update docs

RELEASE_NOTES.md

@@ -1,3 +1,6 @@
+### 3.1.0
+* Add support for MainCommand attribute.
+
 ### 3.0.1
 * Bugfix usage string rendering issue where description might span multiple lines.
 

docs/content/tutorial.fsx

@@ -192,6 +192,37 @@ Arguments can specify the following primitives as parameters:
   * `System.Numerics.BigInt`.
   * `byte[]`, which accepts base64 representations.
 
+## Main commands
+
+Arguments carrying the [MainCommand](reference/argu-arguattributes-maincommandattribute.html) 
+attribute can be used to specify the main set of arguments for the CLI.
+These arguments can be passed without the need to specify a switch identifier.
+
+*)
+
+type WGetArguments =
+    | Quiet
+    | No_Check_Certificate
+    | [<MainCommand; ExactlyOnce; Last>] Urls of url:string list
+
+(**
+
+which generates the syntax
+
+    [lang=console]
+    USAGE: fsianycpu.exe [--help] [--quiet] [--no-check-certificate] <url>...
+
+    URLS:
+
+        <url>...              List of urls to download from.
+
+    OPTIONS:
+
+        --quiet               Turn off Wget's output.
+        --no-check-certificate
+                              Don't check the server certificate.
+        --help                display this list of options.
+
 ## Optional and List parameters
 
 Additionally, it is possible to specify argument parameters that are either optional or lists:

src/Argu/PreCompute.fs

@@ -403,12 +403,8 @@ let rec private preComputeUnionCaseArgInfo (stack : Type list) (helpParam : Help
 
     // extract the description string for given union case
     let description = 
-        try dummy.Usage.Split([|'\n'|], StringSplitOptions.RemoveEmptyEntries) |> Array.toList
-        with _ -> 
-            arguExn "Error generating usage string from IArgParserTemplate for case %O." uci
-
-    if List.isEmpty description then
-        arguExn "Usage string for case '%O' was empty." uci
+        try dummy.Usage.Split('\n') |> Array.toList
+        with _ -> arguExn "Error generating usage string from IArgParserTemplate for case %O." uci
 
     let uai = {
         UnionCaseInfo = uci
@@ -464,10 +460,7 @@ and private preComputeUnionArgInfoInner (stack : Type list) (helpParam : HelpPar
             let description = 
                 match t.TryGetAttribute<HelpDescriptionAttribute> () with
                 | None -> [defaultHelpDescription]
-                | Some attr -> 
-                    match attr.Description.Split([|'\n'|], StringSplitOptions.RemoveEmptyEntries) with
-                    | [||] -> arguExn "Text defined in HelpDescriptionAttribute was empty."
-                    | descr -> Array.toList descr
+                | Some attr -> attr.Description.Split('\n') |> Array.toList
 
             { Flags = helpSwitches ; Description = description }