Better error handling using do (#5890)

* adds `capture-errors` flag for `do`

* adds `get-type` core command to get type

* fmt

* add tests in example

* fmt

* fix tests

* manually revert previous changes related to `get-type`

* adds method to check for error name using `into string`

* fix clippy

crates/nu-protocol/src/shell_error.rs

@@ -724,6 +724,10 @@ impl From<Box<dyn std::error::Error + Send + Sync>> for ShellError {
     }
 }
 
+pub fn into_code(err: &ShellError) -> Option<String> {
+    err.code().map(|code| code.to_string())
+}
+
 pub fn did_you_mean(possibilities: &[String], tried: &str) -> Option<String> {
     let mut possible_matches: Vec<_> = possibilities
         .iter()

crates/nu-protocol/src/syntax_shape.rs

@@ -92,6 +92,9 @@ pub enum SyntaxShape {
     /// A record value
     Record,
 
+    /// An error value
+    Error,
+
     /// A custom shape with custom completion logic
     Custom(Box<SyntaxShape>, DeclId),
 }
@@ -112,6 +115,7 @@ impl SyntaxShape {
             SyntaxShape::Filesize => Type::Filesize,
             SyntaxShape::FullCellPath => Type::Any,
             SyntaxShape::GlobPattern => Type::String,
+            SyntaxShape::Error => Type::Error,
             SyntaxShape::ImportPattern => Type::Any,
             SyntaxShape::Int => Type::Int,
             SyntaxShape::List(x) => {
@@ -168,6 +172,7 @@ impl Display for SyntaxShape {
             SyntaxShape::Signature => write!(f, "signature"),
             SyntaxShape::Expression => write!(f, "expression"),
             SyntaxShape::Boolean => write!(f, "bool"),
+            SyntaxShape::Error => write!(f, "error"),
             SyntaxShape::Custom(x, _) => write!(f, "custom<{}>", x),
         }
     }