
> +test_expect_success 'git config - variable name - __git_compute_first_level_config_vars_for_section' '
> +	test_completion "git config submodule." <<-\EOF
> +	submodule.active Z
> +	submodule.alternateErrorStrategy Z
> +	submodule.alternateLocation Z
> +	submodule.fetchJobs Z
> +	submodule.propagateBranches Z
> +	submodule.recurse Z
> +	EOF
> +'
> +

Shouldn't we verify that we know to complete both first-level config
vars as well as the user-specified submodule names here?

Patrick

>  test_expect_success 'git config - value' '
>  	test_completion "git config color.pager " <<-\EOF
>  	false Z
> -- 
> gitgitgadget
> 
>