another round of cleanups

djellemah · Jun 9, 2024 · 8b2806f · 8b2806f
1 parent b21c0af
commit 8b2806f
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Showing 4 changed files with 72 additions and 64 deletions.
diff --git a/src/bindings.rs b/src/bindings.rs
@@ -267,24 +267,20 @@ pub mod exports {
             let result1 = <_GuestImpl as Guest>::gettree(wit_bindgen::rt::string_lift(bytes0));
             let ptr2 = _RET_AREA.0.as_mut_ptr() as i32;
             match result1 {
-              Ok(e) => { {
-                *((ptr2 + 0) as *mut u8) = (0i32) as u8;
+              Some(e) => {
+                *((ptr2 + 0) as *mut u8) = (1i32) as u8;
                 let vec3 = (e.into_bytes()).into_boxed_slice();
                 let ptr3 = vec3.as_ptr() as i32;
                 let len3 = vec3.len() as i32;
                 ::core::mem::forget(vec3);
                 *((ptr2 + 8) as *mut i32) = len3;
                 *((ptr2 + 4) as *mut i32) = ptr3;
-              } },
-              Err(e) => { {
-                *((ptr2 + 0) as *mut u8) = (1i32) as u8;
-                let vec4 = (e.into_bytes()).into_boxed_slice();
-                let ptr4 = vec4.as_ptr() as i32;
-                let len4 = vec4.len() as i32;
-                ::core::mem::forget(vec4);
-                *((ptr2 + 8) as *mut i32) = len4;
-                *((ptr2 + 4) as *mut i32) = ptr4;
-              } },
+              },
+              None => {
+                {
+                  *((ptr2 + 0) as *mut u8) = (0i32) as u8;
+                }
+              },
             };ptr2
           }
 
