setting: SubcommandHelpShowsLongForm implemented

Refactoring and better test cases

Refactored SubcommandHelpShowsLongForm to
UseLongFormatForHelpSubcommand.
Tests and docuemntation examples use about and long_about instead of
(before/after)_help.

Removed commented out tests

Linting: Fix trailing new line

Updated change log, refactored tests and doc str

Reordered items in the Changelog
New test added and old tests removed that were redundant
Doc string for AppSettings::UseLongFormatForHelpSubcommand fixed

CHANGELOG.md

@@ -56,6 +56,7 @@ TODO: `cargo`, `std` features
   * **Error**
     * `Error::print`
 * **Added Settings**
+  * `AppSettings::UseLongFormatForHelpSubcommand`
   * `ArgSettings::HideEnv`
 
 #### Enhancements

src/build/app/settings.rs

@@ -48,6 +48,7 @@ bitflags! {
         const HELP_REQUIRED                  = 1 << 40;
         const SUBCOMMAND_PRECEDENCE_OVER_ARG = 1 << 41;
         const DISABLE_HELP_FLAG              = 1 << 42;
+        const USE_LONG_FORMAT_FOR_HELP_SC    = 1 << 43;
     }
 }
 
@@ -126,6 +127,8 @@ impl_settings! { AppSettings, AppFlags,
         => Flags::SC_REQUIRED,
     SubcommandRequiredElseHelp("subcommandrequiredelsehelp")
         => Flags::SC_REQUIRED_ELSE_HELP,
+    UseLongFormatForHelpSubcommand("uselongformatforhelpsubcommand")
+        => Flags::USE_LONG_FORMAT_FOR_HELP_SC,
     TrailingVarArg("trailingvararg")
         => Flags::TRAILING_VARARG,
     UnifiedHelpMessage("unifiedhelpmessage")
@@ -904,6 +907,28 @@ pub enum AppSettings {
     /// [``]: ./struct..html
     SubcommandRequiredElseHelp,
 
+    /// Specifies that the help subcommand should print the [long format] help message.
+    ///
+    /// **NOTE:** This setting is useless if [`AppSettings::DisableHelpSubcommand`] or [`AppSettings::NoAutoHelp`] is set,
+    /// or if the app contains no subcommands at all.
+    ///
+    /// # Examples
+    ///
+    /// ```rust
+    /// # use clap::{App, Arg, AppSettings};
+    /// App::new("myprog")
+    ///     .setting(AppSettings::UseLongFormatForHelpSubcommand)
+    ///     .subcommand(App::new("test")
+    ///         .arg(Arg::new("foo")
+    ///             .about("short form about message")
+    ///             .long_about("long form about message")
+    ///         )
+    ///     )
+    ///     .get_matches();
+    /// ```
+    /// [long format]: App::long_about
+    UseLongFormatForHelpSubcommand,
+
     /// Specifies that any invalid UTF-8 code points should be treated as an error and fail
     /// with a [`ErrorKind::InvalidUtf8`] error.
     ///
@@ -1159,6 +1184,12 @@ mod test {
             "subcommandrequiredelsehelp".parse::<AppSettings>().unwrap(),
             AppSettings::SubcommandRequiredElseHelp
         );
+        assert_eq!(
+            "uselongformatforhelpsubcommand"
+                .parse::<AppSettings>()
+                .unwrap(),
+            AppSettings::UseLongFormatForHelpSubcommand
+        );
         assert_eq!(
             "strictutf8".parse::<AppSettings>().unwrap(),
             AppSettings::StrictUtf8

src/parse/parser.rs

@@ -808,7 +808,7 @@ impl<'help, 'app> Parser<'help, 'app> {
             parser.app.bin_name = Some(format!("{} {}", bin_name, parser.app.name));
         }
 
-        Err(parser.help_err(false))
+        Err(parser.help_err(self.app.is_set(AS::UseLongFormatForHelpSubcommand)))
     }
 
     fn is_new_arg(&self, arg_os: &ArgStr, last_result: &ParseResult) -> bool {

tests/app_settings.rs

@@ -97,6 +97,57 @@ SUBCOMMANDS:
     help    Prints this message or the help of the given subcommand(s)
     info";
 
+static LONG_FORMAT_FOR_HELP_SUBCOMMAND: &str = "myprog-test 
+
+USAGE:
+    myprog test [foo]
+
+ARGS:
+    <foo>
+            long form about message
+
+FLAGS:
+    -h, --help
+            Prints help information
+
+    -V, --version
+            Prints version information";
+
+static LONG_FORMAT_FOR_NESTED_HELP_SUBCOMMAND: &str = "myprog-test-nested 
+
+long form about message
+
+USAGE:
+    myprog test nested
+
+FLAGS:
+    -h, --help
+            Prints help information
+
+    -V, --version
+            Prints version information";
+
+static LONG_FORMAT_SINGLE_ARG_HELP_SUBCOMMAND: &str = "myprog 
+
+USAGE:
+    myprog [foo] [SUBCOMMAND]
+
+ARGS:
+    <foo>
+            long form about message
+
+FLAGS:
+    -h, --help
+            Prints help information
+
+    -V, --version
+            Prints version information
+
+SUBCOMMANDS:
+    help
+            Prints this message or the help of the given subcommand(s)
+    test";
+
 #[test]
 fn sub_command_negate_required() {
     App::new("sub_command_negate")
@@ -1022,3 +1073,59 @@ fn aaos_option_use_delim_false() {
         &["one,two"]
     );
 }
+
+#[test]
+fn nested_help_subcommand_with_global_setting() {
+    let m = App::new("myprog")
+        .global_setting(AppSettings::UseLongFormatForHelpSubcommand)
+        .subcommand(
+            App::new("test").subcommand(
+                App::new("nested")
+                    .about("short form about message")
+                    .long_about("long form about message"),
+            ),
+        );
+    assert!(utils::compare_output(
+        m,
+        "myprog test help nested",
+        LONG_FORMAT_FOR_NESTED_HELP_SUBCOMMAND,
+        false
+    ));
+}
+
+#[test]
+fn single_arg_help_with_long_format_setting() {
+    let m = App::new("myprog")
+        .setting(AppSettings::UseLongFormatForHelpSubcommand)
+        .subcommand(App::new("test"))
+        .arg(
+            Arg::new("foo")
+                .about("short form about message")
+                .long_about("long form about message"),
+        );
+    assert!(utils::compare_output(
+        m,
+        "myprog help",
+        LONG_FORMAT_SINGLE_ARG_HELP_SUBCOMMAND,
+        false
+    ));
+}
+
+#[test]
+fn use_long_format_for_help_subcommand_with_setting() {
+    let m = App::new("myprog")
+        .setting(AppSettings::UseLongFormatForHelpSubcommand)
+        .subcommand(
+            App::new("test").arg(
+                Arg::new("foo")
+                    .about("short form about message")
+                    .long_about("long form about message"),
+            ),
+        );
+    assert!(utils::compare_output(
+        m,
+        "myprog help test",
+        LONG_FORMAT_FOR_HELP_SUBCOMMAND,
+        false
+    ));
+}