perf: optimize processor pipeline to avoid redundant reprocessing

Modify picker event handlers to restart only the affected processor instead
of restarting from the matcher. When sorter changes, restart sort processor
with matcher output. When renderer changes, restart render processor with
sorter output. This avoids redundant matching operations.

Also implement copy-on-write for sort processor to prevent modifying the
input array, ensuring pipeline integrity.

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <[email protected]>

Author: lambdalisue

denops/fall/picker.ts

@@ -559,13 +559,9 @@ export class Picker<T extends Detail> implements AsyncDisposable {
         this.#sortProcessor.sorterIndex = index;
         this.#listComponent.title = this.#getExtensionIndicator();
         reserve((denops) => {
-          // NOTE:
-          // We need to restart from the matcher processor because
-          // sorters and renderers applies changes in-place thus
-          // the items would be polluted.
-          this.#matchProcessor.start(denops, {
-            items: this.#collectProcessor.items,
-            query: this.#inputComponent.cmdline,
+          // Restart the sort processor with items from the match processor
+          this.#sortProcessor.start(denops, {
+            items: this.#matchProcessor.items,
           });
         });
         break;
@@ -574,13 +570,9 @@ export class Picker<T extends Detail> implements AsyncDisposable {
         this.#sortProcessor.sorterIndex = event.index;
         this.#listComponent.title = this.#getExtensionIndicator();
         reserve((denops) => {
-          // NOTE:
-          // We need to restart from the matcher processor because
-          // sorters and renderers applies changes in-place thus
-          // the items would be polluted.
-          this.#matchProcessor.start(denops, {
-            items: this.#collectProcessor.items,
-            query: this.#inputComponent.cmdline,
+          // Restart the sort processor with items from the match processor
+          this.#sortProcessor.start(denops, {
+            items: this.#matchProcessor.items,
           });
         });
         break;
@@ -596,13 +588,9 @@ export class Picker<T extends Detail> implements AsyncDisposable {
         this.#renderProcessor.rendererIndex = index;
         this.#listComponent.title = this.#getExtensionIndicator();
         reserve((denops) => {
-          // NOTE:
-          // We need to restart from the matcher processor because
-          // sorters and renderers applies changes in-place thus
-          // the items would be polluted.
-          this.#matchProcessor.start(denops, {
-            items: this.#collectProcessor.items,
-            query: this.#inputComponent.cmdline,
+          // Restart the render processor with items from the sort processor
+          this.#renderProcessor.start(denops, {
+            items: this.#sortProcessor.items,
           });
         });
         break;
@@ -611,13 +599,9 @@ export class Picker<T extends Detail> implements AsyncDisposable {
         this.#renderProcessor.rendererIndex = event.index;
         this.#listComponent.title = this.#getExtensionIndicator();
         reserve((denops) => {
-          // NOTE:
-          // We need to restart from the matcher processor because
-          // sorters and renderers applies changes in-place thus
-          // the items would be polluted.
-          this.#matchProcessor.start(denops, {
-            items: this.#collectProcessor.items,
-            query: this.#inputComponent.cmdline,
+          // Restart the render processor with items from the sort processor
+          this.#renderProcessor.start(denops, {
+            items: this.#sortProcessor.items,
           });
         });
         break;

denops/fall/processor/sort.ts

@@ -59,7 +59,7 @@ export class SortProcessor<T extends Detail> implements Disposable {
     }
   }
 
-  start(denops: Denops, { items }: { items: IdItem<T>[] }): void {
+  start(denops: Denops, { items }: { items: readonly IdItem<T>[] }): void {
     this.#validateAvailability();
     if (this.#processing) {
       // Keep most recent start request for later.
@@ -70,14 +70,17 @@ export class SortProcessor<T extends Detail> implements Disposable {
       dispatch({ type: "sort-processor-started" });
       const signal = this.#controller.signal;
 
+      // Create a shallow copy of the items array
+      const cloned = items.slice();
+
       await this.#sorter?.sort(
         denops,
-        { items },
+        { items: cloned },
         { signal },
       );
       signal.throwIfAborted();
 
-      this.#items = items;
+      this.#items = cloned;
       dispatch({ type: "sort-processor-succeeded" });
     })();
     this.#processing

denops/fall/processor/sort_test.ts

@@ -120,7 +120,7 @@ Deno.test("SortProcessor", async (t) => {
   );
 
   await t.step(
-    "start sort items in-place",
+    "start sorts items without modifying original array (copy-on-write)",
     async () => {
       await using stack = new AsyncDisposableStack();
       stack.defer(async () => {
@@ -133,10 +133,11 @@ Deno.test("SortProcessor", async (t) => {
       const processor = stack.use(
         new SortProcessor([sorter]),
       );
-      const cloned = items.slice();
-      processor.start(denops, { items: cloned });
+      const original = items.slice();
+      processor.start(denops, { items: original });
 
-      assertEquals(cloned, [
+      // Original array should not be modified
+      assertEquals(original, [
         { id: 0, value: "0", detail: {} },
         { id: 1, value: "1", detail: {} },
         { id: 2, value: "2", detail: {} },
@@ -145,7 +146,15 @@ Deno.test("SortProcessor", async (t) => {
       notify.notify();
       await flushPromises();
 
-      assertEquals(cloned, [
+      // Original array should still not be modified
+      assertEquals(original, [
+        { id: 0, value: "0", detail: {} },
+        { id: 1, value: "1", detail: {} },
+        { id: 2, value: "2", detail: {} },
+      ]);
+
+      // Processor should have sorted items
+      assertEquals(processor.items, [
         { id: 2, value: "2", detail: {} },
         { id: 1, value: "1", detail: {} },
         { id: 0, value: "0", detail: {} },