allow conversion (with loss of precision) for arbitrary precision POS…

…IXct objects (#533)

* allow conversion (with loss of precision) for arbitrary precision POSIXct objects

* version bump

* use debug instead of warn

* docs note

* fix test, add note

Project.toml

@@ -1,7 +1,7 @@
 name = "RCall"
 uuid = "6f49c342-dc21-5d91-9882-a32aef131414"
 authors = ["Douglas Bates <[email protected]>", "Randy Lai <[email protected]>", "Simon Byrne <[email protected]>"]
-version = "0.14.2"
+version = "0.14.3"
 
 [deps]
 CategoricalArrays = "324d7699-5711-5eae-9e2f-1d82baa6b597"
@@ -23,6 +23,7 @@ CategoricalArrays = "0.8, 0.9, 0.10"
 Conda = "1.4"
 DataFrames = "0.21, 0.22, 1.0"
 DataStructures = "0.5, 0.6, 0.7, 0.8, 0.9, 0.10, 0.11, 0.12, 0.13, 0.14, 0.15, 0.16, 0.17, 0.18"
+Logging = "0, 1"
 Preferences = "1"
 Requires = "0.5.2, 1"
 StatsModels = "0.6, 0.7"
@@ -33,10 +34,11 @@ julia = "1.6"
 AxisArrays = "39de3d68-74b9-583c-8d2d-e117c070f3a9"
 CondaPkg = "992eb4ea-22a4-4c89-a5bb-47a3300528ab"
 Dates = "ade2ca70-3891-5945-98fb-dc099432e06a"
+Logging = "56ddb016-857b-54e1-b83d-db4d58db5568"
 Pkg = "44cfe95a-1eb2-52ea-b672-e2afdf69b78f"
 REPL = "3fa0cd96-eef1-5676-8a61-b3b8758bbffb"
 Random = "9a3f8284-a2c9-5f02-9a11-845980a1fd5c"
 Test = "8dfed614-e22c-5e08-85e1-65c5234f0b40"
 
 [targets]
-test = ["Dates", "AxisArrays", "REPL", "Test", "Random", "CondaPkg", "Pkg"]
+test = ["Dates", "AxisArrays", "REPL", "Test", "Random", "CondaPkg", "Pkg", "Logging"]

docs/src/conversions.md

@@ -74,6 +74,20 @@ r = robject(d)
 rcopy(r)
 ```
 
+Note that R's `POSIXct` supports higher precision than DateTime:
+
+```@example 1
+r = reval("as.POSIXct('2020-10-09 12:09:46.1234')")
+```
+
+```@example 1
+d = rcopy(r)
+```
+
+!!! note "Conversions to `DateTime` are given in UTC!"
+    `POSIXct` stores times internally as UTC with a timezone attribute.
+    The conversion to `DateTime` necessarily strips away timezone information, resulting in UTC values.
+
 ## DataFrames
 
 ```@example 1

src/convert/datetime.jl

@@ -6,8 +6,15 @@ rcopy(::Type{Date}, s::Ptr{RealSxp}) = rcopy(Date, s[1])
 rcopy(::Type{DateTime}, s::Ptr{RealSxp}) = rcopy(DateTime, s[1])
 
 rcopy(::Type{Date}, x::Float64) = Date(Dates.UTInstant(Dates.Day((isnan(x) ? 0 : x) + 719163)))
-rcopy(::Type{DateTime}, x::Float64) =
-    DateTime(Dates.UTInstant(Dates.Millisecond(((isnan(x) ? 0 : x) + 62135683200) * 1000)))
+function rcopy(::Type{DateTime}, x::Float64)
+    ms = ((isnan(x) ? 0 : x) + 62135683200) * 1_000
+    ms_int = round(Int, ms)
+    if ms != ms_int
+        @debug "Precision lost in conversion to DateTime"
+    end
+
+    return DateTime(Dates.UTInstant(Millisecond(ms_int)))
+end
 
 # implicit conversion `rcopy(d)`.
 function rcopytype(::Type{RClass{:Date}}, s::Ptr{RealSxp})

test/convert/datetime.jl

@@ -135,3 +135,13 @@ r = RObject(d)
 @test ismissing(rcopy(r)[2])
 @test rcopy(Array, r)[[1,3]] == d[[1,3]]
 @test ismissing(rcopy(Array, r)[2])
+
+# note that POSIXct stores times internaly as UTC, but assumes local
+# timezone information
+@test rcopy(R"as.POSIXct('2020-10-09 12:09:46', tz='UTC')") == DateTime("2020-10-09T12:09:46")
+
+# microseconds on R side #396
+@test_logs((:debug, "Precision lost in conversion to DateTime"),
+            min_level=Logging.Debug,
+            rcopy(R"as.POSIXct('2020-10-09 12:09:46.1234')"))
+@test rcopy(R"as.POSIXct('2020-10-09 12:09:46.1234', tz='UTC')") == DateTime("2020-10-09T12:09:46.123")

test/runtests.jl

@@ -1,4 +1,5 @@
 using RCall
+using Logging
 using Test
 
 using DataStructures: OrderedDict