kitten.sh
1---
2title: Migration
3order: 2
4---
5
6This page lists breaking changes and migration guides for
7various major releases of Wonka.
8
9## v4.0.0
10
11In `v4.0.0` of Wonka, we've migrated to BuckleScript v7 and
12`genType` for automatic type generation for TypeScript. The
13Flow types are derived from the automatic types and are generated
14by `flowgen`.
15
16This may mean that `bsb-native` and Dune/Esy builds are temporarily
17broken, as they haven't been tested yet. If so, they will be fixed
18in a future minor release. Please stick with `v3.2.2` if you're having
19trouble.
20
21This release has no breaking changes for Reason/OCaml in terms of
22API changes. You can use the library exactly as you have before.
23
24**For TypeScript and Flow some APIs have changed**.
25
26### New TypeScript and Flow typings
27
28The type for `Subscription`, `Observer`, and `Subject` have changed.
29These used to be exposed as tuples (fixed-size arrays) in the past,
30but are now compiled to objects, due to the upgrade to BuckleScript v7.
31
32If you're using `subscribe`, `makeSubject`, or `make` you will have
33to change some of your types. If you don't, you won't have to update
34any of your code and can even mix Wonka `v4.0.0` with `v3.2.2` in the
35same bundle.
36
37The `Subscription` type has changed from `[() => void]` to
38`{ unsubscribe: (_: void) => void }`:
39
40```ts
41import { subscribe } from 'wonka';
42
43// Before:
44const [unsubscribe] = subscribe(source);
45// After:
46const { unsubscribe } = subscribe(source);
47```
48
49The `Observer` type has changed similarly, so you'll have to
50update your code if you're using `make`:
51
52```ts
53import { make } from 'wonka';
54
55// Before:
56const source = make(([next, complete]) => /* ... */);
57// After:
58const source = make(({ next, complete }) => /* ... */);
59```
60
61And lastly the `Subject` type has changed as well, so update
62your usage of `makeSubject`:
63
64```ts
65import { makeSubject } from 'wonka';
66
67// Before:
68const [source, next, complete] = makeSubject();
69// After:
70const { source, next, complete } = makeSubject();
71```
72
73### Improvements
74
75The test suite has been rewritten from scratch to improve our
76testing of some tricky edge cases. In most cases operators have
77been updated to behave more nicely and closer to the spec and
78as expected. This is especially true if you're using synchronous
79sources or iterables a lot.
80
81Wonka has reached a much higher test coverage and operators like
82`merge` and `switchMap` will now behave as expected with synchronous
83sources.
84
85This is the list of operators that have changed. If your code has
86been working before, you _shouldn't see any different behaviour_.
87The changed operators will simply have received bugfixes and will
88behave more predictably (and hopefully correctly) in certain edge cases!
89
90- [`buffer`](./api/operators.md#buffer)
91- [`combine`](./api/operators.md#combine)
92- [`debounce`](./api/operators.md#debounce)
93- [`delay`](./api/operators.md#delay)
94- [`sample`](./api/operators.md#sample)
95- [`skipUntil`](./api/operators.md#skipuntil)
96- [`take`](./api/operators.md#take)
97- [`takeLast`](./api/operators.md#takelast)
98- [`takeWhile`](./api/operators.md#takewhile)
99- [`switchMap`](./api/operators.md#switchmap)
100- [`mergeMap`](./api/operators.md#mergemap)
101- [`concatMap`](./api/operators.md#concatmap)
102- [`switchAll`](./api/operators.md#switchall)
103- [`mergeAll`](./api/operators.md#mergeall)
104- [`concatAll`](./api/operators.md#concatall)
105- [`merge`](./api/operators.md#merge)
106- [`concat`](./api/operators.md#concat)
107
108The `take` operator is the only one that has been changed to fix
109a notable new usage case. It can now accept a maximum of `0` or below,
110to close the source immediately.