[issue14282] lib2to3.fixer_util.touch_import('__future__', ...) can lead to SyntaxError in code

2012-03-13 Thread Martin v . Löwis 

Martin v. Löwis mar...@v.loewis.de added the comment:

I think that's actually a bug in python-modernize, not in touch_import - or, 
rather, touch_import shouldn't be used to add future imports.

Instead, I think there should be a touch_future function which adds a future 
import, taking into account that future imports need to go before all other 
imports, but after a possible docstring.

--
nosy: +loewis

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[issue14282] lib2to3.fixer_util.touch_import('__future__', ...) can lead to SyntaxError in code

2012-03-13 Thread Martin v . Löwis 

Martin v. Löwis mar...@v.loewis.de added the comment:

Instead of changing touch_import, I propose to add a function similar to

https://github.com/loewis/python-modernize/commit/0db885e616807d0cc6859b4035d81fd260b06a67

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[issue14282] lib2to3.fixer_util.touch_import('__future__', ...) can lead to SyntaxError in code

2012-03-13 Thread Luke Macken 

Luke Macken lmac...@redhat.com added the comment:

Yep, that seems like the right solution. Thanks, Martin.

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[issue14282] lib2to3.fixer_util.touch_import('__future__', ...) can lead to SyntaxError in code

2012-03-13 Thread Benjamin Peterson 

Changes by Benjamin Peterson benja...@python.org:


--
resolution:  - works for me
status: open - closed

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[issue14282] lib2to3.fixer_util.touch_import('__future__', ...) can lead to SyntaxError in code

2012-03-12 Thread Luke Macken 

New submission from Luke Macken lmac...@redhat.com:

Problem:


lib2to3.fixer_util.touch_import('__future__', ...)  will insert the import 
statement below all other imports. This will then trigger the following error:

SyntaxError: from __future__ imports must occur at the beginning of the file


How to reproduce the issue (using modernize, which uses lib2to3):

$ git clone https://github.com/mitsuhiko/python-modernize.git
$ cd python-modernize
$ echo  EOF  test.py
# test.py
Test case for lib2to3.fixer_util.touch_import('__future__', ...)
import os
print hi
EOF

$ python modernize.py test.py
--- test.py (original)
+++ test.py (refactored)
@@ -1,4 +1,5 @@
 # test.py
 Test case for lib2to3.fixer_util.touch_import('__future__', ...)
 import os
-print hi
+from __future__ import print_function
+print(hi)

$ python3 test.py
  File test.py, line 4
from __future__ import print_function
^
  SyntaxError: from __future__ imports must occur at the beginning of the 
file


The following patch to lib2to3 seems to solve the issue:

--- /usr/lib64/python2.7/lib2to3/fixer_util.py.orig 2012-03-09 
21:53:10.841083479 -0800
+++ /usr/lib64/python2.7/lib2to3/fixer_util.py  2012-03-09 
21:58:18.678946683 -0800
@@ -306,14 +306,15 @@
 # figure out where to insert the new import.  First try to find
 # the first import and then skip to the last one.
 insert_pos = offset = 0
-for idx, node in enumerate(root.children):
-if not is_import_stmt(node):
-continue
-for offset, node2 in enumerate(root.children[idx:]):
-if not is_import_stmt(node2):
-break
-insert_pos = idx + offset
-break
+if package != '__future__':
+for idx, node in enumerate(root.children):
+if not is_import_stmt(node):
+continue
+for offset, node2 in enumerate(root.children[idx:]):
+if not is_import_stmt(node2):
+break
+insert_pos = idx + offset
+break

 # if there are no imports where we can insert, find the docstring.
 # if that also fails, we stick to the beginning of the file


After the patch, all is well:

$ python modernize.py test.py
--- test.py (original)
+++ test.py (refactored)
@@ -1,4 +1,5 @@
 # test.py
 Test case for lib2to3.fixer_util.touch_import('__future__', ...)
+from __future__ import print_function
 import os
-print hi
+print(hi)

$ python3 test.py
hi

--
components: 2to3 (2.x to 3.x conversion tool)
messages: 155569
nosy: lmacken
priority: normal
severity: normal
status: open
title: lib2to3.fixer_util.touch_import('__future__', ...) can lead to 
SyntaxError in code
type: behavior

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[issue14282] lib2to3.fixer_util.touch_import('__future__', ...) can lead to SyntaxError in code

2012-03-12 Thread Luke Macken 

Changes by Luke Macken lmac...@redhat.com:


--
keywords: +patch
Added file: 
http://bugs.python.org/file24814/python-lib2to3-touch-future-import.patch

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