fix(amazonq): max 20k char for inline supplementalContext (#6366)

## Problem
In some rare cases, the total supplementalContext length exceeds 20k
character. With recent service side changes, we need to make sure the
total supplementalContext length do not exceed 20k in any situation.

## Solution
Make sure the total supplementalContext length do not exceed 20k in any
situation. Drop when necessary.

This is not customer facing so no change log is attached.


---

- 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-72b26a2d-3647-4d07-b0ef-92238e3f0050.json

@@ -0,0 +1,4 @@
+{
+	"type": "Bug Fix",
+	"description": "Fix inline completion supplementalContext length exceeding maximum in certain cases"
+}

packages/amazonq/test/unit/codewhisperer/util/crossFileContextUtil.test.ts

@@ -8,7 +8,12 @@ import * as FakeTimers from '@sinonjs/fake-timers'
 import * as vscode from 'vscode'
 import * as sinon from 'sinon'
 import * as crossFile from 'aws-core-vscode/codewhisperer'
-import { aStringWithLineCount, createMockTextEditor, installFakeClock } from 'aws-core-vscode/test'
+import {
+    aLongStringWithLineCount,
+    aStringWithLineCount,
+    createMockTextEditor,
+    installFakeClock,
+} from 'aws-core-vscode/test'
 import { FeatureConfigProvider, crossFileContextConfig } from 'aws-core-vscode/codewhisperer'
 import {
     assertTabCount,
@@ -71,8 +76,8 @@ describe('crossFileContextUtil', function () {
             assert.strictEqual(actual.supplementalContextItems[2].content.split('\n').length, 50)
         })
 
-        it('for t1 group, should return repomap + opentabs context', async function () {
-            await toTextEditor(aStringWithLineCount(200), 'CrossFile.java', tempFolder, { preview: false })
+        it('for t1 group, should return repomap + opentabs context, should not exceed 20k total length', async function () {
+            await toTextEditor(aLongStringWithLineCount(200), 'CrossFile.java', tempFolder, { preview: false })
             const myCurrentEditor = await toTextEditor('', 'TargetFile.java', tempFolder, {
                 preview: false,
             })
@@ -85,25 +90,23 @@ describe('crossFileContextUtil', function () {
                 .withArgs(sinon.match.any, sinon.match.any, 'codemap')
                 .resolves([
                     {
-                        content: 'foo',
+                        content: 'foo'.repeat(3000),
                         score: 0,
                         filePath: 'q-inline',
                     },
                 ])
 
             const actual = await crossFile.fetchSupplementalContextForSrc(myCurrentEditor, fakeCancellationToken)
             assert.ok(actual)
-            assert.strictEqual(actual.supplementalContextItems.length, 4)
+            assert.strictEqual(actual.supplementalContextItems.length, 3)
             assert.strictEqual(actual?.strategy, 'codemap')
             assert.deepEqual(actual?.supplementalContextItems[0], {
-                content: 'foo',
+                content: 'foo'.repeat(3000),
                 score: 0,
                 filePath: 'q-inline',
             })
-
             assert.strictEqual(actual.supplementalContextItems[1].content.split('\n').length, 50)
             assert.strictEqual(actual.supplementalContextItems[2].content.split('\n').length, 50)
-            assert.strictEqual(actual.supplementalContextItems[3].content.split('\n').length, 50)
         })
 
         it.skip('for t2 group, should return global bm25 context and no repomap', async function () {

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

@@ -84,6 +84,7 @@ export const lineBreakWin = '\r\n'
 
 export const supplementalContextTimeoutInMs = 100
 
+export const supplementalContextMaxTotalLength = 20480
 /**
  * Ux of recommendations
  */

packages/core/src/codewhisperer/util/supplementalContext/crossFileContextUtil.ts

@@ -7,7 +7,11 @@ import * as vscode from 'vscode'
 import { FeatureConfigProvider, fs } from '../../../shared'
 import path = require('path')
 import { BM25Document, BM25Okapi } from './rankBm25'
-import { crossFileContextConfig, supplementalContextTimeoutInMs } from '../../models/constants'
+import {
+    crossFileContextConfig,
+    supplementalContextTimeoutInMs,
+    supplementalContextMaxTotalLength,
+} from '../../models/constants'
 import { isTestFile } from './codeParsingUtil'
 import { getFileDistance } from '../../../shared/filesystemUtilities'
 import { getOpenFilesInWindow } from '../../../shared/utilities/editorUtilities'
@@ -99,13 +103,22 @@ export async function fetchSupplementalContextForSrc(
                 const opentabsContext = await fetchOpentabsContext(editor, cancellationToken)
                 const codemap = await fetchProjectContext(editor, 'codemap')
 
+                function addToResult(items: CodeWhispererSupplementalContextItem[]) {
+                    for (const item of items) {
+                        const curLen = result.reduce((acc, i) => acc + i.content.length, 0)
+                        if (curLen + item.content.length < supplementalContextMaxTotalLength) {
+                            result.push(item)
+                        }
+                    }
+                }
+
                 if (codemap && codemap.length > 0) {
-                    result.push(...codemap)
+                    addToResult(codemap)
                     hasCodemap = true
                 }
 
                 if (opentabsContext && opentabsContext.length > 0) {
-                    result.push(...opentabsContext)
+                    addToResult(opentabsContext)
                     hasOpentabs = true
                 }
 

packages/core/src/test/codewhisperer/testUtil.ts

@@ -329,3 +329,12 @@ export function aStringWithLineCount(lineCount: number, start: number = 0): stri
 
     return s.trimEnd()
 }
+
+export function aLongStringWithLineCount(lineCount: number, start: number = 0): string {
+    let s = ''
+    for (let i = start; i < start + lineCount; i++) {
+        s += `a`.repeat(100) + `line${i}\n`
+    }
+
+    return s.trimEnd()
+}