@@ -295,16 +291,12 @@ pub mod exports {
             unsafe extern "C" fn __post_return_gettree(arg0: i32,) {
               let l0 = i32::from(*((arg0 + 0) as *const u8));
               match l0 {
-                0 => {
+                0 => (),
+                _ => {
                   let l1 = *((arg0 + 4) as *const i32);
                   let l2 = *((arg0 + 8) as *const i32);
                   wit_bindgen::rt::dealloc(l1, (l2) as usize, 1);
                 },
-                _ => {
-                  let l3 = *((arg0 + 4) as *const i32);
-                  let l4 = *((arg0 + 8) as *const i32);
-                  wit_bindgen::rt::dealloc(l3, (l4) as usize, 1);
-                },
               }
             }
           };
@@ -370,7 +362,7 @@ pub mod exports {
           fn listpaths() -> wit_bindgen::rt::vec::Vec::<wit_bindgen::rt::string::String>;
           fn addtree(path: wit_bindgen::rt::string::String,json: wit_bindgen::rt::string::String,) -> Result<(),wit_bindgen::rt::string::String>;
           /// fetch an entire subtree rooted at path
-          fn gettree(path: wit_bindgen::rt::string::String,) -> Result<wit_bindgen::rt::string::String,wit_bindgen::rt::string::String>;
+          fn gettree(path: wit_bindgen::rt::string::String,) -> Option<wit_bindgen::rt::string::String>;
           fn delete(path: wit_bindgen::rt::string::String,);
           fn drop();
         }
@@ -391,7 +383,7 @@ pub mod exports {
 #[cfg(target_arch = "wasm32")]
 #[link_section = "component-type:slkvs"]
 #[doc(hidden)]
-pub static __WIT_BINDGEN_COMPONENT_TYPE: [u8; 775] = [3, 0, 5, 115, 108, 107, 118, 115, 0, 97, 115, 109, 13, 0, 1, 0, 7, 199, 1, 1, 65, 2, 1, 66, 18, 1, 64, 2, 4, 112, 97, 116, 104, 115, 5, 118, 97, 108, 117, 101, 115, 1, 0, 4, 0, 3, 97, 100, 100, 1, 0, 1, 107, 115, 1, 64, 1, 4, 112, 97, 116, 104, 115, 0, 1, 4, 0, 3, 103, 101, 116, 1, 2, 1, 112, 115, 1, 64, 0, 0, 3, 4, 0, 9, 108, 105, 115, 116, 112, 97, 116, 104, 115, 1, 4, 1, 106, 0, 1, 115, 1, 64, 2, 4, 112, 97, 116, 104, 115, 4, 106, 115, 111, 110, 115, 0, 5, 4, 0, 7, 97, 100, 100, 116, 114, 101, 101, 1, 6, 1, 106, 1, 115, 1, 115, 1, 64, 1, 4, 112, 97, 116, 104, 115, 0, 7, 4, 0, 7, 103, 101, 116, 116, 114, 101, 101, 1, 8, 1, 64, 1, 4, 112, 97, 116, 104, 115, 1, 0, 4, 0, 6, 100, 101, 108, 101, 116, 101, 1, 9, 1, 64, 0, 1, 0, 4, 0, 4, 100, 114, 111, 112, 1, 10, 4, 1, 19, 103, 111, 108, 101, 109, 58, 99, 111, 109, 112, 111, 110, 101, 110, 116, 47, 97, 112, 105, 5, 0, 11, 9, 1, 0, 3, 97, 112, 105, 3, 0, 0, 7, 228, 1, 1, 65, 2, 1, 65, 2, 1, 66, 18, 1, 64, 2, 4, 112, 97, 116, 104, 115, 5, 118, 97, 108, 117, 101, 115, 1, 0, 4, 0, 3, 97, 100, 100, 1, 0, 1, 107, 115, 1, 64, 1, 4, 112, 97, 116, 104, 115, 0, 1, 4, 0, 3, 103, 101, 116, 1, 2, 1, 112, 115, 1, 64, 0, 0, 3, 4, 0, 9, 108, 105, 115, 116, 112, 97, 116, 104, 115, 1, 4, 1, 106, 0, 1, 115, 1, 64, 2, 4, 112, 97, 116, 104, 115, 4, 106, 115, 111, 110, 115, 0, 5, 4, 0, 7, 97, 100, 100, 116, 114, 101, 101, 1, 6, 1, 106, 1, 115, 1, 115, 1, 64, 1, 4, 112, 97, 116, 104, 115, 0, 7, 4, 0, 7, 103, 101, 116, 116, 114, 101, 101, 1, 8, 1, 64, 1, 4, 112, 97, 116, 104, 115, 1, 0, 4, 0, 6, 100, 101, 108, 101, 116, 101, 1, 9, 1, 64, 0, 1, 0, 4, 0, 4, 100, 114, 111, 112, 1, 10, 4, 1, 19, 103, 111, 108, 101, 109, 58, 99, 111, 109, 112, 111, 110, 101, 110, 116, 47, 97, 112, 105, 5, 0, 4, 1, 21, 103, 111, 108, 101, 109, 58, 99, 111, 109, 112, 111, 110, 101, 110, 116, 47, 115, 108, 107, 118, 115, 4, 0, 11, 11, 1, 0, 5, 115, 108, 107, 118, 115, 3, 2, 0, 0, 227, 1, 12, 112, 97, 99, 107, 97, 103, 101, 45, 100, 111, 99, 115, 0, 123, 34, 105, 110, 116, 101, 114, 102, 97, 99, 101, 115, 34, 58, 123, 34, 97, 112, 105, 34, 58, 123, 34, 100, 111, 99, 115, 34, 58, 34, 70, 111, 114, 32, 109, 111, 114, 101, 32, 100, 101, 116, 97, 105, 108, 115, 32, 97, 98, 111, 117, 116, 32, 116, 104, 101, 32, 87, 73, 84, 32, 115, 121, 110, 116, 97, 120, 44, 32, 115, 101, 101, 92, 110, 104, 116, 116, 112, 115, 58, 47, 47, 103, 105, 116, 104, 117, 98, 46, 99, 111, 109, 47, 87, 101, 98, 65, 115, 115, 101, 109, 98, 108, 