This switched `codegen` from the `autopep8` formatting to the `black`
one, and applies it to `bulk_mad_generator.py` as well. We can enroll
more python scripts to it in the future.
Previously, we were using 8.0.0rc1.
In particular, this upgrade means we need to explicitly
import more rules, as they've been moved out of the core bazel repo.
This generates test source files from code blocks in class docstrings.
By default the test code is generated as is, but it can optionally:
* be wrapped in a function providing an adequate context using
`@rust.doc_test_function(name, *, lifetimes=(), return_type="()", **kwargs)`,
with `kwargs` providing both generic and normal params depending on
capitalization
* be skipped altogether using `@rust.skip_doc_test`
So for example an annotation like
```python
@rust.doc_test_function("foo",
lifetimes=("a",),
T="Eq",
x="&'a T",
y="&'a T",
return_type="&'a T")
```
will result in the following wrapper:
```rust
fn foo<'a, T: Eq>(x: &'a T, y: &'a T) -> &'a T {
// example code here
}
```
This allows to group together related AST classes to reuse the same
test source and extraction. For example this is useful for
`EnumDecl/EnumCaseDecl/EnumElementDecl`, where this is applied to.
