From 924c68ca956091d5d35661f64ab054d879c15f91 Mon Sep 17 00:00:00 2001
From: Sheetal Nandi <shkamat@microsoft.com>
Date: Wed, 10 Aug 2022 16:56:54 -0700
Subject: [PATCH] use cache for program creation on watch mode. (#49958)

---
 src/compiler/watchPublic.ts | 13 +++++++++++--
 1 file changed, 11 insertions(+), 2 deletions(-)

diff --git a/src/compiler/watchPublic.ts b/src/compiler/watchPublic.ts
index 2fd07372a873a..51f58d396c59c 100644
--- a/src/compiler/watchPublic.ts
+++ b/src/compiler/watchPublic.ts
@@ -445,7 +445,11 @@ namespace ts {
 
             // All resolutions are invalid if user provided resolutions
             const hasInvalidatedResolution = resolutionCache.createHasInvalidatedResolution(userProvidedResolution);
-            if (isProgramUptoDate(getCurrentProgram(), rootFileNames, compilerOptions, getSourceVersion, fileExists, hasInvalidatedResolution, hasChangedAutomaticTypeDirectiveNames, getParsedCommandLine, projectReferences)) {
+            const {
+                originalReadFile, originalFileExists, originalDirectoryExists,
+                originalCreateDirectory, originalWriteFile,
+            } = changeCompilerHostLikeToUseCache(compilerHost, toPath);
+            if (isProgramUptoDate(getCurrentProgram(), rootFileNames, compilerOptions, getSourceVersion, fileName => compilerHost.fileExists(fileName), hasInvalidatedResolution, hasChangedAutomaticTypeDirectiveNames, getParsedCommandLine, projectReferences)) {
                 if (hasChangedConfigFileParsingErrors) {
                     if (reportFileChangeDetectedOnCreateProgram) {
                         reportWatchDiagnostic(Diagnostics.File_change_detected_Starting_incremental_compilation);
@@ -462,11 +466,16 @@ namespace ts {
             }
 
             reportFileChangeDetectedOnCreateProgram = false;
-
             if (host.afterProgramCreate && program !== builderProgram) {
                 host.afterProgramCreate(builderProgram);
             }
 
+            compilerHost.readFile = originalReadFile;
+            compilerHost.fileExists = originalFileExists;
+            compilerHost.directoryExists = originalDirectoryExists;
+            compilerHost.createDirectory = originalCreateDirectory;
+            compilerHost.writeFile = originalWriteFile!;
+
             return builderProgram;
         }