BUG FIX: Globals tied to a function environment would get decoupled f…

…rom the function for some future backends, including sequential and multicore [#608]

DESCRIPTION

@@ -1,5 +1,5 @@
 Package: future
-Version: 1.25.0-9010
+Version: 1.25.0-9011
 Title: Unified Parallel and Distributed Processing in R for Everyone
 Imports:
     digest,

NEWS

@@ -1,7 +1,7 @@
 Package: future
 ===============
 
-Version: 1.25.0-9010 [2022-05-06]
+Version: 1.25.0-9011 [2022-05-06]
 
 SIGNIFICANT CHANGES:
 
@@ -21,6 +21,15 @@ SIGNIFICANT CHANGES:
 
 BUG FIXES:
 
+ * Globals tied to a function environment would get decoupled from the
+   function for some future backends, including sequential and
+   multicore.  For example, with 'a' would be decoupled from g() in
+   g <- local({ a <- 0; function() a }). This would cause problems if
+   we also defined h <-local({ a <- 1; function() a }) and attempted a
+   future as future({ h() - g() }).  This future would incorrectly
+   resolve to value 0 for sequential and multicore futures, although
+   the value should be h() - g() = 1.
+
  * Use of data.table in cluster and multisession futures broke in
    future 1.25.0, resulting in errors such as "Error in
    setalloccol(ans) : verbose must be TRUE or FALSE". See above

R/utils.R

@@ -176,14 +176,19 @@ assign_globals <- function(envir, globals, exclude = getOption("future.assign_gl
       e <- environment(global)
       if (!inherits_from_namespace(e)) {
         w <- where[[name]]
-        ## FIXME: Can we remove this?
-        ## Here I'm just being overly conservative ## /HB 2021-06-15
-        if (identical(w, emptyenv())) {
+
+        ## If a global has 'where' %in% emptyenv() or globalenv(),
+        ## then it should be moved to the 'envir' environment.
+        ## Related to:
+        ## * https://github.com/HenrikBengtsson/future/issues/475
+        ## * https://github.com/HenrikBengtsson/future/issues/515
+        ## * https://github.com/HenrikBengtsson/future/issues/608
+        if (identical(w, emptyenv()) || identical(w, globalenv())) {
           environment(global) <- envir
+          where[[name]] <- envir
+          globals[[name]] <- global
           if (debug) {
             mdebugf("- reassign environment for %s", sQuote(name))
-            where[[name]] <- envir
-            globals[[name]] <- global
           }
         }
       }

tests/globals,S4methods.R

@@ -5,30 +5,37 @@ keepWhere <- getOption("future.globals.keepWhere")
 
 message("*** Globals - S4 methods ...")
 
-setGeneric("my_fcn", function(x) {
-    standardGeneric("my_fcn")
-})
+setGeneric("my_fcn", function(x) standardGeneric("my_fcn"))
 
-setMethod("my_fcn", methods::signature(x = "numeric"), function(x) {
-  x^2
-})
+setMethod("my_fcn", signature(x = "numeric"), function(x) { x^2 })
 
 truth <- my_fcn(3)
 
 for (strategy in supportedStrategies()) {
   message("Type of future: ", strategy)
   plan(strategy)
 
-  ## WORKAROUND: https://github.com/HenrikBengtsson/future/issues/615
-  ## Apply workaround if and only if 'future.globals.keepWhere' is not set
-  if (is.null(keepWhere) && strategy %in% c("sequential", "multicore")) {
-    options(future.globals.keepWhere = TRUE)
-  }
-
-  f <- future({ my_fcn(3) })
+  ## Assert that S4 generic function 'my_fcn()' is exported
+  f <- future({ my_fcn }, lazy = TRUE)
+  rm(list = "my_fcn")
   v <- value(f)
   print(v)
-  stopifnot(v == truth)
+  stopifnot(
+    is.function(v),
+    inherits(v, "nonstandardGenericFunction")
+  )
+  my_fcn <- v
+
+  ## FIXME:
+  ## Just like S3 methods, S4 methods are not picked up
+  ## https://github.com/HenrikBengtsson/future/issues/615
+  f <- future({ my_fcn(3) }, lazy = TRUE)
+  res <- tryCatch({
+    v <- value(f)
+  }, error = identity)
+  print(res)
+  stopifnot(inherits(res, "error"))
+  ## stopifnot(v == truth)
 
   ## Make sure to reset option, if changed
   options(future.globals.keepWhere = keepWhere)