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Kevin Ushey

2016-Oct-24 17:51 UTC

[Rd] improve 'package not installed' load errors?

Hi R-devel,

One of the more common issues that new R users see, and become stumped
by, is error messages during package load of the form:
> library(ggplot2)Error in loadNamespace(j <- i[[1L]], c(lib.loc, .libPaths()),
versionCheck = vI[[j]]) :
  there is no package called 'Rcpp'
Error: package or namespace load failed for 'ggplot2'

Typically, error messages of this form are caused simply by one or
more dependent packages (in this case, 'Rcpp') not being installed or
available on the current library paths. (A side question, which I do
not know the answer to, is how users get themselves into this state.)

I believe it would be helpful for new users if the error message
reported here was a bit more direct, e.g.
> library(ggplot2)Error: 'ggplot2' depends on package 'Rcpp', but 'Rcpp'
is not installed
consider installing 'Rcpp' with install.packages("Rcpp")

In other words, it might be helpful to avoid printing the
'loadNamespace()' call on error (since it's mostly just scary /
uninformative), and check up-front that the package is installed
before attempting to call 'loadNamespace()'. I'm sure a number of
novice users will still just throw their hands up in the air and say
"I don't know what to do", but I think this would help steer a
number
of users in the right direction.

(The prescription to suggest installing a package from CRAN if
available might be a step too far, but I think making it more clear
that the error is due to a missing dependent package would help.)

Any thoughts?
Kevin

Fox, John

2016-Oct-24 18:19 UTC

head link

[Rd] improve 'package not installed' load errors?

Dear Kevin,

As others have mentioned, it's my sense that this kind of error has become
more frequent -- at least I see students who encounter these errors more
frequently. I agree that a less cryptic error message might help.

Best,
 John
--------------------------------------
John Fox, Professor
McMaster University
Hamilton, Ontario, Canada
Web: socserv.mcmaster.ca/jfox


> -----Original Message-----
> From: R-devel [mailto:r-devel-bounces at r-project.org] On Behalf Of Kevin
> Ushey
> Sent: Monday, October 24, 2016 1:51 PM
> To: R-devel <r-devel at r-project.org>
> Subject: [Rd] improve 'package not installed' load errors?
> 
> Hi R-devel,
> 
> One of the more common issues that new R users see, and become stumped
> by, is error messages during package load of the form:
> 
> > library(ggplot2)
> Error in loadNamespace(j <- i[[1L]], c(lib.loc, .libPaths()),
> versionCheck = vI[[j]]) :
>   there is no package called 'Rcpp'
> Error: package or namespace load failed for 'ggplot2'
> 
> Typically, error messages of this form are caused simply by one or more
> dependent packages (in this case, 'Rcpp') not being installed or
> available on the current library paths. (A side question, which I do not
> know the answer to, is how users get themselves into this state.)
> 
> I believe it would be helpful for new users if the error message
> reported here was a bit more direct, e.g.
> 
> > library(ggplot2)
> Error: 'ggplot2' depends on package 'Rcpp', but
'Rcpp' is not installed
> consider installing 'Rcpp' with install.packages("Rcpp")
> 
> In other words, it might be helpful to avoid printing the
> 'loadNamespace()' call on error (since it's mostly just scary /
> uninformative), and check up-front that the package is installed before
> attempting to call 'loadNamespace()'. I'm sure a number of
novice users
> will still just throw their hands up in the air and say "I don't
know
> what to do", but I think this would help steer a number of users in
the
> right direction.
> 
> (The prescription to suggest installing a package from CRAN if available
> might be a step too far, but I think making it more clear that the error
> is due to a missing dependent package would help.)
> 
> Any thoughts?
> Kevin
> 
> ______________________________________________
> R-devel at r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-devel

Duncan Murdoch

2016-Oct-24 18:54 UTC

head link

[Rd] improve 'package not installed' load errors?

On 24/10/2016 1:51 PM, Kevin Ushey wrote:> Hi R-devel,
>
> One of the more common issues that new R users see, and become stumped
> by, is error messages during package load of the form:
>
> > library(ggplot2)
> Error in loadNamespace(j <- i[[1L]], c(lib.loc, .libPaths()),
> versionCheck = vI[[j]]) :
>    there is no package called 'Rcpp'
> Error: package or namespace load failed for 'ggplot2'
>
> Typically, error messages of this form are caused simply by one or
> more dependent packages (in this case, 'Rcpp') not being installed
or
> available on the current library paths. (A side question, which I do
> not know the answer to, is how users get themselves into this state.)
I think one way to get here is to be running with several libraries.  
You install ggplot2 while Rcpp is available, but in a different part of 
the .libPaths list, then in a later session try to use it with a 
different .libPaths setting.>
> I believe it would be helpful for new users if the error message
> reported here was a bit more direct, e.g.
>
> > library(ggplot2)
> Error: 'ggplot2' depends on package 'Rcpp', but
'Rcpp' is not installed
> consider installing 'Rcpp' with install.packages("Rcpp")
The risk with this message is that Rcpp may really be installed, but 
it's just not currently on .libPaths.  Detecting that situation and 
reporting on it looks like it would be relatively hard:  it would mean 
the ggplot2 installation needs to record where it found all 
dependencies, and if at some later time it doesn't find one, see if that 
location still exists and would still work (in which case the message 
should suggest modifying .libPaths).  I think that's too much work.

