Re: 2 line patch to allow plpythonu functions to return

Tom Lane wrote:
> This sort of thing normally requires more thought than just removing
> the safety check. What happens when the python code does/doesn't return
> a value, in both cases (declared return type void or not)?

Attached is a more complete patch:

- if the function is declared to return void, we only accept "None" as
the return value from Python. Returning anything else produces an error.

- if the function is declared to return void and Python returns "None",
we return this to PG as a void datum (*not* NULL)

- if the function is not declared to return void and Python returns
"None", we return this to PG as a NULL datum

One minor inconsistency is that PL/PgSQL (for example) actually
disallows "RETURN expr;" in void-returning functions: only "RETURN;" can
be used. In PL/Python we don't place any restrictions on the syntax of
the function: "return expr" is allowed in void-returning functions so
long as `expr' evaluates to None. I don't think this is a major problem,
though.

The error message for the first case isn't quite right, and I need to
update the "expected" regression tests and possibly the documentation.
But otherwise I'll apply this patch to HEAD tomorrow, barring any
objections.

-Neil