feat: get sub container directly when getting value (#175)

crates/loro-common/src/error.rs

@@ -38,6 +38,8 @@ pub enum LoroError {
     ArgErr(Box<str>),
     #[error("Auto commit has not started. The doc is readonly when detached. You should ensure autocommit is on and the doc and the state is attached.")]
     AutoCommitNotStarted,
+    #[error("The doc is already dropped")]
+    DocDropError,
     // #[error("the data for key `{0}` is not available")]
     // Redaction(String),
     // #[error("invalid header (expected {expected:?}, found {found:?})")]

crates/loro-internal/src/handler.rs

@@ -124,18 +124,24 @@ impl Handler {
 impl Handler {
     fn new(
         txn: Weak<Mutex<Option<Transaction>>>,
-        value: ContainerIdx,
+        idx: ContainerIdx,
         state: Weak<Mutex<DocState>>,
     ) -> Self {
-        match value.get_type() {
+        match idx.get_type() {
-            ContainerType::Map => Self::Map(MapHandler::new(txn, value, state)),
+            ContainerType::Map => Self::Map(MapHandler::new(txn, idx, state)),
-            ContainerType::List => Self::List(ListHandler::new(txn, value, state)),
+            ContainerType::List => Self::List(ListHandler::new(txn, idx, state)),
-            ContainerType::Tree => Self::Tree(TreeHandler::new(txn, value, state)),
+            ContainerType::Tree => Self::Tree(TreeHandler::new(txn, idx, state)),
-            ContainerType::Text => Self::Text(TextHandler::new(txn, value, state)),
+            ContainerType::Text => Self::Text(TextHandler::new(txn, idx, state)),
         }
     }
 }
 
+#[derive(Clone, EnumAsInner, Debug)]
+pub enum ValueOrContainer {
+    Value(LoroValue),
+    Container(Handler),
+}
+
 impl TextHandler {
     pub fn new(
         txn: Weak<Mutex<Option<Transaction>>>,
@@ -758,6 +764,30 @@ impl ListHandler {
             })
     }
 
+    /// Get value at given index, if it's a container, return a handler to the container
+    pub fn get_(&self, index: usize) -> Option<ValueOrContainer> {
+        let mutex = &self.state.upgrade().unwrap();
+        let doc_state = &mutex.lock().unwrap();
+        doc_state.with_state(self.container_idx, |state| {
+            let a = state.as_list_state().unwrap();
+            match a.get(index) {
+                Some(v) => {
+                    if let LoroValue::Container(id) = v {
+                        let idx = doc_state.arena.register_container(id);
+                        Some(ValueOrContainer::Container(Handler::new(
+                            self.txn.clone(),
+                            idx,
+                            self.state.clone(),
+                        )))
+                    } else {
+                        Some(ValueOrContainer::Value(v.clone()))
+                    }
+                }
+                None => None,
+            }
+        })
+    }
+
     pub fn for_each<I>(&self, mut f: I)
     where
         I: FnMut(&LoroValue),
@@ -946,6 +976,28 @@ impl MapHandler {
             })
     }
 
+    /// Get the value at given key, if value is a container, return a handler to the container
+    pub fn get_(&self, key: &str) -> Option<ValueOrContainer> {
+        let mutex = &self.state.upgrade().unwrap();
+        let doc_state = mutex.lock().unwrap();
+        doc_state.with_state(self.container_idx, |state| {
+            let a = state.as_map_state().unwrap();
+            let value = a.get(key);
+            match value {
+                Some(LoroValue::Container(container_id)) => {
+                    let idx = doc_state.arena.register_container(container_id);
+                    Some(ValueOrContainer::Container(Handler::new(
+                        self.txn.clone(),
+                        idx,
+                        self.state.clone(),
+                    )))
+                }
+                Some(value) => Some(ValueOrContainer::Value(value.clone())),
+                None => None,
+            }
+        })
+    }
+
     pub fn id(&self) -> ContainerID {
         self.state
             .upgrade()

crates/loro-wasm/src/lib.rs

@@ -6,7 +6,9 @@ use loro_internal::{
         ContainerID,
     },
     event::{Diff, Index},
-    handler::{ListHandler, MapHandler, TextDelta, TextHandler, TreeHandler},
+    handler::{
+        Handler, ListHandler, MapHandler, TextDelta, TextHandler, TreeHandler, ValueOrContainer,
+    },
     id::{Counter, PeerID, TreeID, ID},
     obs::SubID,
     version::Frontiers,
@@ -1231,7 +1233,7 @@ impl LoroMap {
         Ok(())
     }
 
