[issue28143] ASDL compatibility with Python 3 system interpreter

[Cheryl Sabella]

Change by Cheryl Sabella :


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resolution:  -> wont fix
stage: patch review -> resolved
status: open -> closed

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[issue28143] ASDL compatibility with Python 3 system interpreter

[Malthe Borch]

Change by Malthe Borch :


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pull_requests: +4052
stage: needs patch -> patch review

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[issue28143] ASDL compatibility with Python 3 system interpreter

[Serhiy Storchaka]

Serhiy Storchaka  added the comment:

Do you mind to create a pull request on GitHub Malthe?

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stage:  -> needs patch

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[issue28143] ASDL compatibility with Python 3 system interpreter

[Serhiy Storchaka]

Serhiy Storchaka added the comment:

print in Python 2 doesn't add a space after whitespace characters except a 
space ('\t', '\n', '\r', etc).

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nosy: +serhiy.storchaka

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[issue28143] ASDL compatibility with Python 3 system interpreter

[Malthe Borch]

Malthe Borch added the comment:

You're right. The trailing comma just suppresses the newline. I updated the 
patch.

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Added file: 
http://bugs.python.org/file45105/0001-Allow-make-to-be-run-under-Python-3.patch

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[issue28143] ASDL compatibility with Python 3 system interpreter

[Martin Panter]

Martin Panter added the comment:

Are you sure about adding the space after tab? I am no Python 2 expert, but I 
don’t see it:

$ python2 -c 'print "\t", ""' | cat -A
^I$

Anyway, I’m not happy applying this patch unless it is clear that raising the 
Python version required to rebuild ASDL stuff is okay in the 2.7 branch. Maybe 
a query to the python-dev mail list might help.

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[issue28143] ASDL compatibility with Python 3 system interpreter

[Malthe Borch]

Malthe Borch added the comment:

I have updated the patch with requested changes.

Note that the original code also added space after '\t' characters. I have not 
changed this on purpose.

--
Added file: 
http://bugs.python.org/file44801/0001-Allow-make-to-be-run-under-Python-3.patch

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[issue28143] ASDL compatibility with Python 3 system interpreter

[Martin Panter]

Martin Panter added the comment:

That would get the patch mostly working with 2.6+. Is it okay to break Python < 
2.6 support? I know there was an OS X Tiger buildbot using 2.5 until recently; 
see Issue 28039.

Personally, I would rather focus on the problems with make dependencies, build 
configuration, etc, rather than changing what versions of Python the code runs 
on.

Regarding CRLFs on Windows: the existing code opens files in binary mode (wb), 
so Windows will not translate \n into CRLF. Changing this behaviour is separate 
to the goal of Python 3 compatibility. IMO the build process should not change 
the contents of checked-in files, regardless of whether there is a version 
control system like Mercurial or Git in use or not. See also Issue 27425.

On the other hand, the Python 3 code does use text mode with CRLF translation, 
so maybe it is not a big deal. (I never built Python on Windows, so I don’t 
know.)

+++ b/Parser/spark.py
@@ -171,7 +171,7 @@ class GenericParser:
-rules = string.split(doc)
+rules = str.split(doc)

This would read better as doc.split(); see 
.

@@ -825,15 +828,15 @@ class GenericASTMatcher(GenericParser):
-print '\t', item
+print('\t', item)
 for (lhs, rhs), pos in states[item[0]].items:
-print '\t\t', lhs, '::=',
+print('\t\t', lhs, '::=', end=" ")
. . .
+print(string.join(rhs[:pos]), end=" ")
+print('.', end=" ")
+print(string.join(rhs[pos:]))

The string quoting is inconsistent. Also, I suspect string.join() is not right 
for Python 3. And you are adding an extra space after the '\t' characters.

For what it’s worth, here are some similar changes made to the Py 3 branch:

r57749: raise syntax
r51578: `. . .` → repr()
http://svn.python.org/view?view=revision=55329: Unpack tuples inside 
functions (Malthe’s patch unpacks as the function is called instead); map() → 
list comprehension
http://svn.python.org/view?view=revision=55143: Various Py 3 changes
r59154: Write files in text mode
r53189: Avoid has_key()
http://svn.python.org/view?view=revision=55167: xrange() → range()

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[issue28143] ASDL compatibility with Python 3 system interpreter

[Malthe Borch]

Malthe Borch added the comment:

I forgot to add "from __future__ import print_function" to the beginning of 
"asdl.py" and "spark.py". It should then work on Python 2.

