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 +1,39 @@
+%% 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)
+  %% FIXME: only allow safe characters inside "..."
+  if ~isempty (strfind (native_path, '"'))
+    error ('cygpath: native path %s must not contain "', native_path);
+  end
+
+  [status, out] = system (['cygpath -u "' native_path '"']);
+  if status ~= 0
+    error ('cygpath: cygpath exited with status %d', status);
+  end
+
+  posix_path = regexprep (out, '[\r]?[\n]$', ''); % strip trailing newline
+  assert (logical (regexp (posix_path, '^[^\r\n]+$'))); % validate path
+end

inst/private/python_env_is_cygwin_like.m

@@ -0,0 +1,54 @@
+%% 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;
+    return
+  end
+
+  if ispc ()
+    if system ('where /q cygpath') ~= 0
+      r = false;
+      python_env_is_cygwin_like_memo = r;
+      return
+    end
+
+    [status, out] = system ([pyexec ' -c "import os; print(os.name)"']);
+    if status ~= 0
+      error ('python_env_is_cygwin_like: %s exited with status %d', ...
+             pyexec, status);
+    end
+    r = ~isempty (regexp (out, 'posix', 'match'));
+    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.
 %%
@@ -131,6 +132,10 @@
       error ('system ipc: failed to close %s (fd %d) after writing', ...
 	     tmpfilename, fd);
     end
+
+    if python_env_is_cygwin_like (pyexec)
+      tmpfilename = cygpath (tmpfilename);
+    end
     [status, out] = system ([pyexec ' ' tmpfilename]);
   end