Subject: Re: [PATCH v4] pretty-formats: add hard truncation, without ellipsis, options

From: Junio C Hamano <[email-masked]>
Date: Fri, 25 Nov 2022 16:11:04 +0900

Philip Oakley <[email-masked]> writes:

> On 22/11/2022 00:57, Junio C Hamano wrote:
>> Philip Oakley <[email-masked]> writes:
>>
>>>> As a design question, what should "Trunc" do in such a case now?  I
>>>> do not think we can still call it "hard truncate" if the feature
>>>> gives "[][]" (i.e. fill only 4 display columns, resulting in a
>>>> string that is not wide enough) or "[][][]" (i.e. exceed 5 columns
>>>> that are given), but of course chomping a letter in the middle is
>>>> not acceptable behaviour, so ...
>>> The design had already covered those cases. The author already had those
>>> thoughts
>> Sorry, I was saying that none of
>>
>>  * giving only [][] to fill only 4 display columns, without filling
>>    the given 5 display columns,
>>
>>  * giving [][][] to fill 6 display columns, exceeding the given 5
>>    display columns,
>>
>>  * giving [][][ that chomps a letter in the middle, in a failed
>>    attempt to fill exactly 5 displya columns.
>>
>> would be a sensible design of the behaviour for "Trunc", so I am not
>> sure what "had already covered" really mean...
>>
> I'm still unsure what you are trying to say here.
>
> Is this a question about the prior `trunc`, `mtrunc`, and `ltrunc`
> design and tests?
> e.g. how complete are their tests?

No.  As I said, the existing lowercase ones may already be buggy (I
didn't check), in that they may do "[][].." or "[][][]" when told to
"trunc" fill a string with four or more double-width letters into a
5 display space.  But the point is at least for these with ellipsis
it is fairly clear what the desired behaviour is.  For "trunc" in
the above example, I think the right thing for it to do would be to
do "[][].", i.e. consume exactly 5 display columns, and avoid
exceeding the given space by not giving two dots but just one.

But with "hard truncate", I do not think we can define any sensible
behaviour when we ask it to do the same.  Giving "[][]" leaves one
display space unconsumed and giving "[][][]" would exceed the given
space, so anything you would write after that would be unaligned on
the line.

As to the tests, the question was, whatever the designed behaviour
for the above case, if they record the design choice made by this
series (even though, as I said, I suspect no design choice for the
"hard-fill/trunc odd number of columns with a run of double-width
letters" problem is satisfactory).