further relaxation of 1590.04 and 1590.07; base R ordering of identical strings in different encodings (#4494)

Author: mattdowle

inst/tests/tests.Rraw

@@ -8140,17 +8140,17 @@ test(1590.02, x1==x2)
 test(1590.03, forderv(    c(x2,x1,x1,x2)), integer())     # desirable consistent result given identical(x1, x2)
                                                           #           ^^ data.table consistent over time regardless of which version of R or locale
 baseR = base::order(c(x2,x1,x1,x2))
-  # Even though C locale and identical(x1,x2), base R considers the encoding too; i.e. orders the same-encoding together.
-  # In R <= 4.0.0, base R put x2 (UTF-8) before x1 (latin1).
-  # Then in R-devel around May 2020, R-devel on Windows started putting x1 before x2.
-  # Jan emailed R-devel on 23 May 2020. PR#4492 retained this test of base R but relaxed the encoding to be in either order.
-  # It's good to know that baseR changed. We still want to know in future if base R changes again (so we relaxed 1590.04 and 1590.07 rather than remove them).
-test(1590.04, identical(baseR, INT(1,4,2,3)) || identical(baseR, INT(2,3,1,4)))
+  # Even though C locale and identical(x1,x2), base R<=4.0.0 considers the encoding too; i.e. orders the encoding together x2 (UTF-8) before x1 (latin1).
+  # Then around May 2020, R-devel (but just on Windows) started either respecting identical() like data.table has always done, or put latin1 before UTF-8.
+  # Jan emailed R-devel on 23 May 2020.
+  # We relaxed 1590.04 and 1590.07 (tests of base R behaviour) rather than remove them, PR#4492 and its follow-up. But these two tests
+  # are so relaxed now that they barely testing anything. It appears base R behaviour is undefined in this rare case of identical strings in different encodings.
+test(1590.04, identical(baseR, INT(1,4,2,3)) || identical(baseR, INT(2,3,1,4)) || identical(baseR, 1:4))
 Encoding(x2) = "unknown"
 test(1590.05, x1!=x2)
 test(1590.06, forderv(    c(x2,x1,x1,x2)), INT(1,4,2,3))  # consistent with Windows-1252 result, tested further below
 baseR = base::order(c(x2,x1,x1,x2))
-test(1590.07, identical(baseR, INT(1,4,2,3)) || identical(baseR, INT(2,3,1,4)))
+test(1590.07, identical(baseR, INT(1,4,2,3)) || identical(baseR, INT(2,3,1,4)) || identical(baseR, 1:4))
 Sys.setlocale("LC_CTYPE", ctype)
 Sys.setlocale("LC_COLLATE", collate)
 test(1590.08, Sys.getlocale(), oldlocale)  # checked restored locale fully back to how it was before this test