## Summary
This PR removes the `todo!()` around `IpyEscapeCommand` in the
formatter.
The `NeedsParentheses` trait needs to be implemented which always return
`Never`. The reason being that if an escape command is parenthesized,
then that's not parsed as an escape command. IOW, the parentheses
shouldn't be present around an escape command.
In the similar way, the `CanSkipOptionalParenthesesVisitor` will skip
this node.
## Test Plan
Updated the `unformatted.ipynb` fixture with new cells containing
IPython escape commands and the corresponding snapshot was verified.
Also, tested it out in a few open source repositories containing
notebooks (`openai/openai-cookbook`, `huggingface/notebooks`).
#### New cells in `unformatted.ipynb`
**Cell 2**
```markdown
A markdown cell
```
**Cell 3**
```python
def some_function(foo, bar):
pass
%matplotlib inline
```
**Cell 4**
```python
foo = %pwd
def some_function(foo,bar,):
foo = %pwd
print(foo
)
```
fixes: #8204
**Summary** `ruff format --diff` is similar to `ruff format --check`,
but we don't only error with the list of file that would be formatted,
but also show a diff between the unformatted input and the formatted
output.
```console
$ ruff format --diff scratch.py scratch.pyi scratch.ipynb
warning: `ruff format` is not yet stable, and subject to change in future versions.
--- scratch.ipynb
+++ scratch.ipynb
@@ -1,3 +1,4 @@
import numpy
-maths = (numpy.arange(100)**2).sum()
-stats= numpy.asarray([1,2,3,4]).median()
+
+maths = (numpy.arange(100) ** 2).sum()
+stats = numpy.asarray([1, 2, 3, 4]).median()
--- scratch.py
+++ scratch.py
@@ -1,3 +1,3 @@
x = 1
-y=2
+y = 2
z = 3
2 files would be reformatted, 1 file left unchanged
```
With `--diff`, the summary message gets printed to stderr to allow e.g.
`ruff format --diff . > format.patch`.
At the moment, jupyter notebooks are formatted as code diffs, while
everything else is a real diff that could be applied. This means that
the diffs containing jupyter notebooks are not real diffs and can't be
applied. We could change this to json diffs, but they are hard to read.
We could also split the diff option into a human diff option, where we
deviate from the machine readable diff constraints, and a proper machine
readable, appliable diff output that you can pipe into other tools.
To make the tests work, the results (and errors, if any) are sorted
before printing them. Previously, the print order was random, i.e. two
identical runs could have different output.
Open question: Should this go into the markdown docs? Or will this be
subsumed by the integration of the formatter into `ruff check`?
**Test plan** Fixtures for the change and no change cases, including a
jupyter notebook and for file input and stdin.
Fixes#7231
---------
Co-authored-by: Micha Reiser <micha@reiser.io>
Dhruv Manilawala
konsti