[issue40807] Codeop: Show warnings once during _maybe_compile

[STINNER Victor]

Change by STINNER Victor :


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nosy: +vstinner
nosy_count: 5.0 -> 6.0
pull_requests: +20976
pull_request: https://github.com/python/cpython/pull/21838

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[issue40807] Codeop: Show warnings once during _maybe_compile

[Matthias Bussonnier]

Matthias Bussonnier  added the comment:

I think that might have introduce https://bugs.python.org/issue41520 where now 
`warnings.simplefilter('error', SyntaxWarning)` is silently ignored...

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[issue40807] Codeop: Show warnings once during _maybe_compile

[Terry J. Reedy]

Terry J. Reedy  added the comment:

The 3.7 backport is needed but required a revised example.  The changeset is 
4b378acb97a575892c0e372a6bb0c17da1ccdf3e.

PRs 20486, 20639, 20672, and 20673 are the main patch.  PRs 20646 and 20647 for 
3.8 and 3.7 backport a test_codeop import change made elsewhere and not 
backported.  The alternative would have been changing our backport to the older 
naming convention.

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resolution:  -> fixed
stage: patch review -> resolved
status: open -> closed

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[issue40807] Codeop: Show warnings once during _maybe_compile

[miss-islington]

miss-islington  added the comment:


New changeset c067183605cf84bb1a246635f52827251d0476f8 by Miss Islington (bot) 
in branch '3.8':
bpo-40807: Show warnings once from codeop._maybe_compile (GH-20486)
https://github.com/python/cpython/commit/c067183605cf84bb1a246635f52827251d0476f8


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[issue40807] Codeop: Show warnings once during _maybe_compile

[miss-islington]

Change by miss-islington :


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pull_requests: +19888
pull_request: https://github.com/python/cpython/pull/20672

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[issue40807] Codeop: Show warnings once during _maybe_compile

[miss-islington]

Change by miss-islington :


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pull_requests: +19889
pull_request: https://github.com/python/cpython/pull/20673

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[issue40807] Codeop: Show warnings once during _maybe_compile

[Terry J. Reedy]

Terry J. Reedy  added the comment:

This is a spinoff of #37824.

My above comments about compile are wrong.  The example nests '' within ''.  
And, with freshly compiled master, I found an example where Deprecation 
warning, but not SyntaxWarning, accompanies SyntaxError, and which requires 
trailing \n.

>>> compile("if'\e' is 1: 1", '', 'single')
DeprecationWarning...
SyntaxError: unexpected EOF while parsing
>>> compile("if'\e' is 1: 1\n", '', 'single')
DeprecationWarning...
SyntaxWarning...


Interactively,
>>> if'\e' is 1: 1
:1: DeprecationWarning: invalid escape sequence \e
... 
:1: SyntaxWarning: "is" with a literal. Did you mean "=="?
>>>

In IDLE, DeprecationWarning is repeated, but that is another issue.

The secondary prompts seems like a bug,  The statement is complete and entering 
anything but a comment is a SyntaxError.  (A comment results in another ... 
prompt.)

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[issue40807] Codeop: Show warnings once during _maybe_compile

[Terry J. Reedy]

Terry J. Reedy  added the comment:


New changeset 12d3061c7819a73d891dcce44327410eaf0e1bc2 by Miss Islington (bot) 
in branch '3.7':
[3.8] bpo-40807: Backport test_codeop change [GH-19670]
https://github.com/python/cpython/commit/12d3061c7819a73d891dcce44327410eaf0e1bc2


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[issue40807] Codeop: Show warnings once during _maybe_compile

[Terry J. Reedy]

Terry J. Reedy  added the comment:


New changeset a5d6aba318ead9cc756ba750a70da41f5def3f8f by Terry Jan Reedy in 
branch '3.8':
[3.8] bpo-40807: Backport test_codeop change [GH-19670]
https://github.com/python/cpython/commit/a5d6aba318ead9cc756ba750a70da41f5def3f8f


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[issue40807] Codeop: Show warnings once during _maybe_compile

[miss-islington]

Change by miss-islington :


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pull_requests: +19867
pull_request: https://github.com/python/cpython/pull/20647

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[issue40807] Codeop: Show warnings once during _maybe_compile

[Terry J. Reedy]

Change by Terry J. Reedy :


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pull_requests: +19866
pull_request: https://github.com/python/cpython/pull/20646

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[issue40807] Codeop: Show warnings once during _maybe_compile

[miss-islington]

miss-islington  added the comment:


New changeset 3dfe549bfa08a099b88efd030669359199f31064 by Miss Islington (bot) 
in branch '3.9':
bpo-40807: Show warnings once from codeop._maybe_compile (GH-20486)
https://github.com/python/cpython/commit/3dfe549bfa08a099b88efd030669359199f31064


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[issue40807] Codeop: Show warnings once during _maybe_compile

[miss-islington]

Change by miss-islington :


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pull_request: https://github.com/python/cpython/pull/20641

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[issue40807] Codeop: Show warnings once during _maybe_compile

[miss-islington]

Change by miss-islington :


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pull_requests: +19860
pull_request: https://github.com/python/cpython/pull/20640

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[issue40807] Codeop: Show warnings once during _maybe_compile

[miss-islington]

Change by miss-islington :


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nosy: +miss-islington
nosy_count: 3.0 -> 4.0
pull_requests: +19859
pull_request: https://github.com/python/cpython/pull/20639

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[issue40807] Codeop: Show warnings once during _maybe_compile

[Terry J. Reedy]

Terry J. Reedy  added the comment:


New changeset 052d3fc0907be253cfd64b2c737a0b0aca586011 by Cheryl Sabella in 
branch 'master':
bpo-40807: Show warnings once from codeop._maybe_compile (#20486)
https://github.com/python/cpython/commit/052d3fc0907be253cfd64b2c737a0b0aca586011


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[issue40807] Codeop: Show warnings once during _maybe_compile

[Terry J. Reedy]

Terry J. Reedy  added the comment:

I am not sure if 3 compiles are always needed.  At one time, compile required a 
final '\n' to not raise, but that is no longer true.  And as near as I can 
tell, 'code without final newline\n' and 'code without final newline\n\n' 
always compile the same.  Certainly, Shell does not need to compile without a 
final newline.  But we can look at this in a separate issue.  If IDLE's 
requirement is different from code.II's, I believe it could pass its own 
compile function.

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[issue40807] Codeop: Show warnings once during _maybe_compile

[Terry J. Reedy]

Terry J. Reedy  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:
:1: DeprecationWarning: invalid escape sequence \e
...
versus
>>> compile('if '\e' is 1:\n', '', 'single')
  File "", 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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[issue40807] CODEOP: Show warnings once during _maybe_compile

[Cheryl Sabella]

New submission from Cheryl Sabella :

When calling `codeop._maybe_compile`, `compile` is run three times.  If the 
code being compiled causes a warning message, the warning is generated each 
time that `compile` is called, thus (possibly) showing the message three times.


See msg370163 and that issue for context.

--
components: Library (Lib)
messages: 370208
nosy: cheryl.sabella
priority: normal
severity: normal
status: open
title: CODEOP: Show warnings once during _maybe_compile
type: enhancement
versions: Python 3.10, Python 3.9

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[issue40807] CODEOP: Show warnings once during _maybe_compile

[Cheryl Sabella]

Change by Cheryl Sabella :


--
keywords: +patch
pull_requests: +19735
stage:  -> patch review
pull_request: https://github.com/python/cpython/pull/20486

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