feat(ext/fetch): support fetching local files (#12545)

Closes #11925
Closes #2150

Co-authored-by: Bert Belder <bertbelder@gmail.com>

1 files changed, 52 insertions, 0 deletions

diff --git a/ext/fetch/fs_fetch_handler.rs b/ext/fetch/fs_fetch_handler.rs
new file mode 100644
index 000000000..82cbc4ecb
--- /dev/null
+++ b/ext/fetch/fs_fetch_handler.rs
@@ -0,0 +1,52 @@
+// Copyright 2018-2021 the Deno authors. All rights reserved. MIT license.
+
+use crate::CancelHandle;
+use crate::CancelableResponseFuture;
+use crate::FetchHandler;
+use crate::FetchRequestBodyResource;
+
+use deno_core::error::type_error;
+use deno_core::futures::FutureExt;
+use deno_core::futures::TryFutureExt;
+use deno_core::url::Url;
+use deno_core::CancelFuture;
+use reqwest::StatusCode;
+use std::rc::Rc;
+use tokio_util::io::ReaderStream;
+
+/// An implementation which tries to read file URLs from the file system via
+/// tokio::fs.
+#[derive(Clone)]
+pub struct FsFetchHandler;
+
+impl FetchHandler for FsFetchHandler {
+  fn fetch_file(
+    &mut self,
+    url: Url,
+  ) -> (
+    CancelableResponseFuture,
+    Option<FetchRequestBodyResource>,
+    Option<Rc<CancelHandle>>,
+  ) {
+    let cancel_handle = CancelHandle::new_rc();
+    let response_fut = async move {
+      let path = url.to_file_path()?;
+      let file = tokio::fs::File::open(path).map_err(|_| ()).await?;
+      let stream = ReaderStream::new(file);
+      let body = reqwest::Body::wrap_stream(stream);
+      let response = http::Response::builder()
+        .status(StatusCode::OK)
+        .body(body)
+        .map_err(|_| ())?
+        .into();
+      Ok::<_, ()>(response)
+    }
+    .map_err(move |_| {
+      type_error("NetworkError when attempting to fetch resource.")
+    })
+    .or_cancel(&cancel_handle)
+    .boxed_local();
+
+    (response_fut, None, Some(cancel_handle))
+  }
+}