add rendered and json error messages in try/catch (#14082)

# Description

This PR adds a couple more options for dealing with try/catch errors. It
adds a `json` version of the error and a `rendered` version of the
error. It also respects the error_style configuration point.

![image](https://github.com/user-attachments/assets/32574f07-f511-40c0-8b57-de5f6f13a9c4)


# User-Facing Changes
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helps us keep track of breaking changes. -->

# Tests + Formatting
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crates/nu-cmd-lang/src/core_commands/try_.rs

@@ -107,7 +107,11 @@ fn run_catch(
 
     if let Some(catch) = catch {
         stack.set_last_error(&error);
-        let error = error.into_value(span);
+        let fancy_errors = match engine_state.get_config().error_style {
+            nu_protocol::ErrorStyle::Fancy => true,
+            nu_protocol::ErrorStyle::Plain => false,
+        };
+        let error = error.into_value(span, fancy_errors);
         let block = engine_state.get_block(catch.block_id);
         // Put the error value in the positional closure var
         if let Some(var) = block.signature.get_positional(0) {

crates/nu-command/tests/commands/try_.rs

@@ -126,3 +126,20 @@ fn prints_only_if_last_pipeline() {
     let actual = nu!("try { ['should not print'] | every 1 }; 'last value'");
     assert_eq!(actual.out, "last value");
 }
+
+#[test]
+fn get_error_columns() {
+    let actual = nu!(" try { non_existent_command } catch {|err| $err} | columns | to json -r");
+    assert_eq!(
+        actual.out,
+        "[\"msg\",\"debug\",\"raw\",\"rendered\",\"json\"]"
+    );
+}
+
+#[test]
+fn get_json_error() {
+    let actual = nu!("try { non_existent_command } catch {|err| $err} | get json | from json | update labels.span {{start: 0 end: 0}} | to json -r");
+    assert_eq!(
+        actual.out, "{\"msg\":\"External command failed\",\"labels\":[{\"text\":\"Command `non_existent_command` not found\",\"span\":{\"start\":0,\"end\":0}}],\"code\":\"nu::shell::external_command\",\"url\":null,\"help\":\"`non_existent_command` is neither a Nushell built-in or a known external command\",\"inner\":[]}"
+    );
+}

crates/nu-engine/src/eval_ir.rs

@@ -220,8 +220,17 @@ fn eval_ir_block_impl<D: DebugContext>(
             }
             Err(err) => {
                 if let Some(error_handler) = ctx.stack.error_handlers.pop(ctx.error_handler_base) {
+                    let fancy_errors = match ctx.engine_state.get_config().error_style {
+                        nu_protocol::ErrorStyle::Fancy => true,
+                        nu_protocol::ErrorStyle::Plain => false,
+                    };
                     // If an error handler is set, branch there
-                    prepare_error_handler(ctx, error_handler, Some(err.into_spanned(*span)));
+                    prepare_error_handler(
+                        ctx,
+                        error_handler,
+                        Some(err.into_spanned(*span)),
+                        fancy_errors,
+                    );
                     pc = error_handler.handler_index;
                 } else {
                     // If not, exit the block with the error
@@ -246,6 +255,7 @@ fn prepare_error_handler(
     ctx: &mut EvalContext<'_>,
     error_handler: ErrorHandler,
     error: Option<Spanned<ShellError>>,
+    fancy_errors: bool,
 ) {
     if let Some(reg_id) = error_handler.error_register {
         if let Some(error) = error {
@@ -254,7 +264,10 @@ fn prepare_error_handler(
             // Create the error value and put it in the register
             ctx.put_reg(
                 reg_id,
-                error.item.into_value(error.span).into_pipeline_data(),
+                error
+                    .item
+                    .into_value(error.span, fancy_errors)
+                    .into_pipeline_data(),
             );
         } else {
             // Set the register to empty

crates/nu-protocol/Cargo.toml

@@ -35,6 +35,7 @@ miette = { workspace = true, features = ["fancy-no-backtrace"] }
 num-format = { workspace = true }
 rmp-serde = { workspace = true, optional = true }
 serde = { workspace = true }
+serde_json = { workspace = true }
 thiserror = "1.0"
 typetag = "0.2"
 os_pipe = { workspace = true, features = ["io_safety"] }

crates/nu-protocol/src/errors/labeled_error.rs

@@ -139,6 +139,23 @@ impl LabeledError {
         self
     }
 
+    pub fn render_error_to_string(diag: impl miette::Diagnostic, fancy_errors: bool) -> String {
+        let theme = if fancy_errors {
+            miette::GraphicalTheme::unicode()
+        } else {
+            miette::GraphicalTheme::none()
+        };
+
+        let mut out = String::new();
+        miette::GraphicalReportHandler::new()
+            .with_width(80)
+            .with_theme(theme)
+            .render_report(&mut out, &diag)
+            .unwrap_or_default();
+
+        out
+    }
+
     /// Create a [`LabeledError`] from a type that implements [`miette::Diagnostic`].
     ///
     /// # Example

crates/nu-protocol/src/errors/shell_error.rs

@@ -1474,13 +1474,16 @@ impl ShellError {
         self.external_exit_code().map(|e| e.item).unwrap_or(1)
     }
 
-    pub fn into_value(self, span: Span) -> Value {
+    pub fn into_value(self, span: Span, fancy_errors: bool) -> Value {
         let exit_code = self.external_exit_code();
 
         let mut record = record! {
             "msg" => Value::string(self.to_string(), span),
             "debug" => Value::string(format!("{self:?}"), span),
-            "raw" => Value::error(self, span),
+            "raw" => Value::error(self.clone(), span),
+            // "labeled_error" => Value::string(LabeledError::from_diagnostic_and_render(self.clone()), span),
+            "rendered" => Value::string(ShellError::render_error_to_string(self.clone(), fancy_errors), span),
+            "json" => Value::string(serde_json::to_string(&self).expect("Could not serialize error"), span),
         };
 
         if let Some(code) = exit_code {
@@ -1499,6 +1502,21 @@ impl ShellError {
             span,
         )
     }
+    pub fn render_error_to_string(diag: impl miette::Diagnostic, fancy_errors: bool) -> String {
+        let theme = if fancy_errors {
+            miette::GraphicalTheme::unicode()
+        } else {
+            miette::GraphicalTheme::none()
+        };
+        let mut out = String::new();
+        miette::GraphicalReportHandler::new()
+            .with_width(80)
+            .with_theme(theme)
+            .render_report(&mut out, &diag)
+            .unwrap_or_default();
+
+        out
+    }
 }
 
 impl From<io::Error> for ShellError {