Fix fread clipboard handling on Windows (fixes #1292)

NEWS.md

@@ -40,6 +40,8 @@
 
 5. Non-equi joins combining an equality condition with two inequality conditions on the same column (e.g., `on = .(id == id, val >= lo, val <= hi)`) no longer error, [#7641](https://github.com/Rdatatable/data.table/issues/7641). The internal `chmatchdup` remapping of duplicate `rightcols` was overwriting the original column indices, causing downstream code to reference non-existent columns. Thanks @tarun-t for the report and fix, and @aitap for the diagnosis.
 
+`fread()` now supports reading from the system clipboard by passing `input="clipboard"`, implemented for Windows, macOS (via `pbpaste`), and Linux (via `wl-paste`, `xclip`, or `xsel`), [#1292](https://github.com/Rdatatable/data.table/issues/1292). Thanks @mbacou for the report, @ben-schwen and @aitab for the suggestion, and @AmanKashyap0807 for the fix.
+
 ### Notes
 
 1. {data.table} now depends on R 3.5.0 (2018).

R/fread.R

@@ -63,6 +63,42 @@ 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 (identical(tolower(input), "clipboard")) {
+      os_type = .Platform$OS.type
+      if (identical(os_type, "windows")) {
+        clip = tryCatch(utils::readClipboard(),
+          error = function(e) stopf("Reading clipboard failed on Windows: %s", conditionMessage(e))
+        )
+      } else if (identical(os_type, "unix")) {
+        # Valid on macOS, Linux, BSD, etc.
+        clip_cmd = if (nzchar(Sys.which("pbpaste"))) {
+          "pbpaste"
+        } else if (nzchar(Sys.which("wl-paste"))) {
+          "wl-paste --no-newline"
+        } else if (nzchar(Sys.which("xclip"))) {
+          "xclip -o -selection clipboard"
+        } else if (nzchar(Sys.which("xsel"))) {
+          "xsel --clipboard --output"
+        } else {
+          stopf("Clipboard reading on Unix-like systems requires 'pbpaste', 'wl-paste', 'xclip', or 'xsel' to be installed.")
+        }
+        clip = tryCatch(system(clip_cmd, intern = TRUE),
+          error = function(e) stopf("Reading clipboard failed: %s", conditionMessage(e))
+        )
+        status = attr(clip, "status")
+        if (!is.null(status) && status != 0L) {
+          stopf("Reading clipboard failed (exit %d). Ensure '%s' is working.", status, clip_cmd)
+        }
+      } else {
+        warning("Clipboard reading is not supported on this platform.", call. = FALSE)
+        return(data.table())
+      }
+      if (!length(clip) || !any(nzchar(trimws(clip)))) {
+        stopf("Clipboard is empty.")
+      }
+      writeLines(clip, tmpFile <- tempfile(tmpdir=tmpdir))
+      file = tmpFile
+      on.exit(unlink(tmpFile), add=TRUE)
     } 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

@@ -21520,3 +21520,48 @@ 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$OS.type == "windows") local({
+  temp = c("a\tb", "1\t2")
+  utils::writeClipboard(temp)
+  on.exit(utils::writeClipboard(""), add = TRUE)
+  test(2366, fread("clipboard"), data.table(a = 1L, b = 2L))
+})
+
+# Test fread clipboard input on macOS (issue #1292)
+if (.Platform$OS.type == "unix" && identical(Sys.info()[["sysname"]], "Darwin")) local({
+  if (nzchar(Sys.which("pbcopy"))) {
+    con = pipe("pbcopy", "w")
+    writeLines(c("a\tb", "1\t2"), con)
+    close(con)
+    on.exit({
+      cl = pipe("pbcopy", "w")
+      writeLines("", cl)
+      close(cl)
+    }, add=TRUE)
+    test(2366.1, fread("clipboard"), data.table(a=1L, b=2L))
+  }
+})
+
+# Test fread clipboard input on Linux via xclip/xsel/wl-paste (issue #1292)
+if (.Platform$OS.type == "unix" && identical(Sys.info()[["sysname"]], "Linux")) local({
+  has_wl     = nzchar(Sys.which("wl-copy")) && nzchar(Sys.which("wl-paste"))
+  has_xclip  = nzchar(Sys.which("xclip"))
+  has_xsel   = nzchar(Sys.which("xsel"))
+  writer = if (has_wl) "wl-copy"
+           else if (has_xclip)       "xclip -i -selection clipboard"
+           else if (has_xsel)        "xsel --clipboard --input"
+           else                      ""
+  if (nzchar(writer)) {
+    con = pipe(writer, "w")
+    writeLines(c("a\tb", "1\t2"), con)
+    close(con)
+    on.exit({
+      cl = pipe(writer, "w")
+      writeLines("", cl)
+      close(cl)
+    }, add=TRUE)
+    test(2366.2, fread("clipboard"), data.table(a=1L, b=2L))
+  }
+})