Make fields.get return an option

crates/test-programs/src/bin/api_proxy.rs

@@ -24,15 +24,15 @@ impl bindings::exports::wasi::http::incoming_handler::Guest for T {
         let req_hdrs = request.headers();
 
         assert!(
-            req_hdrs.get(&header).is_empty(),
+            req_hdrs.get(&header).is_none(),
             "forbidden `custom-forbidden-header` found in request"
         );
 
         assert!(req_hdrs.delete(&header).is_err());
         assert!(req_hdrs.append(&header, &b"no".to_vec()).is_err());
 
         assert!(
-            req_hdrs.get(&header).is_empty(),
+            req_hdrs.get(&header).is_none(),
             "append of forbidden header succeeded"
         );
 

crates/wasi-http/src/types_impl.rs

@@ -144,19 +144,24 @@ impl<T: WasiHttpView> crate::bindings::http::types::HostFields for T {
         &mut self,
         fields: Resource<HostFields>,
         name: String,
-    ) -> wasmtime::Result<Vec<Vec<u8>>> {
+    ) -> wasmtime::Result<Option<Vec<Vec<u8>>>> {
+        let fields = get_fields(self.table(), &fields).context("[fields_get] getting fields")?;
+
         let header = match hyper::header::HeaderName::from_bytes(name.as_bytes()) {
             Ok(header) => header,
-            Err(_) => return Ok(vec![]),
+            Err(_) => return Ok(None),
         };
 
-        let res = get_fields(self.table(), &fields)
-            .context("[fields_get] getting fields")?
-            .get_all(header)
+        if !fields.contains_key(&header) {
+            return Ok(None);
+        }
+
+        let res = fields
+            .get_all(&header)
             .into_iter()
             .map(|val| val.as_bytes().to_owned())
             .collect();
-        Ok(res)
+        Ok(Some(res))
     }
 
     fn set(

crates/wasi-http/wit/deps/http/types.wit

@@ -169,8 +169,10 @@ interface types {
       entries: list<tuple<field-key,field-value>>
     ) -> result<fields, header-error>;
 
-    /// Get all of the values corresponding to a key.
-    get: func(name: field-key) -> list<field-value>;
+    /// Get all of the values corresponding to a key. Returns a `none` value
+    /// when the key isn't present, to distinguish from the case where it's
+    /// present but empty.
+    get: func(name: field-key) -> option<list<field-value>>;
 
     /// Set all of the values for a key. Clears any existing values for that
     /// key, if they have been set.

crates/wasi/wit/deps/http/types.wit

@@ -169,8 +169,10 @@ interface types {
       entries: list<tuple<field-key,field-value>>
     ) -> result<fields, header-error>;
 
-    /// Get all of the values corresponding to a key.
-    get: func(name: field-key) -> list<field-value>;
+    /// Get all of the values corresponding to a key. Returns a `none` value
+    /// when the key isn't present, to distinguish from the case where it's
+    /// present but empty.
+    get: func(name: field-key) -> option<list<field-value>>;
 
     /// Set all of the values for a key. Clears any existing values for that
     /// key, if they have been set.