--filter argument for split (#1681)

tests/by-util/test_split.rs

@@ -4,6 +4,8 @@ extern crate regex;
 use self::rand::{thread_rng, Rng};
 use self::regex::Regex;
 use crate::common::util::*;
+#[cfg(not(windows))]
+use std::env;
 use std::fs::{read_dir, File};
 use std::io::Write;
 use std::path::Path;
@@ -32,6 +34,7 @@ impl Glob {
         self.collect().len()
     }
 
+    /// Get all files in `self.directory` that match `self.regex`
     fn collect(&self) -> Vec<String> {
         read_dir(Path::new(&self.directory.subdir))
             .unwrap()
@@ -49,6 +52,7 @@ impl Glob {
             .collect()
     }
 
+    /// Accumulate bytes of all files in `self.collect()`
     fn collate(&self) -> Vec<u8> {
         let mut files = self.collect();
         files.sort();
@@ -60,11 +64,16 @@ impl Glob {
     }
 }
 
+/// File handle that user can add random bytes (line-formatted or not) to
 struct RandomFile {
     inner: File,
 }
 
 impl RandomFile {
+    /// Size of each line that's being generated
+    const LINESIZE: usize = 32;
+
+    /// `create()` file handle located at `at` / `name`
     fn new(at: &AtPath, name: &str) -> RandomFile {
         RandomFile {
             inner: File::create(&at.plus(name)).unwrap(),
@@ -81,11 +90,11 @@ impl RandomFile {
         let _ = write!(self.inner, "{}", random_chars(n));
     }
 
+    /// Add n lines each of size `RandomFile::LINESIZE`
     fn add_lines(&mut self, lines: usize) {
-        let line_size: usize = 32;
         let mut n = lines;
         while n > 0 {
-            let _ = writeln!(self.inner, "{}", random_chars(line_size));
+            let _ = writeln!(self.inner, "{}", random_chars(RandomFile::LINESIZE));
             n -= 1;
         }
     }
@@ -156,3 +165,64 @@ fn test_split_additional_suffix() {
     assert_eq!(glob.count(), 2);
     assert_eq!(glob.collate(), at.read(name).into_bytes());
 }
+
+// note: the test_filter* tests below are unix-only
+// windows support has been waived for now because of the difficulty of getting
+// the `cmd` call right
+// see https://github.com/rust-lang/rust/issues/29494
+
+#[test]
+#[cfg(unix)]
+fn test_filter() {
+    // like `test_split_default()` but run a command before writing
+    let (at, mut ucmd) = at_and_ucmd!();
+    let name = "filtered";
+    let glob = Glob::new(&at, ".", r"x[[:alpha:]][[:alpha:]]$");
+    let n_lines = 3;
+    RandomFile::new(&at, name).add_lines(n_lines);
+
+    // change all characters to 'i'
+    ucmd.args(&["--filter=sed s/./i/g > $FILE", name])
+        .succeeds();
+    // assert all characters are 'i' / no character is not 'i'
+    // (assert that command succeded)
+    assert!(
+        glob.collate().iter().find(|&&c| {
+            // is not i
+            c != ('i' as u8)
+            // is not newline
+            && c != ('\n' as u8)
+        }) == None
+    );
+}
+
+#[test]
+#[cfg(unix)]
+fn test_filter_with_env_var_set() {
+    // This test will ensure that if $FILE env var was set before running --filter, it'll stay that
+    // way
+    // implemented like `test_split_default()` but run a command before writing
+    let (at, mut ucmd) = at_and_ucmd!();
+    let name = "filtered";
+    let glob = Glob::new(&at, ".", r"x[[:alpha:]][[:alpha:]]$");
+    let n_lines = 3;
+    RandomFile::new(&at, name).add_lines(n_lines);
+
+    let env_var_value = "somevalue";
+    env::set_var("FILE", &env_var_value);
+    ucmd.args(&[format!("--filter={}", "cat > $FILE").as_str(), name])
+        .succeeds();
+    assert_eq!(glob.collate(), at.read(name).into_bytes());
+    assert!(env::var("FILE").unwrap_or("var was unset".to_owned()) == env_var_value);
+}
+
+#[test]
+#[cfg(unix)]
+fn test_filter_command_fails() {
+    let (at, mut ucmd) = at_and_ucmd!();
+    let name = "filter-will-fail";
+    RandomFile::new(&at, name).add_lines(4);
+
+    ucmd.args(&["--filter=/a/path/that/totally/does/not/exist", name])
+        .fails();
+}