This patch changes the preview style so that string splitters respect
Unicode East Asian Width[^1] property. If you are not familiar to CJK
languages it is not clear immediately. Let me elaborate with some
examples.
Traditionally, East Asian characters (including punctuation) have
taken up space twice than European letters and stops when they are
rendered in monospace typeset. Compare the following characters:
```
abcdefg.
글、字。
```
The characters at the first line are half-width, and the second line
are full-width. (Also note that the last character with a small
circle, the East Asian period, is also full-width.) Therefore, if we
want to prevent those full-width characters to exceed the maximum
columns per line, we need to count their *width* rather than the number
of characters. Again, the following characters:
```
글、字。
```
These are just 4 characters, but their total width is 8.
Suppose we want to maintain up to 4 columns per line with the following
text:
```
abcdefg.
글、字。
```
How should it be then? We want it to look like:
```
abcd
efg.
글、
字。
```
However, Black currently turns it into like this:
```
abcd
efg.
글、字。
```
It's because Black currently counts the number of characters in the line
instead of measuring their width. So, how could we measure the width?
How can we tell if a character is full- or half-width? What if half-width
characters and full-width ones are mixed in a line? That's why Unicode
defined an attribute named `East_Asian_Width`. Unicode grouped every
single character according to their width in fixed-width typeset.
This partially addresses #1197, but only for string splitters. The other
parts need to be fixed as well in future patches.
This was implemented by copying rich's own approach to handling wide
characters: generate a table using wcwidth, check it into source
control, and use in to drive helper functions in Black's logic. This
gets us the best of both worlds: accuracy and performance (and let's us
update as per our stability policy too!).
Co-authored-by: Jelle Zijlstra <jelle.zijlstra@gmail.com>
Fixes#3506
We can't simply escape the quotes in a naked f-string when merging string groups, because backslashes are invalid.
The quotes in f-string expressions should be toggled (this is safe since quotes can't be reused).
This fix also means implicitly concatenated f-strings with different quotes can now be merged or quote-normalized by changing the quotes used in expressions. e.g.:
```diff
raise sa_exc.UnboundExecutionError(
"Could not locate a bind configured on "
- f'{", ".join(context)} or this Session.'
+ f"{', '.join(context)} or this Session."
)
```
The bug is in the `get_leaves_inside_matching_brackets` on the third line below:
```python
assert xxxxxxxxx.xxxxxxxxx.xxxxxxxxx(
xxxxxxxxx
).xxxxxxxxxxxxxxxxxx(), (
"xxx {xxxxxxxxx} xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx"
)
```
Including the invisible paren, third line is `).xxxxxxxxxxxxxxxxxx()), (`, that it has a matched pair then an unmatched closing paren afterwards. This PR ensures the returned leaves are actually matched.
Fixes#3414.
Currently, empty and whitespace-only (with or without newlines) are
not modified. In some discussions (issues and pull requests) consensus
was to reformat whitespace-only files to empty or single-character
files, preserving line endings when possible. With that said, this
commit introduces the following behaviors:
* Empty files are left as is
* Whitespace-only files (no newline) reformat into empty files
* Whitespace-only files (1 or more newlines) reformat into a single
newline character
To implement these changes, we moved the initial check at
`format_file_contents` that raises `NothingChanged` if the source
(with no whitespaces) is an empty string. In the case of *.ipynb
files, `format_ipynb_string` checks a similar condition and removed
whitespaces. In the case of Python files, `format_str_once` includes a
check on the output that returns the correct newline character if
possible or an empty string otherwise.
Signed-off-by: Antonio Ossa Guerra <aaossa@uc.cl>
Fix a crash when formatting some dicts with parenthesis-wrapped long
string keys. When LL[0] is an atom string, we need to check the atom
node's siblings instead of LL[0] itself, e.g.:
dictsetmaker
atom
STRING '"This is a really long string that can\'t be expected to fit in one line and is used as a nested dict\'s key"'
/atom
COLON ':'
atom
LSQB ' ' '['
listmaker
STRING '"value"'
COMMA ','
STRING ' ' '"value"'
/listmaker
RSQB ']'
/atom
COMMA ','
/dictsetmaker
Adds parentheses around implicit string concatenations when it's inside
a list, set, or tuple. Except when it's only element and there's no trailing
comma.
Looking at the order of the transformers here, we need to "wrap in
parens" before string_split runs. So my solution is to introduce a
"collaboration" between StringSplitter and StringParenWrapper where the
splitter "skips" the split until the wrapper adds the parens (and then
the line after the paren is split by StringSplitter) in another pass.
I have also considered an alternative approach, where I tried to add a
different "string paren wrapper" class, and it runs before string_split.
Then I found out it requires a different do_transform implementation
than StringParenWrapper.do_transform, since the later assumes it runs
after the delimiter_split transform. So I stopped researching that
route.
Originally function calls were also included in this change, but given
missing commas should usually result in a runtime error and the scary
amount of changes this cause on downstream code, they were removed in
later revisions.
Fixes#2734: a standalone comment causes strings to be merged into one far too long (and requiring two passes to do so).
Co-authored-by: Richard Si <63936253+ichard26@users.noreply.github.com>
Doing so is invalid. Note this only fixes the preview style since the
logic putting closing docstring quotes on their own line if they violate
the line length limit is quite new.
Co-authored-by: Jelle Zijlstra <jelle.zijlstra@gmail.com>
