Report file change detected only once when save takes place multiple times before timeout

Author: sheetalkamat

src/compiler/tsbuild.ts

@@ -507,6 +507,7 @@ namespace ts {
         const configFileCache = createConfigFileCache(host);
         let context = createBuildContext(defaultOptions);
         let timerToBuildInvalidatedProject: any;
+        let reportFileChangeDetected = false;
 
         const existingWatchersForWildcards = createMap<WildcardDirectoryWatcher>();
         return {
@@ -584,7 +585,7 @@ namespace ts {
         }
 
         function invalidateProjectAndScheduleBuilds(resolved: ResolvedConfigFileName) {
-            reportWatchStatus(Diagnostics.File_change_detected_Starting_incremental_compilation);
+            reportFileChangeDetected = true;
             invalidateProject(resolved);
             scheduleBuildInvalidatedProject();
         }
@@ -817,6 +818,10 @@ namespace ts {
 
         function buildInvalidatedProject() {
             timerToBuildInvalidatedProject = undefined;
+            if (reportFileChangeDetected) {
+                reportFileChangeDetected = false;
+                reportWatchStatus(Diagnostics.File_change_detected_Starting_incremental_compilation);
+            }
             const buildProject = context.getNextInvalidatedProject();
             buildSomeProjects(p => p === buildProject);
             if (context.hasPendingInvalidatedProjects()) {

src/testRunner/unittests/tsbuildWatchMode.ts

@@ -112,9 +112,22 @@ export class someClass { }`);
             // Another change requeues and builds it
             verifyChange(core[1].content);
 
+            // Two changes together report only single time message: File change detected. Starting incremental compilation...
+            const outputFileStamps = getOutputFileStamps(host);
+            const change1 = `${core[1].content}
+export class someClass { }`;
+            host.writeFile(core[1].path, change1);
+            host.writeFile(core[1].path, `${change1}
+export class someClass2 { }`);
+            verifyChangeAfterTimeout(outputFileStamps);
+
             function verifyChange(coreContent: string) {
                 const outputFileStamps = getOutputFileStamps(host);
                 host.writeFile(core[1].path, coreContent);
+                verifyChangeAfterTimeout(outputFileStamps);
+            }
+
+            function verifyChangeAfterTimeout(outputFileStamps: OutputFileStamp[]) {
                 host.checkTimeoutQueueLengthAndRun(1); // Builds core
                 const changedCore = getOutputFileStamps(host);
                 verifyChangedFiles(changedCore, outputFileStamps, [