Remove Derivation.tapImmediate()

This is now just an extra flag on `Derivation.onChange()`

packages/dataverse/src/derivations/IDerivation.ts

@@ -18,9 +18,13 @@ export interface IDerivation<V> {
   isHot: boolean
 
   /**
-   * Returns a `Tappable` of the changes of this derivation.
+   * Calls `listener` with a fresh value every time the prism _has_ a new value, throttled by Ticker.
    */
-  onChange(ticker: Ticker, listener: (v: V) => void): VoidFn
+  onChange(
+    ticker: Ticker,
+    listener: (v: V) => void,
+    immediate?: boolean,
+  ): VoidFn
 
   onStale(cb: () => void): VoidFn
 
@@ -29,17 +33,6 @@ export interface IDerivation<V> {
    */
   keepHot(): VoidFn
 
-  /**
-   * Convenience method that taps (subscribes to) the derivation using `this.changes(ticker).tap(fn)` and immediately calls
-   * the callback with the current value.
-   *
-   * @param ticker - The ticker to use for batching.
-   * @param fn - The callback to call on update.
-   *
-   * @see onChange
-   */
-  tapImmediate(ticker: Ticker, fn: (cb: V) => void): VoidFn
-
   /**
    * Add a derivation as a dependent of this derivation.
    *

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

@@ -222,8 +222,18 @@ class PrismDerivation<V> implements IDerivation<V> {
     return this._state.hot
   }
 
-  onChange(ticker: Ticker, listener: (v: V) => void): VoidFn {
-    return new DerivationEmitter(this, ticker).tappable().tap(listener)
+  onChange(
+    ticker: Ticker,
+    listener: (v: V) => void,
+    immediate: boolean = false,
+  ): VoidFn {
+    const unsubscribe = new DerivationEmitter(this, ticker)
+      .tappable()
+      .tap(listener)
+    if (immediate) {
+      listener(this.getValue())
+    }
+    return unsubscribe
   }
 
   /**
@@ -245,21 +255,6 @@ class PrismDerivation<V> implements IDerivation<V> {
     return this.onStale(() => {})
   }
 
-  /**
-   * Convenience method that taps (subscribes to) the derivation using `this.changes(ticker).tap(fn)` and immediately calls
-   * the callback with the current value.
-   *
-   * @param ticker - The ticker to use for batching.
-   * @param fn - The callback to call on update.
-   *
-   * @see onChange
-   */
-  tapImmediate(ticker: Ticker, fn: (cb: V) => void): VoidFn {
-    const untap = this.onChange(ticker, fn)
-    fn(this.getValue())
-    return untap
-  }
-
   /**
    * Add a derivation as a dependent of this derivation.
    *

packages/dataverse/src/utils/Tappable.ts

@@ -72,13 +72,6 @@ export default class Tappable<V> {
     }
   }
 
-  /*
-   * tapImmediate(cb: Listener<V>): Untap {
-   *   const ret = this.tap(cb)
-   *   return ret
-   * }
-   */
-
   private _removeTapperById(id: number) {
     this._tappers.delete(id)
     this._check()