Limit inference to a maximum of 100 results at a time to prevent

spot performance issues.

Add new envrionment variable call ASTROID_MAX_INFERABLE to tune
the max inferable amount of values at a time.

Close #579
Close PyCQA/pylint#2251

1 files changed, 24 insertions, 0 deletions

diff --git a/astroid/util.py b/astroid/util.py
index a5310970..8497b34a 100644
--- a/astroid/util.py
+++ b/astroid/util.py
@@ -5,6 +5,7 @@
 # For details: https://github.com/PyCQA/astroid/blob/master/COPYING.LESSER
 
 import warnings
+from itertools import islice
 
 import importlib
 import lazy_object_proxy
@@ -126,5 +127,28 @@ def proxy_alias(alias_name, node_type):
     return proxy(lambda: node_type)
 
 
+def limit_inference(iterator, size):
+    """Limit inference amount.
+
+    Limit inference amount to help with performance issues with
+    exponentially exploding possible results.
+
+    :param iterator: Inference generator to limit
+    :type iterator: Iterator(NodeNG)
+
+    :param size: Maximum mount of nodes yielded plus an
+        Uninferable at the end if limit reached
+    :type size: int
+
+    :yields: A possibly modified generator
+    :rtype param: Iterable
+    """
+    yield from islice(iterator, size)
+    has_more = next(iterator, False)
+    if has_more is not False:
+        yield Uninferable
+        return
+
+
 # Backwards-compatibility aliases
 YES = Uninferable