Persist resolutions in services

Author: sheetalkamat

src/compiler/watchPublic.ts

@@ -4,16 +4,21 @@ namespace ts {
         getCurrentDirectory(): string;
         readFile(fileName: string): string | undefined;
     }
-    export function readBuilderProgram(compilerOptions: CompilerOptions, host: ReadBuildProgramHost) {
-        if (outFileWithoutPersistResolutions(compilerOptions)) return undefined;
+    /*@internal*/
+    export function readBuildInfoForProgram(compilerOptions: CompilerOptions, host: ReadBuildProgramHost) {
         const buildInfoPath = getTsBuildInfoEmitOutputFilePath(compilerOptions);
         if (!buildInfoPath) return undefined;
-        const content = host.readFile(buildInfoPath);
+        const content = host.readFile?.(buildInfoPath);
         if (!content) return undefined;
         const buildInfo = getBuildInfo(content);
         if (buildInfo.version !== version) return undefined;
-        if (!buildInfo.program) return undefined;
-        return createBuildProgramUsingProgramBuildInfo(buildInfo.program, buildInfoPath, host);
+        return { buildInfo, buildInfoPath };
+    }
+    export function readBuilderProgram(compilerOptions: CompilerOptions, host: ReadBuildProgramHost) {
+        if (outFileWithoutPersistResolutions(compilerOptions)) return undefined;
+        const result = readBuildInfoForProgram(compilerOptions, host);
+        if (!result?.buildInfo.program) return undefined;
+        return createBuildProgramUsingProgramBuildInfo(result.buildInfo.program, result.buildInfoPath, host);
     }
 
     export interface CleanPersistedProgramOfTsBuildInfoHost {

src/services/services.ts

@@ -1272,6 +1272,15 @@ namespace ts {
             return sourceFile;
         }
 
+        function getOldProgram(options: CompilerOptions, compilerHost: CompilerHost): Program | ProgramFromBuildInfo | undefined {
+            if (program) return program;
+            if (!options.persistResolutions) return undefined;
+            const buildInfoResult = readBuildInfoForProgram(options, compilerHost);
+            if (!buildInfoResult?.buildInfo.program?.peristedProgram) return undefined;
+            const result = createProgramFromBuildInfo(buildInfoResult.buildInfo.program, buildInfoResult.buildInfoPath, compilerHost);
+            return result?.program;
+        }
+
         function synchronizeHostData(): void {
             Debug.assert(languageServiceMode !== LanguageServiceMode.Syntactic);
             // perform fast check if host supports it
@@ -1361,7 +1370,7 @@ namespace ts {
                 rootNames: rootFileNames,
                 options: newSettings,
                 host: compilerHost,
-                oldProgram: program,
+                oldProgram: getOldProgram(newSettings, compilerHost),
                 projectReferences
             });
 

tests/baselines/reference/tsserver/persistResolutions/uses-saved-resolution-for-program.js

@@ -33,32 +33,11 @@ FileWatcher:: Added:: WatchInfo: /user/username/projects/myproject/src/globalFil
 FileWatcher:: Added:: WatchInfo: /user/username/projects/myproject/src/globalMain.ts 500 undefined WatchType: Closed Script info
 FileWatcher:: Added:: WatchInfo: /user/username/projects/myproject/src/types.ts 500 undefined WatchType: Closed Script info
 Starting updateGraphWorker: Project: /user/username/projects/myproject/tsconfig.json
-======== Resolving module './filePresent' from '/user/username/projects/myproject/src/anotherFileReusingResolution.ts'. ========
-Module resolution kind is not specified, using 'Classic'.
-File '/user/username/projects/myproject/src/filePresent.ts' exist - use it as a name resolution result.
-======== Module name './filePresent' was successfully resolved to '/user/username/projects/myproject/src/filePresent.ts'. ========
-======== Resolving module './fileNotFound' from '/user/username/projects/myproject/src/anotherFileReusingResolution.ts'. ========
-Module resolution kind is not specified, using 'Classic'.
-File '/user/username/projects/myproject/src/fileNotFound.ts' does not exist.
-File '/user/username/projects/myproject/src/fileNotFound.tsx' does not exist.
-File '/user/username/projects/myproject/src/fileNotFound.d.ts' does not exist.
-File '/user/username/projects/myproject/src/fileNotFound.js' does not exist.
-File '/user/username/projects/myproject/src/fileNotFound.jsx' does not exist.
-======== Module name './fileNotFound' was not resolved. ========
-======== Resolving module './filePresent' from '/user/username/projects/myproject/src/main.ts'. ========
-Resolution for module './filePresent' was found in cache from location '/user/username/projects/myproject/src'.
-======== Module name './filePresent' was successfully resolved to '/user/username/projects/myproject/src/filePresent.ts'. ========
-======== Resolving module './filePresent' from '/user/username/projects/myproject/src/main.ts'. ========
-Resolution for module './filePresent' was found in cache from location '/user/username/projects/myproject/src'.
-======== Module name './filePresent' was successfully resolved to '/user/username/projects/myproject/src/filePresent.ts'. ========
-======== Resolving module './fileNotFound' from '/user/username/projects/myproject/src/main.ts'. ========
-Resolution for module './fileNotFound' was found in cache from location '/user/username/projects/myproject/src'.
-======== Module name './fileNotFound' was not resolved. ========
 FileWatcher:: Added:: WatchInfo: /a/lib/lib.d.ts 500 undefined WatchType: Closed Script info
 FileWatcher:: Added:: WatchInfo: /user/username/projects/myproject/src/globalFileNotFound.ts 500 undefined Project: /user/username/projects/myproject/tsconfig.json WatchType: Missing file
 DirectoryWatcher:: Added:: WatchInfo: /user/username/projects/myproject/node_modules/@types 1 undefined Project: /user/username/projects/myproject/tsconfig.json WatchType: Type roots
 Elapsed:: *ms DirectoryWatcher:: Added:: WatchInfo: /user/username/projects/myproject/node_modules/@types 1 undefined Project: /user/username/projects/myproject/tsconfig.json WatchType: Type roots
-Finishing updateGraphWorker: Project: /user/username/projects/myproject/tsconfig.json Version: 1 structureChanged: true structureIsReused:: Not Elapsed:: *ms
+Finishing updateGraphWorker: Project: /user/username/projects/myproject/tsconfig.json Version: 1 structureChanged: true structureIsReused:: Completely Elapsed:: *ms
 Project '/user/username/projects/myproject/tsconfig.json' (Configured)
 	Files (9)
 	/a/lib/lib.d.ts