private/python_ipc_system: Convert to Cygwin path when needed.

This should fix some errors when Python is running in Cygwin-like
environment. But there could still be errors in other places.

See gnu-octave#1182.

* inst/private/cygpath.m: New function.
* inst/private/python_env_is_cygwin_like.m: New function.
* inst/private/python_ipc_system.m: Use them.

inst/private/cygpath.m

@@ -0,0 +1,50 @@
+%% Copyright (C) 2022 Alex Vong
+%%
+%% This file is part of OctSymPy.
+%%
+%% OctSymPy is free software; you can redistribute it and/or modify
+%% it under the terms of the GNU General Public License as published
+%% by the Free Software Foundation; either version 3 of the License,
+%% or (at your option) any later version.
+%%
+%% This software is distributed in the hope that it will be useful,
+%% but WITHOUT ANY WARRANTY; without even the implied warranty
+%% of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See
+%% the GNU General Public License for more details.
+%%
+%% You should have received a copy of the GNU General Public
+%% License along with this software; see the file COPYING.
+%% If not, see <https://www.gnu.org/licenses/>.
+
+%% -*- texinfo -*-
+%% @defun  cygpath ()
+%% Convert Windows native path to Cygwin POSIX-style path.
+%%
+%% @seealso{python_env_is_cygwin_like}
+%% @end defun
+
+function posix_path = cygpath (native_path)
+  args = {'-u', native_path};
+  [fin, fout, pid] = popen2 ('cygpath', args);
+  if pid == -1
+    error ('cygpath: failed to create cygpath subprocess');
+  end
+
+  assert (fclose (fin) == 0);
+
+  err = errno ('EAGAIN');
+  while err == errno ('EAGAIN')
+    pause (0.1);
+    posix_path = fgetl (fout);
+    err = errno ();
+  end
+
+  assert (ischar (posix_path));
+  assert (feof (fout));
+  assert (fclose (fout) == 0);
+
+  [retpid, status, msg] = waitpid (pid);
+  if retpid < 0
+    error ('cygpath: failed to wait for python: %s', msg);
+  end
+end

inst/private/python_env_is_cygwin_like.m

@@ -0,0 +1,64 @@
+%% Copyright (C) 2022 Alex Vong
+%%
+%% This file is part of OctSymPy.
+%%
+%% OctSymPy is free software; you can redistribute it and/or modify
+%% it under the terms of the GNU General Public License as published
+%% by the Free Software Foundation; either version 3 of the License,
+%% or (at your option) any later version.
+%%
+%% This software is distributed in the hope that it will be useful,
+%% but WITHOUT ANY WARRANTY; without even the implied warranty
+%% of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See
+%% the GNU General Public License for more details.
+%%
+%% You should have received a copy of the GNU General Public
+%% License along with this software; see the file COPYING.
+%% If not, see <https://www.gnu.org/licenses/>.
+
+%% -*- texinfo -*-
+%% @defun  python_env_is_cygwin_like (pyexec)
+%% Check if Python @var{pyexec} is running in a Cygwin-like POSIX environment,
+%% such as Cygwin or MSYS2.  The result is memoized to speed up subsequent
+%% calls.
+%%
+%% @seealso{cygpath}
+%% @end defun
+
+function r = python_env_is_cygwin_like (pyexec)
+  persistent python_env_is_cygwin_like_memo
+
+  if ~isempty (python_env_is_cygwin_like_memo)
+    r = python_env_is_cygwin_like_memo;
+  elseif ispc ()
+    args = {'-c', 'import os; print(os.name)'};
+    [fin, fout, pid] = popen2 (pyexec, args);
+    if pid == -1
+      error ('python_env_is_cygwin_like: failed to create python subprocess');
+    end
+
+    assert (fclose (fin) == 0);
+
+    err = errno ('EAGAIN');
+    while err == errno ('EAGAIN')
+      pause (0.1);
+      os = fgetl (fout);
+      err = errno ();
+    end
+
+    assert (ischar (os));
+    assert (feof (fout));
+    assert (fclose (fout) == 0);
+
+    [retpid, status, msg] = waitpid (pid);
+    if retpid < 0
+      error ('python_env_is_cygwin_like: failed to wait for python: %s', msg);
+    end
+
+    r = strcmp (os, 'posix');
+    python_env_is_cygwin_like_memo = r;
+  else
+    r = false;
+    python_env_is_cygwin_like_memo = r;
+  end
+end

inst/private/python_ipc_system.m

@@ -1,4 +1,5 @@
 %% Copyright (C) 2014-2016, 2022 Colin B. Macdonald
+%% Copyright (C) 2022 Alex Vong
 %%
 %% This file is part of OctSymPy.
 %%
@@ -131,7 +132,13 @@
       error ('system ipc: failed to close %s (fd %d) after writing', ...
 	     tmpfilename, fd);
     end
-    [status, out] = system ([pyexec ' ' tmpfilename]);
+
+    if python_env_is_cygwin_like (pyexec)
+      converted_tmpfilename = cygpath (tmpfilename);
+    else
+      converted_tmpfilename = tmpfilename;
+    end
+    [status, out] = system ([pyexec ' ' converted_tmpfilename]);
   end
 
   info.raw = out;