Add support for an onDocChange option to query abort handlers

FEATURE: When registering an `abort` handler for a completion query, you can now use
the `onDocChange` option to indicate that your query should be aborted as soon as the
document changes while it is running.

See https://discuss.codemirror.net/t/debounce-completionsource-individually/8431

src/completion.ts

@@ -83,6 +83,8 @@ export interface CompletionSection {
 export class CompletionContext {
   /// @internal
   abortListeners: (() => void)[] | null = []
+  /// @internal
+  abortOnDocChange = false
 
   /// Create a new completion context. (Mostly useful for testing
   /// completion sources—in the editor, the extension will create
@@ -132,8 +134,19 @@ export class CompletionContext {
   /// Allows you to register abort handlers, which will be called when
   /// the query is
   /// [aborted](#autocomplete.CompletionContext.aborted).
-  addEventListener(type: "abort", listener: () => void) {
-    if (type == "abort" && this.abortListeners) this.abortListeners.push(listener)
+  ///
+  /// By default, running queries will not be aborted for regular
+  /// typing or backspacing, on the assumption that they are likely to
+  /// return a result with a
+  /// [`validFor`](#autocomplete.CompletionResult.validFor) field that
+  /// allows the result to be used after all. Passing `onDocChange:
+  /// true` will cause this query to be aborted for any document
+  /// change.
+  addEventListener(type: "abort", listener: () => void, options?: {onDocChange: boolean}) {
+    if (type == "abort" && this.abortListeners) {
+      this.abortListeners.push(listener)
+      if (options && options.onDocChange) this.abortOnDocChange = true
+    }
   }
 }
 

src/view.ts

@@ -92,6 +92,7 @@ export const completionPlugin = ViewPlugin.fromClass(class implements PluginValu
     for (let i = 0; i < this.running.length; i++) {
       let query = this.running[i]
       if (doesReset ||
+          query.context.abortOnDocChange && update.docChanged ||
           query.updates.length + update.transactions.length > MaxUpdateCount && Date.now() - query.time > MinAbortTime) {
         for (let handler of query.context.abortListeners!) {
           try { handler() }