paste: cleanup multi-stdin support (#1803)

cleaner impl for multi-stdin support

tests/by-util/test_paste.rs

@@ -1,5 +1,67 @@
 use crate::common::util::*;
 
+struct TestData<'b> {
+    name: &'b str,
+    args: &'b [&'b str],
+    ins: &'b [&'b str],
+    out: &'b str,
+}
+
+static EXAMPLE_DATA: &'static [TestData<'static>] = &[
+    // Ensure that paste properly handles files lacking a final newline.
+    TestData {
+        name: "no-nl-1",
+        args: &[],
+        ins: &["a", "b"],
+        out: "a\tb\n",
+    },
+    TestData {
+        name: "no-nl-2",
+        args: &[],
+        ins: &["a\n", "b"],
+        out: "a\tb\n",
+    },
+    TestData {
+        name: "no-nl-3",
+        args: &[],
+        ins: &["a", "b\n"],
+        out: "a\tb\n",
+    },
+    TestData {
+        name: "no-nl-4",
+        args: &[],
+        ins: &["a\n", "b\n"],
+        out: "a\tb\n",
+    },
+    // Same as above, but with a two lines in each input file and the
+    // addition of the -d option to make SPACE be the output
+    // delimiter.
+    TestData {
+        name: "no-nla-1",
+        args: &["-d", " "],
+        ins: &["1\na", "2\nb"],
+        out: "1 2\na b\n",
+    },
+    TestData {
+        name: "no-nla-2",
+        args: &["-d", " "],
+        ins: &["1\na\n", "2\nb"],
+        out: "1 2\na b\n",
+    },
+    TestData {
+        name: "no-nla-3",
+        args: &["-d", " "],
+        ins: &["1\na", "2\nb\n"],
+        out: "1 2\na b\n",
+    },
+    TestData {
+        name: "no-nla-4",
+        args: &["-d", " "],
+        ins: &["1\na\n", "2\nb\n"],
+        out: "1 2\na b\n",
+    },
+];
+
 #[test]
 fn test_combine_pairs_of_lines() {
     for s in vec!["-s", "--serial"] {
@@ -22,3 +84,21 @@ fn test_multi_stdin() {
             .stdout_is_fixture("html_colors.expected");
     }
 }
+
+#[test]
+fn test_data() {
+    for example in EXAMPLE_DATA {
+        let (at, mut ucmd) = at_and_ucmd!();
+        let mut ins = vec![];
+        for (i, _in) in example.ins.iter().enumerate() {
+            let file = format!("in{}", i);
+            at.write(&file, _in);
+            ins.push(file);
+        }
+        println!("{}", example.name);
+        ucmd.args(example.args)
+            .args(&ins)
+            .succeeds()
+            .stdout_is(example.out);
+    }
+}