Merge pull request #271 from aslynatilla/porting-echo

Porting echo command

crates/nu-command/src/core_commands/echo.rs

@@ -0,0 +1,66 @@
+use nu_engine::CallExt;
+use nu_protocol::ast::Call;
+use nu_protocol::engine::{Command, EngineState, Stack};
+use nu_protocol::{
+    Example, PipelineData, ShellError, Signature, Span, SyntaxShape, Value, ValueStream,
+};
+
+#[derive(Clone)]
+pub struct Echo;
+
+impl Command for Echo {
+    fn name(&self) -> &str {
+        "echo"
+    }
+
+    fn usage(&self) -> &str {
+        "Echo the arguments back to the user."
+    }
+
+    fn signature(&self) -> Signature {
+        Signature::build("echo").rest("rest", SyntaxShape::Any, "the values to echo")
+    }
+
+    fn run(
+        &self,
+        engine_state: &EngineState,
+        stack: &mut Stack,
+        call: &Call,
+        _input: PipelineData,
+    ) -> Result<PipelineData, ShellError> {
+        call.rest(engine_state, stack, 0).map(|to_be_echoed| {
+            PipelineData::Stream(ValueStream::from_stream(
+                to_be_echoed.into_iter(),
+                engine_state.ctrlc.clone(),
+            ))
+        })
+    }
+
+    fn examples(&self) -> Vec<Example> {
+        vec![
+            Example {
+                description: "Put a hello message in the pipeline",
+                example: "echo 'hello'",
+                result: Some(Value::List {
+                    vals: vec![Value::test_string("hello")],
+                    span: Span::new(0, 0),
+                }),
+            },
+            Example {
+                description: "Print the value of the special '$nu' variable",
+                example: "echo $nu",
+                result: None,
+            },
+        ]
+    }
+}
+
+#[cfg(test)]
+mod test {
+    #[test]
+    fn test_examples() {
+        use super::Echo;
+        use crate::test_examples;
+        test_examples(Echo {})
+    }
+}

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

@@ -1,6 +1,7 @@
 mod alias;
 mod def;
 mod do_;
+mod echo;
 mod export_def;
 mod for_;
 mod help;
@@ -14,6 +15,7 @@ mod use_;
 pub use alias::Alias;
 pub use def::Def;
 pub use do_::Do;
+pub use echo::Echo;
 pub use export_def::ExportDef;
 pub use for_::For;
 pub use help::Help;

crates/nu-command/src/default_context.rs

@@ -30,6 +30,7 @@ pub fn create_default_context() -> EngineState {
             Def,
             Do,
             Each,
+            Echo,
             ExportDef,
             External,
             For,