add support for fetching from a related alias url when the data

isn't found in the cache..

casimport/__init__.py

@@ -26,6 +26,7 @@ import contextlib
 import glob
 import hashlib
 import importlib.resources
+import mock
 import os.path
 import pathlib
 import shutil
@@ -167,7 +168,15 @@ class CASFinder(MetaPathFinder, Loader):
 		self._aliases.update(self._parsealiases(aliases))
 
 	@staticmethod
-	def _parsealiases(data):
+	def _makebasichashurl(url):
+		try:
+			hashurl = urllib.parse.urlparse(url)
+		except AttributeError:
+			hashurl = url
+		return urllib.parse.urlunparse(hashurl[:3] + ('', '', ''))
+
+	@classmethod
+	def _parsealiases(cls, data):
 		ret = {}
 
 		lines = data.split('\n')
@@ -178,6 +187,13 @@ class CASFinder(MetaPathFinder, Loader):
 			name, hash = i.split()
 			ret.setdefault(name, []).append(hash)
 
+		# split out the hashes
+		for items in list(ret.values()):
+			lst = [ x for x in items if not x.startswith('hash://') ]
+			for h in [ x for x in items if x.startswith('hash://') ]:
+				h = cls._makebasichashurl(h)
+				ret[h] = lst
+
 		return ret
 
 	def disconnect(self):
@@ -245,10 +261,24 @@ class CASFinder(MetaPathFinder, Loader):
 				try:
 					data = load.fetch_data(url)
 					break
-				except:
+				except Exception:
 					pass
+
 			else:
-				raise ValueError('unable to find loader for url %s' % repr(urllib.parse.urlunparse(url)))
+				for url in self._aliases[self._makebasichashurl(url)]:
+					url = urllib.parse.urlparse(url)
+					for load in self._loaders:
+						try:
+							data = load.fetch_data(url)
+							break
+						except Exception:
+							pass
+					else:
+						continue
+
+					break
+				else:
+					raise ValueError('unable to find loader for url %s' % repr(urllib.parse.urlunparse(url)))
 
 			exec(data, module.__dict__)
 
@@ -402,7 +432,10 @@ class Test(unittest.TestCase):
 				'hello': [
 					'hash://sha256/330884aa2febb5e19fb7194ec6a69ed11dd3d77122f1a5175ee93e73cf0161c3?type=text/x-python',
 					'ipfs://bafkreibtbcckul7lwxqz7nyzj3dknhwrdxj5o4jc6gsroxxjhzz46albym',
-				]
+				],
+				'hash://sha256/330884aa2febb5e19fb7194ec6a69ed11dd3d77122f1a5175ee93e73cf0161c3': [
+					'ipfs://bafkreibtbcckul7lwxqz7nyzj3dknhwrdxj5o4jc6gsroxxjhzz46albym',
+				],
 			})
 
 	def test_aliasimports(self):
@@ -430,9 +463,45 @@ class Test(unittest.TestCase):
 
 					# and pulled in the method
 					self.assertTrue(hasattr(randpkg, 'hello'))
+
+					del sys.modules['randpkg']
 			finally:
 				sys.path.remove(fixdir)
 
+	def test_aliasipfsimports(self):
+		# add the test module's path
+		fixdir = str(self.fixtures)
+		sys.path.append(fixdir)
+
+		# that a fake ipfsloader
+		with open(self.fixtures / 'hello.py') as fp:
+			# that returns the correct data
+			fakedata = fp.read()
+
+		def fakeload(url, fd=fakedata):
+			if url.scheme != 'ipfs' or url.netloc != 'bafkreibtbcckul7lwxqz7nyzj3dknhwrdxj5o4jc6gsroxxjhzz46albym':
+				raise ValueError
+
+			return fd
+
+		fakeipfsloader = mock.MagicMock()
+		fakeipfsloader.fetch_data = fakeload
+
+		try:
+			with CASFinder() as f, \
+			    tempattrset(sys.modules[__name__], 'load_aliases',
+			    f.load_aliases):
+
+				f.register(fakeipfsloader)
+
+				# that the import is successful
+				import randpkg
+
+				# and pulled in the method
+				self.assertTrue(hasattr(randpkg, 'hello'))
+		finally:
+			sys.path.remove(fixdir)
+
 	def test_overlappingaliases(self):
 		# make sure that an aliases file is consistent and does not
 		# override other urls.  That is that any hashes are consistent,