Duncan Murdoch
2021-Jun-30 12:16 UTC
[Rd] S3 dispatch does not work for generics defined inside an environment
On 30/06/2021 7:37 a.m., Taras Zakharko wrote:> Thats not how I read the code? Consider this snippet from registerS3method: > > genfun <- get(genname, envir = envir) > if (.isMethodsDispatchOn() && methods::is(genfun, "genericFunction")) > genfun <- methods::finalDefaultMethod(genfun at default) > if (typeof(genfun) == "closure") > environment(genfun) > else .BaseNamespaceEnv > > This is the environment where the method cache (.__S3MethodsTable__.) will be updated. The problem hoverer, the with the default setting of _R_S3_METHOD_LOOKUP_USE_TOPENV_AS_DEFENV_ this is *not* the environment where R will look for the method cache. Manually injecting the entry into the method cache of the top environment instead works like a charm. > > The envir argument is just for looking up the generic function.Yes, I think you're right: the method is registered in the environment of the generic. I think by default it is searched for in the topenv() of that environment. In most cases those are the same thing, but in your code they aren't the same: the topenv is the global environment. So I think I'd agree this is a bug. I'd say the bug is in registerS3method, which should pay attention to the _R_S3_METHOD_LOOKUP_USE_TOPENV_AS_DEFENV_ setting when it computes defenv. Here's a workaround that copies methods to the appropriate place: fixS3registrations <- function(genericname, envir = parent.frame()) { generic <- get(genericname, envir=envir) genenv <- environment(generic) top <- topenv(genenv) if (!identical(genenv, top)) { toptable <- top[[".__S3MethodsTable__."]] if (is.null(toptable)) { toptable <- new.env(hash = TRUE, parent = baseenv()) top[[".__S3MethodsTable__."]] <- toptable } table <- genenv[[".__S3MethodsTable__."]] if (!is.null(table)) { methodnames <- ls(table, pattern = paste0(genericname, "[.][^.]*$")) for (m in methodnames) toptable[[m]] <- table[[m]] } } } env <- local({ # define the generic function and the method myfun <- function(x) UseMethod("myfun") myfun.myclass <- function(x) print("called myfun.myclass") # register the method .S3method("myfun", "myclass", myfun.myclass) fixS3registrations("myfun") environment() }) env$myfun(structure(0, class = "myclass")) #> [1] "called myfun.myclass" Duncan Murdoch> > Best, > > Taras > > > >> On 30 Jun 2021, at 13:29, Duncan Murdoch <murdoch.duncan at gmail.com> wrote: >> >> On 30/06/2021 7:23 a.m., Taras Zakharko wrote: >>> I had another glance at the code and now I?m convinced that this is the bug in registerS3method(). Default R behavior (in objects.c) appears to be to look for method definitions in the top environment, not the defining environment, but registerS3method() registers the method in the defining environment. I think registerS3method() should be changed to something like: >> >> It registers wherever you ask it to. The default is the defining environment. >> >> .S3method is the one that always uses the defining environment, since it has no way to override the default. >> >> Duncan Murdoch >> >>> - if (typeof(genfun) == "closure?) >>> - environment(genfun) >>> ------------ >>> + if (typeof(genfun) == "closure?) >>> + if(isFALSE(Sys.getenv("_R_S3_METHOD_LOOKUP_USE_TOPENV_AS_DEFENV_?)) environment(genfun) else topenv(environment(genfun)) >>> in order to match the behavior of do_usemethod() >>> Best, >>> Taras >>>> On 30 Jun 2021, at 12:51, Taras Zakharko <taras.zakharko at uzh.ch> wrote: >>>> >>>> @Duncan: .S3method() calls registerS3method() with appropriate environmental argument under the good, so that?s not the problem. >>>> >>>> Anyway, I?ve been doing some debugging and I think I have found the issue. The following snippet in src/objects.c (https://github.com/wch/r-source/blob/ecc633b37d77fdd1cb27dda74d7f6b3684f0c01c/src/main/objects.c#L525) sets the global lookup_use_topenv_as_defenv variable: >>>> >>>> >>>> if(lookup_use_topenv_as_defenv == -1) { >>>> lookup = getenv("_R_S3_METHOD_LOOKUP_USE_TOPENV_AS_DEFENV_"); >>>> lookup_use_topenv_as_defenv >>>> ((lookup != NULL) && StringFalse(lookup)) ? 