That is, with the imported print-function, the incompatibilities that Martin 
pointed out are no longer there.

As for Windows, I would think that printing out CRLFs is the correct behavior? 
I don't use Windows personally.

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[issue28143] ASDL compatibility with Python 3 system interpreter

[Martin Panter]

Martin Panter added the comment:

This patch ports the logic written for Issue 26662 to Python 2. Basically, 
configure searches for commands called python2.7, python2, and python (in order 
of priority), and sets PYTHON_FOR_GEN to the result. PYTHON_FOR_GEN could be 
overridden by the user if desired. If no Python command is found, the build 
fails with an error message:

Cannot generate /home/proj/python/cpython/Python/Python-ast.c, python not found 
!
To skip re-generation of /home/proj/python/cpython/Python/Python-ast.c run 
 or .
Otherwise, set python in PATH and run configure or run .
--- Python/Python-ast.c ---
*** [Python/Python-ast.c] Error code 1

However if it finds “python” and that turns out to be version 3, it will still 
have the same problem as now, and you will have to manually use “make touch” or 
similar.

--
Added file: http://bugs.python.org/file44732/PYTHON_FOR_GEN.patch

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[issue28143] ASDL compatibility with Python 3 system interpreter

[R. David Murray]

R. David Murray added the comment:

If we go that route it doesn't, from a certain point of view, solve the problem 
for systems that *only* ship python3...but I think we can ignore that issue: 
IMO it would be fine in that scenario to say that if you want to run the 
python2 regen scripts you have to install python2.  Especially since you can do 
that by building from source using the checked in artifacts.

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[issue28143] ASDL compatibility with Python 3 system interpreter

[Martin Panter]

Martin Panter added the comment:

Another option I forgot to point out is that some of the other regeneration 
Python scripts (in Py 2 and/or 3; I forget which) have some autoconf magic to 
figure out the right installed python command to use. We should probably use 
that for Py 2’s ASDL script.

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[issue28143] ASDL compatibility with Python 3 system interpreter

[R. David Murray]

R. David Murray added the comment:

Yes, by "fix this" I meant make it work under both python2 and python3.  But 
failing that, the status quo wins.

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[issue28143] ASDL compatibility with Python 3 system interpreter

[Martin Panter]

Martin Panter added the comment:

It seems a terrible idea to require Python 3 to be installed in order to 
regenerate the boot files for a Python 2 build. Maybe if we can figure out the 
minimum installed Python version expected for these ASDL scripts in 2.7, and 
maintain that while adding Python 3 support. But even that seems risky.

Your changes obviously make the files incompatible with Python 2:

print()  # Prints an empty tuple
print("Error visiting", repr(object))  # Prints a 2-tuple
f = open(p, "w")  # Writes CRLFs on Windows (I think; it’s been a while)

If we do go down this road, it may be worth looking at what has already been 
done to the corresponding scripts in Python 3.

But you may not actually need to regenerate the files. If you are building from 
the source directory, try “make touch” after generating the makefile. In 
general, try “touch Include/Python-ast.h Python/Python-ast.c”.

I would like to see this be made easier for both Python 2 and 3. I suggested 
some other ideas in Issue 23404.

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nosy: +martin.panter

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[issue28143] ASDL compatibility with Python 3 system interpreter

[R. David Murray]

R. David Murray added the comment:

It's probably not a bad thing to fix this, but you should be able to avoid the 
problem by using 'make touch' before building.  It should not be necessary to 
have a running python to build python; all the build artifacts are checked in.  
Specifically, the release tarballs should build without an existing python, and 
if they don't, that's a release packaging problem.

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nosy: +r.david.murray

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[issue28143] ASDL compatibility with Python 3 system interpreter

[Serhiy Storchaka]

Changes by Serhiy Storchaka :


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nosy: +benjamin.peterson

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[issue28143] ASDL compatibility with Python 3 system interpreter

[Malthe Borch]

New submission from Malthe Borch:

Many systems today use Python 3 as the default interpreter "python". The Python 
2.7 build fails because of syntax incompatibility.

Attached patch fixes this.

--
components: Build
files: 0001-Allow-make-to-be-run-under-Python-3.patch
keywords: patch
messages: 276401
nosy: malthe
priority: normal
severity: normal
status: open
title: ASDL compatibility with Python 3 system interpreter
type: compile error
versions: Python 2.7
Added file: 
http://bugs.python.org/file44654/0001-Allow-make-to-be-run-under-Python-3.patch

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