fix(amazonq): Bring back aws#3129, add 200ms delay before rendering suggestion if user is actively typing (aws#7675)

## Problem

aws#3129 this change was not
migrated when we move inline completion to Flare.

## Solution

Replicate PR aws#3129 in the
new code path.

---

- Treat all work as PUBLIC. Private `feature/x` branches will not be
squash-merged at release time.
- Your code changes must meet the guidelines in
[CONTRIBUTING.md](https://github.com/aws/aws-toolkit-vscode/blob/master/CONTRIBUTING.md#guidelines).
- License: I confirm that my contribution is made under the terms of the
Apache 2.0 license.

Author: leigaol

packages/amazonq/.changes/next-release/Bug Fix-45aef014-07f3-4511-a9f6-d7233077784c.json

@@ -0,0 +1,4 @@
+{
+	"type": "Bug Fix",
+	"description": "Slightly delay rendering inline completion when user is typing"
+}

packages/amazonq/src/app/inline/completion.ts

@@ -2,7 +2,7 @@
  * Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
  * SPDX-License-Identifier: Apache-2.0
  */
-import * as vscode from 'vscode'
+
 import {
     CancellationToken,
     InlineCompletionContext,
@@ -46,9 +46,7 @@ import { Experiments, getLogger, sleep } from 'aws-core-vscode/shared'
 import { debounce, messageUtils } from 'aws-core-vscode/utils'
 import { showEdits } from './EditRendering/imageRenderer'
 import { ICursorUpdateRecorder } from './cursorUpdateManager'
-
-let lastDocumentDeleteEvent: vscode.TextDocumentChangeEvent | undefined = undefined
-let lastDocumentDeleteTime = 0
+import { DocumentEventListener } from './documentEventListener'
 
 export class InlineCompletionManager implements Disposable {
     private disposable: Disposable
@@ -60,7 +58,7 @@ export class InlineCompletionManager implements Disposable {
 
     private inlineTutorialAnnotation: InlineTutorialAnnotation
     private readonly logSessionResultMessageName = 'aws/logInlineCompletionSessionResults'
-    private documentChangeListener: Disposable
+    private documentEventListener: DocumentEventListener
 
     constructor(
         languageClient: LanguageClient,
@@ -74,24 +72,19 @@ export class InlineCompletionManager implements Disposable {
         this.lineTracker = lineTracker
         this.recommendationService = new RecommendationService(this.sessionManager, cursorUpdateRecorder)
         this.inlineTutorialAnnotation = inlineTutorialAnnotation
+        this.documentEventListener = new DocumentEventListener()
         this.inlineCompletionProvider = new AmazonQInlineCompletionItemProvider(
             languageClient,
             this.recommendationService,
             this.sessionManager,
-            this.inlineTutorialAnnotation
+            this.inlineTutorialAnnotation,
+            this.documentEventListener
         )
 
-        this.documentChangeListener = vscode.workspace.onDidChangeTextDocument((e) => {
-            if (e.contentChanges.length === 1 && e.contentChanges[0].text === '') {
-                lastDocumentDeleteEvent = e
-                lastDocumentDeleteTime = performance.now()
-            }
-        })
         this.disposable = languages.registerInlineCompletionItemProvider(
             CodeWhispererConstants.platformLanguageIds,
             this.inlineCompletionProvider
         )
-
         this.lineTracker.ready()
     }
 
@@ -104,8 +97,8 @@ export class InlineCompletionManager implements Disposable {
             this.disposable.dispose()
             this.lineTracker.dispose()
         }
-        if (this.documentChangeListener) {
-            this.documentChangeListener.dispose()
+        if (this.documentEventListener) {
+            this.documentEventListener.dispose()
         }
     }
 
