From 1ab16e2426819af2c534e8a99b98f244626de512 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Bartek=20Iwa=C5=84czuk?= <biwanczuk@gmail.com>
Date: Sun, 5 Mar 2023 18:42:52 -0400
Subject: refactor(core): InternalModuleLoader checks if all files were used
 (#18005)

This commit changes "InternalModuleLoader" from "deno_core" to
store a list of used modules during snapshotting. If a module was not
used during snapshotting "InternalModuleLoader" will panic in its "Drop"
handler signaling to the embedder that they made a mistake somewhere.
---
 core/modules.rs | 37 +++++++++++++++++++++++++++++++++++++
 1 file changed, 37 insertions(+)

(limited to 'core')

diff --git a/core/modules.rs b/core/modules.rs
index b6220bb3b..3d335f8eb 100644
--- a/core/modules.rs
+++ b/core/modules.rs
@@ -328,6 +328,7 @@ pub type InternalModuleLoaderCb =
 pub struct InternalModuleLoader {
   module_loader: Rc<dyn ModuleLoader>,
   esm_sources: Vec<ExtensionFileSource>,
+  used_esm_sources: RefCell<HashMap<String, bool>>,
   maybe_load_callback: Option<InternalModuleLoaderCb>,
 }
 
@@ -336,6 +337,7 @@ impl Default for InternalModuleLoader {
     Self {
       module_loader: Rc::new(NoopModuleLoader),
       esm_sources: vec![],
+      used_esm_sources: RefCell::new(HashMap::default()),
       maybe_load_callback: None,
     }
   }
@@ -347,14 +349,43 @@ impl InternalModuleLoader {
     esm_sources: Vec<ExtensionFileSource>,
     maybe_load_callback: Option<InternalModuleLoaderCb>,
   ) -> Self {
+    let used_esm_sources: HashMap<String, bool> = esm_sources
+      .iter()
+      .map(|file_source| (file_source.specifier.to_string(), false))
+      .collect();
+
     InternalModuleLoader {
       module_loader: module_loader.unwrap_or_else(|| Rc::new(NoopModuleLoader)),
       esm_sources,
+      used_esm_sources: RefCell::new(used_esm_sources),
       maybe_load_callback,
     }
   }
 }
 
+impl Drop for InternalModuleLoader {
+  fn drop(&mut self) {
+    let used_esm_sources = self.used_esm_sources.get_mut();
+    let unused_modules: Vec<_> = used_esm_sources
+      .iter()
+      .filter(|(_s, v)| !*v)
+      .map(|(s, _)| s)
+      .collect();
+
+    if !unused_modules.is_empty() {
+      let mut msg =
+      "Following modules were passed to InternalModuleLoader but never used:\n"
+        .to_string();
+      for m in unused_modules {
+        msg.push_str("  - ");
+        msg.push_str(m);
+        msg.push('\n');
+      }
+      panic!("{}", msg);
+    }
+  }
+}
+
 impl ModuleLoader for InternalModuleLoader {
   fn resolve(
     &self,
@@ -400,6 +431,12 @@ impl ModuleLoader for InternalModuleLoader {
       .find(|file_source| file_source.specifier == module_specifier.as_str());
 
     if let Some(file_source) = maybe_file_source {
+      {
+        let mut used_esm_sources = self.used_esm_sources.borrow_mut();
+        let used = used_esm_sources.get_mut(&file_source.specifier).unwrap();
+        *used = true;
+      }
+
       let result = if let Some(load_callback) = &self.maybe_load_callback {
         load_callback(file_source)
       } else {
-- 
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