From 7828746cc948e29c89c43b519ab83edde5f122dc Mon Sep 17 00:00:00 2001
From: Sheetal Nandi <shkamat@microsoft.com>
Date: Mon, 23 Oct 2017 19:05:38 -0700
Subject: [PATCH] Set the files found during node_modules search correctly when
 reusing existing program structure This marks files reused correctly as from
 external library resulting in not using them for files to be emitted and
 computed for output structure Fixes #19327

---
 src/compiler/program.ts               | 4 ++++
 src/harness/unittests/tscWatchMode.ts | 1 +
 2 files changed, 5 insertions(+)

diff --git a/src/compiler/program.ts b/src/compiler/program.ts
index 1d325983f5f..0ff78a77ecd 100755
--- a/src/compiler/program.ts
+++ b/src/compiler/program.ts
@@ -1049,6 +1049,10 @@ namespace ts {
             // update fileName -> file mapping
             for (let i = 0; i < newSourceFiles.length; i++) {
                 filesByName.set(filePaths[i], newSourceFiles[i]);
+                // Set the file as found during node modules search if it was found that way in old progra,
+                if (oldProgram.isSourceFileFromExternalLibrary(oldProgram.getSourceFileByPath(filePaths[i]))) {
+                    sourceFilesFoundSearchingNodeModules.set(filePaths[i], true);
+                }
             }
 
             files = newSourceFiles;
diff --git a/src/harness/unittests/tscWatchMode.ts b/src/harness/unittests/tscWatchMode.ts
index 10ed8ea8da3..c5aba73f2ac 100644
--- a/src/harness/unittests/tscWatchMode.ts
+++ b/src/harness/unittests/tscWatchMode.ts
@@ -1927,6 +1927,7 @@ declare module "fs" {
             expectedFiles[1].isExpectedToEmit = false;
             host.reloadFS(programFiles.concat(configFile));
             host.runQueuedTimeoutCallbacks();
+            checkProgramActualFiles(watch(), programFiles.map(f => f.path));
             checkOutputErrors(host, emptyArray);
             verifyExpectedFiles(expectedFiles);