Split the plugin crate (#12563)

# Description

This breaks `nu-plugin` up into four crates:

- `nu-plugin-protocol`: just the type definitions for the protocol, no
I/O. If someone wanted to wire up something more bare metal, maybe for
async I/O, they could use this.
- `nu-plugin-core`: the shared stuff between engine/plugin. Less stable
interface.
- `nu-plugin-engine`: everything required for the engine to talk to
plugins. Less stable interface.
- `nu-plugin`: everything required for the plugin to talk to the engine,
what plugin developers use. Should be the most stable interface.

No changes are made to the interface exposed by `nu-plugin` - it should
all still be there. Re-exports from `nu-plugin-protocol` or
`nu-plugin-core` are used as required. Plugins shouldn't ever have to
use those crates directly.

This should be somewhat faster to compile as `nu-plugin-engine` and
`nu-plugin` can compile in parallel, and the engine doesn't need
`nu-plugin` and plugins don't need `nu-plugin-engine` (except for test
support), so that should reduce what needs to be compiled too.

The only significant change here other than splitting stuff up was to
break the `source` out of `PluginCustomValue` and create a new
`PluginCustomValueWithSource` type that contains that instead. One bonus
of that is we get rid of the option and it's now more type-safe, but it
also means that the logic for that stuff (actually running the plugin
for custom value ops) can live entirely within the `nu-plugin-engine`
crate.

# User-Facing Changes
- New crates.
- Added `local-socket` feature for `nu` to try to make it possible to
compile without that support if needed.

# Tests + Formatting
- 🟢 `toolkit fmt`
- 🟢 `toolkit clippy`
- 🟢 `toolkit test`
- 🟢 `toolkit test stdlib`

crates/nu-plugin-test-support/Cargo.toml

@@ -6,6 +6,9 @@ license = "MIT"
 description = "Testing support for Nushell plugins"
 repository = "https://github.com/nushell/nushell/tree/main/crates/nu-plugin-test-support"
 
+[lib]
+bench = false
+
 # See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
 
 [dependencies]
@@ -13,6 +16,9 @@ nu-engine = { path = "../nu-engine", version = "0.92.3", features = ["plugin"] }
 nu-protocol = { path = "../nu-protocol", version = "0.92.3", features = ["plugin"] }
 nu-parser = { path = "../nu-parser", version = "0.92.3", features = ["plugin"] }
 nu-plugin = { path = "../nu-plugin", version = "0.92.3" }
+nu-plugin-core = { path = "../nu-plugin-core", version = "0.92.3" }
+nu-plugin-engine = { path = "../nu-plugin-engine", version = "0.92.3" }
+nu-plugin-protocol = { path = "../nu-plugin-protocol", version = "0.92.3" }
 nu-cmd-lang = { path = "../nu-cmd-lang", version = "0.92.3" }
 nu-ansi-term = { workspace = true }
 similar = "2.5"

crates/nu-plugin-test-support/src/fake_persistent_plugin.rs

@@ -3,7 +3,7 @@ use std::{
     sync::{Arc, OnceLock},
 };
 
-use nu_plugin::{GetPlugin, PluginInterface};
+use nu_plugin_engine::{GetPlugin, PluginInterface};
 use nu_protocol::{
     engine::{EngineState, Stack},
     PluginGcConfig, PluginIdentity, RegisteredPlugin, ShellError,

crates/nu-plugin-test-support/src/fake_register.rs

@@ -1,6 +1,7 @@
 use std::{ops::Deref, sync::Arc};
 
-use nu_plugin::{create_plugin_signature, Plugin, PluginDeclaration};
+use nu_plugin::{create_plugin_signature, Plugin};
+use nu_plugin_engine::PluginDeclaration;
 use nu_protocol::{engine::StateWorkingSet, RegisteredPlugin, ShellError};
 
 use crate::{fake_persistent_plugin::FakePersistentPlugin, spawn_fake_plugin::spawn_fake_plugin};

