From m@ech|er @end|ng |rom @t@t@m@th@ethz@ch  Wed Oct 12 10:17:28 2022
From: m@ech|er @end|ng |rom @t@t@m@th@ethz@ch (Martin Maechler)
Date: Wed, 12 Oct 2022 10:17:28 +0200
Subject: [Rd] Bug with `[<-.POSIXlt` on specific OSes
In-Reply-To: <25413.33085.344041.49718@hornik.net>
References: <CABzLhzy0eTEAnb36raY5h_P=4+Dnm9uX0k0DB557zntD2qMLxg@mail.gmail.com>
 <CABzLhzxNNce6eEOnnv0fSpLRiZ70FC3-YadS2PeWOFSJfN6Zaw@mail.gmail.com>
 <25413.33085.344041.49718@hornik.net>
Message-ID: <25414.30744.139721.871865@stat.math.ethz.ch>

>>>>> Kurt Hornik 
>>>>>     on Tue, 11 Oct 2022 16:44:13 +0200 writes:

>>>>> Davis Vaughan writes:
    >> I've got a bit more information about this one. It seems like it
    >> (only? not sure) appears when `TZ = "UTC"`, which is why I didn't see
    >> it before on my Mac, which defaults to `TZ = ""`. I think this is at
    >> least explainable by the fact that those "optional" fields aren't
    >> technically needed when the time zone is UTC.

    > Exactly.  Debugging `[<-.POSIlt` with

    > x <- as.POSIXlt(as.POSIXct("2013-01-31", tz = "America/Chicago"))
    > Sys.setenv(TZ = "UTC")
    > x[1] <- NA

    > shows we get into

    > value <- unclass(as.POSIXlt(value))
    > if (ici) {
    > for (n in names(x)) names(x[[n]]) <- nms
    > }
    > for (n in names(x)) x[[n]][i] <- value[[n]]

    > where

    > Browse[2]> names(value)
    > [1] "sec"   "min"   "hour"  "mday"  "mon"   "year"  "wday"  "yday"  "isdst"
    > Browse[2]> names(x)
    > [1] "sec"    "min"    "hour"   "mday"   "mon"    "year"   "wday"   "yday"  
    > [9] "isdst"  "zone"   "gmtoff"

    > Without having looked at the code, the docs say

    > ?zone? (Optional.) The abbreviation for the time zone in force at
    > that time: ?""? if unknown (but ?""? might also be used for
    > UTC).

    > ?gmtoff? (Optional.) The offset in seconds from GMT: positive
    > values are East of the meridian.  Usually ?NA? if unknown,
    > but ?0? could mean unknown.

    > so perhaps we should fill with the values for the unknown case?

    > -k

Well,

I think you both know  I'm in the midst of dealing with these
issues, to fix both

[.POSIXlt  and
[<-.POSIXlt

Yes, one needs a way to not only "fill" the partially filled
entries but also to *normalize* out-of-range values
(say negative seconds, minutes > 60, etc)

All this is available in our C code, but not on the R level,
so yesterday, I wrote a C function to be called via .Internal(.)
from a new R that provides this.

Provisionally called

   balancePOXIXlt()

because it both balances the 9 to 11 list-components of POSIXlt
and it also puts all numbers of (sec, min, hour, mday, mon)
into a correct range (and also computes correctl wday and yday numbers).
but I'm happy for proposals of better names.
I had contemplated  validatePOSIXlt() as alternative, but then
dismissed that as in some sense we now do agree that
"imbalanced" POSIXlt's are not really invalid ..

.. and yes, to Davis:  Even though I've spent so many hours with
POSIXlt, POSIXct and Date during the last week, I'm still
surprised more often than I like by the effects of timezone
settings there.

