Refined checking for assignment vs other python operators in the new input transformation/prefiltering system. This makes it once again possible for magics to do useful things which involve python operator characters (e.g. 'cd /'). Also added tests to verify this.

IPython/prefilter.py

@@ -138,8 +138,9 b' def prefilter(line_info, ip):'
                    checkIPyAutocall,
                    checkMultiLineShell,
                    checkEscChars,
-                   checkPythonChars,
+                   checkAssignment,
                    checkAutomagic,
+                   checkPythonOps,
                    checkAlias,
                    checkAutocall,
                    ]:
@@ -203,23 +204,26 b' def checkEscChars(l_info,ip):'
     else:
         return None
     
-def checkPythonChars(l_info,ip):
-    """If the 'rest' of the line begins with an (in)equality, assginment,
-    function call or tuple comma, we should simply execute the line
-    (regardless of whether or not there's a possible alias, automagic or
-    autocall expansion).  This both avoids spurious geattr() accesses on
-    objects upon assignment, and also allows users to assign to either alias
-    or magic names true python variables (the magic/alias systems always
-    take second seat to true python code).  E.g. ls='hi', or ls,that=1,2"""
-    if l_info.theRest and l_info.theRest[0] in '!=()<>,+*/%^&|':
+
+def checkAssignment(l_info,ip):
+    """Check to see if user is assigning to a var for the first time, in
+    which case we want to avoid any sort of automagic / autocall games.
+    
+    This allows users to assign to either alias or magic names true python
+    variables (the magic/alias systems always take second seat to true
+    python code).  E.g. ls='hi', or ls,that=1,2"""
+    if l_info.theRest and l_info.theRest[0] in '=,':
         return ip.handle_normal
     else:
         return None
 
+
 def checkAutomagic(l_info,ip):
     """If the iFun is magic, and automagic is on, run it.  Note: normal,
     non-auto magic would already have been triggered via '%' in
-    check_esc_chars. This just checks for automagic."""
+    check_esc_chars. This just checks for automagic.  Also, before
+    triggering the magic handler, make sure that there is nothing in the
+    user namespace which could shadow it."""
     if not ip.rc.automagic or not hasattr(ip,'magic_'+l_info.iFun):
         return None
 
@@ -234,6 +238,17 b' def checkAutomagic(l_info,ip):'
     return ip.handle_magic
 
     
+def checkPythonOps(l_info,ip):
+    """If the 'rest' of the line begins with a function call or pretty much
+    any python operator, we should simply execute the line (regardless of
+    whether or not there's a possible alias or autocall expansion).  This
+    avoids spurious (and very confusing) geattr() accesses."""
+    if l_info.theRest and l_info.theRest[0] in '!=()<>,+*/%^&|':
+        return ip.handle_normal
+    else:
+        return None
+
+
 def checkAlias(l_info,ip):
     "Check if the initital identifier on the line is an alias."
     # Note: aliases can not contain '.'

test/test_prefilter.py

@@ -206,22 +206,25 b' run_handler_tests(['
     # Without automagic, only shows up with explicit escape
     ( 'cpaste', handle_normal),
     ( '%cpaste', handle_magic),
-    ( '%does_not_exist', handle_magic)
+    ( '%does_not_exist', handle_magic),
     ])
 ip.options.automagic = 1
 run_handler_tests([
     ( 'cpaste',          handle_magic),
     ( '%cpaste',         handle_magic),
     ( 'does_not_exist',  handle_normal),
-    ( '%does_not_exist', handle_magic)])
+    ( '%does_not_exist', handle_magic),
+    ( 'cd /',            handle_magic),
+    ( 'cd = 2',          handle_normal),
+    ])
 
 # If next elt starts with anything that could be an assignment, func call,
 # etc, we don't call the magic func, unless explicitly escaped to do so.
-magic_killing_tests = []
-for c in list('!=()<>,'):
-    magic_killing_tests.append(('cpaste %s killed_automagic' % c, handle_normal))
-    magic_killing_tests.append(('%%cpaste %s escaped_magic' % c,   handle_magic))
-run_handler_tests(magic_killing_tests)
+#magic_killing_tests = []
+#for c in list('!=()<>,'):
+#    magic_killing_tests.append(('cpaste %s killed_automagic' % c, handle_normal))
+#    magic_killing_tests.append(('%%cpaste %s escaped_magic' % c,   handle_magic))
+#run_handler_tests(magic_killing_tests)
 
 # magic on indented continuation lines -- on iff multi_line_specials == 1
 ip.options.multi_line_specials = 0