From 03bb4e4cf82fa9d28168bb46089b465e1f4f8261 2017-08-18 09:30:23
From: Min RK <benjaminrk@gmail.com>
Date: 2017-08-18 09:30:23
Subject: [PATCH] Merge pull request #10743 from takluyver/limit-no-completions

Limit number of completions returned
---

diff --git a/.gitignore b/.gitignore
index 675b53e..e697112 100644
--- a/.gitignore
+++ b/.gitignore
@@ -5,6 +5,7 @@ _build
 docs/man/*.gz
 docs/source/api/generated
 docs/source/config/options
+docs/source/config/shortcuts/*.csv
 docs/source/interactive/magics-generated.txt
 docs/source/config/shortcuts/*.csv
 docs/gh-pages
diff --git a/IPython/core/completer.py b/IPython/core/completer.py
index eecf6ff..18905b1 100644
--- a/IPython/core/completer.py
+++ b/IPython/core/completer.py
@@ -161,6 +161,9 @@ if sys.platform == 'win32':
 else:
     PROTECTABLES = ' ()[]{}?=\\|;:\'#*"^&'
 
+# Protect against returning an enormous number of completions which the frontend
+# may have trouble processing.
+MATCHES_LIMIT = 500
 
 _deprecation_readline_sentinel = object()
 
@@ -1943,7 +1946,8 @@ class IPCompleter(Completer):
             for meth in (self.unicode_name_matches, back_latex_name_matches, back_unicode_name_matches):
                 name_text, name_matches = meth(base_text)
                 if name_text:
-                    return name_text, name_matches, [meth.__qualname__]*len(name_matches), ()
+                    return name_text, name_matches[:MATCHES_LIMIT], \
+                           [meth.__qualname__]*min(len(name_matches), MATCHES_LIMIT), ()
         
 
         # If no line buffer is given, assume the input text is all there was
@@ -1955,11 +1959,10 @@ class IPCompleter(Completer):
 
         # Do magic arg matches
         for matcher in self.magic_arg_matchers:
-            matches = [(m, matcher.__qualname__) for m in matcher(line_buffer)]
+            matches = list(matcher(line_buffer))[:MATCHES_LIMIT]
             if matches:
-                matches2 = [m[0] for m in matches]
-                origins = [m[1] for m in matches]
-                return text, matches2, origins, ()
+                origins = [matcher.__qualname__] * len(matches)
+                return text, matches, origins, ()
 
         # Start with a clean slate of completions
         matches = []
@@ -2006,7 +2009,8 @@ class IPCompleter(Completer):
                 seen.add(t)
 
         _filtered_matches = sorted(
-            set(filtered_matches), key=lambda x: completions_sorting_key(x[0]))
+            set(filtered_matches), key=lambda x: completions_sorting_key(x[0]))\
+            [:MATCHES_LIMIT]
 
         _matches = [m[0] for m in _filtered_matches]
         origins = [m[1] for m in _filtered_matches]