Change the signature of Derivation.changes() to Derivation.onChange()

This way, we no longer expose the `Tappable` interface so we can remove it later.

packages/dataverse/src/derivations/IDerivation.ts

@@ -1,6 +1,5 @@
 import type Ticker from '../Ticker'
 import type {$IntentionalAny, VoidFn} from '../types'
-import type Tappable from '../utils/Tappable'
 
 type IDependent = (msgComingFrom: IDerivation<$IntentionalAny>) => void
 
@@ -21,7 +20,7 @@ export interface IDerivation<V> {
   /**
    * Returns a `Tappable` of the changes of this derivation.
    */
-  changes(ticker: Ticker): Tappable<V>
+  onChange(ticker: Ticker, listener: (v: V) => void): VoidFn
 
   onStale(cb: () => void): VoidFn
 
@@ -37,7 +36,7 @@ export interface IDerivation<V> {
    * @param ticker - The ticker to use for batching.
    * @param fn - The callback to call on update.
    *
-   * @see changes
+   * @see onChange
    */
   tapImmediate(ticker: Ticker, fn: (cb: V) => void): VoidFn
 

packages/dataverse/src/derivations/iterateOver.ts

@@ -19,7 +19,7 @@ export default function* iterateOver<V>(
 
   const ticker = new Ticker()
 
-  const untap = d.changes(ticker).tap((v) => {})
+  const untap = d.onChange(ticker, (v) => {})
 
   try {
     while (true) {

packages/dataverse/src/derivations/prism/prism.test.ts

@@ -21,7 +21,7 @@ describe('prism', () => {
     expect(d.getValue()).toEqual('fooboo')
 
     const changes: Array<$FixMe> = []
-    d.changes(ticker).tap((c) => {
+    d.onChange(ticker, (c) => {
       changes.push(c)
     })
 
@@ -112,7 +112,7 @@ describe('prism', () => {
         return n
       })
 
-      const untap = derivation.changes(ticker).tap((change) => {
+      const untap = derivation.onChange(ticker, (change) => {
         sequence.push({change})
       })
 
@@ -172,7 +172,7 @@ describe('prism', () => {
         return n
       })
 
-      const untap = derivation.changes(ticker).tap((change) => {
+      const untap = derivation.onChange(ticker, (change) => {
         sequence.push({change})
       })
 

packages/dataverse/src/derivations/prism/prism.ts

@@ -1,7 +1,6 @@
 import type Ticker from '../../Ticker'
 import type {$IntentionalAny, VoidFn} from '../../types'
 import Stack from '../../utils/Stack'
-import type Tappable from '../../utils/Tappable'
 import DerivationEmitter from '../DerivationEmitter'
 import type {IDerivation} from '../IDerivation'
 import {isDerivation} from '../IDerivation'
@@ -223,11 +222,8 @@ class PrismDerivation<V> implements IDerivation<V> {
     return this._state.hot
   }
 
-  /**
-   * Returns a `Tappable` of the changes of this derivation.
-   */
-  changes(ticker: Ticker): Tappable<V> {
-    return new DerivationEmitter(this, ticker).tappable()
+  onChange(ticker: Ticker, listener: (v: V) => void): VoidFn {
+    return new DerivationEmitter(this, ticker).tappable().tap(listener)
   }
 
   /**
@@ -256,10 +252,10 @@ class PrismDerivation<V> implements IDerivation<V> {
    * @param ticker - The ticker to use for batching.
    * @param fn - The callback to call on update.
    *
-   * @see changes
+   * @see onChange
    */
   tapImmediate(ticker: Ticker, fn: (cb: V) => void): VoidFn {
-    const untap = this.changes(ticker).tap(fn)
+    const untap = this.onChange(ticker, fn)
     fn(this.getValue())
     return untap
   }

packages/dataverse/src/integration.test.ts

@@ -20,7 +20,7 @@ describe(`v2 atom`, () => {
       expect(d.getValue()).toEqual(0)
       const ticker = new Ticker()
       const changes: number[] = []
-      d.changes(ticker).tap((c) => {
+      d.onChange(ticker, (c) => {
         changes.push(c)
       })
       a.setState({...data, bar: 1})