paste: cleanup multi-stdin support (#1803)

cleaner impl for multi-stdin support

src/uu/paste/src/paste.rs

@@ -12,7 +12,7 @@ extern crate uucore;
 
 use clap::{App, Arg};
 use std::fs::File;
-use std::io::{stdin, BufRead, BufReader, Stdin};
+use std::io::{stdin, BufRead, BufReader, Read};
 use std::iter::repeat;
 use std::path::Path;
 
@@ -26,26 +26,14 @@ mod options {
     pub const FILE: &str = "file";
 }
 
-// We need this trait to wrap both BufReader and Stdin. We need
-// `read_line` function only, but Stdin does not provide BufRead
-// unless lock function is called, which prevents us from using stdin
-// multiple times
-trait ReadLine {
-    fn read_line(&mut self, buf: &mut String) -> std::io::Result<usize>;
-}
-
-struct StdinReadLine(Stdin);
-struct BufReadReadLine<R: BufRead>(R);
-
-impl ReadLine for StdinReadLine {
-    fn read_line(&mut self, buf: &mut String) -> std::io::Result<usize> {
-        return self.0.read_line(buf);
-    }
-}
-
-impl<R: BufRead> ReadLine for BufReadReadLine<R> {
-    fn read_line(&mut self, buf: &mut String) -> std::io::Result<usize> {
-        return self.0.read_line(buf);
+// Wraps BufReader and stdin
+fn read_line<R: Read>(
+    reader: Option<&mut BufReader<R>>,
+    buf: &mut String,
+) -> std::io::Result<usize> {
+    match reader {
+        Some(reader) => reader.read_line(buf),
+        None => stdin().read_line(buf),
     }
 }
 
@@ -89,14 +77,14 @@ pub fn uumain(args: impl uucore::Args) -> i32 {
 }
 
 fn paste(filenames: Vec<String>, serial: bool, delimiters: String) {
-    let mut files: Vec<Box<dyn ReadLine>> = filenames
+    let mut files: Vec<_> = filenames
         .into_iter()
         .map(|name| {
             if name == "-" {
-                Box::new(StdinReadLine(stdin())) as Box<dyn ReadLine>
+                None
             } else {
                 let r = crash_if_err!(1, File::open(Path::new(&name)));
-                Box::new(BufReadReadLine(BufReader::new(r))) as Box<dyn ReadLine>
+                Some(BufReader::new(r))
             }
         })
         .collect();
@@ -112,7 +100,7 @@ fn paste(filenames: Vec<String>, serial: bool, delimiters: String) {
             let mut output = String::new();
             loop {
                 let mut line = String::new();
-                match file.read_line(&mut line) {
+                match read_line(file.as_mut(), &mut line) {
                     Ok(0) => break,
                     Ok(_) => {
                         output.push_str(line.trim_end());
@@ -134,7 +122,7 @@ fn paste(filenames: Vec<String>, serial: bool, delimiters: String) {
                     eof_count += 1;
                 } else {
                     let mut line = String::new();
-                    match file.read_line(&mut line) {
+                    match read_line(file.as_mut(), &mut line) {
                         Ok(0) => {
                             eof[i] = true;
                             eof_count += 1;

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);
+    }
+}

tests/common/util.rs

@@ -261,8 +261,7 @@ impl AtPath {
     }
 
     pub fn write(&self, name: &str, contents: &str) {
-        let mut f = self.open(name);
-        let _ = f.write(contents.as_bytes());
+        let _ = std::fs::write(self.plus(name), contents);
     }
 
     pub fn append(&self, name: &str, contents: &str) {