>>>>> Michael Chirico via R-devel
>>>>> on Thu, 10 Aug 2023 23:56:45 -0700 writes:
> Here's a trivial patch that offers some improvement:
> Index: src/library/methods/R/methodsTable.R
> ===================================================================
> --- src/library/methods/R/methodsTable.R (revision 84931)
> +++ src/library/methods/R/methodsTable.R (working copy)
> @@ -752,11 +752,12 @@
> if(length(methods) == 1L)
> return(methods[[1L]]) # the method
> else if(length(methods) == 0L) {
> - cnames <- paste0("\"", vapply(classes, as.character, ""), "\"",
> + cnames <- paste0(head(fdef@signature, length(classes)), "=\"",
> vapply(classes, as.character, ""), "\"",
> collapse = ", ")
> stop(gettextf("unable to find an inherited method for function %s
> for signature %s",
> sQuote(fdef@generic),
> sQuote(cnames)),
> + call. = FALSE,
> domain = NA)
> }
> else
> Here's the upshot for the example on DBI:
> dbGetQuery(connection = conn, query = query)
> Error: unable to find an inherited method for function ‘dbGetQuery’
> for signature ‘conn="missing", statement="missing"’
> I don't have any confidence about edge cases / robustness of this
> patch for generic S4 use cases (make check-all seems fine),
Good you checked, but you are right that that's not all enough to be sure:
Checking error *messages* is not something we do often {not
the least because you'd need to consider message translations
and hence ensure you only check in case of English ...}.
> but I don't suppose a full patch would be dramatically different from the
> above.
I agree: The patch looks to make sense to me, too,
while I'm not entirely sure about the extra call. = FALSE
(which I of course understand you'd prefer for the above example)
Now I'd like to find an example that only uses packages with priority
base | Recommended
Martin
--
Martin Maechler
ETH Zurich and R Core team
> Mike C
> On Thu, Aug 10, 2023 at 12:39 PM Gabriel Becker <gabembec...@gmail.com>
wrote:
>>
>> I just want to add my 2 cents that I think it would be very useful and
beneficial to improve S4 to surface that information as well.
>>
>> More information about the way that the dispatch failed would be of
great help in situations like the one Michael pointed out.
>>
>> ~G
>>
>> On Thu, Aug 10, 2023 at 9:59 AM Michael Chirico via R-devel
<r-devel@r-project.org> wrote:
>>>
>>> I forwarded that along to the original reporter with positive feedback
>>> -- including the argument names is definitely a big help for cuing
>>> what exactly is missing.
>>>
>>> Would a patch to do something similar for S4 be useful?
>>>
>>> On Thu, Aug 10, 2023 at 6:46 AM Hadley Wickham <h.wick...@gmail.com>
wrote:
>>> >
>>> > Hi Michael,
>>> >
>>> > I can't help with S4, but I can help to make sure this isn't a problem
>>> > with S7. What do you think of the current error message? Do you see
>>> > anything obvious we could do to improve?
>>> >
>>> > library(S7)
>>> >
>>> > dbGetQuery <- new_generic("dbGetQuery", c("conn", "statement"))
>>> > dbGetQuery(connection = NULL, query = NULL)
>>> > #> Error: Can't find method for generic `dbGetQuery(conn, statement)`:
>>> > #> - conn : MISSING
>>> > #> - statement: MISSING
>>> >
>>> > Hadley
>>> >
>>> > On Wed, Aug 9, 2023 at 10:02 PM Michael Chirico via R-devel
>>> > <r-devel@r-project.org> wrote:
>>> > >
>>> > > I fielded a debugging request from a non-expert user today. At root
>>> > > was running the following:
>>> > >
>>> > > dbGetQuery(connection = conn, query = query)
>>> > >
>>> > > The problem is that they've named the arguments incorrectly -- it
>>> > > should have been [1]:
>>> > >
>>> > > dbGetQuery(conn = conn, statement = query)
>>> > >
>>> > > The problem is that the error message "looks" highly confusing to
the
>>> > > untrained eye:
>>> > >
>>> > > Error in (function (classes, fdef, mtable) : unable to find an
>>> > > inherited method for function ‘dbGetQuery’ for signature ‘"missing",
>>> > > "missing"’
>>> > >
>>> > > In retrospect, of course, this makes sense -- the mis-named
arguments
>>> > > are getting picked up by '...', leaving the required arguments
>>> > > missing.
>>> > >
>>> > > But I was left wondering how we could help users right their own
ship here.
>>> > >
>>> > > Would it help to mention the argument names? To include some code
>>> > > checking for weird combinations of missing arguments? Any other
>>> > > suggestions?
>>> > >
>>> > > Mike C
>>> > >
>>> > > [1]
https://github.com/r-dbi/DBI/blob/97934c885749dd87a6beb10e8ccb6a5ebea3675e/R/dbGetQuery.R#L62-L64
______________________________________________
R-devel@r-project.org mailing list
https://stat.ethz.ch/mailman/listinfo/r-devel
