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From: Derrick Stolee <stolee@gmail.com>
To: Elijah Newren <newren@gmail.com>
Cc: "Elijah Newren via GitGitGadget" <gitgitgadget@gmail.com>,
	"Git Mailing List" <git@vger.kernel.org>,
	"Martin Melka" <martin.melka@gmail.com>,
	"SZEDER Gábor" <szeder.dev@gmail.com>,
	"Samuel Lijin" <sxlijin@gmail.com>,
	"Nguyễn Thái Ngọc Duy" <pclouds@gmail.com>
Subject: Re: [PATCH 4/6] dir: move setting of nested_repo next to its actual usage
Date: Thu, 30 Jan 2020 11:00:48 -0500
Message-ID: <1bc41d94-5d4d-4157-fc00-08b97fb20738@gmail.com> (raw)
In-Reply-To: <CABPp-BFbXJRW38CeGy78b22MfZ8cNizexCM-+n-ODqy+fOo2uw@mail.gmail.com>

On 1/30/2020 10:45 AM, Elijah Newren wrote:
> On Thu, Jan 30, 2020 at 7:33 AM Derrick Stolee <stolee@gmail.com> wrote:
>>
>> On 1/29/2020 5:03 PM, Elijah Newren via GitGitGadget wrote:
>>> From: Elijah Newren <newren@gmail.com>
>>>
>>> Signed-off-by: Elijah Newren <newren@gmail.com>
>>> ---
>>>  dir.c | 3 ++-
>>>  1 file changed, 2 insertions(+), 1 deletion(-)
>>>
>>> diff --git a/dir.c b/dir.c
>>> index 225f0bc082..ef3307718a 100644
>>> --- a/dir.c
>>> +++ b/dir.c
>>> @@ -1659,7 +1659,7 @@ static enum path_treatment treat_directory(struct dir_struct *dir,
>>>       const char *dirname, int len, int baselen, int excluded,
>>>       const struct pathspec *pathspec)
>>>  {
>>> -     int nested_repo = 0;
>>> +     int nested_repo;
>>>
>>>       /* The "len-1" is to strip the final '/' */
>>>       switch (directory_exists_in_index(istate, dirname, len-1)) {
>>> @@ -1670,6 +1670,7 @@ static enum path_treatment treat_directory(struct dir_struct *dir,
>>>               return path_none;
>>>
>>>       case index_nonexistent:
>>> +             nested_repo = 0;
>>
>> I had to look at this code in-full from en/fill-directory-fixes-more to
>> be sure that this case was the only use of nested_repo. However, I found
>> that this switch statement is unnecessarily complicated. By converting
>> the switch to multiple "if" statements, I noticed that the third case
>> actually has a "break" statement that can lead to the final "fourth case"
>> outside the switch statement.
>>
>> Hopefully the patch below is a worthy replacement for this one:
>>
>> -->8--
>>
>> From b5c04e6e028cb6c7f9e78fbdd2182383d928fe6d Mon Sep 17 00:00:00 2001
>> From: Derrick Stolee <dstolee@microsoft.com>
>> Date: Thu, 30 Jan 2020 15:28:39 +0000
>> Subject: [PATCH] dir: refactor treat_directory to clarify variable scope
>>
>> The nested_repo variable in treat_directory() is created and
>> initialized before a multi-case switch statement, but is only
>> used by one case. In fact, this switch is very asymmetrical,
>> as the first two cases are simple but the third is more
>> complicated than the rest of the method.
>>
>> Extract the switch statement into a series of "if" statements.
>> This simplifies the trivial cases, while highlighting the fact
>> that a "break" statement in a condition of the third case
>> actually leads to jumping to the fourth case (after the switch).
>> This assists a reader who provides an initial scan to notice
>> there is a second way to approach the "show_other_directories"
>> case than simply the response from directory_exists_in_index().
> 
> Wait, I'm lost.  Wasn't that break statement the only way to get to
> the "show_other_directories" block of code after the switch statement?
>  I can't see where the second way is; am I missing something?

Ah, I guess I didn't realize that exist_status didn't have a fourth
mode. I was assuming that normally the switch would not hit any of
the case statements was the way you would _assume_ to hit the block
after the switch.

So yes, my statement is incorrect, but the intention is correct:
the flow of this method is very confusing.

> That is, unless directory_exists_in_index() suddenly starts returning
> some value other than the three current possibilities.  Perhaps we
> should throw a BUG() if we get anything other than index_directory,
> index_gitdir, or index_nonexistent.
> 
>>
>> Signed-off-by: Derrick Stolee <dstolee@microsoft.com>
>> ---
>>  dir.c | 17 ++++++++---------
>>  1 file changed, 8 insertions(+), 9 deletions(-)
>>
>> diff --git a/dir.c b/dir.c
>> index b460211e61..e48812efe6 100644
>> --- a/dir.c
>> +++ b/dir.c
>> @@ -1659,17 +1659,16 @@ static enum path_treatment treat_directory(struct dir_struct *dir,
>>         const char *dirname, int len, int baselen, int exclude,
>>         const struct pathspec *pathspec)
>>  {
>> -       int nested_repo = 0;
>> -
>>         /* The "len-1" is to strip the final '/' */
>> -       switch (directory_exists_in_index(istate, dirname, len-1)) {
>> -       case index_directory:
>> -               return path_recurse;
>> +       enum exist_status status = directory_exists_in_index(istate, dirname, len-1);
>>
>> -       case index_gitdir:
>> +       if (status == index_directory)
>> +               return path_recurse;
>> +       if (status == index_gitdir)
>>                 return path_none;
>>
>> -       case index_nonexistent:
>> +       if (status == index_nonexistent) {

Since exist_status only has three options, this "if" is redundant.

