Re: [PATCH v3 1/1] quote: handle numm and empty strings in sq_quote_buf_pretty

[Garima Singh <garimasigit@gmail.com>]

On 10/7/2019 1:27 PM, Eric Sunshine wrote:
> On Mon, Oct 7, 2019 at 12:17 PM Garima Singh via GitGitGadget
> <gitgitgadget@gmail.com> wrote:
>> quote: handle numm and empty strings in sq_quote_buf_pretty
> 
> What is "numm"?

Typo. Fixing in next update. 

> What does it mean to "handle" these things? A possible rewrite of the
> subject to explain the problem more precisely rather than using
> generalizations might be:
> 
>     sq_quote_buf_pretty: don't drop empty arguments
> 
>> The sq_quote_buf_pretty() function does not emit anything
>> when the incoming string is empty, but the function is to
>> accumulate command line arguments, properly quoted as
>> necessary, and the right way to add an argument that is an
>> empty string is to show it quoted, i.e. ''. We warn the caller
>> with the BUG macro is they pass in a NULL.
> 
> s/is they/if they/

Typo. Fixing in next update. 

> By including the final sentence in this paragraph, the reader is
> confused into thinking that warning the caller with BUG() is the
> overall purpose of this patch and is the "fix" for the stated problem.
> At minimum, the final sentence should be yanked out to its own
> paragraph or, better yet, dropped altogether since it's of little
> importance in the overall scheme of the patch.
> 
> As a reader of this commit message, I find it difficult to understand
> what problem it's trying to solve since the problem and solution and
> existing behavior are presented in a circuitous way which doesn't make
> any of them stand out clearly. Here's a possible rewrite:
> 
>     sq_quote_buf_pretty: don't drop empty arguments
> 
>     Empty arguments passed on a command-line should be represented by
>     a zero-length quoted string, however, sq_quote_buf_pretty()
>     incorrectly drops these arguments altogether. Fix this problem by
>     ensuring that such arguments are emitted as '' instead.

Works for me. Thanks! 

>> Reported by: Junio Hamano <gitster@pobox.com>
>> Signed-off-by: Garima Singh <garima.singh@microsoft.com>
>> ---
>> diff --git a/quote.c b/quote.c
>> @@ -48,6 +48,16 @@ void sq_quote_buf_pretty(struct strbuf *dst, const char *src)
>> +       /* In case of null tokens, warn the user of the BUG in their call. */
>> +       if (!src)
>> +               BUG("Cannot append a NULL token to the buffer");
> 
> The comment merely repeats what the code itself already says clearly,
> thus adds no value and ought to be dropped.
> 
> Moreover, this entire check seems superfluous since the program will
> crash anyhow as soon as 'src' is dereferenced (just below), thus the
> programmer will find out soon enough about the error. I'd suggest
> dropping this check entirely since it's not adding any value.
> 

Fair enough. Removing the comment. Leaving the check. I would
rather the caller of the function know what went wrong instead
of a segfault. 

>> diff --git a/t/t0014-alias.sh b/t/t0014-alias.sh
>> @@ -37,4 +37,11 @@ test_expect_success 'looping aliases - internal execution' '
>> +test_expect_success 'run-command parses empty args properly, using sq_quote_buf_pretty' '
> 
> Is "parses" the correct word? Should it be "formats" or something?
> 
Sure. 

> Also, the bit about "using sq_quote_buf_pretty" lets an implementation
> detail bleed unnecessarily into the test suite, and that detail could
> become outdated at some point (say, if some function ever replaces
> that one, for instance). It should be sufficient for the test title
> merely to mention that it is checking that empty arguments are handled
> properly. So, perhaps:
> 
>     test_expect_success 'run-command formats empty args properly' '
> 

Sure.