0 : 1; >>>> } >>>> >>>> Isn?t that supposed to be >>>> >>>> lookup_use_topenv_as_defenv = ((lookup != NULL) && StringFalse(lookup)) ? 1 : 0; >>>> >>>> instead? >>>> >>>> The way the code works right now, methods will be looked up in top environment exactly if _R_S3_METHOD_LOOKUP_USE_TOPENV_AS_DEFENV_ is not set. This seems incompatible with what registerS3method() does (setting the .__S3MethodsTable__. on the defining environment instead of the topenv). When I change 0 and 1 around, everything works as expected. >>>> >>>> In the meantime, I can work around it by manually injecting __S3MethodsTable__ into .GlobalEnv (which is my topenv here). >>>> >>>> I can open a bug report, but I would like to wait for some more comments. >>>> >>>> Best, >>>> >>>> Taras >>>> >>>>> On 30 Jun 2021, at 12:39, Joshua Ulrich <josh.m.ulrich at gmail.com> wrote: >>>>> >>>>> On Wed, Jun 30, 2021 at 5:17 AM Duncan Murdoch <murdoch.duncan at gmail.com> wrote: >>>>>> >>>>>> On 30/06/2021 5:22 a.m., Taras Zakharko wrote: >>>>>>> Dear all, >>>>>>> >>>>>>> I have a generic function and a bunch of methods defined in a separate environment. Here is a reduced example: >>>>>>> >>>>>>> env <- local({ >>>>>>> # define the generic function and the method >>>>>>> myfun <- function(x) UseMethod("myfun") >>>>>>> myfun.myclass <- function(x) print("called myfun.myclass?) >>>>>>> >>>>>>> # register the method >>>>>>> .S3method("myfun", "myclass", myfun.myclass) >>>>>>> >>>>>>> environment() >>>>>>> }) >>>>>>> >>>>>>> Since the method has been registered, I hoped that invocation like this would work: >>>>>>> >>>>>>> env$myfun(structure(0, class = "myclass?)) >>>>>>> >>>>>>> However, this results in a ?no applicable method" error. >>>>>>> >>>>>>> It is my understanding that registerS3method (called by .S3method) will install the method string in the .__S3MethodsTable__. table of the environment where the generic function is defined, and this table is subsequently used by usemethod() inside R, so I am puzzled that the dispatch does not work. I checked and the .__S3MethodsTable__. of env is indeed setup correctly. I also tried manually adding the method string to the global .__S3MethodsTable__. inside .BaseNamespaceEnv to no effect. >>>>>>> >>>>>>> In fact, the only way to make it work is to define either myfun or myfun.myclas in the global environment, which is something I would like to avoid. >>>>>>> >>>>>>> Thank you in advance for any pointers! >>>>>>> >>>>>> >>>>>> registerS3method has an additional parameter "envir" which I believe >>>>>> would end up set to env in your code. So this works: >>>>>> >>>>>>> eval(expression(myfun(structure(0, class = "myclass"))), envir = env) >>>>>> [1] "called myfun.myclass" >>>>>> >>>>>> You could probably also call registerS3method with envir specified >>>>>> appropriately and get your original expression to work. >>>>>> >>>>> That doesn't seem to work on 4.1.0 for me. The code below worked for >>>>> me in Oct-2020, though I'm not sure what version of R I was using at >>>>> the time. I was slow to upgrade to 4.0, so it was probably the latest >>>>> 3.x version. >>>>> >>>>> env <- new.env() >>>>> local({ >>>>> # define the generic function and the method >>>>> myfun <- function(x) { UseMethod("myfun", x) } >>>>> >>>>> # register the method >>>>> registerS3method("myfun", "myclass", >>>>> function(x) { print("called myfun.myclass") }, >>>>> envir = env) >>>>> }, envir = env) >>>>> attach(env) >>>>> myfun(structure(0, class = "myclass")) >>>>> >>>>> >>>>>> Duncan Murdoch >>>>>> >>>>>> ______________________________________________ >>>>>> R-devel at r-project.org mailing list >>>>>> https://stat.ethz.ch/mailman/listinfo/r-devel >>>>> >>>>> >>>>> >>>>> -- >>>>> Joshua Ulrich | about.me/joshuaulrich >>>>> FOSS Trading | www.fosstrading.com >>>> >>> ______________________________________________ >>> R-devel at r-project.org mailing list >>> https://stat.ethz.ch/mailman/listinfo/r-devel >
Taras Zakharko
2021-Jun-30 13:20 UTC
[Rd] S3 dispatch does not work for generics defined inside an environment
