Add fields.has to query if a header is present in a fields

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.has(&header),
             "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.has(&header),
             "append of forbidden header succeeded"
         );
 

crates/wasi-http/src/types_impl.rs

@@ -145,20 +145,34 @@ impl<T: WasiHttpView> crate::bindings::http::types::HostFields for T {
         fields: Resource<HostFields>,
         name: String,
     ) -> wasmtime::Result<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![]),
         };
 
-        let res = get_fields(self.table(), &fields)
-            .context("[fields_get] getting fields")?
-            .get_all(header)
+        if !fields.contains_key(&header) {
+            return Ok(vec![]);
+        }
+
+        let res = fields
+            .get_all(&header)
             .into_iter()
             .map(|val| val.as_bytes().to_owned())
             .collect();
         Ok(res)
     }
 
+    fn has(&mut self, fields: Resource<HostFields>, name: String) -> wasmtime::Result<bool> {
+        let fields = get_fields(self.table(), &fields).context("[fields_get] getting fields")?;
+
+        match hyper::header::HeaderName::from_bytes(name.as_bytes()) {
+            Ok(header) => Ok(fields.contains_key(&header)),
+            Err(_) => Ok(false),
+        }
+    }
+
     fn set(
         &mut self,
         fields: Resource<HostFields>,

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

@@ -169,9 +169,16 @@ interface types {
       entries: list<tuple<field-key,field-value>>
     ) -> result<fields, header-error>;
 
-    /// Get all of the values corresponding to a key.
+    /// Get all of the values corresponding to a key. If the key is not present
+    /// in this `fields`, an empty list is returned. However, if the key is
+    /// present but empty, this is represented by a list with one or more
+    /// empty field-values present.
     get: func(name: field-key) -> list<field-value>;
 
+    /// Returns `true` when the key is present in this `fields`. If the key is
+    /// syntactically invalid, `false` is returned.
+    has: func(name: field-key) -> bool;
+
     /// Set all of the values for a key. Clears any existing values for that
     /// key, if they have been set.
     ///
@@ -191,7 +198,7 @@ interface types {
     append: func(name: field-key, value: field-value) -> result<_, header-error>;
 
     /// Retrieve the full set of keys and values in the Fields. Like the
-    /// constructor, the list represents each key-value pair. 
+    /// constructor, the list represents each key-value pair.
     ///
     /// The outer list represents each key-value pair in the Fields. Keys
     /// which have multiple values are represented by multiple entries in this
@@ -308,8 +315,9 @@ interface types {
     headers: func() -> headers;
   }
 
-  /// Parameters for making an HTTP Request. Each of these parameters is an
-  /// optional timeout, applicable to the transport layer of the HTTP protocol.
+  /// Parameters for making an HTTP Request. Each of these parameters is
+  /// currently an optional timeout applicable to the transport layer of the
+  /// HTTP protocol.
   ///
   /// These timeouts are separate from any the user may use to bound a
   /// blocking call to `wasi:io/poll.poll`.

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

@@ -169,9 +169,16 @@ interface types {
       entries: list<tuple<field-key,field-value>>
     ) -> result<fields, header-error>;
 
-    /// Get all of the values corresponding to a key.
+    /// Get all of the values corresponding to a key. If the key is not present
+    /// in this `fields`, an empty list is returned. However, if the key is
+    /// present but empty, this is represented by a list with one or more
+    /// empty field-values present.
     get: func(name: field-key) -> list<field-value>;
 
+    /// Returns `true` when the key is present in this `fields`. If the key is
+    /// syntactically invalid, `false` is returned.
+    has: func(name: field-key) -> bool;
+
     /// Set all of the values for a key. Clears any existing values for that
     /// key, if they have been set.
     ///
@@ -191,7 +198,7 @@ interface types {
     append: func(name: field-key, value: field-value) -> result<_, header-error>;
 
     /// Retrieve the full set of keys and values in the Fields. Like the
-    /// constructor, the list represents each key-value pair. 
+    /// constructor, the list represents each key-value pair.
     ///
     /// The outer list represents each key-value pair in the Fields. Keys
     /// which have multiple values are represented by multiple entries in this
@@ -308,8 +315,9 @@ interface types {
     headers: func() -> headers;
   }
 
-  /// Parameters for making an HTTP Request. Each of these parameters is an
-  /// optional timeout, applicable to the transport layer of the HTTP protocol.
+  /// Parameters for making an HTTP Request. Each of these parameters is
+  /// currently an optional timeout applicable to the transport layer of the
+  /// HTTP protocol.
   ///
   /// These timeouts are separate from any the user may use to bound a
   /// blocking call to `wasi:io/poll.poll`.