121, 47, 99, 111, 109, 112, 111, 110, 101, 110, 116, 45, 109, 111, 100, 101, 108, 47, 98, 108, 111, 98, 47, 109, 97, 105, 110, 47, 100, 101, 115, 105, 103, 110, 47, 109, 118, 112, 47, 87, 73, 84, 46, 109, 100, 34, 44, 34, 102, 117, 110, 99, 115, 34, 58, 123, 34, 103, 101, 116, 116, 114, 101, 101, 34, 58, 34, 102, 101, 116, 99, 104, 32, 97, 110, 32, 101, 110, 116, 105, 114, 101, 32, 115, 117, 98, 116, 114, 101, 101, 32, 114, 111, 111, 116, 101, 100, 32, 97, 116, 32, 112, 97, 116, 104, 34, 125, 125, 125, 125, 0, 70, 9, 112, 114, 111, 100, 117, 99, 101, 114, 115, 1, 12, 112, 114, 111, 99, 101, 115, 115, 101, 100, 45, 98, 121, 2, 13, 119, 105, 116, 45, 99, 111, 109, 112, 111, 110, 101, 110, 116, 6, 48, 46, 49, 56, 46, 50, 16, 119, 105, 116, 45, 98, 105, 110, 100, 103, 101, 110, 45, 114, 117, 115, 116, 6, 48, 46, 49, 54, 46, 48];
+pub static __WIT_BINDGEN_COMPONENT_TYPE: [u8; 741] = [3, 0, 5, 115, 108, 107, 118, 115, 0, 97, 115, 109, 13, 0, 1, 0, 7, 182, 1, 1, 65, 2, 1, 66, 16, 1, 64, 2, 4, 112, 97, 116, 104, 115, 5, 118, 97, 108, 117, 101, 115, 1, 0, 4, 0, 3, 97, 100, 100, 1, 0, 1, 107, 115, 1, 64, 1, 4, 112, 97, 116, 104, 115, 0, 1, 4, 0, 3, 103, 101, 116, 1, 2, 1, 112, 115, 1, 64, 0, 0, 3, 4, 0, 9, 108, 105, 115, 116, 112, 97, 116, 104, 115, 1, 4, 1, 106, 0, 1, 115, 1, 64, 2, 4, 112, 97, 116, 104, 115, 4, 106, 115, 111, 110, 115, 0, 5, 4, 0, 7, 97, 100, 100, 116, 114, 101, 101, 1, 6, 4, 0, 7, 103, 101, 116, 116, 114, 101, 101, 1, 2, 1, 64, 1, 4, 112, 97, 116, 104, 115, 1, 0, 4, 0, 6, 100, 101, 108, 101, 116, 101, 1, 7, 1, 64, 0, 1, 0, 4, 0, 4, 100, 114, 111, 112, 1, 8, 4, 1, 19, 103, 111, 108, 101, 109, 58, 99, 111, 109, 112, 111, 110, 101, 110, 116, 47, 97, 112, 105, 5, 0, 11, 9, 1, 0, 3, 97, 112, 105, 3, 0, 0, 7, 211, 1, 1, 65, 2, 1, 65, 2, 1, 66, 16, 1, 64, 2, 4, 112, 97, 116, 104, 115, 5, 118, 97, 108, 117, 101, 115, 1, 0, 4, 0, 3, 97, 100, 100, 1, 0, 1, 107, 115, 1, 64, 1, 4, 112, 97, 116, 104, 115, 0, 1, 4, 0, 3, 103, 101, 116, 1, 2, 1, 112, 115, 1, 64, 0, 0, 3, 4, 0, 9, 108, 105, 115, 116, 112, 97, 116, 104, 115, 1, 4, 1, 106, 0, 1, 115, 1, 64, 2, 4, 112, 97, 116, 104, 115, 4, 106, 115, 111, 110, 115, 0, 5, 4, 0, 7, 97, 100, 100, 116, 114, 101, 101, 1, 6, 4, 0, 7, 103, 101, 116, 116, 114, 101, 101, 1, 2, 1, 64, 1, 4, 112, 97, 116, 104, 115, 1, 0, 4, 0, 6, 100, 101, 108, 101, 116, 101, 1, 7, 1, 64, 0, 1, 0, 4, 0, 4, 100, 114, 111, 112, 1, 8, 4, 1, 19, 103, 111, 108, 101, 109, 58, 99, 111, 109, 112, 111, 110, 101, 110, 116, 47, 97, 112, 105, 5, 0, 4, 1, 21, 103, 111, 108, 101, 109, 58, 99, 111, 109, 112, 111, 110, 101, 110, 116, 47, 115, 108, 107, 118, 115, 4, 0, 11, 11, 1, 0, 5, 115, 108, 107, 118, 115, 3, 2, 0, 0, 227, 1, 12, 112, 97, 99, 107, 97, 103, 101, 45, 100, 111, 99, 115, 0, 123, 34, 105, 110, 116, 101, 114, 102, 97, 99, 101, 115, 34, 58, 123, 34, 97, 112, 105, 34, 58, 123, 34, 100, 111, 99, 115, 34, 58, 34, 70, 111, 114, 32, 109, 111, 114, 101, 32, 100, 101, 116, 97, 105, 108, 115, 32, 97, 98, 111, 117, 116, 32, 116, 104, 101, 32, 87, 73, 84, 32, 115, 121, 110, 116, 97, 120, 44, 32, 115, 101, 101, 92, 110, 104, 116, 116, 112, 115, 58, 47, 47, 103, 105, 116, 104, 117, 98, 46, 99, 111, 109, 47, 87, 101, 98, 65, 115, 115, 101, 109, 98, 108, 121, 47, 99, 111, 109, 112, 111, 110, 101, 110, 116, 45, 109, 111, 100, 101, 108, 47, 98, 108, 111, 98, 47, 109, 97, 105, 110, 47, 100, 101, 115, 105, 103, 110, 47, 109, 118, 112, 47, 87, 73, 84, 46, 109, 100, 34, 44, 34, 102, 117, 110, 99, 115, 34, 58, 123, 34, 103, 101, 116, 116, 114, 101, 101, 34, 58, 34, 102, 101, 116, 99, 104, 32, 97, 110, 32, 101, 110, 116, 105, 114, 101, 32, 115, 117, 98, 116, 114, 101, 101, 32, 114, 111, 111, 116, 101, 100, 32, 97, 116, 32, 112, 97, 116, 104, 34, 125, 125, 125, 125, 0, 70, 9, 112, 114, 111, 100, 117, 99, 101, 114, 115, 1, 12, 112, 114, 111, 99, 101, 115, 115, 101, 100, 45, 98, 121, 2, 13, 119, 105, 116, 45, 99, 111, 109, 112, 111, 110, 101, 110, 116, 6, 48, 46, 49, 56, 46, 50, 16, 119, 105, 116, 45, 98, 105, 110, 100, 103, 101, 110, 45, 114, 117, 115, 116, 6, 48, 46, 49, 54, 46, 48];
 