crates/nu-plugin-test-support/src/plugin_test.rs

@@ -4,7 +4,9 @@ use nu_ansi_term::Style;
 use nu_cmd_lang::create_default_context;
 use nu_engine::eval_block;
 use nu_parser::parse;
-use nu_plugin::{Plugin, PluginCommand, PluginCustomValue, PluginSource};
+use nu_plugin::{Plugin, PluginCommand};
+use nu_plugin_engine::{PluginCustomValueWithSource, PluginSource, WithSource};
+use nu_plugin_protocol::PluginCustomValue;
 use nu_protocol::{
     debugger::WithoutDebug,
     engine::{EngineState, Stack, StateWorkingSet},
@@ -135,13 +137,14 @@ impl PluginTest {
         // Serialize custom values in the input
         let source = self.source.clone();
         let input = input.map(
-            move |mut value| match PluginCustomValue::serialize_custom_values_in(&mut value) {
-                Ok(()) => {
+            move |mut value| {
+                let result = PluginCustomValue::serialize_custom_values_in(&mut value)
                     // Make sure to mark them with the source so they pass correctly, too.
-                    let _ = PluginCustomValue::add_source_in(&mut value, &source);
-                    value
+                    .and_then(|_| PluginCustomValueWithSource::add_source_in(&mut value, &source));
+                match result {
+                    Ok(()) => value,
+                    Err(err) => Value::error(err, value.span()),
                 }
-                Err(err) => Value::error(err, value.span()),
             },
             None,
         )?;
@@ -151,7 +154,9 @@ impl PluginTest {
         eval_block::<WithoutDebug>(&self.engine_state, &mut stack, &block, input)?.map(
             |mut value| {
                 // Make sure to deserialize custom values
-                match PluginCustomValue::deserialize_custom_values_in(&mut value) {
+                let result = PluginCustomValueWithSource::remove_source_in(&mut value)
+                    .and_then(|_| PluginCustomValue::deserialize_custom_values_in(&mut value));
+                match result {
                     Ok(()) => value,
                     Err(err) => Value::error(err, value.span()),
                 }
@@ -284,12 +289,12 @@ impl PluginTest {
         match (a, b) {
             (Value::Custom { val, .. }, _) => {
                 // We have to serialize both custom values before handing them to the plugin
-                let mut serialized =
-                    PluginCustomValue::serialize_from_custom_value(val.as_ref(), a.span())?;
-                serialized.set_source(Some(self.source.clone()));
+                let serialized =
+                    PluginCustomValue::serialize_from_custom_value(val.as_ref(), a.span())?
+                        .with_source(self.source.clone());
                 let mut b_serialized = b.clone();
                 PluginCustomValue::serialize_custom_values_in(&mut b_serialized)?;
-                PluginCustomValue::add_source_in(&mut b_serialized, &self.source)?;
+                PluginCustomValueWithSource::add_source_in(&mut b_serialized, &self.source)?;
                 // Now get the plugin reference and execute the comparison
                 let persistent = self.source.persistent(None)?.get_plugin(None)?;
                 let ordering = persistent.custom_value_partial_cmp(serialized, b_serialized)?;
@@ -354,8 +359,8 @@ impl PluginTest {
         val: &dyn CustomValue,
         span: Span,
     ) -> Result<Value, ShellError> {
-        let mut serialized = PluginCustomValue::serialize_from_custom_value(val, span)?;
-        serialized.set_source(Some(self.source.clone()));
+        let serialized = PluginCustomValue::serialize_from_custom_value(val, span)?
+            .with_source(self.source.clone());
         let persistent = self.source.persistent(None)?.get_plugin(None)?;
         persistent.custom_value_to_base_value(serialized.into_spanned(span))
     }

crates/nu-plugin-test-support/src/spawn_fake_plugin.rs

@@ -1,9 +1,9 @@
 use std::sync::{mpsc, Arc};
 
-use nu_plugin::{
-    InterfaceManager, Plugin, PluginInput, PluginInterfaceManager, PluginOutput, PluginRead,
-    PluginSource, PluginWrite,
-};
+use nu_plugin::Plugin;
+use nu_plugin_core::{InterfaceManager, PluginRead, PluginWrite};
+use nu_plugin_engine::{PluginInterfaceManager, PluginSource};
+use nu_plugin_protocol::{PluginInput, PluginOutput};
 use nu_protocol::{PluginIdentity, ShellError};
 
 use crate::fake_persistent_plugin::FakePersistentPlugin;