Use a datasource for all file arguments in read_table

Fixes #552

NEWS.md

@@ -1,5 +1,7 @@
 # readr 1.0.0.9000
 
+* `read_table()` can now handle `pipe()` connections (#552).
+
 * parsing problems in `read_delim()` and `read_fwf()` when columns are skipped using col_types now report the correct column name (#573, @cb4ds)
 
 * `parse_time()` now correctly handles 12 AM/PM (#579).

R/read_table.R

@@ -30,11 +30,12 @@ read_table <- function(file, col_names = TRUE, col_types = NULL,
                        locale = default_locale(), na = "NA", skip = 0,
                        n_max = Inf, guess_max = min(n_max, 1000),
                        progress = show_progress(), comment = "") {
-  columns <- fwf_empty(file, skip = skip, n = guess_max, comment = comment)
+  ds <- datasource(file, skip = skip)
+  columns <- fwf_empty(ds, skip = skip, n = guess_max, comment = comment)
   tokenizer <- tokenizer_fwf(columns$begin, columns$end, na = na, comment = comment)
 
   spec <- col_spec_standardise(
-    file = file, skip = skip, n = guess_max,
+    file = ds, skip = skip, n = guess_max,
     col_names = col_names, col_types = col_types,
     locale = locale, tokenizer = tokenizer
   )
@@ -43,7 +44,7 @@ read_table <- function(file, col_names = TRUE, col_types = NULL,
      print(spec, n = getOption("readr.num_columns", 20))
   }
 
-  ds <- datasource(file, skip = skip + isTRUE(col_names))
+  ds <- datasource(file = ds, skip = skip + isTRUE(col_names))
   res <- read_tokens(ds, tokenizer, spec$cols, names(spec$cols), locale_ = locale,
     n_max = n_max, progress = progress)
   attr(res, "spec") <- spec

R/source.R

@@ -33,6 +33,8 @@
 #' close(con)
 datasource <- function(file, skip = 0, comment = "") {
   if (inherits(file, "source")) {
+    if (!missing(skip)) { file$skip <- skip }
+    if (!missing(comment)) { file$comment <- comment }
     file
   } else if (is.connection(file)) {
     datasource_connection(file, skip, comment)

tests/testthat/test-read-fwf.R

@@ -133,3 +133,8 @@ test_that("read_table silently reads ragged last column", {
   x <- read_table("foo bar\n1   2\n3   4\n5   6\n", progress = FALSE)
   expect_equal(x$foo, c(1, 3, 5))
 })
+
+test_that("read_table can read from a pipe (552)", {
+  x <- read_table(pipe("echo a b c && echo 1 2 3 && echo 4 5 6"))
+  expect_equal(x$a, c(1, 4))
+})