[Rd] stopifnot

[Suharto Anggono Suharto Anggono]

My points:
- The 'withCallingHandlers' construct that is used in current 'stopifnot' code has no effect. Without it, the warning message is the same. The overridden warning is not raised. The original warning stays.
- Overriding call in error and warning to 'cl.i' doesn't always give better outcome. The original call may be "narrower" than 'cl.i'.

I have found these examples.
identity(is.na(log()))
identity(is.na(log("a")))

Error message from the first contains full call. Error message from the second doesn't.

So, how about being "natural", not using 'withCallingHandlers' and 'tryCatch' in 'stopifnot'?

Another thing: currently,
stopifnot(exprs=TRUE)
fails.

A patch:
--- stop.R	2019-02-27 16:15:45.324167577 +0000
+++ stop_new.R	2019-02-27 16:22:15.936203541 +0000
@@ -1,7 +1,7 @@
 #  File src/library/base/R/stop.R
 #  Part of the R package, https://www.R-project.org
 #
-#  Copyright (C) 1995-2018 The R Core Team
+#  Copyright (C) 1995-2019 The R Core Team
 #
 #  This program is free software; you can redistribute it and/or modify
 #  it under the terms of the GNU General Public License as published by
@@ -33,25 +33,27 @@
 
 stopifnot <- function(..., exprs, local = TRUE)
 {
+    n <- ...length()
     missE <- missing(exprs)
-    cl <-
 	if(missE) {  ## use '...' instead of exprs
-	    match.call(expand.dots=FALSE)$...
 	} else {
-	    if(...length())
+	    if(n)
 		stop("Must use 'exprs' or unnamed expressions, but not both")
 	    envir <- if (isTRUE(local)) parent.frame()
 		     else if(isFALSE(local)) .GlobalEnv
 		     else if (is.environment(local)) local
 		     else stop("'local' must be TRUE, FALSE or an environment")
 	    exprs <- substitute(exprs) # protect from evaluation
-	    E1 <- exprs[[1]]
+	    E1 <- if(is.call(exprs)) exprs[[1]]
+	    cl <-
 	    if(identical(quote(`{`), E1)) # { ... }
-		do.call(expression, as.list(exprs[-1]))
+		exprs[-1]
 	    else if(identical(quote(expression), E1))
 		eval(exprs, envir=envir)
 	    else
 		as.expression(exprs) # or fail ..
+	    if(!is.null(names(cl))) names(cl) <- NULL
+	    return(eval(as.call(c(sys.call()[[1]], as.list(cl))), envir=envir))
 	}
     Dparse <- function(call, cutoff = 60L) {
 	ch <- deparse(call, width.cutoff = cutoff)
@@ -62,14 +64,10 @@
     abbrev <- function(ae, n = 3L)
 	paste(c(head(ae, n), if(length(ae) > n) "...."), collapse="\n  ")
     ##
-    for (i in seq_along(cl)) {
-	cl.i <- cl[[i]]
-	## r <- eval(cl.i, ..)   # with correct warn/err messages:
-	r <- withCallingHandlers(
-		tryCatch(if(missE) ...elt(i) else eval(cl.i, envir=envir),
-			 error = function(e) { e$call <- cl.i; stop(e) }),
-		warning = function(w) { w$call <- cl.i; w })
+    for (i in seq_len(n)) {
+	r <- ...elt(i)
 	if (!(is.logical(r) && !anyNA(r) && all(r))) {
+	    cl.i <- match.call(expand.dots=FALSE)$...[[i]]
 	    msg <- ## special case for decently written 'all.equal(*)':
 		if(is.call(cl.i) && identical(cl.i[[1]], quote(all.equal)) &&
 		   (is.null(ni <- names(cl.i)) || length(cl.i) == 3L ||
@@ -84,7 +82,11 @@
 				     "%s are not all TRUE"),
 			    Dparse(cl.i))
 
-	    stop(simpleError(msg, call = sys.call(-1)))
+	    p <- sys.parent()
+	    if(p && identical(sys.function(p), stopifnot) &&
+	       !eval(expression(missE), p)) # originally stopifnot(exprs=*)
+		p <- sys.parent(2)
+	    stop(simpleError(msg, call = if(p) sys.call(p)))
 	}
     }
     invisible()

--------------------------------------------
On Wed, 27/2/19, Martin Maechler <maechler using stat.math.ethz.ch> wrote:

 Subject: Re: [Rd] stopifnot

 Cc: r-devel using r-project.org
 Date: Wednesday, 27 February, 2019, 5:36 PM

>>>>> Suharto Anggono Suharto Anggono via R-devel 
>>>>>    on Sun, 24 Feb 2019 14:22:48 +0000 writes:

    >> From https://github.com/HenrikBengtsson/Wishlist-for-R/issues/70 :
    > ... and follow up note from 2018-03-15: Ouch... in R-devel, stopifnot() has become yet 4-5 times slower;

    > ...
    > which is due to a complete rewrite using tryCatch() and withCallingHandlers().