>> +               int nested_repo = 0;
>>                 if ((dir->flags & DIR_SKIP_NESTED_GIT) ||
>>                     !(dir->flags & DIR_NO_GITLINKS)) {
>>                         struct strbuf sb = STRBUF_INIT;
>> @@ -1682,7 +1681,7 @@ static enum path_treatment treat_directory(struct dir_struct *dir,
>>                                 (exclude ? path_excluded : path_untracked));
>>
>>                 if (dir->flags & DIR_SHOW_OTHER_DIRECTORIES)
>> -                       break;
>> +                       goto show_other_directories;

It would be better to nest the rest of this block in an 
if (!(dir->flags & DIR_SHOW_OTHER_DIRECTORIES))

>>                 if (exclude &&
>>                         (dir->flags & DIR_SHOW_IGNORED_TOO) &&
>>                         (dir->flags & DIR_SHOW_IGNORED_TOO_MODE_MATCHING)) {
>> @@ -1711,7 +1710,7 @@ static enum path_treatment treat_directory(struct dir_struct *dir,
>>         }
> 
> I'd say we'd want to add a BUG("Unhandled value for
> directory_exists_in_index: %d\n", status); right here.
> 
>>
>>         /* This is the "show_other_directories" case */
>> -
>> +show_other_directories:

...allowing us to drop this.

>>         if (!(dir->flags & DIR_HIDE_EMPTY_DIRECTORIES))
>>                 return exclude ? path_excluded : path_untracked;
>>
>> --
>> 2.25.0.vfs.1.1
> 
> Otherwise, the patch looks good to me and I'll be happy to replace my
> patch with this one.
 
Let me send a v2 of this patch now that you've pointed out my error. It
is worth making this method clearer before you expand substantially on
this final case.