 #[inline(never)]
 #[doc(hidden)]

diff --git a/src/lib.rs b/src/lib.rs
@@ -32,14 +32,11 @@ impl Guest for Component {
 
     fn addtree(path: String, json: String) -> Result<(), String> {
         let rv = STATE.with_borrow_mut(|db| db.addtree(path, json.clone()));
-        rv.map_err(|str| {
-            println!("{json:?}");
-            str.to_string()
-        })
+        rv.map_err(|st| st.to_string())
     }
 
-    fn gettree(path: String) -> Result<String,String> {
-        STATE.with_borrow(|state| state.gettree(path).map_err(|v| v.to_string()) )
+    fn gettree(path: String) -> Option<String> {
+        STATE.with_borrow(|state| state.gettree(path) )
     }
 
     fn drop() {

diff --git a/src/tree.rs b/src/tree.rs
@@ -1,6 +1,4 @@
-#[allow(unused_imports)]
-use std::cell::RefCell;
-
+/// Steps in a json path. Each step is either a key (for an object) or an index (for an array)
 #[derive(Debug, Clone, PartialOrd, Ord, PartialEq, Eq, Hash)]
 pub enum Step {
   Key(String),
@@ -10,7 +8,7 @@ pub enum Step {
 impl std::fmt::Display for &Step {
   fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> Result<(), std::fmt::Error> {
     match self {
-      Step::Key(v) => write!(f, "{v}"),
+      Step::Key(v) => f.write_str(v),
       Step::Index(i) => write!(f, "{i}"),
     }
   }
@@ -30,24 +28,38 @@ impl std::fmt::Display for SchemaPath {
     let string_parts = self.0
       .iter()
       .map(|step| step.to_string())
-      .collect::<Vec<String>>();
+      .collect::<Vec<_>>();
 
