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-command/src/conversions/into/string.rs

@@ -2,8 +2,8 @@ use nu_engine::CallExt;
 use nu_protocol::{
     ast::{Call, CellPath},
     engine::{Command, EngineState, Stack},
-    Category, Config, Example, IntoPipelineData, PipelineData, ShellError, Signature, Span,
-    SyntaxShape, Value,
+    into_code, Category, Config, Example, IntoPipelineData, PipelineData, ShellError, Signature,
+    Span, SyntaxShape, Value,
 };
 
 // TODO num_format::SystemLocale once platform-specific dependencies are stable (see Cargo.toml)
@@ -247,6 +247,15 @@ pub fn action(
             val: input.into_string(", ", config),
             span,
         },
+        Value::Error { error } => Value::String {
+            val: {
+                match into_code(error) {
+                    Some(code) => code,
+                    None => "".to_string(),
+                }
+            },
+            span,
+        },
         Value::Nothing { .. } => Value::String {
             val: "".to_string(),
             span,

crates/nu-command/src/core_commands/do_.rs

@@ -1,7 +1,9 @@
 use nu_engine::{eval_block, CallExt};
 use nu_protocol::ast::Call;
 use nu_protocol::engine::{CaptureBlock, Command, EngineState, Stack};
-use nu_protocol::{Category, Example, PipelineData, Signature, SyntaxShape, Value};
+use nu_protocol::{
+    Category, Example, IntoPipelineData, PipelineData, Signature, SyntaxShape, Value,
+};
 
 #[derive(Clone)]
 pub struct Do;
@@ -23,6 +25,11 @@ impl Command for Do {
                 "ignore errors as the block runs",
                 Some('i'),
             )
+            .switch(
+                "capture-errors",
+                "capture errors as the block runs and return it",
+                Some('c'),
+            )
             .rest("rest", SyntaxShape::Any, "the parameter(s) for the block")
             .category(Category::Core)
     }
@@ -37,6 +44,7 @@ impl Command for Do {
         let block: CaptureBlock = call.req(engine_state, stack, 0)?;
         let rest: Vec<Value> = call.rest(engine_state, stack, 1)?;
         let ignore_errors = call.has_flag("ignore-errors");
+        let capture_errors = call.has_flag("capture-errors");
 
         let mut stack = stack.captures_to_stack(&block.captures);
         let block = engine_state.get_block(block.block_id);
@@ -85,7 +93,7 @@ impl Command for Do {
             block,
             input,
             call.redirect_stdout,
-            ignore_errors,
+            ignore_errors || capture_errors,
         );
 
         if ignore_errors {
@@ -93,6 +101,11 @@ impl Command for Do {
                 Ok(x) => Ok(x),
                 Err(_) => Ok(PipelineData::new(call.head)),
             }
+        } else if capture_errors {
+            match result {
+                Ok(x) => Ok(x),
+                Err(err) => Ok((Value::Error { error: err }).into_pipeline_data()),
+            }
         } else {
             result
         }