@@ -211,7 +204,8 @@ export class AmazonQInlineCompletionItemProvider implements InlineCompletionItem
         private readonly languageClient: LanguageClient,
         private readonly recommendationService: RecommendationService,
         private readonly sessionManager: SessionManager,
-        private readonly inlineTutorialAnnotation: InlineTutorialAnnotation
+        private readonly inlineTutorialAnnotation: InlineTutorialAnnotation,
+        private readonly documentEventListener: DocumentEventListener
     ) {}
 
     private readonly logSessionResultMessageName = 'aws/logInlineCompletionSessionResults'
@@ -251,8 +245,7 @@ export class AmazonQInlineCompletionItemProvider implements InlineCompletionItem
         await sleep(1)
         // prevent user deletion invoking auto trigger
         // this is a best effort estimate of deletion
-        const timeDiff = Math.abs(performance.now() - lastDocumentDeleteTime)
-        if (timeDiff < 500 && lastDocumentDeleteEvent && lastDocumentDeleteEvent.document.uri === document.uri) {
+        if (this.documentEventListener.isLastEventDeletion(document.uri.fsPath)) {
             getLogger().debug('Skip auto trigger when deleting code')
             return []
         }
@@ -393,6 +386,20 @@ ${itemLog}
                 return []
             }
 
+            // delay the suggestion rendeing if user is actively typing
+            // see https://github.com/aws/aws-toolkit-vscode/commit/a537602a96f498f372ed61ec9d82cf8577a9d854
+            for (let i = 0; i < 30; i++) {
+                const lastDocumentChange = this.documentEventListener.getLastDocumentChangeEvent(document.uri.fsPath)
+                if (
+                    lastDocumentChange &&
+                    performance.now() - lastDocumentChange.timestamp < CodeWhispererConstants.inlineSuggestionShowDelay
+                ) {
+                    await sleep(CodeWhispererConstants.showRecommendationTimerPollPeriod)
+                } else {
+                    break
+                }
+            }
+
             // the user typed characters from invoking suggestion cursor position to receiving suggestion position
             const typeahead = document.getText(new Range(position, editor.selection.active))
 

packages/amazonq/src/app/inline/documentEventListener.ts

@@ -0,0 +1,50 @@
+/*!
+ * Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
+ * SPDX-License-Identifier: Apache-2.0
+ */
+import * as vscode from 'vscode'
+
+export interface DocumentChangeEvent {
+    event: vscode.TextDocumentChangeEvent
+    timestamp: number
+}
+
+export class DocumentEventListener {
+    private lastDocumentChangeEventMap: Map<string, DocumentChangeEvent> = new Map()
+    private documentChangeListener: vscode.Disposable
+    private _maxDocument = 1000
+
+    constructor() {
+        this.documentChangeListener = vscode.workspace.onDidChangeTextDocument((e) => {
+            if (e.contentChanges.length > 0) {
+                if (this.lastDocumentChangeEventMap.size > this._maxDocument) {
+                    this.lastDocumentChangeEventMap.clear()
+                }
+                this.lastDocumentChangeEventMap.set(e.document.uri.fsPath, { event: e, timestamp: performance.now() })
+            }
+        })
+    }
+
+    public isLastEventDeletion(filepath: string): boolean {
+        const result = this.lastDocumentChangeEventMap.get(filepath)
+        if (result) {
+            const event = result.event
+            const eventTime = result.timestamp
+            const isDelete =
+                (event && event.contentChanges.length === 1 && event.contentChanges[0].text === '') || false
+            const timeDiff = Math.abs(performance.now() - eventTime)
+            return timeDiff < 500 && isDelete
+        }
+        return false
+    }
+
+    public getLastDocumentChangeEvent(filepath: string): DocumentChangeEvent | undefined {
+        return this.lastDocumentChangeEventMap.get(filepath)
+    }
+
+    public dispose(): void {
+        if (this.documentChangeListener) {
+            this.documentChangeListener.dispose()
+        }
+    }
+}

