Skip to content

bpo-43149: Improve error message for exception group without parentheses #24467

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Merged
merged 1 commit into from
Feb 7, 2021
Merged

bpo-43149: Improve error message for exception group without parentheses #24467

Show file tree
Hide file tree
Changes from all commits
Commits
Show all changes
1 commit
Select commit
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
11 changes: 9 additions & 2 deletions Grammar/python.gram
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -201,9 +201,10 @@ try_stmt[stmt_ty]:
| 'try' &&':' b=block f=finally_block { _Py_Try(b, NULL, NULL, f, EXTRA) }
| 'try' &&':' b=block ex[asdl_excepthandler_seq*]=except_block+ el=[else_block] f=[finally_block] { _Py_Try(b, ex, el, f, EXTRA) }
except_block[excepthandler_ty]:
| 'except' e=expression t=['as' z=NAME { z }] &&':' b=block {
| 'except' e=expression t=['as' z=NAME { z }] ':' b=block {
_Py_ExceptHandler(e, (t) ? ((expr_ty) t)->v.Name.id : NULL, b, EXTRA) }
| 'except' &&':' b=block { _Py_ExceptHandler(NULL, NULL, b, EXTRA) }
| 'except' ':' b=block { _Py_ExceptHandler(NULL, NULL, b, EXTRA) }
| invalid_except_block
finally_block[asdl_stmt_seq*]: 'finally' ':' a=block { a }

return_stmt[stmt_ty]:
Expand Down Expand Up @@ -737,3 +738,9 @@ invalid_import_from_targets:
invalid_with_stmt:
| [ASYNC] 'with' ','.(expression ['as' star_target])+ &&':'
| [ASYNC] 'with' '(' ','.(expressions ['as' star_target])+ ','? ')' &&':'

invalid_except_block:
| 'except' a=expression ',' expressions ['as' NAME ] ':' {
RAISE_SYNTAX_ERROR_KNOWN_LOCATION(a, "exception group must be parenthesized") }
| 'except' expression ['as' NAME ] &&':'
| 'except' &&':'
33 changes: 33 additions & 0 deletions Lib/test/test_syntax.py
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -835,6 +835,39 @@
...
SyntaxError: invalid syntax

Check that an exception group with missing parentheses
Copy link
Contributor

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

This terminology conflicts with PEP 654 exception groups

cc @iritkatriel

Copy link
Member Author

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

Thanks for pointing that out. If exceptions group pep is merged we will surely change this sentence.

On the other hand, do you have some alternative phasing for the error you think would be clearer?

Copy link
Contributor

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

isinstance calls this thing a classinfo

Copy link
Contributor

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

https://docs.python.org/3.10/library/functions.html#isinstance

Copy link
Member Author

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

Unfortunately I find that even more confusing :(

Copy link
Member

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

exception sequence?

Copy link
Member

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

"multiple exception types"?

Copy link
Contributor

@graingert graingert May 8, 2021 •
edited
Loading

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

I started a mailing list thread in python-dev@python.org "a name for the ExceptHandler.type when it is a literal tuple of types"

Copy link
Contributor

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

@iritkatriel yeah I like it: SyntaxError: multiple exception types must be parenthesized

Copy link
Member Author

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

Opened #25996

raise a custom exception

>>> try:
... pass
... except A, B:
... pass
Traceback (most recent call last):
SyntaxError: exception group must be parenthesized

>>> try:
... pass
... except A, B, C:
... pass
Traceback (most recent call last):
SyntaxError: exception group must be parenthesized

>>> try:
... pass
... except A, B, C as blech:
... pass
Traceback (most recent call last):
SyntaxError: exception group must be parenthesized

>>> try:
... pass
... except A, B, C as blech:
... pass
... finally:
... pass
Traceback (most recent call last):
SyntaxError: exception group must be parenthesized


>>> f(a=23, a=234)
Traceback (most recent call last):
Expand Down
2 changes: 2 additions & 0 deletions Misc/NEWS.d/next/Core and Builtins/2021-02-07-03-27-14.bpo-43149.0umPKD.rst
View file
Open in desktop
Original file line number Diff line number Diff line change
@@ -0,0 +1,2 @@
Improve the error message in the parser for exception groups without
parentheses. Patch by Pablo Galindo.
Loading