widechar_width no longer classifies U+1F41F as widened-in-9, so the
width no longer changes.
Since we're interested in testing the change here, we need a different
emoji.
Just use 🥁, which was introduced in 9 as wide, and therefore widened
in 9.
This makes it so we treat backspaces as width -1, but never go below a
0 total width when talking about *lines*, like in screen or string
length --visible.
Fixes#8277.
Because we are, ultimately, interested in how many cells a string
occupies, we *have* to handle carriage return (`\r`) and line
feed (`\n`).
A carriage return sets the current tally to 0, and only the longest
tally is kept. The idea here is that the last position is the same as
the last position of the longest string. So:
abcdef\r123
ends up looking like
123def
which is the same width as abcdef, 6.
A line feed meanwhile means we flush the current tally and start a new
one. Every line is printed separately, even if it's given as one.
That's because, well, counting the width over multiple lines
doesn't *help*.
As a sidenote: This is necessarily imperfect, because, while we may
know the width of the terminal ($COLUMNS), we don't know the current
cursor position. So we can only give the width, and the user can then
figure something out on their own.
But for the common case of figuring out how wide the prompt is, this
should do.
* string: Allow `collect --no-empty` to avoid empty ellision
Currently we still have that issue where
test -n (thing | string collect)
can return true if `thing` doesn't print anything, because the
collected argument will still be removed.
So, what we do is allow `--no-empty` to be used, in which case we
print one empty argument.
This means
test -n (thing | string collect -n)
can now be safely used.
"no-empty" isn't the best name for this flag, but string's design
really incentivizes reusing names, and it's not *terrible*.
* Switch to `--allow-empty`
`--no-empty` does the exact opposite for `string split` and split0.
Since `-a`/`--allow-empty` already exists, use it.
This used to print a literal DEL character in the output for `bind`,
which wouldn't actually show up and made it hard to figure out what
the key was.
So we just escape it back to how we actually used it - `\x7f`.
Fixes#7631.
E.g. if we do `string match -q`, and we find a match, nothing about
the input can change anything, so we quit early.
This is mainly useful for performance, but it also allows `string`
with `-q` to be used with infinite input (e.g. `yes`).
Alternative to #7495.
If the padding is not divisible by the char's width without remainder,
we pad the remainder with spaces, so the total width of the output is correct.
Also add completions, changelog entry, adjust documentation, add examples
with emoji and some tests. Apply some minor style nitpicks and avoid extra
allocations of the input strings.
It's now good enough to do so.
We don't allow grid-alignment:
```fish
complete -c foo -s b -l barnanana -a '(something)'
complete -c foo -s z -a '(something)'
```
becomes
```fish
complete -c foo -s b -l barnanana -a '(something)'
complete -c foo -s z -a '(something)'
```
It's just more trouble than it is worth.
The one part I'd change:
We align and/or'd parts of an if-condition with the in-block code:
```fish
if true
and false
dosomething
end
```
becomes
```fish
if true
and false
dosomething
end
```
but it's not used terribly much and if we ever fix it we can just
reindent.
The `--entire` would enable output even though the `--quiet` should
have silenced it. These two don't make any sense together so print an
error, because the user could have just left off the `-q`.
Previously when propagating explicitly separated output, we would early-out
if the buffer was empty, where empty meant contains no characters. However
it may contain one or more empty strings, in which case we should propagate
those strings.
Remove this footgun "empty" function and handle this properly.
Fixes#5987
