command-line suggestions

IPython/config/application.py

@@ -51,20 +51,25 @@
 modes that involve setting multiple options together.
 
 Flags *always* begin with '--', never just one '-'.
-""".strip() # trim newlines of front and back
+""".strip() # trim newlines off front and back
 
 alias_description = """
 These are commonly set parameters, given abbreviated aliases for convenience.
 They are set in the same `name=value` way as class parameters, where
 <name> is replaced by the real parameter for which it is an alias.
-""".strip() # trim newlines of front and back
+
+Setting parameters will *never* be prefixed with '-'.
+
+This line is evaluated in Python, so simple expressions are allowed, e.g.
+    `C.a=range(3)`   For setting C.a=[0,1,2]
+""".strip() # trim newlines off front and back
 
 keyvalue_description = """
 Parameters are set from command-line arguments of the form:
 `Class.trait=value`.  Parameters will *never* be prefixed with '-'.
 This line is evaluated in Python, so simple expressions are allowed, e.g.
-    `C.a='range(3)'`   For setting C.a=[0,1,2]
-""".strip() # trim newlines of front and back
+    `C.a=range(3)`   For setting C.a=[0,1,2]
+""".strip() # trim newlines off front and back
 
 #-----------------------------------------------------------------------------
 # Application class

IPython/config/loader.py

@@ -326,7 +326,8 @@ class CommandLineConfigLoader(ConfigLoader):
     """
 
 kv_pattern = re.compile(r'[A-Za-z]\w*(\.\w+)*\=.*')
-flag_pattern = re.compile(r'\-\-\w+(\-\w)*')
+flag_pattern = re.compile(r'\-\-\w+(\-\w)*$')
+bad_assign_pattern = re.compile(r'\-+.*\=.*')
 
 class KeyValueConfigLoader(CommandLineConfigLoader):
     """A config loader that loads key value pairs from the command line.
@@ -460,7 +461,22 @@ def load_config(self, argv=None, aliases=None, flags=None):
                     raise ValueError("Invalid flag: %r"%flag)
             elif item.startswith('-'):
                 # this shouldn't ever be valid
-                raise ArgumentError("Invalid argument: %r"%item)
+                stripped = item.lstrip('-')
+                msg = "Invalid argument: '%s'"%item
+                suggest = None
+                if '=' in stripped:
+                    # this is an assignment, but with one or more leading '-'
+                    suggest = stripped
+                elif stripped in flags:
+                    # this is a known flag with one (or more than two)
+                    # leading '-'
+                    suggest = '--'+stripped
+
+                if suggest:
+                    # add suggestion to error message
+                    msg += ".  Did you mean '%s'?"%suggest
+
+                raise ArgumentError(msg)
             else:
                 # keep all args that aren't valid in a list, 
                 # in case our parent knows what to do with them.