I'd like to propose that the whenever the length of condition passed to an if or a while statement differs from one, an error is produced rather than just a warning as today:
> x <- 1:2 > if (x == 1) message("x == 1") x == 1 Warning message: In if (x == 1) message("x == 1") : the condition has length > 1 and only the first element will be used There are probably legacy reasons for why this is accepted by R in the first place, but I cannot imagine than anyone wants to use an if/while statement this way on purpose. The warning about this misuse, was introduced in November 2002 (R-devel thread 'vector arguments to if()'; https://stat.ethz.ch/pipermail/r-devel/2002-November/025537.html). Below is patch (also attached) that introduces option 'check.condition' such that when TRUE, it will generate an error rather than a warning (default). This option allows for a smooth migration as it can be added to 'R CMD check --as-cran' and developers can give time to check and fix their packages. Eventually, check.condition=TRUE can become the new default. With options(check.condition = TRUE), one gets: > x <- 1:2 > if (x == 1) message("x == 1") Error in if (x == 1) message("x == 1") : the condition has length > 1 and > while (x < 2) message("x < 2") Error in while (x < 2) message("x < 2") : the condition has length > 1 Index: src/library/base/man/options.Rd =================================================================== --- src/library/base/man/options.Rd (revision 72298) +++ src/library/base/man/options.Rd (working copy) @@ -86,6 +86,11 @@ vector (atomic or \code{\link{list}}) is extended, by something like \code{x <- 1:3; x[5] <- 6}.} + \item{\code{check.condition}:}{logical, defaulting to \code{FALSE}. If + \code{TRUE}, an error is produced whenever the condition to an + \code{if} or a \code{while} control statement is of length greater + than one. If \code{FALSE}, a \link{warning} is produced.} + \item{\code{CBoundsCheck}:}{logical, controlling whether \code{\link{.C}} and \code{\link{.Fortran}} make copies to check for array over-runs on the atomic vector arguments. @@ -445,6 +450,7 @@ \tabular{ll}{ \code{add.smooth} \tab \code{TRUE}\cr \code{check.bounds} \tab \code{FALSE}\cr + \code{check.condition} \tab \code{FALSE}\cr \code{continue} \tab \code{"+ "}\cr \code{digits} \tab \code{7}\cr \code{echo} \tab \code{TRUE}\cr Index: src/library/utils/R/completion.R =================================================================== --- src/library/utils/R/completion.R (revision 72298) +++ src/library/utils/R/completion.R (working copy) @@ -1304,8 +1304,8 @@ "plt", "ps", "pty", "smo", "srt", "tck", "tcl", "usr", "xaxp", "xaxs", "xaxt", "xpd", "yaxp", "yaxs", "yaxt") - options <- c("add.smooth", "browser", "check.bounds", "continue", - "contrasts", "defaultPackages", "demo.ask", "device", + options <- c("add.smooth", "browser", "check.bounds", "check.condition", + "continue", "contrasts", "defaultPackages", "demo.ask", "device", "digits", "dvipscmd", "echo", "editor", "encoding", "example.ask", "expressions", "help.search.types", "help.try.all.packages", "htmlhelp", "HTTPUserAgent", Index: src/main/eval.c =================================================================== --- src/main/eval.c (revision 72298) +++ src/main/eval.c (working copy) @@ -1851,9 +1851,13 @@ Rboolean cond = NA_LOGICAL; if (length(s) > 1) { + int check = asInteger(GetOption1(install("check.condition"))); PROTECT(s); /* needed as per PR#15990. call gets protected by warningcall() */ - warningcall(call, - _("the condition has length > 1 and only the first element will be used")); + if(check != NA_INTEGER && check > 0) + errorcall(call, _("the condition has length > 1")); + else + warningcall(call, + _("the condition has length > 1 and only the first element will be used")); UNPROTECT(1); } if (length(s) > 0) { Index: src/main/options.c =================================================================== --- src/main/options.c (revision 72298) +++ src/main/options.c (working copy) @@ -65,6 +65,7 @@ * "timeout" ./connections.c * "check.bounds" + * "check.condition" * "error" * "error.messages" * "show.error.messages" @@ -248,9 +249,9 @@ char *p; #ifdef HAVE_RL_COMPLETION_MATCHES + PROTECT(v = val = allocList(22)); +#else PROTECT(v = val = allocList(21)); -#else - PROTECT(v = val = allocList(20)); #endif SET_TAG(v, install("prompt")); @@ -289,6 +290,10 @@ SETCAR(v, ScalarLogical(0)); /* no checking */ v = CDR(v); + SET_TAG(v, install("check.condition")); + SETCAR(v, ScalarLogical(0)); /* no checking */ + v = CDR(v); + p = getenv("R_KEEP_PKG_SOURCE"); R_KeepSource = (p && (strcmp(p, "yes") == 0)) ? 