Even a simple change like

Error: 'ggplot2' depends on package 'Rcpp', but 'Rcpp'
was not found


might not be easy (which function knows both names?)  However, if you 
want to suggest a patch to implement this, I would take a look.

Duncan Murdoch
>
> In other words, it might be helpful to avoid printing the
> 'loadNamespace()' call on error (since it's mostly just scary /
> uninformative), and check up-front that the package is installed
> before attempting to call 'loadNamespace()'. I'm sure a number
of
> novice users will still just throw their hands up in the air and say
> "I don't know what to do", but I think this would help steer
a number
> of users in the right direction.
>
> (The prescription to suggest installing a package from CRAN if
> available might be a step too far, but I think making it more clear
> that the error is due to a missing dependent package would help.)
>
> Any thoughts?
> Kevin
>
> ______________________________________________
> R-devel at r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-devel

Martin Maechler

2016-Oct-26 09:52 UTC

head link

[Rd] improve 'package not installed' load errors?

>>>>> Duncan Murdoch <murdoch.duncan at gmail.com>
>>>>>     on Mon, 24 Oct 2016 14:54:16 -0400 writes:
    > On 24/10/2016 1:51 PM, Kevin Ushey wrote:
    >> Hi R-devel,
    >> 
    >> One of the more common issues that new R users see, and become
stumped
    >> by, is error messages during package load of the form:
    >> 
    >> > library(ggplot2)
    >> Error in loadNamespace(j <- i[[1L]], c(lib.loc, .libPaths()),
    >> versionCheck = vI[[j]]) :
    >> there is no package called 'Rcpp'
    >> Error: package or namespace load failed for 'ggplot2'
    >> 
    >> Typically, error messages of this form are caused simply by one or
    >> more dependent packages (in this case, 'Rcpp') not being
installed or
    >> available on the current library paths. (A side question, which I
do
    >> not know the answer to, is how users get themselves into this
state.)

    > I think one way to get here is to be running with several libraries.  
    > You install ggplot2 while Rcpp is available, but in a different part of
    > the .libPaths list, then in a later session try to use it with a 
    > different .libPaths setting.
    >> 
    >> I believe it would be helpful for new users if the error message
    >> reported here was a bit more direct, e.g.
    >> 
    >> > library(ggplot2)
    >> Error: 'ggplot2' depends on package 'Rcpp', but
'Rcpp' is not installed
    >> consider installing 'Rcpp' with
install.packages("Rcpp")

    > The risk with this message is that Rcpp may really be installed, but 
    > it's just not currently on .libPaths.  Detecting that situation and
    > reporting on it looks like it would be relatively hard:  it would mean 
    > the ggplot2 installation needs to record where it found all 
    > dependencies, and if at some later time it doesn't find one, see if
that
    > location still exists and would still work (in which case the message 
    > should suggest modifying .libPaths).  I think that's too much work.

    > Even a simple change like

    > Error: 'ggplot2' depends on package 'Rcpp', but
'Rcpp' was not found


    > might not be easy (which function knows both names?)  

    > However, if you want to suggest a patch to implement this,
    > I would take a look. 

I woul want to take a look, even before that. Our current error
handling here should be revised, I think : 

For library() the user sees *two* error messages: In my "setup"
((where I did fiddle with .libPaths() to provoke the error,
  exactly as Duncan mentioned)), I have
>> > library(ggplot2)
1. >> Error in loadNamespace(i, c(lib.loc, .libPaths()), versionCheck =
vI[[i]]) : >>   there is no package called ?gtable?
2. >> Error: package or namespace load failed for ?ggplot2?

and together they at least give a good clue to the user (yes,
not easy enough for the beginner, I agree).

However, because the above is already a kludge (only one of the
two error messages is part of the error that is signalled !!!),
the situation is even worse if the user (or her code) uses require():
>> > require(ggplot2)
>> Loading required package: ggplot2
>> Error in loadNamespace(i, c(lib.loc, .libPaths()), versionCheck =
vI[[i]]) :
>>   there is no package called ?gtable?
>> > 
Only the 2nd of  library()'s "Error" messages is transfered to
require()
[or any other caller of library() !]
and that is in itself very unsatisfactory.