Thanks,
-Stolee

  reply index

Thread overview: 68+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-01-29 22:03 [PATCH 0/6] Avoid multiple recursive calls for same path in read_directory_recursive() Elijah Newren via GitGitGadget
2020-01-29 22:03 ` [PATCH 1/6] dir: consolidate treat_path() and treat_one_path() Elijah Newren via GitGitGadget
2020-01-29 22:03 ` [PATCH 2/6] dir: fix broken comment Elijah Newren via GitGitGadget
2020-01-29 22:03 ` [PATCH 3/6] dir: fix confusion based on variable tense Elijah Newren via GitGitGadget
2020-01-30 15:20   ` Derrick Stolee
2020-01-31 18:04   ` SZEDER Gábor
2020-01-31 18:17     ` Elijah Newren
2020-01-29 22:03 ` [PATCH 4/6] dir: move setting of nested_repo next to its actual usage Elijah Newren via GitGitGadget
2020-01-30 15:33   ` Derrick Stolee
2020-01-30 15:45     ` Elijah Newren
2020-01-30 16:00       ` Derrick Stolee [this message]
2020-01-30 16:10         ` Derrick Stolee
2020-01-30 16:20           ` Elijah Newren
2020-01-30 18:17             ` Derrick Stolee
2020-01-29 22:03 ` [PATCH 5/6] dir: replace exponential algorithm with a linear one Elijah Newren via GitGitGadget
2020-01-30 15:55   ` Derrick Stolee
2020-01-30 17:13     ` Elijah Newren
2020-01-30 17:45       ` Elijah Newren
2020-01-31 17:13   ` SZEDER Gábor
2020-01-31 17:47     ` Elijah Newren
2020-01-29 22:03 ` [PATCH 6/6] t7063: blindly accept diffs Elijah Newren via GitGitGadget
2020-01-31 18:31 ` [PATCH v2 0/6] Avoid multiple recursive calls for same path in read_directory_recursive() Elijah Newren via GitGitGadget
2020-01-31 18:31   ` [PATCH v2 1/6] dir: consolidate treat_path() and treat_one_path() Elijah Newren via GitGitGadget
2020-01-31 18:31   ` [PATCH v2 2/6] dir: fix broken comment Elijah Newren via GitGitGadget
2020-01-31 18:31   ` [PATCH v2 3/6] dir: fix confusion based on variable tense Elijah Newren via GitGitGadget
2020-01-31 18:31   ` [PATCH v2 4/6] dir: refactor treat_directory to clarify control flow Derrick Stolee via GitGitGadget
2020-01-31 18:31   ` [PATCH v2 5/6] dir: replace exponential algorithm with a linear one Elijah Newren via GitGitGadget
2020-01-31 18:31   ` [PATCH v2 6/6] t7063: blindly accept diffs Elijah Newren via GitGitGadget
2020-03-25 19:31   ` [PATCH v3 0/7] Avoid multiple recursive calls for same path in read_directory_recursive() Elijah Newren via GitGitGadget
2020-03-25 19:31     ` [PATCH v3 1/7] t7063: correct broken test expectation Elijah Newren via GitGitGadget
2020-03-26 13:02       ` Derrick Stolee
2020-03-26 21:18         ` Elijah Newren
2020-03-25 19:31     ` [PATCH v3 2/7] dir: fix simple typo in comment Elijah Newren via GitGitGadget
2020-03-25 19:31     ` [PATCH v3 3/7] dir: consolidate treat_path() and treat_one_path() Elijah Newren via GitGitGadget
2020-03-25 19:31     ` [PATCH v3 4/7] dir: fix broken comment Elijah Newren via GitGitGadget
2020-03-25 19:31     ` [PATCH v3 5/7] dir: fix confusion based on variable tense Elijah Newren via GitGitGadget
2020-03-25 19:31     ` [PATCH v3 6/7] dir: refactor treat_directory to clarify control flow Derrick Stolee via GitGitGadget
2020-03-25 19:31     ` [PATCH v3 7/7] dir: replace exponential algorithm with a linear one, fix untracked cache Elijah Newren via GitGitGadget
2020-03-26 13:13       ` Derrick Stolee
2020-03-26 21:27     ` [PATCH v4 0/7] Avoid multiple recursive calls for same path in read_directory_recursive() Elijah Newren via GitGitGadget
2020-03-26 21:27       ` [PATCH v4 1/7] t7063: more thorough status checking Elijah Newren via GitGitGadget
2020-03-27 13:09         ` Derrick Stolee
2020-03-29 18:18           ` Junio C Hamano
2020-03-31 20:15             ` Elijah Newren
2020-03-26 21:27       ` [PATCH v4 2/7] dir: fix simple typo in comment Elijah Newren via GitGitGadget
2020-03-26 21:27       ` [PATCH v4 3/7] dir: consolidate treat_path() and treat_one_path() Elijah Newren via GitGitGadget
2020-03-26 21:27       ` [PATCH v4 4/7] dir: fix broken comment Elijah Newren via GitGitGadget
2020-03-26 21:27       ` [PATCH v4 5/7] dir: fix confusion based on variable tense Elijah Newren via GitGitGadget
2020-03-26 21:27       ` [PATCH v4 6/7] dir: refactor treat_directory to clarify control flow Derrick Stolee via GitGitGadget
2020-03-26 21:27       ` [PATCH v4 7/7] dir: replace exponential algorithm with a linear one Elijah Newren via GitGitGadget
2020-03-27 13:13       ` [PATCH v4 0/7] Avoid multiple recursive calls for same path in read_directory_recursive() Derrick Stolee
2020-03-28 17:33         ` Elijah Newren
2020-03-29 18:20           ` Junio C Hamano
2020-04-01  4:17       ` [PATCH v5 00/12] " Elijah Newren via GitGitGadget
2020-04-01  4:17         ` [PATCH v5 01/12] t7063: more thorough status checking Elijah Newren via GitGitGadget
2020-04-01  4:17         ` [PATCH v5 02/12] t3000: add more testcases testing a variety of ls-files issues Elijah Newren via GitGitGadget
2020-04-01  4:17         ` [PATCH v5 03/12] dir: fix simple typo in comment Elijah Newren via GitGitGadget
2020-04-01  4:17         ` [PATCH v5 04/12] dir: consolidate treat_path() and treat_one_path() Elijah Newren via GitGitGadget
2020-04-01  4:17         ` [PATCH v5 05/12] dir: fix broken comment Elijah Newren via GitGitGadget
2020-04-01  4:17         ` [PATCH v5 06/12] dir: fix confusion based on variable tense Elijah Newren via GitGitGadget
2020-04-01  4:17         ` [PATCH v5 07/12] dir: refactor treat_directory to clarify control flow Derrick Stolee via GitGitGadget
2020-04-01  4:17         ` [PATCH v5 08/12] dir: replace exponential algorithm with a linear one Elijah Newren via GitGitGadget
2020-04-01 13:57           ` Derrick Stolee
2020-04-01 15:59             ` Elijah Newren
2020-04-01  4:17         ` [PATCH v5 09/12] dir: include DIR_KEEP_UNTRACKED_CONTENTS handling in treat_directory() Elijah Newren via GitGitGadget
2020-04-01  4:17         ` [PATCH v5 10/12] dir: replace double pathspec matching with single " Elijah Newren via GitGitGadget
2020-04-01  4:17         ` [PATCH v5 11/12] Fix error-prone fill_directory() API; make it only return matches Elijah Newren via GitGitGadget
2020-04-01  4:17         ` [PATCH v5 12/12] completion: fix 'git add' on paths under an untracked directory Elijah Newren via GitGitGadget

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