Don't leave cruft around in sys.modules when an import fails.

Closes: #214, #225

Squashed from a bunch of commits by @olasd

hy/importer.py

@@ -70,10 +70,15 @@ def import_file_to_module(module_name, fpath):
     """Import content from fpath and puts it into a Python module.
 
     Returns the module."""
+    try:
         _ast = import_file_to_ast(fpath, module_name)
         mod = imp.new_module(module_name)
         mod.__file__ = fpath
         eval(ast_compile(_ast, fpath, "exec"), mod.__dict__)
+    except Exception:
+        sys.modules.pop(module_name, None)
+        raise
+
     return mod
 
 

tests/importer/test_importer.py

@@ -1,4 +1,5 @@
-from hy.importer import import_file_to_module, import_buffer_to_ast
+from hy.importer import import_file_to_module, import_buffer_to_ast, MetaLoader
+import os
 import ast
 
 
@@ -12,3 +13,17 @@ def test_stringer():
     "Make sure the basics of the importer work"
     _ast = import_buffer_to_ast("(defn square [x] (* x x))", '')
     assert type(_ast.body[0]) == ast.FunctionDef
+
+
+def test_imports():
+    path = os.getcwd() + "/tests/resources/importer/a.hy"
+    testLoader = MetaLoader(path)
+
+    def _import_test():
+        try:
+            return testLoader.load_module("tests.resources.importer.a")
+        except:
+            return "Error"
+
+    assert _import_test() == "Error"
+    assert _import_test() != None

tests/resources/importer/a.hy

@@ -0,0 +1 @@
+(thisshouldnotwork)