fix: produce results should never be frozen when returned from nested produces, to prevent 'hiding' drafts. Fixes #935

Author: mweststrate

__tests__/regressions.js

@@ -252,7 +252,7 @@ function runBaseTest(name, useProxies, autoFreeze, useListener) {
 			})
 		})
 
-		test("Nested and chained produce calls throw 'Cannot perform 'get' on a proxy that has been revoked' error", () => {
+		test.only("Nested and chained produce calls throw 'Cannot perform 'get' on a proxy that has been revoked' error", () => {
 			const state = {
 				foo: {
 					bar: {
@@ -267,9 +267,15 @@ function runBaseTest(name, useProxies, autoFreeze, useListener) {
 				draft.foo = produce(draft.foo, fooDraft => {
 					/* another produce call makes this fail */
 					/* no actual mutation necessary to make this happen */
+					// This happened before becouse the outer object is not modified,
+					// so assumed to be safely freezable by Immer, while it actually still
+					// contains a draft of bar, which wasn't retracted since we don't do that in nested
+					// producers, as it can still be modified outside a produce
 				})
 			})
-			JSON.stringify(newState)
+			expect(newState).toEqual({
+				foo: {baz: "apple", bar: {baz: "banana"}}
+			})
 		})
 	})
 }

src/core/finalize.ts

@@ -161,7 +161,8 @@ function finalizeProperty(
 }
 
 function maybeFreeze(scope: ImmerScope, value: any, deep = false) {
-	if (scope.immer_.autoFreeze_ && scope.canAutoFreeze_) {
+	// we never freeze for a non-root scope; as it would prevent pruning for drafts inside wrapping objects
+	if (!scope.parent_ && scope.immer_.autoFreeze_ && scope.canAutoFreeze_) {
 		freeze(value, deep)
 	}
 }

src/core/immerClass.ts

@@ -88,8 +88,6 @@ export class Immer implements ProducersFns {
 		// Only plain objects, arrays, and "immerable classes" are drafted.
 		if (isDraftable(base)) {
 			const scope = enterScope(this)
-			//when base is a draft,can't freeze
-			scope.canAutoFreeze_ = !isDraft(base)
 			const proxy = createProxy(this, base, undefined)
 			let hasError = true
 			try {