feat: implement GetOptions extensions

Author: waynr

object_store/src/extensions.rs

@@ -0,0 +1,35 @@
+use std::{
+    any::{Any, TypeId},
+    collections::HashMap,
+    sync::Arc,
+};
+
+type ExtensionMap = HashMap<TypeId, Ext>;
+type Ext = Arc<dyn Any + Send + Sync + 'static>;
+
+#[derive(Debug, Default, Clone)]
+pub struct Extensions {
+    inner: ExtensionMap,
+}
+
+impl Extensions {
+    fn set_ext<T: Send + Sync + 'static>(&mut self, t: T) {
+        let id = t.type_id();
+        let a = Arc::new(t);
+        self.inner.insert(id, a);
+    }
+
+    fn get_ext<T: Send + Sync + 'static>(&self) -> Option<Arc<T>> {
+        let id = TypeId::of::<T>();
+        self.inner
+            .get(&id)
+            .cloned()
+            .map(|e| Arc::downcast(e).expect("TypeId is always unique"))
+    }
+}
+
+impl From<HashMap<TypeId, Ext>> for Extensions {
+    fn from(inner: HashMap<TypeId, Ext>) -> Self {
+        Self { inner }
+    }
+}

object_store/src/lib.rs

@@ -536,6 +536,7 @@ mod config;
 
 mod tags;
 
+pub use extensions::Extensions;
 pub use tags::TagSet;
 
 pub mod multipart;
@@ -545,6 +546,7 @@ mod upload;
 mod util;
 
 mod attributes;
+mod extensions;
 
 #[cfg(any(feature = "integration", test))]
 pub mod integration;
@@ -910,7 +912,6 @@ pub struct ObjectMeta {
     /// A version indicator for this object
     pub version: Option<String>,
 }
-
 /// Options for a get request, such as range
 #[derive(Debug, Default, Clone)]
 pub struct GetOptions {
@@ -963,6 +964,13 @@ pub struct GetOptions {
     ///
     /// <https://datatracker.ietf.org/doc/html/rfc9110#name-head>
     pub head: bool,
+
+    /// Implementation-specific extensions.  but
+    /// intended for use by [`ObjectStore`] implementations that need to pass context-specific
+    /// information (like tracing spans) via trait methods.
+    ///
+    /// These extensions are ignored entirely by backends offered through this crate.
+    pub extensions: Extensions,
 }
 
 impl GetOptions {