Stdout/Stderr redirection (#7185)

This adds new pipeline connectors called out> and err> which redirect either stdout or stderr to a file. You can also use out+err> (or err+out>) to redirect both streams into a file.

crates/nu-parser/src/flatten.rs

@@ -32,6 +32,10 @@ pub enum FlatShape {
     GlobPattern,
     Variable,
     Flag,
+    Pipe,
+    And,
+    Or,
+    Redirection,
     Custom(DeclId),
 }
 
@@ -63,6 +67,10 @@ impl Display for FlatShape {
             FlatShape::GlobPattern => write!(f, "shape_globpattern"),
             FlatShape::Variable => write!(f, "shape_variable"),
             FlatShape::Flag => write!(f, "shape_flag"),
+            FlatShape::Pipe => write!(f, "shape_pipe"),
+            FlatShape::And => write!(f, "shape_and"),
+            FlatShape::Or => write!(f, "shape_or"),
+            FlatShape::Redirection => write!(f, "shape_redirection"),
             FlatShape::Custom(_) => write!(f, "shape_custom"),
         }
     }
@@ -502,10 +510,30 @@ pub fn flatten_pipeline_element(
     pipeline_element: &PipelineElement,
 ) -> Vec<(Span, FlatShape)> {
     match pipeline_element {
-        PipelineElement::Expression(expr)
-        | PipelineElement::Redirect(expr)
-        | PipelineElement::And(expr)
-        | PipelineElement::Or(expr) => flatten_expression(working_set, expr),
+        PipelineElement::Expression(span, expr) => {
+            if let Some(span) = span {
+                let mut output = vec![(*span, FlatShape::Pipe)];
+                output.append(&mut flatten_expression(working_set, expr));
+                output
+            } else {
+                flatten_expression(working_set, expr)
+            }
+        }
+        PipelineElement::Redirection(span, _, expr) => {
+            let mut output = vec![(*span, FlatShape::Redirection)];
+            output.append(&mut flatten_expression(working_set, expr));
+            output
+        }
+        PipelineElement::And(span, expr) => {
+            let mut output = vec![(*span, FlatShape::And)];
+            output.append(&mut flatten_expression(working_set, expr));
+            output
+        }
+        PipelineElement::Or(span, expr) => {
+            let mut output = vec![(*span, FlatShape::Or)];
+            output.append(&mut flatten_expression(working_set, expr));
+            output
+        }
     }
 }