Add echo command

src/commands/echo.rs

@@ -0,0 +1,72 @@
+use crate::data::Value;
+use crate::errors::ShellError;
+use crate::prelude::*;
+
+use crate::parser::registry::Signature;
+
+pub struct Echo;
+
+impl PerItemCommand for Echo {
+    fn name(&self) -> &str {
+        "echo"
+    }
+
+    fn signature(&self) -> Signature {
+        Signature::build("echo").rest(SyntaxType::Any)
+    }
+
+    fn usage(&self) -> &str {
+        "Echo the argments back to the user."
+    }
+
+    fn run(
+        &self,
+        call_info: &CallInfo,
+        registry: &CommandRegistry,
+        raw_args: &RawCommandArgs,
+        _input: Tagged<Value>,
+    ) -> Result<OutputStream, ShellError> {
+        run(call_info, registry, raw_args)
+    }
+}
+
+fn run(
+    call_info: &CallInfo,
+    _registry: &CommandRegistry,
+    _raw_args: &RawCommandArgs,
+) -> Result<OutputStream, ShellError> {
+    let name = call_info.name_span;
+
+    let mut output = String::new();
+
+    let mut first = true;
+
+    if let Some(ref positional) = call_info.args.positional {
+        for i in positional {
+            match i.as_string() {
+                Ok(s) => {
+                    if !first {
+                        output.push_str(" ");
+                    } else {
+                        first = false;
+                    }
+
+                    output.push_str(&s);
+                }
+                _ => {
+                    return Err(ShellError::labeled_error(
+                        "Expect a string from pipeline",
+                        "not a string-compatible value",
+                        i.span(),
+                    ));
+                }
+            }
+        }
+    }
+
+    let stream = VecDeque::from(vec![Ok(ReturnSuccess::Value(
+        Value::string(output).simple_spanned(name),
+    ))]);
+
+    Ok(stream.to_output_stream())
+}