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 cb3257b37f1f98027aae40c9b4b699c15d88c26a..920b57ea1d93a220897e26006bfff72b79e7816a 100644
--- a/recipe_engine/util.py
+++ b/recipe_engine/util.py
@@ -190,3 +190,72 @@ class StringListIO(object):
   def close(self):
     if not isinstance(self.lines[-1], basestring):
       self.lines[-1] = self.lines[-1].getvalue()
+
+
+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()