initial work on making a cas importing system...

.gitignore

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+.coverage
+*.egg-info
+p
+*.pyc

Makefile

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+MODULES=casimport
+
+VIRTUALENV?=virtualenv-3.7
+
+test:
+	(ls $(MODULES)/*.py | entr sh -c 'python -m coverage run -m unittest $(basename $(MODULES)) && coverage report --omit=p/\* -m -i')
+
+env:
+	($(VIRTUALENV) p && . ./p/bin/activate && pip install -r requirements.txt)

README.md

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+casimport
+=========
+
+Usage
+-----
+
+```
+import casimport
+from cas.v1_f_330884aa2febb5e19fb7194ec6a69ed11dd3d77122f1a5175ee93e73cf0161c3 import hello
+
+print(repr(hello('Alice')))
+```
+
+Defintion of hash:
+v<num>_<type>_<hashvalue>
+
+Currently v1 is defined, and has the following types:
+	f	The hash is the value of the Python source file.
+		Generated via: shasum -a 256 hello.py

casimport/__init__.py

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+import glob
+import hashlib
+import os.path
+import sys
+
+from importlib.abc import MetaPathFinder, Loader
+from importlib.machinery import ModuleSpec
+
+class FileDirCAS(object):
+	def __init__(self, path):
+		self._path = path
+		self._hashes = {}
+
+		for i in glob.glob(os.path.join(path, '*.py')):
+			_, hash = self.read_hash_file(i)
+			self._hashes[hash] = i
+
+	def read_hash_file(self, fname):
+		with open(fname, 'rb') as fp:
+			data = fp.read()
+			hash = hashlib.sha256(data).hexdigest()
+
+		return data, hash
+
+	def is_package(self, hash):
+		return False
+
+	def exec_module(self, hash, module):
+		parts = hash.split('_', 2)
+		fname = self._hashes[parts[2]]
+
+		data, fhash = self.read_hash_file(fname)
+
+		if fhash != parts[2]:
+			raise ValueError('file no longer matches hash on disk')
+
+		exec(data, module.__dict__)
+
+class CASFinder(MetaPathFinder, Loader):
+	def __init__(self):
+		self._loaders = []
+
+		sys.meta_path.append(self)
+
+	def register(self, loader):
+		self._loaders.append(loader)
+
+	# MetaPathFinder methods
+	def find_spec(self, fullname, path, target=None):
+		if path is None:
+			ms = ModuleSpec(fullname, self, is_package=True)
+		else:
+			parts = fullname.split('.')
+			for l in self._loaders:
+				ispkg = l.is_package(parts[1])
+				break
+
+			ms = ModuleSpec(fullname, self, is_package=True, loader_state=(parts[1], l))
+
+		return ms
+
+	def invalidate_caches(self):
+		return None
+
+	# Loader methods
+	def exec_module(self, module):
+		if module.__name__ == 'cas':
+			pass
+		else:
+			hash, load = module.__spec__.loader_state
+			load.exec_module(hash, module)
+
+import unittest
+
+class Test(unittest.TestCase):
+	def test_casimport(self):
+		f = CASFinder()
+		f.register(FileDirCAS(os.path.join(os.path.dirname(__file__), '..', 'fixtures')))
+
+		import cas
+
+		from cas.v1_f_330884aa2febb5e19fb7194ec6a69ed11dd3d77122f1a5175ee93e73cf0161c3 import hello
+
+		name = 'Olof'
+		self.assertEqual(hello(name), 'hello ' + name)

fixtures/hello.py

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+def hello(name):
+	return 'hello %s' % name
+
+import unittest
+
+class Tests(unittest.TestCase):
+	def test_hello(self):
+		self.assertEqual(hello('sam'), 'hello sam')
+		self.assertEqual(hello('bob'), 'hello bob')

requirements.txt

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+# use setup.py for dependancy info
+-e .
+
+-e .[dev]

setup.py

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+#!/usr/bin/env python
+
+from setuptools import setup
+
+setup(name='casimport',
+    version='0.1.0',
+    description='Import python modules via content address.',
+    author='John-Mark Gurney',
+    author_email='jmg@funkthat.com',
+    classifiers=[
+        'Development Status :: 3 - Alpha',
+        'License :: OSI Approved :: BSD License',
+        'Topic :: Security',
+	# XXX - add
+    ],
+    url='https://www.funkthat.com/gitea/jmg/casimport',
+    packages=[ 'casimport', ],
+    install_requires=[
+        'mock',
+    ],
+    extras_require = {
+        'dev': [ 'coverage' ],
+    }
+)