From 29c462410dae6851599ac935817c80017b81c058 2011-05-04 22:04:10
From: MinRK <benjaminrk@gmail.com>
Date: 2011-05-04 22:04:10
Subject: [PATCH] prevent errors in prefilter from crashing IPython

closes gh-216

---

diff --git a/IPython/core/interactiveshell.py b/IPython/core/interactiveshell.py
index 3761dc8..7e130d5 100644
--- a/IPython/core/interactiveshell.py
+++ b/IPython/core/interactiveshell.py
@@ -2130,7 +2130,20 @@ class InteractiveShell(Configurable, Magic):
         
         with self.builtin_trap:
             if len(cell.splitlines()) == 1:
-                cell = self.prefilter_manager.prefilter_lines(cell)
+                try:
+                    cell = self.prefilter_manager.prefilter_lines(cell)
+                except Exception:
+                    # don't allow prefilter errors to crash IPython, because
+                    # user code can be involved (e.g. aliases)
+                    self.showtraceback()
+                    if store_history:
+                        self.history_manager.store_inputs(self.execution_count, 
+                                                          cell, raw_cell)
+
+                    self.logger.log(cell, raw_cell)
+                    self.execution_count += 1
+                    
+                    return
             
             # Store raw and processed history
             if store_history:
diff --git a/IPython/core/tests/test_interactiveshell.py b/IPython/core/tests/test_interactiveshell.py
index 3e930b7..cf1ea96 100644
--- a/IPython/core/tests/test_interactiveshell.py
+++ b/IPython/core/tests/test_interactiveshell.py
@@ -91,3 +91,9 @@ class InteractiveShellTestCase(unittest.TestCase):
         ip = get_ipython()
         ip.run_cell('a = """\n%exit\n"""')
         self.assertEquals(ip.user_ns['a'], '\n%exit\n')
+    
+    def test_alias_crash(self):
+        """Errors in prefilter can't crash IPython"""
+        ip = get_ipython()
+        ip.run_cell('%alias parts echo first %s second %s')
+        ip.run_cell('parts 1')