-    /// Get the value of the key.
+    /// Get the value of the key. If the value is a container, the corresponding handler will be returned.
     ///
     /// @example
     /// ```ts
@@ -1243,7 +1245,12 @@ impl LoroMap {
     /// const bar = map.get("foo");
     /// ```
     pub fn get(&self, key: &str) -> JsValue {
-        self.0.get(key).into()
+        let v = self.0.get_(key);
+        match v {
+            Some(ValueOrContainer::Container(c)) => handler_to_js_value(c),
+            Some(ValueOrContainer::Value(v)) => v.into(),
+            None => JsValue::UNDEFINED,
+        }
     }
 
     /// Get the keys of the map.
@@ -1461,6 +1468,15 @@ impl LoroMap {
     }
 }
 
+fn handler_to_js_value(handler: Handler) -> JsValue {
+    match handler {
+        Handler::Text(t) => LoroText(t).into(),
+        Handler::Map(m) => LoroMap(m).into(),
+        Handler::List(l) => LoroList(l).into(),
+        Handler::Tree(t) => LoroTree(t).into(),
+    }
+}
+
 /// The handler of a list container.
 #[wasm_bindgen]
 pub struct LoroList(ListHandler);
@@ -1502,7 +1518,7 @@ impl LoroList {
         Ok(())
     }
 
-    /// Get the value at the index.
+    /// Get the value at the index. If the value is a container, the corresponding handler will be returned.
     ///
     /// @example
     /// ```ts
@@ -1515,11 +1531,14 @@ impl LoroList {
     /// console.log(list.get(1));  // undefined
     /// ```
     pub fn get(&self, index: usize) -> JsValue {
-        let Some(v) = self.0.get(index) else {
+        let Some(v) = self.0.get_(index) else {
             return JsValue::UNDEFINED;
         };
 
-        JsValue::from(v)
+        match v {
+            ValueOrContainer::Value(v) => v.into(),
+            ValueOrContainer::Container(h) => handler_to_js_value(h),
+        }
     }
 
     /// Get the id of this container.

loro-js/src/index.ts

@@ -53,6 +53,7 @@ export type Value =
   | Uint8Array
   | Value[];
 
+export type Container = LoroList | LoroMap | LoroText | LoroTree;
 export type Prelim = PrelimList | PrelimMap | PrelimText;
 
 /**
@@ -148,7 +149,7 @@ declare module "loro-wasm" {
     insertContainer(pos: number, container: "Tree"): LoroTree;
     insertContainer(pos: number, container: string): never;
 
-    get(index: number): Value;
+    get(index: number): undefined | Value | Container;
     getTyped<Key extends keyof T & number>(loro: Loro, index: Key): T[Key];
     insertTyped<Key extends keyof T & number>(pos: Key, value: T[Key]): void;
     insert(pos: number, value: Value | Prelim): void;
@@ -163,7 +164,7 @@ declare module "loro-wasm" {
     setContainer(key: string, container_type: "Tree"): LoroTree;
     setContainer(key: string, container_type: string): never;
 
-    get(key: string): Value;
+    get(key: string): undefined | Value | Container;
     getTyped<Key extends keyof T & string>(txn: Loro, key: Key): T[Key];
     set(key: string, value: Value | Prelim): void;
     setTyped<Key extends keyof T & string>(key: Key, value: T[Key]): void;

loro-js/tests/basic.test.ts

@@ -84,14 +84,24 @@ describe("list", () => {
     map.set("key", "value");
     const v = list.get(0);
     console.log(v);
-    expect(typeof v).toBe("string");
+    expect(v instanceof LoroMap).toBeTruthy();
-    const m = doc.getMap(v as ContainerID);
+    expect(v.getDeepValue()).toStrictEqual({ key: "value" });
-    expect(m.getDeepValue()).toStrictEqual({ key: "value" });
   });
 
   it.todo("iterate");
 });
 
+describe("map", () => {
+  it("get child container", () => {
+    const doc = new Loro();
+    const map = doc.getMap("map");
+    const list = map.setContainer("key", "List");
+    list.insert(0, 1);
+    expect(map.get("key") instanceof LoroList).toBeTruthy();
+    expect(map.get("key").getDeepValue()).toStrictEqual([1]);
+  });
+});
+
 describe("import", () => {
   it("pending", () => {
     const a = new Loro();