* bpo-42128: Add documentation for the new match-based AST nodes
* Update Doc/library/ast.rst
Co-authored-by: Carol Willing <carolcode@willingconsulting.com>
* Fix trailing whitespace
Co-authored-by: Carol Willing <carolcode@willingconsulting.com>
- Mention that some compiler optimizations might not roundtrip
exactly (such as constant tuples and frozensets).
- Add a warning about it might raise RecursionError on very
complex expressions due to recursive unparsing aspect of ast.unparse
* Remove the slice type.
* Make Slice a kind of the expr type instead of the slice type.
* Replace ExtSlice(slices) with Tuple(slices, Load()).
* Replace Index(value) with a value itself.
All non-terminal nodes in AST for expressions are now of the expr type.
Add ast.unparse() as a function in the ast module that can be used to unparse an
ast.AST object and produce a string with code that would produce an equivalent ast.AST
object when parsed.
This adds a `feature_version` flag to `ast.parse()` (documented) and `compile()` (hidden) that allow tweaking the parser to support older versions of the grammar. In particular if `feature_version` is 5 or 6, the hacks for the `async` and `await` keyword from PEP 492 are reinstated. (For 7 or higher, these are unconditionally treated as keywords, but they are still special tokens rather than `NAME` tokens that the parser driver recognizes.)
https://bugs.python.org/issue35975
The majority of this PR is tediously passing `end_lineno` and `end_col_offset` everywhere. Here are non-trivial points:
* It is not possible to reconstruct end positions in AST "on the fly", some information is lost after an AST node is constructed, so we need two more attributes for every AST node `end_lineno` and `end_col_offset`.
* I add end position information to both CST and AST. Although it may be technically possible to avoid adding end positions to CST, the code becomes more cumbersome and less efficient.
* Since the end position is not known for non-leaf CST nodes while the next token is added, this requires a bit of extra care (see `_PyNode_FinalizeEndPos`). Unless I made some mistake, the algorithm should be linear.
* For statements, I "trim" the end position of suites to not include the terminal newlines and dedent (this seems to be what people would expect), for example in
```python
class C:
pass
pass
```
the end line and end column for the class definition is (2, 8).
* For `end_col_offset` I use the common Python convention for indexing, for example for `pass` the `end_col_offset` is 4 (not 3), so that `[0:4]` gives one the source code that corresponds to the node.
* I added a helper function `ast.get_source_segment()`, to get source text segment corresponding to a given AST node. It is also useful for testing.
An (inevitable) downside of this PR is that AST now takes almost 25% more memory. I think however it is probably justified by the benefits.
Remove the docstring attribute of AST types and restore docstring
expression as a first stmt in their body.
Co-authored-by: INADA Naoki <methane@users.noreply.github.com>
Gregory P. Smith
Serhiy Storchaka
Terry Jan Reedy
anilbey
Hugo van Kemenade
Irit Katriel
Christian Clauss
Raymond Hettinger
Pablo Galindo Salgado
Noah Kantrowitz
HaeckelK
Nick Coghlan
Zackery Spytz
Adrian Freund
Batuhan Taskaya
Matthew Suozzo
Batuhan Taskaya
Edward K. Ream
Batuhan Taşkaya
Gurupad Hegde
Guido van Rossum
Ivan Levkivskyi
Brett Cannon