From 60f21d95258e1611d9cda450e303d126ccdcc560 Mon Sep 17 00:00:00 2001
From: Henning Dieterichs <hdieterichs@microsoft.com>
Date: Thu, 1 Jul 2021 10:42:19 +0200
Subject: [PATCH] Caches ghost text to improve performance.

---
 .../inlineCompletions/ghostTextModel.ts       | 12 +++++++++++-
 .../inlineCompletions/ghostTextWidget.ts      |  6 +++---
 .../inlineCompletionsModel.ts                 | 19 +++++++++++++++++--
 3 files changed, 31 insertions(+), 6 deletions(-)

diff --git a/src/vs/editor/contrib/inlineCompletions/ghostTextModel.ts b/src/vs/editor/contrib/inlineCompletions/ghostTextModel.ts
index f86ff46952d..25ff2d76792 100644
--- a/src/vs/editor/contrib/inlineCompletions/ghostTextModel.ts
+++ b/src/vs/editor/contrib/inlineCompletions/ghostTextModel.ts
@@ -18,21 +18,31 @@ export abstract class DelegatingModel extends Disposable implements GhostTextWid
 	private readonly onDidChangeEmitter = new Emitter<void>();
 	public readonly onDidChange = this.onDidChangeEmitter.event;
 
+	private hasCachedGhostText = false;
+	private cachedGhostText: GhostText | undefined;
+
 	private readonly currentModelRef = this._register(new MutableDisposable<IReference<GhostTextWidgetModel>>());
 	protected get targetModel(): GhostTextWidgetModel | undefined {
 		return this.currentModelRef.value?.object;
 	}
 
 	protected setTargetModel(model: GhostTextWidgetModel | undefined): void {
+		this.currentModelRef.clear();
 		this.currentModelRef.value = model ? createDisposableRef(model, model.onDidChange(() => {
+			this.hasCachedGhostText = false;
 			this.onDidChangeEmitter.fire();
 		})) : undefined;
 
+		this.hasCachedGhostText = false;
 		this.onDidChangeEmitter.fire();
 	}
 
 	public get ghostText(): GhostText | undefined {
-		return this.targetModel?.ghostText;
+		if (!this.hasCachedGhostText) {
+			this.cachedGhostText = this.currentModelRef.value?.object?.ghostText;
+			this.hasCachedGhostText = true;
+		}
+		return this.cachedGhostText;
 	}
 
 	public setExpanded(expanded: boolean): void {
diff --git a/src/vs/editor/contrib/inlineCompletions/ghostTextWidget.ts b/src/vs/editor/contrib/inlineCompletions/ghostTextWidget.ts
index fbc08982840..cff08300855 100644
--- a/src/vs/editor/contrib/inlineCompletions/ghostTextWidget.ts
+++ b/src/vs/editor/contrib/inlineCompletions/ghostTextWidget.ts
@@ -75,14 +75,14 @@ export class GhostTextWidget extends Disposable {
 	}
 
 	private update(): void {
-		if (!this.editor.hasModel() || !this.model.ghostText || this.disposed) {
+		const ghostText = this.model.ghostText;
+
+		if (!this.editor.hasModel() || !ghostText || this.disposed) {
 			this.partsWidget.clear();
 			this.additionalLinesWidget.clear();
 			return;
 		}
 
-		const ghostText = this.model.ghostText;
-
 		const inlineTexts = new Array<InsertedInlineText>();
 		const additionalLines = new Array<LineData>();
 
diff --git a/src/vs/editor/contrib/inlineCompletions/inlineCompletionsModel.ts b/src/vs/editor/contrib/inlineCompletions/inlineCompletionsModel.ts
index 8e461548b7c..459af1ed358 100644
--- a/src/vs/editor/contrib/inlineCompletions/inlineCompletionsModel.ts
+++ b/src/vs/editor/contrib/inlineCompletions/inlineCompletionsModel.ts
@@ -20,7 +20,7 @@ import { EditorOption } from 'vs/editor/common/config/editorOptions';
 import { MutableDisposable } from 'vs/editor/contrib/inlineCompletions/utils';
 import { RedoCommand, UndoCommand } from 'vs/editor/browser/editorExtensions';
 import { CoreEditingCommands } from 'vs/editor/browser/controller/coreCommands';
-import { stringDiff } from 'vs/base/common/diff/diff';
+import { IDiffChange, stringDiff } from 'vs/base/common/diff/diff';
 import { GhostTextWidgetModel, GhostText, BaseGhostTextWidgetModel, GhostTextPart } from 'vs/editor/contrib/inlineCompletions/ghostText';
 
 export class InlineCompletionsModel extends Disposable implements GhostTextWidgetModel {
@@ -499,7 +499,7 @@ export function inlineCompletionToGhostText(inlineCompletion: NormalizedInlineCo
 	// This is a single line string
 	const valueToBeReplaced = textModel.getValueInRange(inlineCompletion.range);
 
-	const changes = stringDiff(valueToBeReplaced, inlineCompletion.text, false);
+	const changes = cachingDiff(valueToBeReplaced, inlineCompletion.text);
 
 	const lineNumber = inlineCompletion.range.startLineNumber;
 
@@ -540,6 +540,21 @@ export function inlineCompletionToGhostText(inlineCompletion: NormalizedInlineCo
 	return new GhostText(lineNumber, parts, 0);
 }
 
+let lastRequest: { originalValue: string, newValue: string, changes: IDiffChange[] } | undefined = undefined;
+function cachingDiff(originalValue: string, newValue: string): readonly IDiffChange[] {
+	if (lastRequest?.originalValue === originalValue && lastRequest?.newValue === newValue) {
+		return lastRequest?.changes;
+	} else {
+		const changes = stringDiff(originalValue, newValue, false);
+		lastRequest = {
+			originalValue,
+			newValue,
+			changes
+		};
+		return changes;
+	}
+}
+
 export interface LiveInlineCompletion extends NormalizedInlineCompletion {
 	sourceProvider: InlineCompletionsProvider;
 	sourceInlineCompletion: InlineCompletion;