NLS: escape backslashes in query string (#6585)

In addition to quotes, we also need to escape backslashes in the
original query string. This is because in search filters like
`content:"..."`, backslashes are used to indicate control sequences.

## Test plan

Added new unit test.

agent/src/cli/command-bench/strategy-chat-nls.ts

@@ -1,5 +1,6 @@
 import path from 'node:path'
 import { graphqlClient, isError } from '@sourcegraph/cody-shared'
+import { escapeNLSQuery } from '../../../../vscode/src/chat/chat-view/handlers/SearchHandler'
 import { version } from '../../../package.json'
 import type { CodyBenchOptions } from './command-bench'
 import {
@@ -75,7 +76,7 @@ async function runNLSSearch(examples: Example[]): Promise<ExampleOutput[]> {
         const repoNames = targetRepoRevs.map(repoRev => repoRev.repoName)
         const repoFilter = 'repo:' + repoNames.join('|')
 
-        const fullQuery = `${repoFilter} content:"${query.replaceAll('"', '\\"')}"`
+        const fullQuery = `${repoFilter} content:"${escapeNLSQuery(query)}"`
         const resultsResp = await graphqlClient.nlsSearchQuery({
             query: fullQuery,
         })

vscode/src/chat/chat-view/handlers/SearchHandler.ts

@@ -45,9 +45,8 @@ export class SearchHandler implements AgentHandler {
             ? 'boost:relevant.repos()'
             : ''
 
-        const query = `content:"${inputTextWithoutContextChips.replaceAll(
-            '"',
-            '\\"'
+        const query = `content:"${escapeNLSQuery(
+            inputTextWithoutContextChips
         )}" ${currentRepoBoost} ${myProjectsBoost} ${scopes.length ? `(${scopes.join(' OR ')})` : ''}`
 
         try {
@@ -75,6 +74,16 @@ export class SearchHandler implements AgentHandler {
     }
 }
 
+export function escapeNLSQuery(query: string): string {
+    return (
+        query
+            // first escape backslashes
+            .replaceAll('\\', '\\\\')
+            // then escape quotes
+            .replaceAll('"', '\\"')
+    )
+}
+
 async function getSearchScopesFromMentions(mentions: ContextItem[]): Promise<string[]> {
     const validMentions = mentions.reduce(
         (groups, mention) => {

vscode/src/chat/chat-view/handlers/__tests__/SearchHandler.test.ts

@@ -0,0 +1,16 @@
+import { describe, expect, it } from 'vitest'
+import { escapeNLSQuery } from '../SearchHandler'
+
+describe('escapeNLSQuery', () => {
+    it('escapes backslashes', () => {
+        expect(escapeNLSQuery('path\\to\\file')).toBe('path\\\\to\\\\file')
+    })
+
+    it('escapes double quotes', () => {
+        expect(escapeNLSQuery(`say "hello"`)).toBe(`say \\"hello\\"`)
+    })
+
+    it('escapes escaped quotes', () => {
+        expect(escapeNLSQuery(`c:\\path\\"file"`)).toBe(`c:\\\\path\\\\\\"file\\"`)
+    })
+})