Subject: Re: [PATCH v2 3/4] rm: expand the index only when necessary

From: Victoria Dye <[email-masked]>
Date: Tue, 9 Aug 2022 17:24:30 -0700

Shaoxuan Yuan wrote:
> Remove the `ensure_full_index()` method so `git-rm` does not always
> expand the index when the expansion is unnecessary, i.e. when
> <pathspec> does not have any possibilities to match anything outside
> of sparse-checkout definition.
> 
> Expand the index when the <pathspec> needs an expanded index, i.e. the
> <pathspec> contains wildcard that may need a full-index or the
> <pathspec> is simply outside of sparse-checkout definition.
> 
> Notice that the test 'rm pathspec expands index when necessary' in
> t1092 *is* testing this code change behavior, though it will be marked
> as 'test_expect_success' only in the next patch, where we officially
> mark `command_requires_full_index = 0`, so the index does not expand
> unless we tell it to do so.
> 
> Notice that because we also want `ensure_full_index` to record the
> stdout and stderr from Git command, a corresponding modification
> is also included in this patch. The reason we want the "sparse-index-out"
> and "sparse-index-err", is that we need to make sure there is no error
> from Git command itself, so we can rely on the `test_region` result
> and determine if the index is expanded or not.

I think this patch might make more sense _after_ patch 4. Without the
changes in patch 4, modifying how a sparse index is handled here doesn't
immediately change any functionality. Then, patch 4 effectively makes its
own changes (enable the sparse index) + "turns on" the changes from this
series, all at once.

I usually recommend trying to make the effects of a patch testable in that
patch (as long as it doesn't make a series more complicated/confusing). In
this case, it looks like you could swap the order of the commits and only
need to adjust the 'test_expect_success'/'test_expect_failure' settings on
the tests, making it a good candidate for this kind of reordering.

All that said, I don't think changing this is worth a re-roll on its own -
it's moreso intended as "things to consider for future series". :) 

> 
> Helped-by: Victoria Dye <[email-masked]>
> Helped-by: Derrick Stolee <[email-masked]>
> Signed-off-by: Shaoxuan Yuan <[email-masked]>
> ---
>  builtin/rm.c                             |  5 +++--
>  t/t1092-sparse-checkout-compatibility.sh | 27 ++++++++++++++++++++++--
>  2 files changed, 28 insertions(+), 4 deletions(-)
> 
> diff --git a/builtin/rm.c b/builtin/rm.c
> index 84a935a16e..58ed924f0d 100644
> --- a/builtin/rm.c
> +++ b/builtin/rm.c
> @@ -296,8 +296,9 @@ int cmd_rm(int argc, const char **argv, const char *prefix)
>  
>  	seen = xcalloc(pathspec.nr, 1);
>  
> -	/* TODO: audit for interaction with sparse-index. */
> -	ensure_full_index(&the_index);
> +	if (pathspec_needs_expanded_index(&the_index, &pathspec))
> +		ensure_full_index(&the_index);
> +
>  	for (i = 0; i < active_nr; i++) {
>  		const struct cache_entry *ce = active_cache[i];
>  
> diff --git a/t/t1092-sparse-checkout-compatibility.sh b/t/t1092-sparse-checkout-compatibility.sh
> index c9300b77dd..94464cf911 100755
> --- a/t/t1092-sparse-checkout-compatibility.sh
> +++ b/t/t1092-sparse-checkout-compatibility.sh
> @@ -1340,10 +1340,14 @@ ensure_not_expanded () {
>  		shift &&
>  		test_must_fail env \
>  			GIT_TRACE2_EVENT="$(pwd)/trace2.txt" \
> -			git -C sparse-index "$@" || return 1
> +			git -C sparse-index "$@" \
> +			>sparse-index-out \
> +			2>sparse-index-error || return 1
>  	else
>  		GIT_TRACE2_EVENT="$(pwd)/trace2.txt" \
> -			git -C sparse-index "$@" || return 1
> +			git -C sparse-index "$@" \
> +			>sparse-index-out \
> +			2>sparse-index-error || return 1
>  	fi &&
>  	test_region ! index ensure_full_index trace2.txt
>  }
> @@ -1910,4 +1914,23 @@ test_expect_failure 'rm pathspec outside sparse definition' '
>  	test_sparse_match git status --porcelain=v2
>  '
>  
> +test_expect_failure 'rm pathspec expands index when necessary' '
> +	init_repos &&
> +
> +	# in-cone pathspec (do not expand)
> +	ensure_not_expanded rm "deep/deep*" &&
> +	test_must_be_empty sparse-index-err &&
> +
> +	# out-of-cone pathspec (expand)
> +	! ensure_not_expanded rm --sparse "folder1/a*" &&
> +	test_must_be_empty sparse-index-err &&
> +
> +	# pathspec that should expand index
> +	! ensure_not_expanded rm "*/a" &&
> +	test_must_be_empty sparse-index-err &&
> +
> +	! ensure_not_expanded rm "**a" &&
> +	test_must_be_empty sparse-index-err
> +'
> +
>  test_done