added example for a config using FromValue

crates/nu_plugin_example/src/commands/config.rs

@@ -1,10 +1,37 @@
+use std::path::PathBuf;
+
 use nu_plugin::{EngineInterface, EvaluatedCall, SimplePluginCommand};
-use nu_protocol::{Category, LabeledError, Signature, Type, Value};
+use nu_protocol::{Category, FromValue, LabeledError, Signature, Spanned, Type, Value};
 
 use crate::ExamplePlugin;
 
 pub struct Config;
 
+/// Example config struct.
+///
+/// Using the `FromValue` derive macro, structs can be easily loaded from [`Value`]s,
+/// similar to serde's `Deserialize` macro.
+/// This is handy for plugin configs or piped data.
+/// All fields must implement [`FromValue`].
+/// For [`Option`] fields, they can be omitted in the config.
+///
+/// This example shows that nested and spanned data work too, so you can describe nested
+/// structures and get spans of values wrapped in [`Spanned`].
+/// Since this config uses only `Option`s, no field is required in the config.
+#[allow(dead_code)]
+#[derive(Debug, FromValue)]
+struct PluginConfig {
+    path: Option<Spanned<PathBuf>>,
+    nested: Option<SubConfig>,
+}
+
+#[allow(dead_code)]
+#[derive(Debug, FromValue)]
+struct SubConfig {
+    bool: bool,
+    string: String,
+}
+
 impl SimplePluginCommand for Config {
     type Plugin = ExamplePlugin;
 
@@ -39,7 +66,11 @@ impl SimplePluginCommand for Config {
     ) -> Result<Value, LabeledError> {
         let config = engine.get_plugin_config()?;
         match config {
-            Some(config) => Ok(config.clone()),
+            Some(value) => {
+                let config = PluginConfig::from_value(value.clone())?;
+                println!("got config {config:?}");
+                Ok(value)
+            }
             None => Err(LabeledError::new("No config sent").with_label(
                 "configuration for this plugin was not found in `$env.config.plugins.example`",
                 call.head,