Start support for commandline args to nu itself (#851)

* cmdline args wip

* WIP

* redirect working

* Add help and examples

* Only show flags in signature of more than help

crates/nu-command/src/filesystem/mod.rs

@@ -14,7 +14,7 @@ pub use cp::Cp;
 pub use ls::Ls;
 pub use mkdir::Mkdir;
 pub use mv::Mv;
-pub use open::Open;
+pub use open::{BufferedReader, Open};
 pub use rm::Rm;
 pub use save::Save;
 pub use touch::Touch;

crates/nu-command/src/filesystem/open.rs

@@ -184,6 +184,12 @@ pub struct BufferedReader<R: Read> {
     input: BufReader<R>,
 }
 
+impl<R: Read> BufferedReader<R> {
+    pub fn new(input: BufReader<R>) -> Self {
+        Self { input }
+    }
+}
+
 impl<R: Read> Iterator for BufferedReader<R> {
     type Item = Result<Vec<u8>, ShellError>;
 

crates/nu-engine/src/documentation.rs

@@ -186,6 +186,10 @@ pub fn get_documentation(
         long_desc.push('\n');
     }
 
+    if !sig.named.is_empty() {
+        long_desc.push_str(&get_flags_section(sig))
+    }
+
     if !sig.required_positional.is_empty()
         || !sig.optional_positional.is_empty()
         || sig.rest_positional.is_some()
@@ -205,13 +209,11 @@ pub fn get_documentation(
             long_desc.push_str(&format!("  ...args: {}\n", rest_positional.desc));
         }
     }
-    if !sig.named.is_empty() {
-        long_desc.push_str(&get_flags_section(sig))
-    }
 
     if !examples.is_empty() {
         long_desc.push_str("\nExamples:");
     }
+
     for example in examples {
         long_desc.push('\n');
         long_desc.push_str("  ");
@@ -222,7 +224,7 @@ pub fn get_documentation(
         } else if let Some(highlighter) = engine_state.find_decl(b"nu-highlight") {
             let decl = engine_state.get_decl(highlighter);
 
-            if let Ok(output) = decl.run(
+            match decl.run(
                 engine_state,
                 stack,
                 &Call::new(),
@@ -232,16 +234,23 @@ pub fn get_documentation(
                 }
                 .into_pipeline_data(),
             ) {
-                let result = output.into_value(Span { start: 0, end: 0 });
-                match result.as_string() {
-                    Ok(s) => {
-                        long_desc.push_str(&format!("\n  > {}\n", s));
-                    }
-                    _ => {
-                        long_desc.push_str(&format!("\n  > {}\n", example.example));
+                Ok(output) => {
+                    let result = output.into_value(Span { start: 0, end: 0 });
+                    match result.as_string() {
+                        Ok(s) => {
+                            long_desc.push_str(&format!("\n  > {}\n", s));
+                        }
+                        _ => {
+                            long_desc.push_str(&format!("\n  > {}\n", example.example));
+                        }
                     }
                 }
+                Err(_) => {
+                    long_desc.push_str(&format!("\n  > {}\n", example.example));
+                }
             }
+        } else {
+            long_desc.push_str(&format!("\n  > {}\n", example.example));
         }
     }
 

crates/nu-parser/src/lib.rs

@@ -12,9 +12,7 @@ pub use flatten::{
 };
 pub use lex::{lex, Token, TokenContents};
 pub use lite_parse::{lite_parse, LiteBlock};
-pub use parse_keywords::{
-    parse_alias, parse_def, parse_def_predecl, parse_let, parse_module, parse_use,
-};
+
 pub use parser::{find_captures_in_expr, parse, trim_quotes, Import};
 
 #[cfg(feature = "plugin")]

crates/nu-protocol/src/example.rs

@@ -1,5 +1,6 @@
 use crate::Value;
 
+#[derive(Debug)]
 pub struct Example {
     pub example: &'static str,
     pub description: &'static str,

crates/nu-protocol/src/signature.rs

@@ -279,6 +279,14 @@ impl Signature {
         one_liner.push_str(&self.name);
         one_liner.push(' ');
 
+        // Note: the call signature needs flags first because on the nu commandline,
+        // flags will precede the script file name. Flags for internal commands can come
+        // either before or after (or around) positional parameters, so there isn't a strong
+        // preference, so we default to the more constrained example.
+        if self.named.len() > 1 {
+            one_liner.push_str("{flags} ");
+        }
+
         for positional in &self.required_positional {
             one_liner.push_str(&get_positional_short_name(positional, true));
         }
@@ -286,18 +294,14 @@ impl Signature {
             one_liner.push_str(&get_positional_short_name(positional, false));
         }
 
-        if self.rest_positional.is_some() {
-            one_liner.push_str("...args ");
+        if let Some(rest) = &self.rest_positional {
+            one_liner.push_str(&format!("...{}", get_positional_short_name(rest, false)));
         }
 
         // if !self.subcommands.is_empty() {
         //     one_liner.push_str("<subcommand> ");
         // }
 
-        if !self.named.is_empty() {
-            one_liner.push_str("{flags} ");
-        }
-
         one_liner
     }