Improved the abort handling for stale watched query results when the query/parameters change. This fixes the edge case where an already fetching query would handle a query change and briefly report isFetching being false before becoming true again.

Author: Chriztiaan

.changeset/real-dolls-peel.md

@@ -0,0 +1,5 @@
+---
+'@powersync/common': patch
+---
+
+Improved the abort handling for stale watched query results when the query/parameters change. This fixes the edge case where an already fetching query would handle a query change and briefly report `isFetching` being false before becoming true again.

packages/common/src/client/watched/processors/AbstractQueryProcessor.ts

@@ -83,6 +83,7 @@ export abstract class AbstractQueryProcessor<
    * Updates the underlying query.
    */
   async updateSettings(settings: Settings) {
+    this.abortController.abort();
     await this.initialized;
 
     if (!this.state.isFetching && this.reportFetching) {
@@ -92,7 +93,7 @@ export abstract class AbstractQueryProcessor<
     }
 
     this.options.watchOptions = settings;
-    this.abortController.abort();
+
     this.abortController = new AbortController();
     await this.runWithReporting(() =>
       this.linkQuery({
@@ -121,7 +122,6 @@ export abstract class AbstractQueryProcessor<
     if (typeof update.data !== 'undefined') {
       await this.iterateAsyncListenersWithError(async (l) => l.onData?.(this.state.data));
     }
-
     await this.iterateAsyncListenersWithError(async (l) => l.onStateChange?.(this.state));
   }
 

packages/common/src/client/watched/processors/DifferentialQueryProcessor.ts

@@ -236,7 +236,7 @@ export class DifferentialQueryProcessor<RowType>
     db.onChangeWithCallback(
       {
         onChange: async () => {
-          if (this.closed) {
+          if (this.closed || abortSignal.aborted) {
             return;
           }
           // This fires for each change of the relevant tables
@@ -256,6 +256,10 @@ export class DifferentialQueryProcessor<RowType>
               db: this.options.db
             });
 
+            if (abortSignal.aborted) {
+              return;
+            }
+
             if (this.reportFetching) {
               partialStateUpdate.isFetching = false;
             }

packages/common/src/client/watched/processors/OnChangeQueryProcessor.ts

@@ -57,7 +57,7 @@ export class OnChangeQueryProcessor<Data> extends AbstractQueryProcessor<Data, W
     db.onChangeWithCallback(
       {
         onChange: async () => {
-          if (this.closed) {
+          if (this.closed || abortSignal.aborted) {
             return;
           }
           // This fires for each change of the relevant tables
@@ -77,6 +77,10 @@ export class OnChangeQueryProcessor<Data> extends AbstractQueryProcessor<Data, W
               db: this.options.db
             });
 
+            if (abortSignal.aborted) {
+              return;
+            }
+
             if (this.reportFetching) {
               partialStateUpdate.isFetching = false;
             }