    >> From https://stat.ethz.ch/pipermail/r-devel/2017-May/074256.html , it seems that 'tryCatch' was used to avoid the following example from giving error message with 'eval' call and 'withCallingHandlers' was meant to handle similar case for warning.
    > tst <- function(y) { stopifnot(is.numeric(y)); y+ 1 }
    > try(tst())

    > However,
    > withCallingHandlers(<something>,
    > warning = function(w) { w$call <- cl.i; w })
    > actally has no effect. In current code of function 'stopifnot', 'eval' is used only in handling stopifnot(exprs=) . The warning message from
    > stopifnot(exprs={warning()})
    > has 'eval' call:
    > In eval(cl.i, envir = envir) : 

    > This may work.
    > withCallingHandlers(<something>,
    > warning = function(w) {
    > w$call <- cl.i; warning(w); invokeRestart("muffleWarning") })


    > Current documentation says:
    > Since R version 3.5.0, expressions are evaluated sequentially, and hence evaluation stops as soon as there is a "non-TRUE", asnindicated by the above conceptual equivalence statement. Further, when such an expression signals an error or warning, its conditionCall() no longer contains the full stopifnot call, but just the erroneous expression.

    > I assume that "no longer contains ..." is supposed to be the effect of the use of 'withCallingHandlers' and 'tryCatch' in 'stopifnot'.

    > Actually, "contains the full stopifnot call" is not always the case in R before version 3.5.0. Normally, the call is the "innermost context".

Thank you Suharto, for thinking about these issues and being
constructive, trying to improve the current state.

Unfortunately, I do not quite understand what you are trying to
say here.

The main somewhat recent changes to stopifnot() have been (in
inverse time ordering)

1) Do what the documentation always promised, namely eval() the
  expressions one by one, and stop evaluation as soon as one of
  them is not all(.) TRUE.
  For that reason, the previously used idiom  'list(...)'
  is a no go, as "of course", it evaluates all the expressions in '...'

2) Try to ensure that warning() and stop()/error messages are
  shown the same {as closely as feasible}  to how they are
  shown outside of stopifnot(.)
            ==> partly the topic of this e-mail.

3) [2.5 years ago:] stopifnot() became smart about all.equal(.) expressions,
  showing the all.equal() string if it was not TRUE:
  In older R versions (<= 3.3.x ?), we had

      > stopifnot(all.equal(pi, 3.1415))
    Error: all.equal(pi, 3.1415) is not TRUE

  where as in R (>= 3.4.0 at least):

      > stopifnot(all.equal(pi, 3.1415)) 
      Error: pi and 3.1415 are not equal:
    Mean relative difference: 2.949255e-05


One example of what I meant with the above documentation ("no
longer contains")  is the following:

In R 3.5.x, 

  > lf <- list(fm = y ~ f(x), osf = ~ sin(x))
  > stopifnot(identical(deparse(lf), deparse(lf, control="all")))
  Warning message:
  In deparse(lf, control = "all") : deparse may be incomplete
  > 

If I change the calling handler to use the
invokeRestart("muffleWarning") which I understand you are
proposing, then the message becomes

  Warning message:
  In identical(deparse(lf, control = "all"), deparse(lf)) :
    deparse may be incomplete

which is less useful as I can no longer see directly which of
the deparse() produced the warning.

    > Example:
    > stopifnot((1:2) + (1:3) > 0)
    > Warning message:
    > In (1:2) + (1:3) :
    >   longer object length is not a multiple of shorter object length

Which is the good answer
(whereas also showing "> 0" in the warning is slightly off).

Again, if I'd use the  ..muffleWarning.. code instead, the above
would change to the worse

    Warning message:
    In (1:2) + (1:3) > 0 :
      longer object length is not a multiple of shorter object length

which "wrongly includes the '> 0'.
So I guess I really don't understand what you are proposing, or
would like to change  ...


    > Example that gives error:
    > stopifnot(is.na(log("a")))
    > R 3.5.0:
    > R 3.3.2:

That's a good one: we want the error message *not to* mention
is.na(.) but just 'log': i.e.,

We'd like  [ R versions <= 3.4.4 ] :

> stopifnot(is.na(log("a")))
Error in log("a") : non-numeric argument to mathematical function

as opposed to [ R version >= 3.5.0 ] :

> stopifnot(is.na(log("a")))
Error in is.na(log("a")) : non-numeric argument to mathematical function

-----------------------------------------

Again, I'm sure I partly failed to understand what you said in
your e-mail and apologize for that.

Of course, I'm happy and glad to discuss improvements to
stopifnot() which improve speed (while retaining important
current functionality)  or also just improve current
functionality
-- e.g. get the "better" error message in the stopifnot(is.na(log("a")))

  example.


High regards,
Martin Maechler