Better generic errors for plugins (and perhaps scripts) (#12236)

# Description
This makes `LabeledError` much more capable of representing close to
everything a `miette::Diagnostic` can, including `ShellError`, and
allows plugins to generate multiple error spans, codes, help, etc.

`LabeledError` is now embeddable within `ShellError` as a transparent
variant.

This could also be used to improve `error make` and `try/catch` to
reflect `LabeledError` exactly in the future.

Also cleaned up some errors in existing plugins.

# User-Facing Changes
Breaking change for plugins. Nicer errors for users.

crates/nu_plugin_example/src/commands/collect_external.rs

@@ -1,5 +1,7 @@
-use nu_plugin::{EngineInterface, EvaluatedCall, LabeledError, PluginCommand};
-use nu_protocol::{Category, PipelineData, PluginExample, PluginSignature, RawStream, Type, Value};
+use nu_plugin::{EngineInterface, EvaluatedCall, PluginCommand};
+use nu_protocol::{
+    Category, LabeledError, PipelineData, PluginExample, PluginSignature, RawStream, Type, Value,
+};
 
 use crate::Example;
 

crates/nu_plugin_example/src/commands/config.rs

@@ -1,5 +1,5 @@
-use nu_plugin::{EngineInterface, EvaluatedCall, LabeledError, SimplePluginCommand};
-use nu_protocol::{Category, PluginSignature, Type, Value};
+use nu_plugin::{EngineInterface, EvaluatedCall, SimplePluginCommand};
+use nu_protocol::{Category, LabeledError, PluginSignature, Type, Value};
 
 use crate::Example;
 
@@ -27,12 +27,10 @@ impl SimplePluginCommand for Config {
         let config = engine.get_plugin_config()?;
         match config {
             Some(config) => Ok(config.clone()),
-            None => Err(LabeledError {
-                label: "No config sent".into(),
-                msg: "Configuration for this plugin was not found in `$env.config.plugins.example`"
-                    .into(),
-                span: Some(call.head),
-            }),
+            None => Err(LabeledError::new("No config sent").with_label(
+                "configuration for this plugin was not found in `$env.config.plugins.example`",
+                call.head,
+            )),
         }
     }
 }

crates/nu_plugin_example/src/commands/disable_gc.rs

@@ -1,5 +1,5 @@
-use nu_plugin::{EngineInterface, EvaluatedCall, LabeledError, SimplePluginCommand};
-use nu_protocol::{Category, PluginSignature, Value};
+use nu_plugin::{EngineInterface, EvaluatedCall, SimplePluginCommand};
+use nu_protocol::{Category, LabeledError, PluginSignature, Value};
 
 use crate::Example;
 

crates/nu_plugin_example/src/commands/env.rs

@@ -1,5 +1,5 @@
-use nu_plugin::{EngineInterface, EvaluatedCall, LabeledError, SimplePluginCommand};
-use nu_protocol::{Category, PluginSignature, SyntaxShape, Type, Value};
+use nu_plugin::{EngineInterface, EvaluatedCall, SimplePluginCommand};
+use nu_protocol::{Category, LabeledError, PluginSignature, SyntaxShape, Type, Value};
 
 use crate::Example;
 
@@ -42,11 +42,8 @@ impl SimplePluginCommand for Env {
                     // Get working directory
                     Ok(Value::string(engine.get_current_dir()?, call.head))
                 }
-                Some(value) => Err(LabeledError {
-                    label: "Invalid arguments".into(),
-                    msg: "--cwd can't be used with --set".into(),
-                    span: Some(value.span()),
-                }),
+                Some(value) => Err(LabeledError::new("Invalid arguments")
+                    .with_label("--cwd can't be used with --set", value.span())),
             }
         } else if let Some(value) = call.get_flag_value("set") {
             // Set single env var

crates/nu_plugin_example/src/commands/for_each.rs

@@ -1,5 +1,7 @@
-use nu_plugin::{EngineInterface, EvaluatedCall, LabeledError, PluginCommand};
-use nu_protocol::{Category, PipelineData, PluginExample, PluginSignature, SyntaxShape, Type};
+use nu_plugin::{EngineInterface, EvaluatedCall, PluginCommand};
+use nu_protocol::{
+    Category, LabeledError, PipelineData, PluginExample, PluginSignature, SyntaxShape, Type,
+};
 
 use crate::Example;
 

crates/nu_plugin_example/src/commands/generate.rs

@@ -1,7 +1,7 @@
-use nu_plugin::{EngineInterface, EvaluatedCall, LabeledError, PluginCommand};
+use nu_plugin::{EngineInterface, EvaluatedCall, PluginCommand};
 use nu_protocol::{
-    Category, IntoInterruptiblePipelineData, PipelineData, PluginExample, PluginSignature,
-    SyntaxShape, Type, Value,
+    Category, IntoInterruptiblePipelineData, LabeledError, PipelineData, PluginExample,
+    PluginSignature, SyntaxShape, Type, Value,
 };
 
 use crate::Example;

crates/nu_plugin_example/src/commands/main.rs

@@ -1,5 +1,5 @@
-use nu_plugin::{EngineInterface, EvaluatedCall, LabeledError, SimplePluginCommand};
-use nu_protocol::{Category, PluginSignature, Value};
+use nu_plugin::{EngineInterface, EvaluatedCall, SimplePluginCommand};
+use nu_protocol::{Category, LabeledError, PluginSignature, Value};
 
 use crate::Example;
 
