Re: improve CREATE EXTENSION error message

Daniel Gustafsson <daniel(at)yesql(dot)se> writes:
>> On 29 Nov 2021, at 22:47, Bossart, Nathan <bossartn(at)amazon(dot)com> wrote:
>> On 11/29/21, 1:38 PM, "Chapman Flack" <chap(at)anastigmatix(dot)net> wrote:
>>> Maybe a larger break with the "This means the extension something something"
>>> formulation, and more on the lines of
>>> HINT: an extension must first be present (for example, installed with a
>>> package manager) on the system where PostgreSQL is running.

>> I like this idea. I can do it this way in the next revision if others
>> agree.

> I think taking it in this direction has merits.

I think "The extension must ..." would read better, otherwise +1.

I don't especially like intertwining the hint choice with the existing
special case for per-version files. Our usual style for conditional
hints can be found in places like sysv_shmem.c, and following that
would lead to a patch roughly like

if ((file = AllocateFile(filename, "r")) == NULL)
{
+ int ext_errno = errno;
+
if (version && errno == ENOENT)
{
/* no auxiliary file for this version */
pfree(filename);
return;
}
ereport(ERROR,
(errcode_for_file_access(),
errmsg("could not open extension control file \"%s\": %m",
- filename)));
+ filename),
+ (ext_errno == ENOENT) ? errhint("...") : 0));
}

regards, tom lane