make help() return a String

derive/src/help.rs

@@ -74,27 +74,27 @@ pub fn help_string(
     }
 
     let options = if !options.is_empty() {
-        quote!(::uutils_args::internal::print_flags(&mut w, #indent, #width, [#(#options),*])?;)
+        quote!(::uutils_args::internal::print_flags(&mut w, #indent, #width, [#(#options),*]);)
     } else {
         quote!()
     };
 
     quote!(
-        let mut w = ::std::io::stdout();
-        use ::std::io::Write;
+        let mut w = String::new();
+        use ::std::fmt::Write;
         writeln!(w, "{} {}",
             option_env!("CARGO_BIN_NAME").unwrap_or(env!("CARGO_PKG_NAME")),
             env!("CARGO_PKG_VERSION"),
-        )?;
+        ).unwrap();
 
-        writeln!(w, "{}", #summary)?;
+        writeln!(w, "{}", #summary).unwrap();
 
-        writeln!(w, "\nUsage:\n  {}", format!(#usage, bin_name))?;
+        writeln!(w, "\nUsage:\n  {}", format!(#usage, bin_name)).unwrap();
 
         #options
 
-        writeln!(w, "{}", #after_options)?;
-        Ok(())
+        writeln!(w, "{}", #after_options).unwrap();
+        w
     )
 }
 

derive/src/lib.rs

@@ -95,7 +95,7 @@ pub fn arguments(input: TokenStream) -> TokenStream {
                 }
             }
 
-            fn help(bin_name: &str) -> ::std::io::Result<()> {
+            fn help(bin_name: &str) -> String {
                 #help_string
             }
 

src/internal.rs

@@ -14,7 +14,7 @@ use crate::error::ErrorKind;
 use crate::value::Value;
 use std::{
     ffi::{OsStr, OsString},
-    io::Write,
+    fmt::Write,
 };
 
 /// Parses an echo-style positional argument
@@ -118,33 +118,32 @@ pub fn print_flags(
     indent_size: usize,
     width: usize,
     options: impl IntoIterator<Item = (&'static str, &'static str)>,
-) -> std::io::Result<()> {
+) {
     let indent = " ".repeat(indent_size);
-    writeln!(w, "\nOptions:")?;
+    writeln!(w, "\nOptions:").unwrap();
     for (flags, help_string) in options {
         let mut help_lines = help_string.lines();
-        write!(w, "{}{}", &indent, &flags)?;
+        write!(w, "{}{}", &indent, &flags).unwrap();
 
         if flags.len() <= width {
             let line = match help_lines.next() {
                 Some(line) => line,
                 None => {
-                    writeln!(w)?;
+                    writeln!(w).unwrap();
                     continue;
                 }
             };
             let help_indent = " ".repeat(width - flags.len() + 2);
-            writeln!(w, "{}{}", help_indent, line)?;
+            writeln!(w, "{}{}", help_indent, line).unwrap();
         } else {
-            writeln!(w)?;
+            writeln!(w).unwrap();
         }
 
         let help_indent = " ".repeat(width + indent_size + 2);
         for line in help_lines {
-            writeln!(w, "{}{}", help_indent, line)?;
+            writeln!(w, "{}{}", help_indent, line).unwrap();
         }
     }
-    Ok(())
 }
 
 #[cfg(test)]

src/lib.rs

@@ -82,7 +82,7 @@ pub trait Arguments: Sized {
     /// Print the help string for this command.
     ///
     /// The `bin_name` specifies the name that executable was called with.
-    fn help(bin_name: &str) -> std::io::Result<()>;
+    fn help(bin_name: &str) -> String;
 
     /// Get the version string for this command.
     fn version() -> String;
@@ -132,7 +132,7 @@ impl<T: Arguments> ArgumentIter<T> {
         })? {
             match arg {
                 Argument::Help => {
-                    T::help(self.parser.bin_name().unwrap()).unwrap();
+                    print!("{}", T::help(self.parser.bin_name().unwrap()));
                     std::process::exit(0);
                 }
                 Argument::Version => {