help "operation"

Author: AmlingPalantir

operation/src/help.rs

@@ -0,0 +1,60 @@
+use opts::parser::OptionsPile;
+use opts::parser::Optionsable;
+use opts::vals::OptionalStringOption;
+use std::sync::Arc;
+use stream::Stream;
+use super::OperationBe;
+use super::OperationRegistrant;
+use validates::Validates;
+use validates::ValidationError;
+use validates::ValidationResult;
+
+#[derive(Default)]
+pub struct Options {
+    name: OptionalStringOption,
+}
+
+pub enum Void {
+}
+
+impl Validates for Options {
+    type Target = Void;
+
+    fn validate(self) -> ValidationResult<Void> {
+        let name = self.name.validate()?;
+        return ValidationError::help(match name {
+            Some(name) => super::REGISTRY.find(&name, &[])?.help(),
+            None => super::REGISTRY.help_list(),
+        });
+    }
+}
+
+pub(crate) type Impl = OperationRegistrant<ImplBe>;
+
+pub(crate) struct ImplBe();
+
+impl Optionsable for ImplBe {
+    type Options = Options;
+
+    fn options(opt: &mut OptionsPile<Options>) {
+        opt.match_extra_soft(|p, a| p.name.maybe_set_str(a), "operation to show help for");
+    }
+}
+
+impl OperationBe for ImplBe {
+    fn names() -> Vec<&'static str> {
+        return vec!["help"];
+    }
+
+    fn help_msg() -> &'static str {
+        return "show help for an operation";
+    }
+
+    fn get_extra(_o: Arc<Void>) -> Vec<String> {
+        panic!();
+    }
+
+    fn stream(_o: Arc<Void>) -> Stream {
+        panic!();
+    }
+}

operation/src/lib.rs

@@ -60,6 +60,7 @@ registry! {
     from_regex,
     from_split,
     grep,
+    help,
     join,
     multiplex,
     parse,
@@ -92,6 +93,7 @@ pub trait OperationBe: Optionsable {
 }
 
 pub trait OperationInbox {
+    fn help(&self) -> Vec<String>;
     fn parse(&self, args: &mut Vec<String>) -> ValidationResult<StreamWrapper>;
 }
 
@@ -126,6 +128,10 @@ impl<B: OperationBe + 'static> OperationInboxImpl<B> where <B::Options as Valida
 }
 
 impl<B: OperationBe + 'static> OperationInbox for OperationInboxImpl<B> where <B::Options as Validates>::Target: Send + Sync {
+    fn help(&self) -> Vec<String> {
+        return Self::static_help();
+    }
+
     fn parse(&self, args: &mut Vec<String>) -> ValidationResult<StreamWrapper> {
         let opt = Self::new_options();
         let o = opt.to_parser().parse(args);