[Sqlalchemy-tickets] [sqlalchemy] #2944: Confusing error message when passing empty list to Insert.values()

[sqlalchemy <mi...@zz...>]

#2944: Confusing error message when passing empty list to Insert.values()
--------------------+-----------------------------------------
 Reporter:  jet57   |           Owner:  zzzeek
     Type:  defect  |          Status:  new
 Priority:  medium  |       Milestone:
Component:  (none)  |        Severity:  no triage selected yet
 Keywords:          |  Progress State:  awaiting triage
--------------------+-----------------------------------------
 When passing a list of dictionaries to Insert.values(), I happened to pass
 an empty list, as in the following test case:


 {{{
 #!/usr/bin/python
 import sqlalchemy
 print sqlalchemy.__version__
 from sqlalchemy import Table, Column, Integer, MetaData, insert
 m = MetaData()
 c1 = Column('c1', Integer)
 t1 = Table('t1', m, c1)
 s = t1.insert().values([])
 }}}

 and obtained the following exception:


 {{{
 0.9.0b1
 Traceback (most recent call last):
   File "sqlalchemybug.py", line 11, in <module>
     s = t1.insert().values([])
   File "<string>", line 1, in <lambda>
   File "/usr/local/lib/python2.7/dist-
 packages/SQLAlchemy-0.9.0b1-py2.7.egg/sqlalchemy/sql/base.py", line 42, in
 _generative
     fn(self, *args[1:], **kw)
   File "/usr/local/lib/python2.7/dist-
 packages/SQLAlchemy-0.9.0b1-py2.7.egg/sqlalchemy/sql/dml.py", line 283, in
 values
     self._process_colparams(v)
   File "/usr/local/lib/python2.7/dist-
 packages/SQLAlchemy-0.9.0b1-py2.7.egg/sqlalchemy/sql/dml.py", line 41, in
 _process_colparams
     isinstance(parameters[0], (list, tuple, dict)):
 IndexError: list index out of range
 }}}

 Upon checking the documentation I note that it does say "This mode is
 indicated by passing a list of ''one or more'' dictionaries/tuples", i.e.
 behaviour on a list of zero dictionaries/tuples is undefined. I feel this
 warrants a more explicit error message, rather than letting the
 {{{IndexError}}} bubble up.

--
Ticket URL: <http://www.sqlalchemy.org/trac/ticket/2944>
sqlalchemy <http://www.sqlalchemy.org/>
The Database Toolkit for Python