    >> In other words, it might be helpful to avoid printing the
    >> 'loadNamespace()' call on error (since it's mostly just
scary /
    >> uninformative), and check up-front that the package is installed
    >> before attempting to call 'loadNamespace()'.

well, yes, one should not use try() there, but tryCatch() anyway :
try() is a wrapper around tryCatch() and I agree the error
message should not be printed which try() *does* by default, but
should be *combined* with the "2nd one" to one error.. which
then also is automatically "transfered" to require() or another
caller.

There is a small problem for producing a really nice error
message : It is *wrong* to assume we can easily use  sub() or
similar to get the dependecy package name ('gtable' or 'Rcpp' in
the above examples) from the error message :

The error message may be and often is translated {{apart from the
 "Error in " of the first error message which is  never
 translated, it seems, but that is different issue(buglet) }} :

a) French:
> Sys.setenv("LANGUAGE"="fr");
Sys.setlocale("LC_MESSAGES", "fr_FR.UTF-8")
> library(ggplot2)Error in loadNamespace(i, c(lib.loc, .libPaths()), versionCheck = vI[[i]]) : 
  aucun package nomm? ?gtable? n'est trouv?
Erreur : le chargement du package ou de l'espace de noms a ?chou? pour
?ggplot2?

b) German:
> Sys.setenv("LANGUAGE"="de");
Sys.setlocale("LC_MESSAGES", "de_CH.UTF-8")
[1] "de_CH.UTF-8"> library(ggplot2)Error in loadNamespace(i, c(lib.loc, .libPaths()), versionCheck = vI[[i]]) : 
  es gibt kein Paket namens ?gtable?
Fehler: Laden von Paket oder Namensraum f?r ?ggplot2?
fehlgeschlagen> 
c) Japanase :
> Sys.setenv("LANGUAGE"="ja");
Sys.setlocale("LC_MESSAGES", "ja_JP.UTF-8")
[1] "ja_JP.UTF-8"> library(ggplot2)Error in loadNamespace(i, c(lib.loc, .libPaths()), versionCheck = vI[[i]]) : 
   ?gtable? ????????????????? 
 ???:  ?ggplot2? ???????????????????????????? > 
We could try to look for the sQuote(.)'d package name
independently of the translation of the error message and use
that in the "merged" error message.


Martin


    >>  I'm sure a number of
    >> novice users will still just throw their hands up in the air and
say
    >> "I don't know what to do", but I think this would
help steer a number
    >> of users in the right direction.
    >> 
    >> (The prescription to suggest installing a package from CRAN if
    >> available might be a step too far, but I think making it more clear
    >> that the error is due to a missing dependent package would help.)
    >> 
    >> Any thoughts?
    >> Kevin

Richard Cotton

2016-Oct-27 08:03 UTC

head link

[Rd] improve 'package not installed' load errors?

> A side question, which I do not know the answer to, is how users get
themselves into this state.
I've fallen over this a few times.  It happens when you have multiple
R sessions running, and R tries to update Rcpp while it is loaded in
the other session.

For example, I'm working on one project, then I open another copy of R
to work on a different project.  Because I have update.packages in my
Rprofile, R occasionally tries to update Rcpp.  If that is loaded in
the first session, then a clean uninstall doesn't happen (the
directory and the dll are left).  Since the directory is still there,
update.packages thinks that the package exists, and I'm left with a
mangled copy of Rcpp that I need to manually remove.

On 24 October 2016 at 20:51, Kevin Ushey <kevinushey at gmail.com>
wrote:> Hi R-devel,
>
> One of the more common issues that new R users see, and become stumped
> by, is error messages during package load of the form:
>
>> library(ggplot2)
> Error in loadNamespace(j <- i[[1L]], c(lib.loc, .libPaths()),
> versionCheck = vI[[j]]) :
>   there is no package called 'Rcpp'
> Error: package or namespace load failed for 'ggplot2'
>
> Typically, error messages of this form are caused simply by one or
> more dependent packages (in this case, 'Rcpp') not being installed
or
> available on the current library paths. (A side question, which I do
> not know the answer to, is how users get themselves into this state.)
>
> I believe it would be helpful for new users if the error message
> reported here was a bit more direct, e.g.
>
>> library(ggplot2)
> Error: 'ggplot2' depends on package 'Rcpp', but
'Rcpp' is not installed
> consider installing 'Rcpp' with install.packages("Rcpp")
>
> In other words, it might be helpful to avoid printing the
> 'loadNamespace()' call on error (since it's mostly just scary /
> uninformative), and check up-front that the package is installed
> before attempting to call 'loadNamespace()'. I'm sure a number
of
> novice users will still just throw their hands up in the air and say
> "I don't know what to do", but I think this would help steer
a number
> of users in the right direction.
>
> (The prescription to suggest installing a package from CRAN if
> available might be a step too far, but I think making it more clear
> that the error is due to a missing dependent package would help.)
>
> Any thoughts?
> Kevin
>
> ______________________________________________
> R-devel at r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-devel


-- 
Regards,
Richie

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