@@ -32,10 +32,7 @@ particularly useful.
         call: &EvaluatedCall,
         _input: &Value,
     ) -> Result<Value, LabeledError> {
-        Err(LabeledError {
-            label: "No subcommand provided".into(),
-            msg: "add --help to see a list of subcommands".into(),
-            span: Some(call.head),
-        })
+        Err(LabeledError::new("No subcommand provided")
+            .with_label("add --help to see a list of subcommands", call.head))
     }
 }

crates/nu_plugin_example/src/commands/one.rs

@@ -1,5 +1,5 @@
-use nu_plugin::{EngineInterface, EvaluatedCall, LabeledError, SimplePluginCommand};
-use nu_protocol::{Category, PluginExample, PluginSignature, SyntaxShape, Value};
+use nu_plugin::{EngineInterface, EvaluatedCall, SimplePluginCommand};
+use nu_protocol::{Category, LabeledError, PluginExample, PluginSignature, SyntaxShape, Value};
 
 use crate::Example;
 

crates/nu_plugin_example/src/commands/seq.rs

@@ -1,6 +1,7 @@
-use nu_plugin::{EngineInterface, EvaluatedCall, LabeledError, PluginCommand};
+use nu_plugin::{EngineInterface, EvaluatedCall, PluginCommand};
 use nu_protocol::{
-    Category, ListStream, PipelineData, PluginExample, PluginSignature, SyntaxShape, Type, Value,
+    Category, LabeledError, ListStream, PipelineData, PluginExample, PluginSignature, SyntaxShape,
+    Type, Value,
 };
 
 use crate::Example;

crates/nu_plugin_example/src/commands/sum.rs

@@ -1,5 +1,7 @@
-use nu_plugin::{EngineInterface, EvaluatedCall, LabeledError, PluginCommand};
-use nu_protocol::{Category, PipelineData, PluginExample, PluginSignature, Span, Type, Value};
+use nu_plugin::{EngineInterface, EvaluatedCall, PluginCommand};
+use nu_protocol::{
+    Category, LabeledError, PipelineData, PluginExample, PluginSignature, Span, Type, Value,
+};
 
 use crate::Example;
 
@@ -33,18 +35,15 @@ impl PluginCommand for Sum {
         input: PipelineData,
     ) -> Result<PipelineData, LabeledError> {
         let mut acc = IntOrFloat::Int(0);
-        let span = input.span();
         for value in input {
             if let Ok(n) = value.as_i64() {
                 acc.add_i64(n);
             } else if let Ok(n) = value.as_f64() {
                 acc.add_f64(n);
             } else {
-                return Err(LabeledError {
-                    label: "Stream only accepts ints and floats".into(),
-                    msg: format!("found {}", value.get_type()),
-                    span,
-                });
+                return Err(LabeledError::new("Sum only accepts ints and floats")
+                    .with_label(format!("found {} in input", value.get_type()), value.span())
+                    .with_label("can't be used here", call.head));
             }
         }
         Ok(PipelineData::Value(acc.to_value(call.head), None))

crates/nu_plugin_example/src/commands/three.rs

@@ -1,5 +1,5 @@
-use nu_plugin::{EngineInterface, EvaluatedCall, LabeledError, SimplePluginCommand};
-use nu_protocol::{Category, PluginSignature, SyntaxShape, Value};
+use nu_plugin::{EngineInterface, EvaluatedCall, SimplePluginCommand};
+use nu_protocol::{Category, LabeledError, PluginSignature, SyntaxShape, Value};
 
 use crate::Example;
 
@@ -31,10 +31,7 @@ impl SimplePluginCommand for Three {
     ) -> Result<Value, LabeledError> {
         plugin.print_values(3, call, input)?;
 
-        Err(LabeledError {
-            label: "ERROR from plugin".into(),
-            msg: "error message pointing to call head span".into(),
-            span: Some(call.head),
-        })
+        Err(LabeledError::new("ERROR from plugin")
+            .with_label("error message pointing to call head span", call.head))
     }
 }

crates/nu_plugin_example/src/commands/two.rs

@@ -1,5 +1,5 @@
-use nu_plugin::{EngineInterface, EvaluatedCall, LabeledError, SimplePluginCommand};
-use nu_protocol::{record, Category, PluginSignature, SyntaxShape, Value};
+use nu_plugin::{EngineInterface, EvaluatedCall, SimplePluginCommand};
+use nu_protocol::{record, Category, LabeledError, PluginSignature, SyntaxShape, Value};
 
 use crate::Example;
 

crates/nu_plugin_example/src/example.rs

@@ -1,5 +1,5 @@
-use nu_plugin::{EvaluatedCall, LabeledError};
-use nu_protocol::Value;
+use nu_plugin::EvaluatedCall;
+use nu_protocol::{LabeledError, Value};
 
 pub struct Example;