Thanks Duncan, I will submit a bug report to R core then. Best, Taras> On 30 Jun 2021, at 14:16, Duncan Murdoch <murdoch.duncan at gmail.com> wrote: > > On 30/06/2021 7:37 a.m., Taras Zakharko wrote: >> Thats not how I read the code? Consider this snippet from registerS3method: >> genfun <- get(genname, envir = envir) >> if (.isMethodsDispatchOn() && methods::is(genfun, "genericFunction")) >> genfun <- methods::finalDefaultMethod(genfun at default) >> if (typeof(genfun) == "closure") >> environment(genfun) >> else .BaseNamespaceEnv >> This is the environment where the method cache (.__S3MethodsTable__.) will be updated. The problem hoverer, the with the default setting of _R_S3_METHOD_LOOKUP_USE_TOPENV_AS_DEFENV_ this is *not* the environment where R will look for the method cache. Manually injecting the entry into the method cache of the top environment instead works like a charm. >> The envir argument is just for looking up the generic function. > > Yes, I think you're right: the method is registered in the environment of the generic. I think by default it is searched for in the topenv() of that environment. > > In most cases those are the same thing, but in your code they aren't the same: the topenv is the global environment. > > So I think I'd agree this is a bug. I'd say the bug is in registerS3method, which should pay attention to the _R_S3_METHOD_LOOKUP_USE_TOPENV_AS_DEFENV_ setting when it computes defenv. > > Here's a workaround that copies methods to the appropriate place: > > fixS3registrations <- function(genericname, envir = parent.frame()) { > generic <- get(genericname, envir=envir) > genenv <- environment(generic) > top <- topenv(genenv) > > if (!identical(genenv, top)) { > toptable <- top[[".__S3MethodsTable__."]] > if (is.null(toptable)) { > toptable <- new.env(hash = TRUE, parent = baseenv()) > top[[".__S3MethodsTable__."]] <- toptable > } > table <- genenv[[".__S3MethodsTable__."]] > if (!is.null(table)) { > methodnames <- ls(table, pattern = paste0(genericname, "[.][^.]*$")) > for (m in methodnames) > toptable[[m]] <- table[[m]] > } > } > } > > env <- local({ > # define the generic function and the method > myfun <- function(x) UseMethod("myfun") > myfun.myclass <- function(x) print("called myfun.myclass") > > # register the method > .S3method("myfun", "myclass", myfun.myclass) > fixS3registrations("myfun") > > environment() > }) > > env$myfun(structure(0, class = "myclass")) > #> [1] "called myfun.myclass" > > > Duncan Murdoch > >> Best, >> Taras >>> On 30 Jun 2021, at 13:29, Duncan Murdoch <murdoch.duncan at gmail.com> wrote: >>> >>> On 30/06/2021 7:23 a.m., Taras Zakharko wrote: >>>> I had another glance at the code and now I?m convinced that this is the bug in registerS3method(). Default R behavior (in objects.c) appears to be to look for method definitions in the top environment, not the defining environment, but registerS3method() registers the method in the defining environment. I think registerS3method() should be changed to something like: >>> >>> It registers wherever you ask it to. The default is the defining environment. >>> >>> .S3method is the one that always uses the defining environment, since it has no way to override the default. >>> >>> Duncan Murdoch >>> >>>> - if (typeof(genfun) == "closure?) >>>> - environment(genfun) >>>> ------------ >>>> + if (typeof(genfun) == "closure?) >>>> + if(isFALSE(Sys.getenv("_R_S3_METHOD_LOOKUP_USE_TOPENV_AS_DEFENV_?)) environment(genfun) else topenv(environment(genfun)) >>>> in order to match the behavior of do_usemethod() >>>> Best, >>>> Taras >>>>> On 30 Jun 2021, at 12:51, Taras Zakharko <taras.zakharko at uzh.ch> wrote: >>>>> >>>>> @Duncan: .S3method() calls registerS3method() with appropriate environmental argument under the good, so that?s not the problem. >>>>> >>>>> Anyway, I?ve been doing some debugging and I think I have found the issue. The following snippet in src/objects.c (https://github.com/wch/r-source/blob/ecc633b37d77fdd1cb27dda74d7f6b3684f0c01c/src/main/objects.c#L525) sets the global lookup_use_topenv_as_defenv variable: >>>>> >>>>> >>>>> if(lookup_use_topenv_as_defenv == -1) { >>>>> lookup = getenv("_R_S3_METHOD_LOOKUP_USE_TOPENV_AS_DEFENV_"); >>>>> lookup_use_topenv_as_defenv >>>>> ((lookup != NULL) && StringFalse(lookup)) ? 