Terry J. Reedy added the comment:
Thank you for making a start on code for this issue. After thinking about this
a few hours, here is what I currently think.
I don't want a tiny module for one function. I would like a module with
objects common to the idle and user processes, in particular things needed by
both pyshell and run modules. This would include things now imported into
pyshell from run. (These were initially imported in the other direction, but
switching sped up run startup.) I would like to refactor and include the near
duplicate warning functions. The imports of io, linecache, and maybe warnings
in the new module would come after the new function is called in the module.
At least initially, I would not include anything dependent on another IDLE
module.
Possible names: runutil, runcom, runshell, ??? (and test_...).
Call the new function fix_path (nearly everything in idlelib is private
already). Add "def unfix_path(): if [path[0] != '': <insert ''>. It is
possible that we will need to return and pass back what, if anything, is
removed. I am not sure yet.
When one runs 'python <path>/file.py', sys.path[0] is <path>, not ''. So one
can start idlelib with, for instance, "python <path-to_idlelib>/idle.py" and
sys.path[0] will be <idledir>. It slows imports slightly and could be removed
(and never re-added). I need to check for other instances of sys.path[0] != ''
and <idledir> additions.
Here is one. Add "print(sys.path, file=sys.__stdout__)" to run.py and run it
and the result in Shell is
['C:\\Programs\\Python36\\lib\\idlelib',
'C:\\Programs\\Python36\\Lib\\idlelib', 'C:\\Programs\\Python36\\python36.zip',
...
If I start IDLE from the console, path (in console) starts with '' instead of
idledir x 2. It appears twice because of the tkinter input. The original
sys.path is the same in both processes. If I then run a file with 'print
sys.path', user-process sys.path begins with filedir, consoledir. I am not
quite how '' is replaced by consoledir, but the presence of consoledir is wrong
(explained elsewhere).
If I start from the icon, output never appears. The result needs to be saved
and displayed otherwise, such as in a tkinter messagebox. If I then run the
same file, path (displayed in Shell) begins with just the file directory.
More experiments are needed, such as starting from Explorer [Edit with IDLE].
We will need some repeated on Linux and MAC
In run.py, would "unfix()" be needed after imports? I think not when running a
file, because pyshell.ModifiedInterpreter.prepend_syspath and MI.run_command
together prepend usercodedir to sys.path. I believe this is true when running
a startup file. So we only need to be concerned about restoring '' (or
anything else deleted) sometime before running user code from the shell.
Within run, all but one of the delayed non-main imports are either duplicates
that can be removed or can be moved to the top, where they will surely run
before sys.path is augmented.
The un-movable delayed pydoc import is in the handle method of
run.MyHandler(RPCHandler(socketserver.BaseRequestHandler)) and is called in the
base .__init__. This must happen *before* run_command sends the rpc request to
modify sys.path. So it should be safe if we do not previously unfix sys.path.
My conclusion: We may sometimes need to restore something so imports in Shell
work the same as in Python REPL. The last possibility is in run.main just
before 'while 1:'.
Importing in the IDLE process and pyshell are messy. As a temporary partial
fix, we could unfix() after the top imports in pyshell, or after the top
imports in pyshell.main, or at the bottom of pyshell.main just before entering
the loop. But if there are any further delayed non-idlelib imports, the IDLE
process remains vulnerable to shadow files. But I don't yet know if this is
possible.
As with run, do we need to explicitly unfix in pyshell? In normal mode,
no user code runs in the idle process. So unfix is not needed. With -n set, I
think unfix is still not needed for user files, as MI.run_command runs the same
userdir prepend in self.locals, where user code is exec'ed. Indeed, in order
to protect all IDLE imports (in the IDLE process), sys.path should be left
reduced *except while running user code in the IDLE process, in -n mode*.
The irreducible problem for -n is that once user code *is* run, the fact that
IDLE simulates python -i and the fact that -n means no Shell restart, the
directory cannot be removed. If there is a conflict, we cannot help it. The
oddity of -n mode is that one can run additional files from other directories
and make sys.path grow indefinitely. Thus files can interfere with each other
as well as with IDLE. In python, one can run dir1/file1.py with -i and
'exec(open(dir2/file2.py).read)', and so on, but exec does not prepend dir2 to
sys.path.
What about the pyshell.main section "# process sys.argv and sys.path"? I think
the sys.path parts are wrong, at least for protecting IDLE imports, and should
be removed.
for i in range(len(sys.path)):
sys.path[i] = os.path.abspath(sys.path[i])
Everything is already absolute except for '' and changing the '' added by
python to abspath('') == getcwd() seems wrong. It makes the IDLE shell
unnecessarily different from the Python REPL. If I run
path-a> python -i path-b/tem.py
I cannot import files in path-a. The same should be true if I run
path-a> python -m idlelib
and then edit and run path-b/tem.py.
elif args:
enable_edit = True
pathx = []
for filename in args:
pathx.append(os.path.dirname(filename))
for dir in pathx:
dir = os.path.abspath(dir)
if not dir in sys.path:
sys.path.insert(0, dir)
These insertions should only happen in -n mode and will happen if and when run,
not before being opened to be edited (which could even fail).
else:
dir = os.getcwd()
if dir not in sys.path:
sys.path.insert(0, dir)
With '' changed (wrongly) to getcwd, this will usually do nothing. If I run
'python', sys.path start with '', not os.getcwd. If I os.chdir(newdir), then
'' refers to newdir, not the startig dir. However, in -n mode
Conclusion: delete the above and add
if not use_subprocess (and other conditions?):
sys.path.insert(0, '')
at the last possible moment, just before
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<http://bugs.python.org/issue26143>
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