Re: Support json_errdetail in FRONTEND builds

> On 14 Mar 2024, at 09:06, Michael Paquier <michael(at)paquier(dot)xyz> wrote:

> I think that it is cleaner to create the new API first, and then
> rely on it, reversing the order of both patches

I agree with this ordering.

> (perhaps the extra destroyStringInfo in freeJsonLexContext() should
> have been moved in 0001).

I wouldn't worry about that, seems fine as is to me.

> See the attached with few tweaks to 0001, previously 0002 @-(at)(dot)
> I'd still need to do a more serious lookup of 0002, previously 0001.

A few small comments:

- *
+*
Whitespace

+ /* don't allow destroys of read-only StringInfos */
+ Assert(str->maxlen != 0);
Considering that StringInfo.c don't own the memory here I think it's warranted
to turn this assert into an elog() to avoid the risk of use-after-free bugs.

+ * The returned allocation is either static or owned by the JsonLexContext and
+ * should not be freed.
The most important part of that comment is at the very end, to help readers I
would reword this to just "The returned pointer should not be freed.", or at
least put that part first.

+#define token_error(lex, format) \
I'm not sure this buys much more than reduced LoC, the expansion isn't
unreadable to the point that the format constraint encoded in the macro is
worth it IMO.

--
Daniel Gustafsson