initial commit: scaffolding

1 files changed, 112 insertions, 0 deletions

diff --git a/node_modules/rxjs/src/internal/operators/OperatorSubscriber.ts b/node_modules/rxjs/src/internal/operators/OperatorSubscriber.ts
new file mode 100644
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--- /dev/null
+++ b/node_modules/rxjs/src/internal/operators/OperatorSubscriber.ts
@@ -0,0 +1,112 @@
+import { Subscriber } from '../Subscriber';
+
+/**
+ * Creates an instance of an `OperatorSubscriber`.
+ * @param destination The downstream subscriber.
+ * @param onNext Handles next values, only called if this subscriber is not stopped or closed. Any
+ * error that occurs in this function is caught and sent to the `error` method of this subscriber.
+ * @param onError Handles errors from the subscription, any errors that occur in this handler are caught
+ * and send to the `destination` error handler.
+ * @param onComplete Handles completion notification from the subscription. Any errors that occur in
+ * this handler are sent to the `destination` error handler.
+ * @param onFinalize Additional teardown logic here. This will only be called on teardown if the
+ * subscriber itself is not already closed. This is called after all other teardown logic is executed.
+ */
+export function createOperatorSubscriber<T>(
+  destination: Subscriber<any>,
+  onNext?: (value: T) => void,
+  onComplete?: () => void,
+  onError?: (err: any) => void,
+  onFinalize?: () => void
+): Subscriber<T> {
+  return new OperatorSubscriber(destination, onNext, onComplete, onError, onFinalize);
+}
+
+/**
+ * A generic helper for allowing operators to be created with a Subscriber and
+ * use closures to capture necessary state from the operator function itself.
+ */
+export class OperatorSubscriber<T> extends Subscriber<T> {
+  /**
+   * Creates an instance of an `OperatorSubscriber`.
+   * @param destination The downstream subscriber.
+   * @param onNext Handles next values, only called if this subscriber is not stopped or closed. Any
+   * error that occurs in this function is caught and sent to the `error` method of this subscriber.
+   * @param onError Handles errors from the subscription, any errors that occur in this handler are caught
+   * and send to the `destination` error handler.
+   * @param onComplete Handles completion notification from the subscription. Any errors that occur in
+   * this handler are sent to the `destination` error handler.
+   * @param onFinalize Additional finalization logic here. This will only be called on finalization if the
+   * subscriber itself is not already closed. This is called after all other finalization logic is executed.
+   * @param shouldUnsubscribe An optional check to see if an unsubscribe call should truly unsubscribe.
+   * NOTE: This currently **ONLY** exists to support the strange behavior of {@link groupBy}, where unsubscription
+   * to the resulting observable does not actually disconnect from the source if there are active subscriptions
+   * to any grouped observable. (DO NOT EXPOSE OR USE EXTERNALLY!!!)
+   */
+  constructor(
+    destination: Subscriber<any>,
+    onNext?: (value: T) => void,
+    onComplete?: () => void,
+    onError?: (err: any) => void,
+    private onFinalize?: () => void,
+    private shouldUnsubscribe?: () => boolean
+  ) {
+    // It's important - for performance reasons - that all of this class's
+    // members are initialized and that they are always initialized in the same
+    // order. This will ensure that all OperatorSubscriber instances have the
+    // same hidden class in V8. This, in turn, will help keep the number of
+    // hidden classes involved in property accesses within the base class as
+    // low as possible. If the number of hidden classes involved exceeds four,
+    // the property accesses will become megamorphic and performance penalties
+    // will be incurred - i.e. inline caches won't be used.
+    //
+    // The reasons for ensuring all instances have the same hidden class are
+    // further discussed in this blog post from Benedikt Meurer:
+    // https://benediktmeurer.de/2018/03/23/impact-of-polymorphism-on-component-based-frameworks-like-react/
+    super(destination);
+    this._next = onNext
+      ? function (this: OperatorSubscriber<T>, value: T) {
+          try {
+            onNext(value);
+          } catch (err) {
+            destination.error(err);
+          }
+        }
+      : super._next;
+    this._error = onError
+      ? function (this: OperatorSubscriber<T>, err: any) {
+          try {
+            onError(err);
+          } catch (err) {
+            // Send any errors that occur down stream.
+            destination.error(err);
+          } finally {
+            // Ensure finalization.
+            this.unsubscribe();
+          }
+        }
+      : super._error;
+    this._complete = onComplete
+      ? function (this: OperatorSubscriber<T>) {
+          try {
+            onComplete();
+          } catch (err) {
+            // Send any errors that occur down stream.
+            destination.error(err);
+          } finally {
+            // Ensure finalization.
+            this.unsubscribe();
+          }
+        }
+      : super._complete;
+  }
+
+  unsubscribe() {
+    if (!this.shouldUnsubscribe || this.shouldUnsubscribe()) {
+      const { closed } = this;
+      super.unsubscribe();
+      // Execute additional teardown if we have any and we didn't already do so.
+      !closed && this.onFinalize?.();
+    }
+  }
+}