Terry J. Reedy <[email protected]> added the comment:
The purpose of code and codeop is to imitate interactive python in python.
Calling compile() thrice is an implementation detail. Exposing that is a bug.
On #37824, Serhiy reported 3 'IDLE' bugs for 3.7 to 3.9: tripled
DeprecationWarning (now joined by SyntaxWarning), printing to console (if
available) instead of Shell, and an exit exception. This issue is continuation
of the triplicate issue, given that the bug is not in IDLE. As a bug, I think
it should still be backported.
I looked more carefully at the behavior of the standard REPL with different
statement inputs. Before executing, if the statement is complete, it may raise
a compile exception, usually SyntaxError, or emit one or more a warnings, once
for each instance. For multiline statements, DeprecationWarnings are emitted
immediately after the line with the deprecated code while SyntaxWarnings are
emitted, if there is no syntax error, just before execution. SyntaxWarnings
for a given slice of code are not repeated. However, at least some of these
details have to be enforced in the UI code that repeatedly calls compile or
_maybe_compile as lines are added, not in compile, and should not be in
_maybe_compile. Both have no memory or previous calls. (I don't think that
IDLE necessarily *must* do the same either.)
Looking at compile itself, it appears that warnings are not emitted if there is
an exception. But I am puzzled at this in 3.9 and master.
>>> if '\e' is 1:
<stdin>:1: DeprecationWarning: invalid escape sequence \e
...
versus
>>> compile('if '\e' is 1:\n', '', 'single')
File "<stdin>", line 1
SyntaxError: unexpected character after line continuation character
Something must cause "'\e'" to be a warning instead of an error.
This is enough to experiment with your patch applied.
----------
nosy: +serhiy.storchaka, terry.reedy
title: CODEOP: Show warnings once during _maybe_compile -> Codeop: Show
warnings once during _maybe_compile
type: enhancement -> behavior
versions: +Python 3.7, Python 3.8
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<https://bugs.python.org/issue40807>
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