false: Align behavior to true and GNU

src/uu/false/src/false.rs

@@ -4,16 +4,43 @@
 //  *
 //  * For the full copyright and license information, please view the LICENSE
 //  * file that was distributed with this source code.
+use clap::{App, AppSettings, ErrorKind};
+use std::io::Write;
+use uucore::error::{set_exit_code, UResult};
 
-use clap::App;
+static ABOUT: &str = "
-use uucore::error::UResult;
+ Returns false, an unsuccessful exit status.
+
+ Immediately returns with the exit status `1`. When invoked with one of the recognized options it
+ will try to write the help or version text. Any IO error during this operation is diagnosed, yet
+ the program will also return `1`.
+";
 
 #[uucore::main]
 pub fn uumain(args: impl uucore::Args) -> UResult<()> {
-    uu_app().get_matches_from(args);
+    let app = uu_app();
-    Err(1.into())
+
+    // Mirror GNU options, always return `1`. In particular even the 'successful' cases of no-op,
+    // and the interrupted display of help and version should return `1`. Also, we return Ok in all
+    // paths to avoid the allocation of an error object, an operation that could, in theory, fail
+    // and unwind through the standard library allocation handling machinery.
+    set_exit_code(1);
+
+    if let Err(err) = app.try_get_matches_from(args) {
+        if let ErrorKind::DisplayHelp | ErrorKind::DisplayVersion = err.kind {
+            if let Err(print_fail) = err.print() {
+                // Try to display this error.
+                let _ = writeln!(std::io::stderr(), "{}: {}", uucore::util_name(), print_fail);
+            }
+        }
+    }
+
+    Ok(())
 }
 
 pub fn uu_app<'a>() -> App<'a> {
     App::new(uucore::util_name())
+        .version(clap::crate_version!())
+        .about(ABOUT)
+        .setting(AppSettings::InferLongArgs)
 }