Martin


    >> I can reproduce this now on my personal Mac:

    >> ```

    >> x <- as.POSIXlt(as.POSIXct("2013-01-31", tz = "America/Chicago"))

    >> Sys.setenv(TZ = "")

    >> x[1] <- NA

    >> x

    >> #> [1] NA


    >> x <- as.POSIXlt(as.POSIXct("2013-01-31", tz = "America/Chicago"))

    >> Sys.setenv(TZ = "America/New_York")

    >> x[1] <- NA

    >> x

    >> #> [1] NA


    >> x <- as.POSIXlt(as.POSIXct("2013-01-31", tz = "America/Chicago"))

    >> Sys.setenv(TZ = "UTC")

    >> x[1] <- NA
    >> #> Error in x[[n]][i] <- value[[n]] : replacement has length zero

    >> x

    >> #> [1] "2013-01-31 CST"
    >> ```

    >> Here are `sessionInfo()` and `Sys.getenv("TZ")` outputs for 3 GitHub
    >> Actions platforms where the bug exists (note they all set `TZ = "UTC"`!):

    >> Linux:

    >> ```

    >>> sessionInfo()

    >> R version 4.2.1 (2022-06-23)

    >> Platform: x86_64-pc-linux-gnu (64-bit)

    >> Running under: Ubuntu 18.04.6 LTS


    >> Matrix products: default

    >> BLAS:   /usr/lib/x86_64-linux-gnu/openblas/libblas.so.3

    >> LAPACK: /usr/lib/x86_64-linux-gnu/libopenblasp-r0.2.20.so


    >> locale:

    >> [1] LC_CTYPE=C.UTF-8       LC_NUMERIC=C           LC_TIME=C.UTF-8

    >> [4] LC_COLLATE=C.UTF-8     LC_MONETARY=C.UTF-8    LC_MESSAGES=C.UTF-8

    >> [7] LC_PAPER=C.UTF-8       LC_NAME=C              LC_ADDRESS=C

    >> [10] LC_TELEPHONE=C         LC_MEASUREMENT=C.UTF-8 LC_IDENTIFICATION=C


    >> attached base packages:

    >> [1] stats     graphics  grDevices utils     datasets  methods   base


    >> loaded via a namespace (and not attached):

    >> [1] compiler_4.2.1


    >>> Sys.getenv("TZ")

    >> [1] "UTC"
    >> ```

    >> Mac:

    >> ```

    >>> sessionInfo()

    >> R version 4.2.1 (2022-06-23)

    >> Platform: x86_64-apple-darwin17.0 (64-bit)

    >> Running under: macOS Big Sur ... 10.16


    >> Matrix products: default

    >> BLAS:
    >> /Library/Frameworks/R.framework/Versions/4.2/Resources/lib/libRblas.0.dylib

    >> LAPACK:
    >> /Library/Frameworks/R.framework/Versions/4.2/Resources/lib/libRlapack.dylib


    >> locale:

    >> [1] en_US.UTF-8/en_US.UTF-8/en_US.UTF-8/C/en_US.UTF-8/en_US.UTF-8


    >> attached base packages:

    >> [1] stats     graphics  grDevices utils     datasets  methods   base


    >> loaded via a namespace (and not attached):

    >> [1] compiler_4.2.1


    >>> Sys.getenv("TZ")

    >> [1] "UTC"
    >> ```

    >> Windows:
    >> This is the best I can get you, sorry (remote worker issues), but note that
    >> it does also say `tz UTC` like the others.

    >> ```
    >> version R version 4.2.1 (2022-06-23 ucrt)
    >> os Windows Server x64 (build 20348)
    >> system x86_64, mingw32
    >> ui RTerm
    >> language (EN)
    >> collate English_United States.utf8
    >> ctype English_United States.utf8
    >> tz UTC
    >> date 2022-10-11
    >> ```

    >> And here is my Mac where the bug doesn't show up by default because `TZ =
    >> ""`:

    >> ```

    >>> sessionInfo()

    >> R version 4.2.1 (2022-06-23)

    >> Platform: x86_64-apple-darwin17.0 (64-bit)

    >> Running under: macOS Big Sur ... 10.16


    >> Matrix products: default

    >> BLAS:
    >> /Library/Frameworks/R.framework/Versions/4.2/Resources/lib/libRblas.0.dylib

    >> LAPACK:
    >> /Library/Frameworks/R.framework/Versions/4.2/Resources/lib/libRlapack.dylib


    >> locale:

