Fix fread clipboard handling on Windows (fixes #1292)

NEWS.md

@@ -38,6 +38,8 @@
 
 4. `rowwiseDT()` now provides a helpful error message when a complex object that is not a list (e.g., a function) is provided as a cell value, instructing the user to wrap it in `list()`, [#7219](https://github.com/Rdatatable/data.table/issues/7219). Thanks @kylebutts for the report and @venom1204 for the fix.
 
+5. `fread()` now recognizes Windows clipboard tokens such as `clipboard`, avoiding shell execution failures, [#1292](https://github.com/Rdatatable/data.table/issues/1292). Thanks @mbacou for the report and @AmanKashyap0807 for the fix.
+
 ### Notes
 
 1. {data.table} now depends on R 3.5.0 (2018).

R/fread.R

@@ -63,6 +63,29 @@ yaml=FALSE, tmpdir=tempdir(), tz="UTC")
       # input is data itself containing at least one \n or \r
     } else if (startsWith(input, " ")) {
       stopf("input= contains no \\n or \\r, but starts with a space. Please remove the leading space, or use text=, file= or cmd=")
+    } else if (grepl("^clipboard(-[0-9]+)?$", tolower(input))) {
+      is_windows = identical(.Platform$OS.type, "windows")
+      if (is_windows) {
+        clip = tryCatch(utils::readClipboard(), error = identity)
+        # for errors due to permissions, clipboard locked or system errors
+        if (inherits(clip, "error")) {
+          stopf("Reading clipboard failed on Windows: %s", conditionMessage(clip))
+        }
+        if (!length(clip) || !all(nzchar(trimws(clip)))) {
+          stopf("Clipboard is empty.")
+        }
+        tmpFile = tempfile(tmpdir=tmpdir)
+        on.exit(unlink(tmpFile), add=TRUE)
+        tryCatch({
+          writeLines(paste(clip, collapse="\n"), tmpFile, useBytes=TRUE)
+          file = tmpFile
+        }, error = function(e) {
+          stopf("Writing clipboard to temporary file failed: %s. Check tmpdir=%s.", conditionMessage(e), tmpdir)
+        })
+      } else {
+        # Note: macOS (pbpaste) and Linux (xclip/xsel) support discussed in #1292
+        stopf("Clipboard reading is supported on Windows only.")
+      }
     } else if (length(grep(' ', input, fixed=TRUE)) && !file.exists(gsub("^file://", "", input))) {  # file name or path containing spaces is not a command. file.exists() doesn't understand file:// (#7550)
       cmd = input
       if (input_has_vars && getOption("datatable.fread.input.cmd.message", TRUE)) {

inst/tests/tests.Rraw

@@ -21515,3 +21515,11 @@ test(2365.1, melt(df_melt, id.vars=1:2), melt(dt_melt, id.vars=1:2))
 df_dcast = data.frame(a = c("x", "y"), b = 1:2, v = 3:4)
 dt_dcast = data.table(a = c("x", "y"), b = 1:2, v = 3:4)
 test(2365.2, dcast(df_dcast, a ~ b, value.var = "v"), dcast(dt_dcast, a ~ b, value.var = "v"))
+
+# Test fread clipboard input on Windows (issue #1292)
+if (.Platform$OS.type == "windows") local({
+  temp <- c("a\tb", "1\t2")
+  utils::writeClipboard(temp)
+  on.exit(utils::writeClipboard(""), add = TRUE)
+  test(2366, fread("clipboard-128"), data.table(a = 1L, b = 2L))
+})