From 7077f0f1f382534bd6e2b49a3d3e3a114da4fc9f Mon Sep 17 00:00:00 2001
From: Lucien Greathouse <me@lpghatguy.com>
Date: Sat, 12 Oct 2019 23:27:12 -0700
Subject: [PATCH] Load user plugins on startup instead of lazily at snapshot
 time

---
 src/common_setup.rs                     |  3 +-
 src/snapshot_middleware/context.rs      | 48 ++++++++++++++++++-------
 src/snapshot_middleware/user_plugins.rs | 48 +------------------------
 3 files changed, 37 insertions(+), 62 deletions(-)

diff --git a/src/common_setup.rs b/src/common_setup.rs
index d21a07d9..50734117 100644
--- a/src/common_setup.rs
+++ b/src/common_setup.rs
@@ -41,8 +41,7 @@ pub fn start<F: VfsFetcher>(
         // If the project file defines no plugins, then there's no need to
         // initialize the snapshot plugin context.
         if !project.plugins.is_empty() {
-            snapshot_context.plugin_context =
-                Some(SnapshotPluginContext::new(project.plugins.clone()));
+            snapshot_context.plugin_context = Some(SnapshotPluginContext::new(&project.plugins));
         }
     }
 
diff --git a/src/snapshot_middleware/context.rs b/src/snapshot_middleware/context.rs
index ba376085..b125b890 100644
--- a/src/snapshot_middleware/context.rs
+++ b/src/snapshot_middleware/context.rs
@@ -1,7 +1,9 @@
-use std::{fmt, ops::Deref, path::PathBuf};
+use std::{fmt, fs, ops::Deref, path::Path};
 
 use rlua::{Lua, RegistryKey};
 
+use super::error::SnapshotError;
+
 #[derive(Debug)]
 pub struct InstanceSnapshotContext {
     /// Holds all the state needed to run user plugins as part of the snapshot
@@ -23,22 +25,42 @@ impl Default for InstanceSnapshotContext {
 pub struct SnapshotPluginContext {
     pub state: IgnoreDebug<Lua>,
 
-    /// Paths to the user plugins files. These paths are generated by the root
-    /// project file, if there is one.
-    pub plugin_paths: Vec<PathBuf>,
-
-    /// Lazy-initialized registry keys pointing to the values returned by each
-    /// user plugin. When processing user plugins, these should be applied in
-    /// order.
-    pub plugin_functions: Option<Vec<RegistryKey>>,
+    /// Registry keys pointing to the values returned by each user plugin. When
+    /// processing user plugins, these should be applied in order.
+    pub plugin_functions: Vec<RegistryKey>,
 }
 
 impl SnapshotPluginContext {
-    pub fn new(plugin_paths: Vec<PathBuf>) -> Self {
+    pub fn new<P: AsRef<Path>>(plugin_paths: &[P]) -> Self {
+        let lua_state = Lua::new();
+
+        let plugin_functions = plugin_paths
+            .iter()
+            .map(|path| {
+                let path = path.as_ref();
+
+                let content =
+                    fs::read_to_string(path).map_err(|err| SnapshotError::wrap(err, path))?;
+
+                lua_state.context(|lua_context| {
+                    // Plugins are currently expected to return a function that will
+                    // be run when a snapshot needs to be generated.
+                    let result = lua_context
+                        .load(&content)
+                        .set_name(&path.display().to_string())?
+                        .call::<_, rlua::Function>(())?;
+
+                    let key = lua_context.create_registry_value(result)?;
+
+                    Ok(key)
+                })
+            })
+            .collect::<Result<Vec<_>, SnapshotError>>()
+            .expect("Plugin initialization error");
+
         Self {
-            state: IgnoreDebug(Lua::new()),
-            plugin_paths,
-            plugin_functions: None,
+            state: IgnoreDebug(lua_state),
+            plugin_functions,
         }
     }
 }
diff --git a/src/snapshot_middleware/user_plugins.rs b/src/snapshot_middleware/user_plugins.rs
index 6e4627ce..f39d9336 100644
--- a/src/snapshot_middleware/user_plugins.rs
+++ b/src/snapshot_middleware/user_plugins.rs
@@ -1,12 +1,7 @@
-use std::{fs, path::Path};
-
-use rlua::{Lua, RegistryKey};
-
 use crate::vfs::{Vfs, VfsEntry, VfsFetcher};
 
 use super::{
     context::InstanceSnapshotContext,
-    error::SnapshotError,
     middleware::{SnapshotInstanceResult, SnapshotMiddleware},
 };
 
@@ -30,23 +25,9 @@ impl SnapshotMiddleware for SnapshotUserPlugins {
             None => return Ok(None),
         };
 
-        // If the plugins listed for use haven't been loaded yet, read them into
-        // memory, run them, and keep the result they return as a registry key
-        // into our Lua state.
-        let keys = match &plugin_context.plugin_functions {
-            Some(keys) => keys,
-            None => {
-                plugin_context.plugin_functions = Some(initialize_plugins(
-                    &plugin_context.state,
-                    &plugin_context.plugin_paths,
-                )?);
-                plugin_context.plugin_functions.as_ref().unwrap()
-            }
-        };
-
         plugin_context.state.context(|lua_context| {
             lua_context.scope(|_scope| {
-                for _key in keys {
+                for _key in &plugin_context.plugin_functions {
                     // TODO: Invoke plugin here and get result out.
 
                     // The current plan for plugins here is to make them work
@@ -85,30 +66,3 @@ impl SnapshotMiddleware for SnapshotUserPlugins {
         Ok(None)
     }
 }
-
-fn initialize_plugins<P: AsRef<Path>>(
-    lua_state: &Lua,
-    plugin_paths: &[P],
-) -> Result<Vec<RegistryKey>, SnapshotError> {
-    plugin_paths
-        .iter()
-        .map(|path| {
-            let path = path.as_ref();
-
-            let content = fs::read_to_string(path).map_err(|err| SnapshotError::wrap(err, path))?;
-
-            lua_state.context(|lua_context| {
-                // Plugins are currently expected to return a function that will
-                // be run when a snapshot needs to be generated.
-                let result = lua_context
-                    .load(&content)
-                    .set_name(&path.display().to_string())?
-                    .call::<_, rlua::Function>(())?;
-
-                let key = lua_context.create_registry_value(result)?;
-
-                Ok(key)
-            })
-        })
-        .collect::<Result<Vec<_>, _>>()
-}