5 files changed, 58 insertions, 12 deletions
diff --git a/core/Cargo.toml b/core/Cargo.toml
index 2b4d40207..a246a7efe 100644
--- a/core/Cargo.toml
+++ b/core/Cargo.toml
@@ -16,6 +16,7 @@ path = "lib.rs"
 [features]
 default = ["v8_use_custom_libcxx"]
 v8_use_custom_libcxx = ["v8/use_custom_libcxx"]
+include_js_files_for_snapshotting = []
 
 [dependencies]
 anyhow.workspace = true
diff --git a/core/extensions.rs b/core/extensions.rs
index ab686d868..f84ab0a91 100644
--- a/core/extensions.rs
+++ b/core/extensions.rs
@@ -1,7 +1,9 @@
 // Copyright 2018-2023 the Deno authors. All rights reserved. MIT license.
 use crate::OpState;
+use anyhow::Context as _;
 use anyhow::Error;
 use std::cell::RefCell;
+use std::path::PathBuf;
 use std::rc::Rc;
 use std::task::Context;
 use v8::fast_api::FastFunction;
@@ -13,8 +15,24 @@ pub enum ExtensionFileSourceCode {
   /// will result in two copies of the source code being included - one in the
   /// snapshot, the other the static string in the `Extension`.
   IncludedInBinary(&'static str),
-  // TODO(bartlomieju): add more variants that allow to read file from the disk,
-  // and not include it in the binary.
+
+  // Source code is loaded from a file on disk. It's meant to be used if the
+  // embedder is creating snapshots. Files will be loaded from the filesystem
+  // during the build time and they will only be present in the V8 snapshot.
+  LoadedFromFsDuringSnapshot(PathBuf),
+}
+
+impl ExtensionFileSourceCode {
+  pub fn load(&self) -> Result<String, Error> {
+    match self {
+      ExtensionFileSourceCode::IncludedInBinary(code) => Ok(code.to_string()),
+      ExtensionFileSourceCode::LoadedFromFsDuringSnapshot(path) => {
+        let msg = format!("Failed to read \"{}\"", path.display());
+        let code = std::fs::read_to_string(path).context(msg)?;
+        Ok(code)
+      }
+    }
+  }
 }
 
 #[derive(Clone, Debug)]
@@ -299,6 +317,7 @@ impl ExtensionBuilder {
 /// - "internal:my_extension/js/01_hello.js"
 /// - "internal:my_extension/js/02_goodbye.js"
 /// ```
+#[cfg(not(feature = "include_js_files_for_snapshotting"))]
 #[macro_export]
 macro_rules! include_js_files {
   (dir $dir:literal, $($file:literal,)+) => {
@@ -323,3 +342,29 @@ macro_rules! include_js_files {
     ]
   };
 }
+
+#[cfg(feature = "include_js_files_for_snapshotting")]
+#[macro_export]
+macro_rules! include_js_files {
+  (dir $dir:literal, $($file:literal,)+) => {
+    vec![
+      $($crate::ExtensionFileSource {
+        specifier: concat!($dir, "/", $file).to_string(),
+        code: $crate::ExtensionFileSourceCode::LoadedFromFsDuringSnapshot(
+          std::path::PathBuf::from(env!("CARGO_MANIFEST_DIR")).join($dir).join($file)
+        ),
+      },)+
+    ]
+  };
+
+  ($($file:literal,)+) => {
+    vec![
+      $($crate::ExtensionFileSource {
+        specifier: $file.to_string(),
+        code: $crate::ExtensionFileSourceCode::LoadedFromFsDuringSnapshot(
+          std::path::PathBuf::from(env!("CARGO_MANIFEST_DIR")).join($file)
+        ),
+      },)+
+    ]
+  };
+}
diff --git a/core/modules.rs b/core/modules.rs
index 43dabf411..f1d4273e8 100644
--- a/core/modules.rs
+++ b/core/modules.rs
@@ -3,7 +3,6 @@
 use crate::bindings;
 use crate::error::generic_error;
 use crate::extensions::ExtensionFileSource;
-use crate::extensions::ExtensionFileSourceCode;
 use crate::module_specifier::ModuleSpecifier;
 use crate::resolve_import;
 use crate::resolve_url;
@@ -403,10 +402,9 @@ impl ModuleLoader for InternalModuleLoader {
       let result = if let Some(load_callback) = &self.maybe_load_callback {
         load_callback(file_source)
       } else {
-        match file_source.code {
-          ExtensionFileSourceCode::IncludedInBinary(code) => {
-            Ok(code.to_string())
-          }
+        match file_source.code.load() {
+          Ok(code) => Ok(code),
+          Err(err) => return futures::future::err(err).boxed_local(),
         }
       };
 
diff --git a/core/runtime.rs b/core/runtime.rs
index ae2b0489b..d098c25b1 100644
--- a/core/runtime.rs
+++ b/core/runtime.rs
@@ -21,7 +21,6 @@ use crate::source_map::SourceMapCache;
 use crate::source_map::SourceMapGetter;
 use crate::Extension;
 use crate::ExtensionFileSource;
-use crate::ExtensionFileSourceCode;
 use crate::NoopModuleLoader;
 use crate::OpMiddlewareFn;
 use crate::OpResult;
@@ -869,14 +868,11 @@ impl JsRuntime {
       {
         let js_files = ext.get_js_sources();
         for file_source in js_files {
-          let ExtensionFileSourceCode::IncludedInBinary(code) =
-            file_source.code;
-
           // TODO(@AaronO): use JsRuntime::execute_static() here to move src off heap
           realm.execute_script(
             self.v8_isolate(),
             &file_source.specifier,
-            code,
+            &file_source.code.load()?,
           )?;
         }
       }
diff --git a/core/snapshot_util.rs b/core/snapshot_util.rs
index a4bf80227..5b0ba92a0 100644
--- a/core/snapshot_util.rs
+++ b/core/snapshot_util.rs
@@ -33,6 +33,12 @@ pub fn create_snapshot(create_snapshot_options: CreateSnapshotOptions) {
     snapshot_module_load_cb: create_snapshot_options.snapshot_module_load_cb,
     ..Default::default()
   });
+  println!(
+    "JsRuntime for snapshot prepared, took {:#?} ({})",
+    Instant::now().saturating_duration_since(mark),
+    create_snapshot_options.snapshot_path.display()
+  );
+  mark = Instant::now();
 
   let snapshot = js_runtime.snapshot();
   let snapshot_slice: &[u8] = &snapshot;