bpo-44180: Fix edge cases in invalid assigment rules in the parser #26283
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The invalid assigment rules are very delicate since the parser can easily raise an invalid assigment when a keyword argument is provided. As they are very deep into the grammar tree, is very difficult to specify in which contexts these rules can be used and in which don't. For that we need to use a different version of the rule that doesn't do error checking in those situations where we don't want the rule to raise (keyword arguments and generator expressions). We also need to check if we are in left-recursive rule, as those can try to eagerly advance the parser even if the parse will fail at the end of the expression. Failing to do this allows the parser to start parsing a call as a tuple and incorrectly identify a keyword argument as an invalid assigment.
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Thanks @pablogsal for the PR |
miss-islington
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May 21, 2021
…ythonGH-26283) The invalid assignment rules are very delicate since the parser can easily raise an invalid assignment when a keyword argument is provided. As they are very deep into the grammar tree, is very difficult to specify in which contexts these rules can be used and in which don't. For that, we need to use a different version of the rule that doesn't do error checking in those situations where we don't want the rule to raise (keyword arguments and generator expressions). We also need to check if we are in left-recursive rule, as those can try to eagerly advance the parser even if the parse will fail at the end of the expression. Failing to do this allows the parser to start parsing a call as a tuple and incorrectly identify a keyword argument as an invalid assignment, before it realizes that it was not a tuple after all. (cherry picked from commit c878a97) Co-authored-by: Pablo Galindo <Pablogsal@gmail.com>
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GH-26292 is a backport of this pull request to the 3.10 branch. |
miss-islington
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…H-26283) The invalid assignment rules are very delicate since the parser can easily raise an invalid assignment when a keyword argument is provided. As they are very deep into the grammar tree, is very difficult to specify in which contexts these rules can be used and in which don't. For that, we need to use a different version of the rule that doesn't do error checking in those situations where we don't want the rule to raise (keyword arguments and generator expressions). We also need to check if we are in left-recursive rule, as those can try to eagerly advance the parser even if the parse will fail at the end of the expression. Failing to do this allows the parser to start parsing a call as a tuple and incorrectly identify a keyword argument as an invalid assignment, before it realizes that it was not a tuple after all. (cherry picked from commit c878a97) Co-authored-by: Pablo Galindo <Pablogsal@gmail.com>
JuniorJPDJ
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Aug 12, 2021
…ythonGH-26283) The invalid assignment rules are very delicate since the parser can easily raise an invalid assignment when a keyword argument is provided. As they are very deep into the grammar tree, is very difficult to specify in which contexts these rules can be used and in which don't. For that, we need to use a different version of the rule that doesn't do error checking in those situations where we don't want the rule to raise (keyword arguments and generator expressions). We also need to check if we are in left-recursive rule, as those can try to eagerly advance the parser even if the parse will fail at the end of the expression. Failing to do this allows the parser to start parsing a call as a tuple and incorrectly identify a keyword argument as an invalid assignment, before it realizes that it was not a tuple after all.
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The invalid assigment rules are very delicate since the parser can
easily raise an invalid assigment when a keyword argument is provided.
As they are very deep into the grammar tree, is very difficult to
specify in which contexts these rules can be used and in which don't.
For that we need to use a different version of the rule that doesn't do
error checking in those situations where we don't want the rule to raise
(keyword arguments and generator expressions).
We also need to check if we are in left-recursive rule, as those can try
to eagerly advance the parser even if the parse will fail at the end of
the expression. Failing to do this allows the parser to start parsing a
call as a tuple and incorrectly identify a keyword argument as an
invalid assigment.
https://bugs.python.org/issue44180