JavaScriptExpert
diff --git a/‎CHANGELOG.md‎
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diff --git a/‎src/types/dynamicobject.ts‎
Lines changed: 3 additions & 1 deletion b/‎src/types/dynamicobject.ts‎
Lines changed: 3 additions & 1 deletion
diff --git a/‎test/base/object-api-proxy.js‎
Lines changed: 21 additions & 1 deletion b/‎test/base/object-api-proxy.js‎
Lines changed: 21 additions & 1 deletion
diff --git a/‎test/base/proxies.js‎
Lines changed: 2 additions & 2 deletions b/‎test/base/proxies.js‎
Lines changed: 2 additions & 2 deletions
@@ -1,3 +1,11 @@
+# 5.5.0 / 4.5.0
+
+(Minor version of `5` was bumped significantly to make the number better correlate together :-))
+
+* `has` now returns true for computed fields
+* `get` now returns a value for computed fields
+* `has` now picks up `removed` / `delete`-ed fields (#1739)
+
 # 5.1.2 / 4.4.2
 
 * Fixed [#1650](https://github.com/mobxjs/mobx/issues/1650), decorating fields with the name `toString` does not behave correctly.
 
@@ -19,7 +19,9 @@ const objectProxyTraps: ProxyHandler<any> = {
         if (name === $mobx || name === "constructor" || name === mobxDidRunLazyInitializersSymbol)
             return true
         const adm = getAdm(target)
-        if (adm.values.get(name as string)) return true
+        // MWE: should `in` operator be reactive? If not, below code path will be faster / more memory efficient
+        // TODO: check performance stats!
+        // if (adm.values.get(name as string)) return true
         if (typeof name === "string") return adm.has(name)
         return (name as any) in target
     },
 
@@ -1,5 +1,7 @@
 const mobx = require("../../src/mobx")
 const {
+    has,
+    autorun,
     when,
     set,
     remove,
@@ -148,7 +150,7 @@ test("has and get are reactive", async () => {
     await p2
 })
 
-test("computed props are not considered part of collections", () => {
+test("computed props are considered part of collections", () => {
     const x = observable({
         get y() {
             return 3
@@ -161,3 +163,21 @@ test("computed props are not considered part of collections", () => {
     expect(values(x)).toEqual([])
     expect(entries(x)).toEqual([])
 })
+
+test("#1739 - delete and undelete should work", () => {
+    const x = observable({})
+
+    const events = []
+    autorun(() => {
+        // events.push("a" in x)
+        events.push(has(x, "a"))
+    })
+
+    x.a = 1
+    x.a++
+    delete x.a
+    x.a = 5
+    delete x.a
+    x.a = 5
+    expect(events).toEqual([false, true, false, true, false, true])
+})
@@ -146,10 +146,10 @@ test("in operator", () => {
             return 5
         }
     })
-    expect("a" in x).toBeTruthy()
-    expect("b" in x).toBeTruthy()
     expect("x" in x).toBeTruthy()
     expect("y" in x).toBeTruthy()
+    expect("a" in x).toBeTruthy()
+    expect("b" in x).toBeTruthy()
     expect("z" in x).toBeTruthy()
     expect("c" in x).toBeFalsy()
     expect("c" in x).toBeFalsy() // not accidentally create