Add 'overlay new' command (#5647)

* Add 'overlay new' command

* Add missing file

crates/nu-parser/src/parse_keywords.rs

@@ -1745,6 +1745,9 @@ pub fn parse_overlay(
                     None,
                 );
             }
+            b"new" => {
+                return parse_overlay_new(working_set, spans, expand_aliases_denylist);
+            }
             b"remove" => {
                 return parse_overlay_remove(working_set, spans, expand_aliases_denylist);
             }
@@ -1802,6 +1805,96 @@ pub fn parse_overlay(
     )
 }
 
+pub fn parse_overlay_new(
+    working_set: &mut StateWorkingSet,
+    spans: &[Span],
+    expand_aliases_denylist: &[usize],
+) -> (Pipeline, Option<ParseError>) {
+    if spans.len() > 1 && working_set.get_span_contents(span(&spans[0..2])) != b"overlay new" {
+        return (
+            garbage_pipeline(spans),
+            Some(ParseError::UnknownState(
+                "internal error: Wrong call name for 'overlay new' command".into(),
+                span(spans),
+            )),
+        );
+    }
+
+    let (call, call_span) = match working_set.find_decl(b"overlay new") {
+        Some(decl_id) => {
+            let (call, mut err) = parse_internal_call(
+                working_set,
+                span(&spans[0..2]),
+                &spans[2..],
+                decl_id,
+                expand_aliases_denylist,
+            );
+            let decl = working_set.get_decl(decl_id);
+
+            let call_span = span(spans);
+
+            err = check_call(call_span, &decl.signature(), &call).or(err);
+            if err.is_some() || call.has_flag("help") {
+                return (
+                    Pipeline::from_vec(vec![Expression {
+                        expr: Expr::Call(call),
+                        span: call_span,
+                        ty: Type::Any,
+                        custom_completion: None,
+                    }]),
+                    err,
+                );
+            }
+
+            (call, call_span)
+        }
+        None => {
+            return (
+                garbage_pipeline(spans),
+                Some(ParseError::UnknownState(
+                    "internal error: 'overlay new' declaration not found".into(),
+                    span(spans),
+                )),
+            )
+        }
+    };
+
+    let (overlay_name, _) = if let Some(expr) = call.positional_nth(0) {
+        if let Some(s) = expr.as_string() {
+            (s, expr.span)
+        } else {
+            return (
+                garbage_pipeline(spans),
+                Some(ParseError::UnknownState(
+                    "internal error: Module name not a string".into(),
+                    expr.span,
+                )),
+            );
+        }
+    } else {
+        return (
+            garbage_pipeline(spans),
+            Some(ParseError::UnknownState(
+                "internal error: Missing required positional after call parsing".into(),
+                call_span,
+            )),
+        );
+    };
+
+    let pipeline = Pipeline::from_vec(vec![Expression {
+        expr: Expr::Call(call),
+        span: span(spans),
+        ty: Type::Any,
+        custom_completion: None,
+    }]);
+
+    let module_id = working_set.add_module(&overlay_name, Module::new());
+
+    working_set.add_overlay(overlay_name.as_bytes().to_vec(), module_id, vec![], vec![]);
+
+    (pipeline, None)
+}
+
 pub fn parse_overlay_add(
     working_set: &mut StateWorkingSet,
     spans: &[Span],