pygopath: Initial draft

Module gopath provides way to import python modules by full path in a Go workspace.

For example

    lonet = gopath.gimport('lab.nexedi.com/kirr/go123/xnet/lonet')

will import either

    lab.nexedi.com/kirr/go123/xnet/lonet.py, or
    lab.nexedi.com/kirr/go123/xnet/lonet/__init__.py

located somewhere under $GOPATH.

.gitignore

+*.py[co]
+__pycache__
+build/
+.tox/
+.cache/
+
+*.o
+*.so
+
+/dist/
+*.egg-info
+
+perf.data*
+core

MANIFEST.in

+recursive-include testdata *.py

README.rst

+=================================================================
+ Pygopath - Import python modules by full path in a Go workspace
+=================================================================
+
+Module `gopath` provides way to import python modules by full path in a Go workspace.
+
+For example
+
+::
+
+    lonet = gopath.gimport('lab.nexedi.com/kirr/go123/xnet/lonet')
+
+will import either
+
+- `lab.nexedi.com/kirr/go123/xnet/lonet.py`, or
+- `lab.nexedi.com/kirr/go123/xnet/lonet/__init__.py`
+
+located in `src/` under `$GOPATH`.

gopath.py

+# Copyright (C) 2018  Nexedi SA and Contributors.
+#                     Kirill Smelkov <kirr@nexedi.com>
+#
+# This program is free software: you can Use, Study, Modify and Redistribute
+# it under the terms of the GNU General Public License version 3, or (at your
+# option) any later version, as published by the Free Software Foundation.
+#
+# You can also Link and Combine this program with other software covered by
+# the terms of any of the Free Software licenses or any of the Open Source
+# Initiative approved licenses and Convey the resulting work. Corresponding
+# source of such a combination shall include the source code for all other
+# software used.
+#
+# This program is distributed WITHOUT ANY WARRANTY; without even the implied
+# warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
+#
+# See COPYING file for full licensing terms.
+# See https://www.nexedi.com/licensing for rationale and options.
+"""Module gopath provides way to import python modules by full path in a Go workspace.
+
+For example
+
+    lonet = gopath.gimport('lab.nexedi.com/kirr/go123/xnet/lonet')
+
+will import either
+
+    lab.nexedi.com/kirr/go123/xnet/lonet.py, or
+    lab.nexedi.com/kirr/go123/xnet/lonet/__init__.py
+
+located in src/ under $GOPATH.
+"""
+
+import os, os.path
+import sys
+import imp
+
+# _gopathv returns $GOPATH vector.
+def _gopathv():
+    gopath = os.environ.get('GOPATH')
+    if gopath is None:
+        # since Go1.8 default GOPATH is ~/go
+        gopath = os.path.expanduser(os.path.join('~', 'go'))
+    return gopath.split(os.path.pathsep)
+
+
+# gimport imports python module or package from fully-qualified module name under $GOPATH.
+def gimport(name):
+    imp.acquire_lock()
+    try:
+        return _gimport(name)
+    finally:
+        imp.release_lock()
+
+def _gimport(name):
+    # we will register imported module into sys.modules with adjusted path.
+    # reason: if we leave dots in place, python emits warning:
+    #   RuntimeWarning: Parent module 'lab.nexedi' not found while handling absolute import
+    #
+    # we put every imported module under `gopath.` namespace with '.' changed to '_'
+    modname = 'gopath.' + name.replace('.', '_')
+
+    try:
+        return sys.modules[modname]
+    except KeyError:
+        # not yet imported
+        pass
+
+    # search for module in every GOPATH entry
+    modpath = None
+    gopathv = _gopathv()
+    for g in gopathv:
+        # module: .../name.py
+        modpath = os.path.join(g, 'src', name + '.py')
+        if os.path.exists(modpath):
+            break
+
+        # package: .../name/__init__.py
+        modpath = os.path.join(g, 'src', name, '__init__.py')
+        if os.path.exists(modpath):
+            break
+
+    else:
+        modpath = None
+
+    if modpath is None:
+        raise ImportError('gopath: no module named %s' % name)
+
+
+    # https://stackoverflow.com/a/67692
+    # TODO py3 support
+    return imp.load_source(modname, modpath)

