truncate: deduplicate fifo check, fix handling of missing files

The fifo check used to include 'metadata(filename)?', which would error
if the file does not exist. In our case however, this is not an error.

src/uu/truncate/src/truncate.rs

@@ -178,13 +178,26 @@ pub fn uu_app() -> Command {
 ///
 /// If the file could not be opened, or there was a problem setting the
 /// size of the file.
-fn file_truncate(filename: &str, create: bool, size: u64) -> std::io::Result<()> {
+fn file_truncate(filename: &str, create: bool, size: u64) -> UResult<()> {
+    #[cfg(unix)]
+    if let Ok(metadata) = std::fs::metadata(filename) {
+        if metadata.file_type().is_fifo() {
+            return Err(USimpleError::new(
+                1,
+                format!(
+                    "cannot open {} for writing: No such device or address",
+                    filename.quote()
+                ),
+            ));
+        }
+    }
     let path = Path::new(filename);
     match OpenOptions::new().write(true).create(create).open(path) {
         Ok(file) => file.set_len(size),
         Err(e) if e.kind() == ErrorKind::NotFound && !create => Ok(()),
         Err(e) => Err(e),
     }
+    .map_err_context(|| format!("cannot open {} for writing", filename.quote()))
 }
 
 /// Truncate files to a size relative to a given file.
@@ -236,19 +249,7 @@ fn truncate_reference_and_size(
     let fsize = metadata.len();
     let tsize = mode.to_size(fsize);
     for filename in filenames {
-        #[cfg(unix)]
-        if std::fs::metadata(filename)?.file_type().is_fifo() {
-            return Err(USimpleError::new(
-                1,
-                format!(
-                    "cannot open {} for writing: No such device or address",
-                    filename.quote()
-                ),
-            ));
-        }
-
-        file_truncate(filename, create, tsize)
-            .map_err_context(|| format!("cannot open {} for writing", filename.quote()))?;
+        file_truncate(filename, create, tsize)?;
     }
     Ok(())
 }
@@ -283,18 +284,7 @@ fn truncate_reference_file_only(
     })?;
     let tsize = metadata.len();
     for filename in filenames {
-        #[cfg(unix)]
-        if std::fs::metadata(filename)?.file_type().is_fifo() {
-            return Err(USimpleError::new(
-                1,
-                format!(
-                    "cannot open {} for writing: No such device or address",
-                    filename.quote()
-                ),
-            ));
-        }
-        file_truncate(filename, create, tsize)
-            .map_err_context(|| format!("cannot open {} for writing", filename.quote()))?;
+        file_truncate(filename, create, tsize)?;
     }
     Ok(())
 }
@@ -340,8 +330,8 @@ fn truncate_size_only(size_string: &str, filenames: &[String], create: bool) ->
             Err(_) => 0,
         };
         let tsize = mode.to_size(fsize);
-        file_truncate(filename, create, tsize)
-            .map_err_context(|| format!("cannot open {} for writing", filename.quote()))?;
+        // TODO: Fix duplicate call to stat
+        file_truncate(filename, create, tsize)?;
     }
     Ok(())
 }

tests/by-util/test_truncate.rs

@@ -266,6 +266,36 @@ fn test_new_file() {
     assert_eq!(at.read_bytes(filename), vec![b'\0'; 8]);
 }
 
+/// Test that truncating a non-existent file creates that file, even in reference-mode.
+#[test]
+fn test_new_file_reference() {
+    let (at, mut ucmd) = at_and_ucmd!();
+    let mut old_file = at.make_file(FILE1);
+    old_file.write_all(b"1234567890").unwrap();
+    let filename = "new_file_that_does_not_exist_yet";
+    ucmd.args(&["-r", FILE1, filename])
+        .succeeds()
+        .no_stdout()
+        .no_stderr();
+    assert!(at.file_exists(filename));
+    assert_eq!(at.read_bytes(filename), vec![b'\0'; 10]);
+}
+
+/// Test that truncating a non-existent file creates that file, even in size-and-reference-mode.
+#[test]
+fn test_new_file_size_and_reference() {
+    let (at, mut ucmd) = at_and_ucmd!();
+    let mut old_file = at.make_file(FILE1);
+    old_file.write_all(b"1234567890").unwrap();
+    let filename = "new_file_that_does_not_exist_yet";
+    ucmd.args(&["-s", "+3", "-r", FILE1, filename])
+        .succeeds()
+        .no_stdout()
+        .no_stderr();
+    assert!(at.file_exists(filename));
+    assert_eq!(at.read_bytes(filename), vec![b'\0'; 13]);
+}
+
 /// Test for not creating a non-existent file.
 #[test]
 fn test_new_file_no_create_size_only() {
@@ -280,7 +310,6 @@ fn test_new_file_no_create_size_only() {
 
 /// Test for not creating a non-existent file.
 #[test]
-#[ignore = "other bug"]
 fn test_new_file_no_create_reference_only() {
     let (at, mut ucmd) = at_and_ucmd!();
     let mut old_file = at.make_file(FILE1);
@@ -295,7 +324,6 @@ fn test_new_file_no_create_reference_only() {
 
 /// Test for not creating a non-existent file.
 #[test]
-#[ignore = "other bug"]
 fn test_new_file_no_create_size_and_reference() {
     let (at, mut ucmd) = at_and_ucmd!();
     let mut old_file = at.make_file(FILE1);