Add pipeline redirection support (#4594)

* redirection

* Remove commented-out

* fix tests

* more fixes

crates/nu-parser/src/known_external.rs

@@ -1,7 +1,7 @@
 use nu_protocol::ast::Expr;
 use nu_protocol::engine::{EngineState, Stack, StateWorkingSet};
-use nu_protocol::PipelineData;
 use nu_protocol::{ast::Call, engine::Command, ShellError, Signature};
+use nu_protocol::{PipelineData, Spanned};
 
 #[derive(Clone)]
 pub struct KnownExternal {
@@ -61,15 +61,25 @@ impl Command for KnownExternal {
                     call.positional.push(arg.clone())
                 }
 
-                // if last_expression {
-                //     call.named.push((
-                //         Spanned {
-                //             item: "last-expression".into(),
-                //             span: head.span,
-                //         },
-                //         None,
-                //     ))
-                // }
+                if call.redirect_stdout {
+                    call.named.push((
+                        Spanned {
+                            item: "redirect-stdout".into(),
+                            span: call_span,
+                        },
+                        None,
+                    ))
+                }
+
+                if call.redirect_stderr {
+                    call.named.push((
+                        Spanned {
+                            item: "redirect-stderr".into(),
+                            span: call_span,
+                        },
+                        None,
+                    ))
+                }
 
                 command.run(engine_state, stack, &call, input)
             }

crates/nu-parser/src/parse_keywords.rs

@@ -579,6 +579,8 @@ pub fn parse_export(
         decl_id: export_decl_id,
         positional: vec![],
         named: vec![],
+        redirect_stdout: true,
+        redirect_stderr: false,
     });
 
     let exportable = if let Some(kw_span) = spans.get(1) {
@@ -986,6 +988,8 @@ pub fn parse_module(
             decl_id: module_decl_id,
             positional: vec![module_name_expr, block_expr],
             named: vec![],
+            redirect_stdout: true,
+            redirect_stderr: false,
         });
 
         (
@@ -1200,6 +1204,8 @@ pub fn parse_use(
         decl_id: use_decl_id,
         positional: vec![import_pattern_expr],
         named: vec![],
+        redirect_stdout: true,
+        redirect_stderr: false,
     });
 
     (
@@ -1399,6 +1405,8 @@ pub fn parse_hide(
             decl_id: hide_decl_id,
             positional: vec![import_pattern_expr],
             named: vec![],
+            redirect_stdout: true,
+            redirect_stderr: false,
         });
 
         (
@@ -1480,6 +1488,8 @@ pub fn parse_let(
                             head: spans[0],
                             positional: vec![lvalue, rvalue],
                             named: vec![],
+                            redirect_stdout: true,
+                            redirect_stderr: false,
                         });
 
                         return (

crates/nu-parser/src/parser.rs

@@ -3420,7 +3420,7 @@ pub fn parse_expression(
                 (
                     Expression {
                         expr: Expr::String(String::new()),
-                        span: spans[pos],
+                        span: Span { start: 0, end: 0 },
                         ty: Type::Nothing,
                         custom_completion: None,
                     },
@@ -3556,6 +3556,8 @@ pub fn parse_expression(
                 decl_id,
                 named: vec![],
                 positional,
+                redirect_stdout: true,
+                redirect_stderr: false,
             }));
 
             (
@@ -4108,6 +4110,8 @@ fn wrap_expr_with_collect(working_set: &mut StateWorkingSet, expr: &Expression)
                 named: vec![],
                 positional: output,
                 decl_id,
+                redirect_stdout: true,
+                redirect_stderr: false,
             })),
             span,
             ty: Type::String,