4e1cf5747a
This PR implements a modification (in preview) to fluent formatting for
method chains: We break _at_ the first call instead of _after_.
For example, we have the following diff between `main` and this PR (with
`line-length=8` so I don't have to stretch out the text):
```diff
x = (
- df.merge()
+ df
+ .merge()
.groupby()
.agg()
.filter()
)
```
## Explanation of current implementation
Recall that we traverse the AST to apply formatting. A method chain,
while read left-to-right, is stored in the AST "in reverse". So if we
start with something like
```python
a.b.c.d().e.f()
```
then the first syntax node we meet is essentially `.f()`. So we have to
peek ahead. And we actually _already_ do this in our current fluent
formatting logic: we peek ahead to count how many calls we have in the
chain to see whether we should be using fluent formatting or now.
In this implementation, we actually _record_ this number inside the enum
for `CallChainLayout`. That is, we make the variant `Fluent` hold an
`AttributeState`. This state can either be:
- The number of call-like attributes preceding the current attribute
- The state `FirstCallOrSubscript` which means we are at the first
call-like attribute in the chain (reading from left to right)
- The state `BeforeFirstCallOrSubscript` which means we are in the
"first group" of attributes, preceding that first call.
In our example, here's what it looks like at each attribute:
```
a.b.c.d().e.f @ Fluent(CallsOrSubscriptsPreceding(1))
a.b.c.d().e @ Fluent(CallsOrSubscriptsPreceding(1))
a.b.c.d @ Fluent(FirstCallOrSubscript)
a.b.c @ Fluent(BeforeFirstCallOrSubscript)
a.b @ Fluent(BeforeFirstCallOrSubscript)
```
Now, as we descend down from the parent expression, we pass along this
little piece of state and modify it as we go to track where we are. This
state doesn't do anything except when we are in `FirstCallOrSubscript`,
in which case we add a soft line break.
Closes #8598
---------
Co-authored-by: Brent Westbrook <36778786+ntBre@users.noreply.github.com>
|
||
|---|---|---|
| .. | ||
| resources/test/fixtures | ||
| src | ||
| tests | ||
| CONTRIBUTING.md | ||
| Cargo.toml | ||
| README.md | ||
| generate.py | ||
| orphan_rules_in_the_formatter.svg | ||
README.md
Ruff Formatter
The Ruff formatter is an extremely fast Python code formatter that ships as part of the ruff
CLI.
Goals
The formatter is designed to be a drop-in replacement for Black, but with an excessive focus on performance and direct integration with Ruff.
Specifically, the formatter is intended to emit near-identical output when run over Black-formatted code. When run over extensive Black-formatted projects like Django and Zulip, > 99.9% of lines are formatted identically. When migrating an existing project from Black to Ruff, you should expect to see a few differences on the margins, but the vast majority of your code should be unchanged.
If you identify deviations in your project, spot-check them against the intentional deviations enumerated below, as well as the unintentional deviations filed in the issue tracker. If you've identified a new deviation, please file an issue.
When run over non-Black-formatted code, the formatter makes some different decisions than Black, and so more deviations should be expected, especially around the treatment of end-of-line comments. For details, see Style Guide.
Getting started
Head to The Ruff Formatter for usage instructions and a comparison to Black.