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
Improving user-friendliness of S4 dispatch failure when mis-naming arguments?
7 messages · Hadley Wickham, Michael Chirico, Gabriel Becker +1 more
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 at 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
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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.wickham at 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 at 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
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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 at 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.wickham at 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 at 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]
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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 at signature, length(classes)), "=\"",
vapply(classes, as.character, ""), "\"",
collapse = ", ")
stop(gettextf("unable to find an inherited method for function %s
for signature %s",
sQuote(fdef at 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), but I
don't suppose a full patch would be dramatically different from the
above.
Mike C
On Thu, Aug 10, 2023 at 12:39?PM Gabriel Becker <gabembecker at 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 at 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.wickham at 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 at 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
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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 at signature, length(classes)), "=\"",
> vapply(classes, as.character, ""), "\"",
> collapse = ", ")
> stop(gettextf("unable to find an inherited method for function %s
> for signature %s",
> sQuote(fdef at 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 <gabembecker at 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 at 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.wickham at 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 at 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
I'm not entirely sure about the extra call. = FALSE
My thinking is the signature of the internal .InheritForDispatch() is not likely to help anyone, in fact having the opposite effect for beginners unsure how to use that info.
Now I'd like to find an example that only uses packages with priority base | Recommended
Sure, here are a few.
library(Matrix)
# searching for Matrix-owned generics
matrix_generics <- getGenerics(where = asNamespace("Matrix"))
matrix_generics at .Data[matrix_generics at package == "Matrix"]
# simple signature, one argument 'x'
symmpart()
# Error: unable to find an inherited method for function ?symmpart?
for signature ?x="missing"?
# more complicated signature, especially including ...
Cholesky(a = 1)
# Error: unable to find an inherited method for function ?Cholesky?
for signature ?A="missing"?
Cholesky(a = 1, perm = TRUE)
# Error: unable to find an inherited method for function ?Cholesky?
for signature ?A="missing"?
Cholesky(a = 1, perm = TRUE, IMult = 2)
# Error: unable to find an inherited method for function ?Cholesky?
for signature ?A="missing"?
---
'base' is a bit harder since stats4 just provides classes over stats
functions, so the missigness error comes from non-S4 code.
library(stats4)
coef()
# Error in coef.default() : argument "object" is missing, with no default
Defining our own generic:
setGeneric("BaseGeneric", \(a, ...) standardGeneric("BaseGeneric"))
BaseGeneric()
# Error: unable to find an inherited method for function ?BaseGeneric?
for signature ?a="missing"?
# getting multiple classes to show up requires setting the signature:
setMethod("BaseGeneric", signature(x = "double", y = "double"), \(x,
y, ...) x + y)
BaseGeneric(X = 1, Y = 2)
# Error: unable to find an inherited method for function ?BaseGeneric?
for signature ?x="missing", y="missing"?
On Fri, Aug 11, 2023 at 2:26?AM Martin Maechler
<maechler at stat.math.ethz.ch> wrote:
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 at signature, length(classes)), "=\"",
> vapply(classes, as.character, ""), "\"",
> collapse = ", ")
> stop(gettextf("unable to find an inherited method for function %s
> for signature %s",
> sQuote(fdef at 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 <gabembecker at 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 at 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.wickham at 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 at 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