## Summary
When visiting AugAssign in evaluation order, the AugAssign `target`
should be visited after it's `value`. Based on my testing, the pseudo
code for `a += b` is effectively:
```python
tmp = a
a = tmp.__iadd__(b)
```
That is, an ideal traversal order would look something like this:
1. load a
2. b
3. op
4. store a
But, there is only a single AST node which captures `a` in the statement
`a += b`, so it cannot be traversed both before and after the traversal
of `b` and the `op`.
Nonetheless, I think traversing `a` after `b` and the `op` makes the
most sense for a number of reasons:
1. All the other assignment expressions traverse their `value`s before
their `target`s. Having `AugAssign` traverse in the same order would be
more consistent.
2. Within the AST, the `ctx` of the `target` for an `AugAssign` is
`Store` (though technically this is a `Load` and `Store` operation, the
AST only indicates it as a `Store`). Since the the store portion of the
`AugAssign` occurs last, I think it makes sense to traverse the `target`
last as well.
The effect of this is marginal, but it may have an impact on the
behavior of #5271.
## Summary
The `Visitor` and `preorder::Visitor` traits provide some convenience
functions, `visit_annotation` and `visit_format_spec`, for handling
annotation and format spec expressions respectively. Both of these
functions accept an `&Expr` and have a default implementation which
delegates to `walk_expr`. The problem with this approach is that any
custom handling done in `visit_expr` will be skipped for annotations and
format specs. Instead, to capture any custom logic implemented in
`visit_expr`, both of these function's default implementations should
delegate to `visit_expr` instead of `walk_expr`.
## Example
Consider the below `Visitor` implementation:
```rust
impl<'a> Visitor<'a> for Example<'a> {
fn visit_expr(&mut self, expr: &'a Expr) {
match expr {
Expr::Name(ExprName { id, .. }) => println!("Visiting {:?}", id),
_ => walk_expr(self, expr),
}
}
}
```
Run on the following Python snippet:
```python
a: b
```
I would expect such a visitor to print the following:
```
Visiting b
Visiting a
```
But it instead prints the following:
```
Visiting a
```
Our custom `visit_expr` handler is not invoked for the annotation.
## Test Plan
Tests added in #5271 caught this behavior.
## Summary
This is a follow up to #5221. Turns out it was easy to restructure the
visitor to get the right order, I'm just dumb 🤷♂️ I've
removed `visit_arg_with_default` entirely from the `Visitor`, although
it still exists as part of `preorder::Visitor`.
## Summary
According to the AST visitor documentation, the AST visitor "visits all
nodes in the AST recursively in evaluation-order". However, the current
traversal fails to meet this specification in a few places.
### Function traversal
```python
order = []
@(order.append("decorator") or (lambda x: x))
def f(
posonly: order.append("posonly annotation") = order.append("posonly default"),
/,
arg: order.append("arg annotation") = order.append("arg default"),
*args: order.append("vararg annotation"),
kwarg: order.append("kwarg annotation") = order.append("kwarg default"),
**kwargs: order.append("kwarg annotation")
) -> order.append("return annotation"):
pass
print(order)
```
Executing the above snippet using CPython 3.10.6 prints the following
result (formatted for readability):
```python
[
'decorator',
'posonly default',
'arg default',
'kwarg default',
'arg annotation',
'posonly annotation',
'vararg annotation',
'kwarg annotation',
'kwarg annotation',
'return annotation',
]
```
Here we can see that decorators are evaluated first, followed by
argument defaults, and annotations are last. The current traversal of a
function's AST does not align with this order.
### Annotated assignment traversal
```python
order = []
x: order.append("annotation") = order.append("expression")
print(order)
```
Executing the above snippet using CPython 3.10.6 prints the following
result:
```python
['expression', 'annotation']
```
Here we can see that an annotated assignments annotation gets evaluated
after the assignment's expression. The current traversal of an annotated
assignment's AST does not align with this order.
## Why?
I'm slowly working on #3946 and porting over some of the logic and tests
from ssort. ssort is very sensitive to AST traversal order, so ensuring
the utmost correctness here is important.
## Test Plan
There doesn't seem to be existing tests for the AST visitor, so I didn't
bother adding tests for these very subtle changes. However, this
behavior will be captured in the tests for the PR which addresses #3946.
## Summary
This PR upgrade RustPython to pull in the changes to `Arguments` (zip
defaults with their identifiers) and all the renames to `CmpOp` and
friends.
This PR productionizes @MichaReiser's suggestion in https://github.com/charliermarsh/ruff/issues/1820#issuecomment-1440204423, by creating a separate crate for the `ast` module (`rust_python_ast`). This will enable us to further split up the `ruff` crate, as we'll be able to create (e.g.) separate sub-linter crates that have access to these common AST utilities.
This was mostly a straightforward copy (with adjustments to module imports), as the few dependencies that _did_ require modifications were handled in #3366, #3367, and #3368.
Charlie Marsh
James Berry
Micha Reiser
Jeong, YunWon