1 : 0; I'm happy to file this via https://bugs.r-project.org, if preferred. /Henrik
Index: src/library/base/man/options.Rd =================================================================== --- src/library/base/man/options.Rd (revision 72298) +++ src/library/base/man/options.Rd (working copy) @@ -86,6 +86,11 @@ vector (atomic or \code{\link{list}}) is extended, by something like \code{x <- 1:3; x[5] <- 6}.} + \item{\code{check.condition}:}{logical, defaulting to \code{FALSE}. If + \code{TRUE}, an error is produced whenever the condition to an + \code{if} or a \code{while} control statement is of length greater + than one. If \code{FALSE}, a \link{warning} is produced.} + \item{\code{CBoundsCheck}:}{logical, controlling whether \code{\link{.C}} and \code{\link{.Fortran}} make copies to check for array over-runs on the atomic vector arguments. @@ -445,6 +450,7 @@ \tabular{ll}{ \code{add.smooth} \tab \code{TRUE}\cr \code{check.bounds} \tab \code{FALSE}\cr + \code{check.condition} \tab \code{FALSE}\cr \code{continue} \tab \code{"+ "}\cr \code{digits} \tab \code{7}\cr \code{echo} \tab \code{TRUE}\cr Index: src/library/utils/R/completion.R =================================================================== --- src/library/utils/R/completion.R (revision 72298) +++ src/library/utils/R/completion.R (working copy) @@ -1304,8 +1304,8 @@ "plt", "ps", "pty", "smo", "srt", "tck", "tcl", "usr", "xaxp", "xaxs", "xaxt", "xpd", "yaxp", "yaxs", "yaxt") - options <- c("add.smooth", "browser", "check.bounds", "continue", - "contrasts", "defaultPackages", "demo.ask", "device", + options <- c("add.smooth", "browser", "check.bounds", "check.condition", + "continue", "contrasts", "defaultPackages", "demo.ask", "device", "digits", "dvipscmd", "echo", "editor", "encoding", "example.ask", "expressions", "help.search.types", "help.try.all.packages", "htmlhelp", "HTTPUserAgent", Index: src/main/eval.c =================================================================== --- src/main/eval.c (revision 72298) +++ src/main/eval.c (working copy) @@ -1851,9 +1851,13 @@ Rboolean cond = NA_LOGICAL; if (length(s) > 1) { + int check = asInteger(GetOption1(install("check.condition"))); PROTECT(s); /* needed as per PR#15990. call gets protected by warningcall() */ - warningcall(call, - _("the condition has length > 1 and only the first element will be used")); + if(check != NA_INTEGER && check > 0) + errorcall(call, _("the condition has length > 1")); + else + warningcall(call, + _("the condition has length > 1 and only the first element will be used")); UNPROTECT(1); } if (length(s) > 0) { Index: src/main/options.c =================================================================== --- src/main/options.c (revision 72298) +++ src/main/options.c (working copy) @@ -65,6 +65,7 @@ * "timeout" ./connections.c * "check.bounds" + * "check.condition" * "error" * "error.messages" * "show.error.messages" @@ -248,9 +249,9 @@ char *p; #ifdef HAVE_RL_COMPLETION_MATCHES + PROTECT(v = val = allocList(22)); +#else PROTECT(v = val = allocList(21)); -#else - PROTECT(v = val = allocList(20)); #endif SET_TAG(v, install("prompt")); @@ -289,6 +290,10 @@ SETCAR(v, ScalarLogical(0)); /* no checking */ v = CDR(v); + SET_TAG(v, install("check.condition")); + SETCAR(v, ScalarLogical(0)); /* no checking */ + v = CDR(v); + p = getenv("R_KEEP_PKG_SOURCE"); R_KeepSource = (p && (strcmp(p, "yes") == 0)) ? 1 : 0;
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