0 : 1; >>>>> } >>>>> >>>>> Isn?t that supposed to be >>>>> >>>>> lookup_use_topenv_as_defenv = ((lookup != NULL) && StringFalse(lookup)) ? 1 : 0; >>>>> >>>>> instead? >>>>> >>>>> The way the code works right now, methods will be looked up in top environment exactly if _R_S3_METHOD_LOOKUP_USE_TOPENV_AS_DEFENV_ is not set. This seems incompatible with what registerS3method() does (setting the .__S3MethodsTable__. on the defining environment instead of the topenv). When I change 0 and 1 around, everything works as expected. >>>>> >>>>> In the meantime, I can work around it by manually injecting __S3MethodsTable__ into .GlobalEnv (which is my topenv here). >>>>> >>>>> I can open a bug report, but I would like to wait for some more comments. >>>>> >>>>> Best, >>>>> >>>>> Taras >>>>> >>>>>> On 30 Jun 2021, at 12:39, Joshua Ulrich <josh.m.ulrich at gmail.com> wrote: >>>>>> >>>>>> On Wed, Jun 30, 2021 at 5:17 AM Duncan Murdoch <murdoch.duncan at gmail.com> wrote: >>>>>>> >>>>>>> On 30/06/2021 5:22 a.m., Taras Zakharko wrote: >>>>>>>> Dear all, >>>>>>>> >>>>>>>> I have a generic function and a bunch of methods defined in a separate environment. Here is a reduced example: >>>>>>>> >>>>>>>> env <- local({ >>>>>>>> # define the generic function and the method >>>>>>>> myfun <- function(x) UseMethod("myfun") >>>>>>>> myfun.myclass <- function(x) print("called myfun.myclass?) >>>>>>>> >>>>>>>> # register the method >>>>>>>> .S3method("myfun", "myclass", myfun.myclass) >>>>>>>> >>>>>>>> environment() >>>>>>>> }) >>>>>>>> >>>>>>>> Since the method has been registered, I hoped that invocation like this would work: >>>>>>>> >>>>>>>> env$myfun(structure(0, class = "myclass?)) >>>>>>>> >>>>>>>> However, this results in a ?no applicable method" error. >>>>>>>> >>>>>>>> It is my understanding that registerS3method (called by .S3method) will install the method string in the .__S3MethodsTable__. table of the environment where the generic function is defined, and this table is subsequently used by usemethod() inside R, so I am puzzled that the dispatch does not work. I checked and the .__S3MethodsTable__. of env is indeed setup correctly. I also tried manually adding the method string to the global .__S3MethodsTable__. inside .BaseNamespaceEnv to no effect. >>>>>>>> >>>>>>>> In fact, the only way to make it work is to define either myfun or myfun.myclas in the global environment, which is something I would like to avoid. >>>>>>>> >>>>>>>> Thank you in advance for any pointers! >>>>>>>> >>>>>>> >>>>>>> registerS3method has an additional parameter "envir" which I believe >>>>>>> would end up set to env in your code. So this works: >>>>>>> >>>>>>>> eval(expression(myfun(structure(0, class = "myclass"))), envir = env) >>>>>>> [1] "called myfun.myclass" >>>>>>> >>>>>>> You could probably also call registerS3method with envir specified >>>>>>> appropriately and get your original expression to work. >>>>>>> >>>>>> That doesn't seem to work on 4.1.0 for me. The code below worked for >>>>>> me in Oct-2020, though I'm not sure what version of R I was using at >>>>>> the time. I was slow to upgrade to 4.0, so it was probably the latest >>>>>> 3.x version. >>>>>> >>>>>> env <- new.env() >>>>>> local({ >>>>>> # define the generic function and the method >>>>>> myfun <- function(x) { UseMethod("myfun", x) } >>>>>> >>>>>> # register the method >>>>>> registerS3method("myfun", "myclass", >>>>>> function(x) { print("called myfun.myclass") }, >>>>>> envir = env) >>>>>> }, envir = env) >>>>>> attach(env) >>>>>> myfun(structure(0, class = "myclass")) >>>>>> >>>>>> >>>>>>> Duncan Murdoch >>>>>>> >>>>>>> ______________________________________________ >>>>>>> R-devel at r-project.org mailing list >>>>>>> https://stat.ethz.ch/mailman/listinfo/r-devel >>>>>> >>>>>> >>>>>> >>>>>> -- >>>>>> Joshua Ulrich | about.me/joshuaulrich >>>>>> FOSS Trading | www.fosstrading.com >>>>> >>>> ______________________________________________ >>>> R-devel at r-project.org mailing list >>>> https://stat.ethz.ch/mailman/listinfo/r-devel >