     f.write_str(&string_parts.join("/"))
   }
 }
 
+// convert a path like "root/things/3/name/first"
+// into &[Key("root"), Key("things"), Index(3), Key("name"), Key("first")]
+fn split_slash_path<S : AsRef<str>>(slash_sep : S) -> Vec<Step> {
+  slash_sep
+    .as_ref()
+    .split('/')
+    .map(|path_step| {
+      // anything that is not parseable as an integer is treated as a key
+      match path_step.parse::<usize>() {
+        Ok(i) => Step::Index(i),
+        Err(_) => Step::Key(path_step.into()),
+      }
+    })
+    .collect::<Vec<_>>()
+}
+
+// E0119 , so can't do mpl<S : AsRef<str>> From<S> for SchemaPath :-(
+impl From<&str> for SchemaPath {
+  fn from(slash_sep: &str) -> Self {
+    Self(split_slash_path(&slash_sep))
+  }
+}
+
 impl From<String> for SchemaPath {
   fn from(slash_sep: String) -> Self {
-    let steps = slash_sep
-      .split('/')
-      .map(|path_step| {
-        match path_step.parse::<usize>() {
-          Ok(i) => Step::Index(i),
-          Err(_) => Step::Key(path_step.into()),
-        }
-      })
-      .collect::<Vec<_>>();
-    Self(steps)
+    Self(split_slash_path(&slash_sep))
   }
 }
 
@@ -122,7 +134,6 @@ impl Add<Step> for &SchemaPath {
 // pub trait LeafStorage = AsRef<str>; also works
 pub trait LeafStorage = AsRef<[u8]>;
 
-#[allow(dead_code)] // because Number and Boolean aren't currently used
 #[derive(Eq, PartialEq, Debug, Clone, Hash, Copy)]
 pub enum Leaf<T>
 where T : LeafStorage, // because we want storage
@@ -204,6 +215,9 @@ impl From<serde_json::Error> for DingString {
   }
 }
 
+// This provides a thin wrapper around the BTree/Hash map and implements
+// function calls coming in from the component. Because it's easier to write
+// tests this way.
 impl LeafPaths {
   pub fn new() -> Self {
     Self(PathMap::new())
@@ -221,7 +235,7 @@ impl LeafPaths {
     self.0.keys().map(ToString::to_string).collect()
   }
 
-  /// Given a path, provide all subpaths
+  /// Given a path, provide all subpaths with their values.
   fn subtree_paths(&self, path: SchemaPath) -> Vec<(SchemaPath,Leaf<String>)> {
     use std::ops::Bound;
 
@@ -292,31 +306,29 @@ impl LeafPaths {
   }
 
   // Given a path and a value, insert keys into json obj until path is empty.
-  // Essentially, the path and the rcp must be traversed in parallel, and new values
-  // must be inserted where necessary. New valuesare either a new collection (ie array or map), or an individual value.
+  // Essentially, the path and the rcp must be traversed in parallel, and new
+  // values must be inserted into the rcp where necessary. New values are
+  // either a new collection (ie array or map), or an individual value.
   //
   // rcp is "recipient", which is kinda like an io, except tree-structured.
   fn traverse_tree<'a,'b>(path: &'a [Step], value: &'a Leaf<String>, rcp : &'b mut serde_json::Value) {
     use serde_json::Value;
 
     // Essentially, a path step is either a key or an index; and a value is a collection or a naked value.
-    match (&path, rcp) {
-      // last step so we can insert value
+    match (path, rcp) {
+      // last step, therefore we can insert value
       ([Step::Key(k)], Value::Object(ref mut map)) => {
         map.insert(k.into(),value.into());
       },
       ([Step::Index(i)], Value::Array(ref mut ary)) => {
-        if *i >= ary.len() {
-          ary.resize(i+1, value.into());
-        } else {
-          println!("array size mismatch {i:?} for {value:?}");
-          ary[*i] = value.into();
-        }
+        if *i != ary.len() { panic!("index {i} unexpected compared to length {}", ary.len()) };
+        ary.push(value.into());
       },
 
       // not the last step, so contruct intermediate and keep going
       ([Step::Key(k), rst @ .. ], Value::Object(ref mut map)) => {
         if let Some(intermediate) = map.get_mut(k) {
+          // we already have an object at this key, so reuse it
           Self::traverse_tree(rst, &value, intermediate);
         } else {
           // Dunno what kind of object it's going to be yet
@@ -330,7 +342,6 @@ impl LeafPaths {
           // we already have an object at this index, so reuse it
           Self::traverse_tree(rst, &value, intermediate);
         } else {
-          if ary.len() > i+1 { panic!("index {i} unexpected compared to length {}", ary.len())}
           // Dunno what kind of object it's going to be yet
           let mut intermediate = serde_json::Value::Null;
           Self::traverse_tree(rst, &value, &mut intermediate);
@@ -360,8 +371,9 @@ impl LeafPaths {
     };
   }
 
