starting to use raises_gathered

peru/async.py

@@ -1,6 +1,7 @@
 import asyncio
 import atexit
 import codecs
+import contextlib
 import io
 import os
 import subprocess
@@ -29,6 +30,7 @@ def run_task(coro):
 
 class GatheredExceptions(PrintableError):
     def __init__(self, exceptions):
+        assert len(exceptions) > 0
         self.exceptions = []
         for e in exceptions:
             # Flatten in the exceptions list of any other GatheredExceptions we
@@ -39,8 +41,13 @@ def __init__(self, exceptions):
             else:
                 self.exceptions.append(e)
 
+        # TODO: Something meaningful here.
         self.message = "{0} errors OMGGGGGG".format(len(self.exceptions))
 
+    def get_only(self):
+        assert len(self.exceptions) == 1, "more than one gathered exception"
+        return self.exceptions[0]
+
 
 @asyncio.coroutine
 def gather_coalescing_exceptions(coros, display, error_str):
@@ -170,3 +177,21 @@ def safe_communicate(process, input=None):
         return (yield from process.communicate())
     else:
         return (yield from process.communicate(input))
+
+
+@contextlib.contextmanager
+def raises_gathered(error_type):
+    '''For use in tests. Many tests expect a single error to be thrown, and
+    want it to be of a specific type. This is a helper method for when that
+    type is inside a gathered exception.'''
+    try:
+        yield
+    except GatheredExceptions as e:
+        # Make sure there is exactly one exception.
+        if len(e.exceptions) != 1:
+            raise
+        inner = e.exceptions[0]
+        # Make sure the exception is the right type.
+        if not isinstance(inner, error_type):
+            raise
+        # Success.

test.py

@@ -23,8 +23,9 @@ def main():
         if var.startswith('PERU_'):
             del os.environ[var]
 
-    # Turn debugging features on for the asyncio library.
-    os.environ['PYTHONASYNCIODEBUG'] = '1'
+    # Turn debugging features on for the asyncio library, if it's unset.
+    if 'PYTHONASYNCIODEBUG' not in os.environ:
+        os.environ['PYTHONASYNCIODEBUG'] = '1'
 
     # Make sure the tests don't create any garbage files in the repo. That
     # tends to happen when we accidentally run something in the current dir

tests/test_sync.py

@@ -4,6 +4,7 @@
 import sys
 import textwrap
 
+from peru.async import raises_gathered, GatheredExceptions
 import peru.cache
 import peru.compat
 import peru.error
@@ -387,7 +388,7 @@ def test_drop_then_pick_is_an_error(self):
             imports:
                 foobar: ./
             ''', module_dir)
-        with self.assertRaises(peru.rule.NoMatchingFilesError):
+        with raises_gathered(peru.rule.NoMatchingFilesError):
             run_peru_command(['sync'], self.test_dir)
 
     def test_rule_with_executable(self):
@@ -430,8 +431,8 @@ def test_rule_with_move_error(self):
         try:
             self.do_integration_test(['sync'],
                                      {'newa': 'foo', 'newb/c': 'bar'})
-        except peru.error.PrintableError as e:
-            assert 'doesntexist' in e.message
+        except GatheredExceptions as e:
+            assert 'doesntexist' in e.get_only().message
 
     def test_rule_with_copied_files(self):
         content = {