fwrite/fread UTF8 and native in file names

NEWS.md

@@ -14,6 +14,9 @@
 
 5. `fwrite()` now accepts `matrix`, (#2613)[https://github.com/Rdatatable/data.table/issues/2613]. Thanks to Michael Chirico for the suggestion and Felipe Parages for implementing. For now matrix input is converted to data.table (which can be costly) before writing. 
 
+6. `fread()` and `fwrite()` can now handle file names in native and UTF-8 encoding, [#3078](https://github.com/Rdatatable/data.table/issues/3078). Thanks to Daniel Possenriede (@dpprdan) for reporting and fixing.
+
+
 #### BUG FIXES
 
 1. Providing an `i` subset expression when attempting to delete a column correctly failed with helpful error, but when the column was missing too created a new column full of `NULL` values, [#3089](https://github.com/Rdatatable/data.table/issues/3089). Thanks to Michael Chirico for reporting.

R/fread.R

@@ -106,6 +106,8 @@ fread <- function(input="",file=NULL,text=NULL,cmd=NULL,sep="auto",sep2="auto",d
       file = decompFile   # don't use 'tmpFile' symbol again, as tmpFile might be the http://domain.org/file.csv.gz download
       on.exit(unlink(decompFile), add=TRUE)
     }
+    file = enc2native(file) # CfreadR cannot handle UTF-8 if that is not the native encoding, see #3078.
+
     input = file
   }
   if (!missing(autostart)) warning("'autostart' is now deprecated and ignored. Consider skip='string' or skip=n");

R/fwrite.R

@@ -68,6 +68,7 @@ fwrite <- function(x, file="", append=FALSE, quote="auto",
       return(invisible())
     }
   }
+  file <- enc2native(file) # CfwriteR cannot handle UTF-8 if that is not the native encoding, see #3078.
   .Call(CfwriteR, x, file, sep, sep2, eol, na, dec, quote, qmethod=="escape", append,
           row.names, col.names, logical01, dateTimeAs, buffMB, nThread,
           showProgress, verbose)

inst/tests/tests.Rraw

@@ -12498,6 +12498,30 @@ test(1964.4, colnames(DT), c("v1","v2"))
 
 test(1965, setDT(list(1, 1:2)), error = 'profile of input lengths')   #3121
 
+# fread/fwrite file name in native and utf-8 encoding, #3078
+if (.Platform$OS.type=="windows") {
+  f = tempfile("\u00f6"); cat("3.14", file = f)
+  fn = enc2native(f); f8 = enc2utf8(f)
+  test(1966.1, fread(fn), data.table(V1=3.14))
+  test(1966.2, fread(f8), data.table(V1=3.14))
+  unlink(c(fn, f8))
+
+  DT = data.table("a"); pth = tempdir()
+  f = "\u00f6.csv"; fp = file.path(pth, f)
+  fpn = enc2native(fp); fp8 = enc2utf8(fp)
+  fwrite(DT, fpn)
+  test(1966.3, list.files(path = pth, pattern = "\\.csv$"), f)
+  unlink(c(fp, file.path(pth, "\u00c3\u00b6.csv")))
+  fwrite(DT, fp8)
+  test(1966.4, list.files(path = pth, pattern = "\\.csv$"), f)
+  unlink(c(fp, file.path(pth, "\u00c3\u00b6.csv")))
+  p = file.path(pth, "\u00fc"); dir.create(p); f = tempfile(tmpdir = p)
+  test(1966.5, fwrite(DT, enc2native(f)), NULL)
+  unlink(f)
+  test(1966.6, fwrite(DT, enc2utf8(f)), NULL)
+  unlink(p, recursive = TRUE)
+}
+
 
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 #  Add new tests above this line  #