packages/amazonq/test/unit/amazonq/apps/inline/completion.test.ts

@@ -28,6 +28,7 @@ import {
 } from 'aws-core-vscode/codewhisperer'
 import { LineTracker } from '../../../../../src/app/inline/stateTracker/lineTracker'
 import { InlineTutorialAnnotation } from '../../../../../src/app/inline/tutorials/inlineTutorialAnnotation'
+import { DocumentEventListener } from '../../../../../src/app/inline/documentEventListener'
 
 describe('InlineCompletionManager', () => {
     let manager: InlineCompletionManager
@@ -243,11 +244,13 @@ describe('InlineCompletionManager', () => {
             let getAllRecommendationsStub: sinon.SinonStub
             let recommendationService: RecommendationService
             let inlineTutorialAnnotation: InlineTutorialAnnotation
+            let documentEventListener: DocumentEventListener
 
             beforeEach(() => {
                 const lineTracker = new LineTracker()
                 inlineTutorialAnnotation = new InlineTutorialAnnotation(lineTracker, mockSessionManager)
                 recommendationService = new RecommendationService(mockSessionManager)
+                documentEventListener = new DocumentEventListener()
                 vsCodeState.isRecommendationsActive = false
                 mockSessionManager = {
                     getActiveSession: getActiveSessionStub,
@@ -271,7 +274,8 @@ describe('InlineCompletionManager', () => {
                         languageClient,
                         recommendationService,
                         mockSessionManager,
-                        inlineTutorialAnnotation
+                        inlineTutorialAnnotation,
+                        documentEventListener
                     )
                     const items = await provider.provideInlineCompletionItems(
                         mockDocument,
@@ -287,7 +291,8 @@ describe('InlineCompletionManager', () => {
                         languageClient,
                         recommendationService,
                         mockSessionManager,
-                        inlineTutorialAnnotation
+                        inlineTutorialAnnotation,
+                        documentEventListener
                     )
                     await provider.provideInlineCompletionItems(mockDocument, mockPosition, mockContext, mockToken)
                 }),
@@ -296,7 +301,8 @@ describe('InlineCompletionManager', () => {
                         languageClient,
                         recommendationService,
                         mockSessionManager,
-                        inlineTutorialAnnotation
+                        inlineTutorialAnnotation,
+                        documentEventListener
                     )
                     getActiveRecommendationStub.returns([
                         {
@@ -326,7 +332,8 @@ describe('InlineCompletionManager', () => {
                         languageClient,
                         recommendationService,
                         mockSessionManager,
-                        inlineTutorialAnnotation
+                        inlineTutorialAnnotation,
+                        documentEventListener
                     )
                     const expectedText = `${mockSuggestions[1].insertText}this is my text`
                     getActiveRecommendationStub.returns([
@@ -352,7 +359,8 @@ describe('InlineCompletionManager', () => {
                         languageClient,
                         recommendationService,
                         mockSessionManager,
-                        inlineTutorialAnnotation
+                        inlineTutorialAnnotation,
+                        documentEventListener
                     )
                     getActiveRecommendationStub.returns([])
                     const messageShown = new Promise((resolve) =>
@@ -385,7 +393,8 @@ describe('InlineCompletionManager', () => {
                         languageClient,
                         recommendationService,
                         mockSessionManager,
-                        inlineTutorialAnnotation
+                        inlineTutorialAnnotation,
+                        documentEventListener
                     )
                     const p1 = provider.provideInlineCompletionItems(mockDocument, mockPosition, mockContext, mockToken)
                     const p2 = provider.provideInlineCompletionItems(mockDocument, mockPosition, mockContext, mockToken)

packages/core/src/codewhisperer/models/constants.ts

@@ -184,6 +184,9 @@ export const identityPoolID = 'us-east-1:70717e99-906f-4add-908c-bd9074a2f5b9'
  */
 export const inlineCompletionsDebounceDelay = 200
 
+// add 200ms more delay on top of inline default 30-50ms
+export const inlineSuggestionShowDelay = 200
+
 export const referenceLog = 'Code Reference Log'
 
 export const suggestionDetailReferenceText = (licenses: string) =>