    >> [1] en_US.UTF-8/en_US.UTF-8/en_US.UTF-8/C/en_US.UTF-8/en_US.UTF-8


    >> attached base packages:

    >> [1] stats     graphics  grDevices utils     datasets  methods   base


    >> loaded via a namespace (and not attached):

    >> [1] compiler_4.2.1


    >>> Sys.getenv("TZ")

    >> [1] ""


    >>> Sys.timezone()

    >> [1] "America/New_York"
    >> ```

    >> -Davis


    >> On Thu, Oct 6, 2022 at 9:33 AM Davis Vaughan <davis at rstudio.com> wrote:

    >>> Hi all,
    >>> 
    >>> I have found another POSIXlt bug while I've been fiddling around with it.
    >>> This one only appears on specific OSes, because it has to do with the fact
    >>> that the `gmtoff` field is optional, and isn't always used on all OSes. It
    >>> also doesn't seem to be specific to r-devel, I think it has been there
    >>> awhile.
    >>> 
    >>> Here is the bug:
    >>> 
    >>> ```
    >>> x <- as.POSIXlt(as.POSIXct("2013-01-31", tz = "America/Chicago"))
    >>> 
    >>> # Oh no!
    >>> x[1] <- NA
    >>> #> Error in x[[n]][i] <- value[[n]] : replacement has length zero
    >>> ```
    >>> 
    >>> If you look at the objects, you can see that `x` has a `gmtoff` field, but
    >>> `NA` (when converted to POSIXlt, which is what `[<-.POSIXlt` does) does not:
    >>> 
    >>> ```
    >>> unclass(x)
    >>> #> $sec
    >>> #> [1] 0
    >>> #>
    >>> #> $min
    >>> #> [1] 0
    >>> #>
    >>> #> $hour
    >>> #> [1] 0
    >>> #>
    >>> #> $mday
    >>> #> [1] 31
    >>> #>
    >>> #> $mon
    >>> #> [1] 0
    >>> #>
    >>> #> $year
    >>> #> [1] 113
    >>> #>
    >>> #> $wday
    >>> #> [1] 4
    >>> #>
    >>> #> $yday
    >>> #> [1] 30
    >>> #>
    >>> #> $isdst
    >>> #> [1] 0
    >>> #>
    >>> #> $zone
    >>> #> [1] "CST"
    >>> #>
    >>> #> $gmtoff
    >>> #> [1] -21600
    >>> #>
    >>> #> attr(,"tzone")
    >>> #> [1] "America/Chicago" "CST"             "CDT"
    >>> 
    >>> unclass(as.POSIXlt(NA))
    >>> #> $sec
    >>> #> [1] NA
    >>> #>
    >>> #> $min
    >>> #> [1] NA
    >>> #>
    >>> #> $hour
    >>> #> [1] NA
    >>> #>
    >>> #> $mday
    >>> #> [1] NA
    >>> #>
    >>> #> $mon
    >>> #> [1] NA
    >>> #>
    >>> #> $year
    >>> #> [1] NA
    >>> #>
    >>> #> $wday
    >>> #> [1] NA
    >>> #>
    >>> #> $yday
    >>> #> [1] NA
    >>> #>
    >>> #> $isdst
    >>> #> [1] -1
    >>> #>
    >>> #> attr(,"tzone")
    >>> #> [1] "UTC"
    >>> ```
    >>> 
    >>> The problem seems to be that `[<-.POSIXlt` assumes that if the field was
    >>> there in `x` then it must also be there in `value`:
    >>> 
    >>> https://github.com/wch/r-source/blob/e10a971dee6a0ab851279c183cc21954d66b3be4/src/library/base/R/datetime.R#L1303-L1304
    >>> 
    >>> But this isn't the case for the `NA` value that was converted to POSIXlt.
    >>> 
    >>> I can't reproduce this on my personal Mac, but it affects the Linux, Mac,
    >>> and Windows machines we use for the lubridate CI checks through GitHub
    >>> Actions.
    >>> 
    >>> Thanks,
    >>> Davis
    >>>



[Rd] Bug with `[<-.POSIXlt` on specific OSes
Martin Maechler