Add LogDog / annotation protobuf support.

recipe_engine/util.py

Index: recipe_engine/util.py
diff --git a/recipe_engine/util.py b/recipe_engine/util.py
index 91c5192c8c7ccad7d5da3e1b04b327b3a796e8df..9b36ca5402a4256e175e6a70ebb74267353168cd 100644
--- a/recipe_engine/util.py
+++ b/recipe_engine/util.py
@@ -228,3 +228,72 @@ class exponential_retry(object):
           time.sleep(retry_delay.total_seconds())
           retry_delay *= 2
     return wrapper
+
+
+class MultiException(Exception):
+  """An exception that aggregates multiple exceptions and summarizes them."""
+
+  def __init__(self):
+    self._inner = []
+
+  def __nonzero__(self):
+    return bool(self._inner)
+
+  def __len__(self):
+    return len(self._inner)
+
+  def __getitem__(self, key):
+    return self._inner[key]
+
+  def __iter__(self):
+    return iter(self._inner)
+
+  def __str__(self):
+    if len(self._inner) == 0:
+      text = 'No exceptions'
+    elif len(self._inner) == 1:
+      text = str(self._inner[0])
+    else:
+      text = str(self._inner[0]) + ', and %d more...' % (len(self._inner)-1)
+    return '%s(%s)' % (type(self).__name__, text)
+
+  def append(self, exc):
+    assert isinstance(exc, BaseException)
+    self._inner.append(exc)
+
+  def raise_if_any(self):
+    if self._inner:
+      raise self
+
+  @contextlib.contextmanager
+  def catch(self, *exc_types):
+    """ContextManager that catches any exception raised during its execution
+    and adds them to the MultiException.
+
+    Args:
+      exc_types (list): A list of exception classes to catch. If empty,
+          Exception will be used.
+    """
+    exc_types = exc_types or (Exception,)
+    try:
+      yield
+    except exc_types as e:
+      self.append(e)
+
+
+@contextlib.contextmanager
+def defer_exceptions_for(it, fn, *exc_types):
+  """Executes "fn" for each element in "it". Any exceptions thrown by "fn" will
+  be deferred until the end of "it", then raised as a single MultiException.
+
+  Args:
+    it (iterable): An iterable to traverse.
+    fn (callable): A function to call for each element in "it".
+    exc_types (list): An optional list of specific exception types to handle.
+        If empty, Exception will be used.
+  """
+  mexc = MultiException()
+  for e in it:
+    with mexc.catch(*exc_types):
+      fn(e)
+  mexc.raise_if_any()