gopath_test.py

+# Copyright (C) 2018  Nexedi SA and Contributors.
+#                     Kirill Smelkov <kirr@nexedi.com>
+#
+# This program is free software: you can Use, Study, Modify and Redistribute
+# it under the terms of the GNU General Public License version 3, or (at your
+# option) any later version, as published by the Free Software Foundation.
+#
+# You can also Link and Combine this program with other software covered by
+# the terms of any of the Free Software licenses or any of the Open Source
+# Initiative approved licenses and Convey the resulting work. Corresponding
+# source of such a combination shall include the source code for all other
+# software used.
+#
+# This program is distributed WITHOUT ANY WARRANTY; without even the implied
+# warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
+#
+# See COPYING file for full licensing terms.
+# See https://www.nexedi.com/licensing for rationale and options.
+
+import os, os.path
+from gopath import gimport
+
+GOPATH_orig = None
+
+def setup_module():
+    # set GOPATH to testdata/src
+    global GOPATH_orig
+    GOPATH_orig = os.environ.get('GOPATH')
+    os.environ['GOPATH'] = '%s/testdata' % (os.path.dirname(__file__),)
+
+def teardown_module():
+    if GOPATH_orig is None:
+        del os.environ['GOPATH']
+    else:
+        os.environ['GOPATH'] = GOPATH_orig
+
+
+def test_import_module():
+    hello = gimport('lab.nexedi.com/kirr/hello')
+    assert hello.TAG == 'gopath: test: hello.py'
+    hello.TAG = 'loaded'
+
+    # verify second gimport does not reload
+    hello2 = gimport('lab.nexedi.com/kirr/hello')
+    assert hello2 is hello
+
+    # even though hello2 is hello - the module could be reloaded.
+    # check it is not the case via .TAG .
+    assert hello.TAG == 'loaded', 'module was reloaded'
+
+
+def test_import_package():
+    world = gimport('lab.nexedi.com/kirr/world')
+    assert world.TAG == 'gopath: test: world/__init__.py'
+    world.TAG = 'loaded'
+
+    # verify second gimport does not reload
+    world2 = gimport('lab.nexedi.com/kirr/world')
+    assert world2 is world
+
+    # even though world2 is world - the module could be reloaded.
+    # check it is not the case via .TAG .
+    assert world.TAG =='loaded', 'module was reloaded'

setup.py

+# pygopath | pythonic package setup
+from setuptools import setup, find_packages
+
+# read file content
+def readfile(path):
+    with open(path, 'r') as f:
+        return f.read()
+
+setup(
+    name        = 'pygopath',
+    version     = '0.0.0.dev1',
+    description = 'Import python modules by full-path in Go workspace',
+    long_description = readfile('README.rst'),
+    url         = 'https://lab.nexedi.com/kirr/pygopath',
+    license     = 'GPLv3+ with wide exception for Open-Source',
+    author      = 'Kirill Smelkov',
+    author_email= 'kirr@nexedi.com',
+
+    keywords    = 'go GOPATH python import',
+
+    # XXX find_packages does not find top-level *.py
+    #packages    = find_packages(),
+    packages    = [''],
+
+    extras_require = {
+                  'test': ['pytest'],
+    },
+
+    classifiers = [_.strip() for _ in """\
+        Development Status :: 3 - Alpha
+        Intended Audience :: Developers\
+    """.splitlines()]
+)

testdata/src/lab.nexedi.com/kirr/hello.py

+TAG  = 'gopath: test: hello.py'

testdata/src/lab.nexedi.com/kirr/world/__init__.py

+TAG = 'gopath: test: world/__init__.py'