fix: memory issues when importing giant mrpack files (#6278)

* feat: dont load mrpacks into memory if they are local imports

* fix: frontend

packages/app-lib/src/util/fetch.rs

@@ -16,7 +16,7 @@ use std::path::{Path, PathBuf};
 use std::sync::LazyLock;
 use std::time::{self};
 use tokio::sync::Semaphore;
-use tokio::{fs::File, io::AsyncWriteExt};
+use tokio::{fs::File, io::AsyncReadExt, io::AsyncWriteExt};
 
 pub const DOWNLOAD_META_HEADER: &str = "modrinth-download-meta";
 
@@ -567,6 +567,34 @@ pub async fn sha1_async(bytes: Bytes) -> crate::Result<String> {
     Ok(hash)
 }
 
+pub async fn sha1_file_async(
+    path: impl AsRef<Path>,
+) -> crate::Result<(u64, String)> {
+    let path = path.as_ref();
+    // Local files can be multi-gigabyte .mrpacks, so hash them without materializing bytes.
+    let mut file = File::open(path)
+        .await
+        .map_err(|e| IOError::with_path(e, path))?;
+    let mut hasher = sha1_smol::Sha1::new();
+    let mut size = 0;
+    let mut buffer = vec![0; 262144];
+
+    loop {
+        let bytes_read = file
+            .read(&mut buffer)
+            .await
+            .map_err(|e| IOError::with_path(e, path))?;
+        if bytes_read == 0 {
+            break;
+        }
+
+        hasher.update(&buffer[..bytes_read]);
+        size += bytes_read as u64;
+    }
+
+    Ok((size, hasher.digest().to_string()))
+}
+
 #[cfg(test)]
 mod tests {
     use super::*;