-  /// Fetch an entire subtree, as a string representation of the json
-  pub fn gettree(&self, path: String) -> Result<String, DingString> {
+  /// Fetch an entire subtree, as a string representation of the json rooted at that path.
+  /// TODO this conflates Null with None
+  pub fn gettree(&self, path: String) -> Option<String> {
     // fetch all subtree paths with their values
     let path = SchemaPath::from(path);
     let subtree_path_values = self.subtree_paths(path);
@@ -371,7 +383,13 @@ impl LeafPaths {
     for (schema_path,value) in subtree_path_values {
       LeafPaths::traverse_tree(&schema_path.0, &value, &mut obj);
     }
-    Ok(obj.to_string())
+    // TODO This is a hack and not entirely correct. There could be exactly one
+    // value at `path`, and it could indeed by null.
+    if obj == serde_json::Value::Null {
+      None
+    } else {
+      Some(obj.to_string())
+    }
   }
 
   pub fn delete(&mut self, path: String) {
@@ -387,7 +405,7 @@ where
   fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> Result<(), std::fmt::Error> {
     use Leaf::*;
     match &self {
-      String(v) => write!(f, "{}", v),
+      String(v) => f.write_str(&v.to_string()),
       Number(v) => write!(f, "{}", v),
       Boolean(v) => write!(f, "{}", v),
       Null => write!(f,"null"),
@@ -396,7 +414,7 @@ where
 }
 
 #[cfg(test)]
-mod external {
+mod t {
   use super::*;
 
   macro_rules! step_of {
@@ -405,6 +423,7 @@ mod external {
     () => ();
   }
 
+  // This is kinda redundant given split_slash_path
   macro_rules! path_of_strs {
     () => ( vec![] );
     ($($x:expr),+ $(,)?) => (SchemaPath(vec![$(step_of!($x)),*]));
@@ -549,7 +568,7 @@ mod external {
 
   #[test]
   fn basic_subtree_order() {
-    let path1 = path_of_strs!["top"];
+    let path1 = SchemaPath(split_slash_path("top"));
     let path2 = path_of_strs!["top","next"];
     let path3 = path_of_strs!["top","next","innter"];
 
@@ -578,7 +597,7 @@ mod external {
     leaf_paths.addtree("another".into(), r#""singular""#.into()).unwrap();
 
     // small subtree
-    let paths = leaf_paths.subtree_paths(path_of_strs!["root","next"]);
+    let paths = leaf_paths.subtree_paths("root/next".into());
     assert_eq!(paths.len(), 1);
     assert_eq!(paths[0].0.to_string(), "root/next/inner");
 
@@ -642,10 +661,10 @@ mod external {
     assert_eq!(json, r#"{"root":{"next":{"inner":"some value"},"stuff":[9,8,7,6,5],"things":[{"name":"one"},{"name":"two"},{"name":"tre"}],"top":"this","wut":null}}"#);
 
     let json = leaf_paths.gettree("root/things".into()).unwrap();
-    assert_eq!(json, "{\"root\":{\"things\":[{\"name\":\"one\"},{\"name\":\"two\"},{\"name\":\"tre\"}]}}");
+    assert_eq!(json, r#"{"root":{"things":[{"name":"one"},{"name":"two"},{"name":"tre"}]}}"#);
 
     let json = leaf_paths.gettree("root/things/1".into()).unwrap();
-    assert_eq!(json, "{\"root\":{\"things\":[{\"name\":\"two\"}]}}");
+    assert_eq!(json, r#"{"root":{"things":[{"name":"two"}]}}"#);
 
     let json = leaf_paths.gettree("does/not/exist/5/really".into()).unwrap();
     assert_eq!(json, "null");

diff --git a/wit/slkvs.wit b/wit/slkvs.wit
@@ -9,7 +9,7 @@ interface api {
   listpaths: func() -> list<string>;
   addtree: func(path: string, json: string) -> result<_,string>;
   // fetch an entire subtree rooted at path
-  gettree: func(path: string) -> result<string,string>;
+  gettree: func(path: string) -> option<string>;
   delete: func(path: string);
   drop: func();
 }