return forEachAncestorDirectory(searchPath, ancestor => {

const fileName = combinePaths(ancestor, configName);

return fileExists(fileName) ? fileName : undefined;

});

const basePath = getDirectoryPath(containingFile);

const referencedFileName = isRootedDiskPath(moduleName) ? moduleName : combinePaths(basePath, moduleName);

return normalizePath(referencedFileName);

let commonPathComponents: string[] | undefined;

const failed = forEach(fileNames, sourceFile => {

// Each file contributes into common source file path

const sourcePathComponents = getNormalizedPathComponents(sourceFile, currentDirectory);

sourcePathComponents.pop(); // The base file name is not part of the common directory path

if (!commonPathComponents) {

// first file

commonPathComponents = sourcePathComponents;

return;

}

const n = Math.min(commonPathComponents.length, sourcePathComponents.length);

for (let i = 0; i < n; i++) {

if (getCanonicalFileName(commonPathComponents[i]) !== getCanonicalFileName(sourcePathComponents[i])) {

if (i === 0) {

// Failed to find any common path component

return true;

}

// New common path found that is 0 -> i-1

commonPathComponents.length = i;

break;

}

}

// If the sourcePathComponents was shorter than the commonPathComponents, truncate to the sourcePathComponents

if (sourcePathComponents.length < commonPathComponents.length) {

commonPathComponents.length = sourcePathComponents.length;

}

});

// A common path can not be found when paths span multiple drives on windows, for example

if (failed) {

return "";

}

if (!commonPathComponents) { // Can happen when all input files are .d.ts files

return currentDirectory;

}

return getPathFromPathComponents(commonPathComponents);

hash: string;

byteOrderMark: boolean;

mtime: Date;

const existingDirectories = createMap<boolean>();

function getCanonicalFileName(fileName: string): string {

// if underlying system can distinguish between two files whose names differs only in cases then file name already in canonical form.

// otherwise use toLowerCase as a canonical form.

return sys.useCaseSensitiveFileNames ? fileName : fileName.toLowerCase();

}

function getSourceFile(fileName: string, languageVersion: ScriptTarget, onError?: (message: string) => void): SourceFile | undefined {

let text: string | undefined;

try {

performance.mark("beforeIORead");

text = sys.readFile(fileName, options.charset);

performance.mark("afterIORead");

performance.measure("I/O Read", "beforeIORead", "afterIORead");

}

catch (e) {

if (onError) {

onError(e.message);

}

text = "";

}

return text !== undefined ? createSourceFile(fileName, text, languageVersion, setParentNodes) : undefined;

}

function directoryExists(directoryPath: string): boolean {

if (existingDirectories.has(directoryPath)) {

return true;

}

if (sys.directoryExists(directoryPath)) {

existingDirectories.set(directoryPath, true);

return true;

}

return false;

}

function ensureDirectoriesExist(directoryPath: string) {

if (directoryPath.length > getRootLength(directoryPath) && !directoryExists(directoryPath)) {

const parentDirectory = getDirectoryPath(directoryPath);

ensureDirectoriesExist(parentDirectory);

sys.createDirectory(directoryPath);

}

}

let outputFingerprints: Map<OutputFingerprint>;

function writeFileIfUpdated(fileName: string, data: string, writeByteOrderMark: boolean): void {

if (!outputFingerprints) {

outputFingerprints = createMap<OutputFingerprint>();

}

const hash = sys.createHash!(data); // TODO: GH#18217

const mtimeBefore = sys.getModifiedTime!(fileName); // TODO: GH#18217

if (mtimeBefore) {

const fingerprint = outputFingerprints.get(fileName);

// If output has not been changed, and the file has no external modification

if (fingerprint &&

fingerprint.byteOrderMark === writeByteOrderMark &&

fingerprint.hash === hash &&

fingerprint.mtime.getTime() === mtimeBefore.getTime()) {

return;

}

}

sys.writeFile(fileName, data, writeByteOrderMark);

const mtimeAfter = sys.getModifiedTime!(fileName); // TODO: GH#18217

outputFingerprints.set(fileName, {

hash,

byteOrderMark: writeByteOrderMark,

mtime: mtimeAfter

});

}

function writeFile(fileName: string, data: string, writeByteOrderMark: boolean, onError?: (message: string) => void) {

try {

performance.mark("beforeIOWrite");

ensureDirectoriesExist(getDirectoryPath(normalizePath(fileName)));

if (isWatchSet(options) && sys.createHash && sys.getModifiedTime) {

writeFileIfUpdated(fileName, data, writeByteOrderMark);

}

else {

sys.writeFile(fileName, data, writeByteOrderMark);

}

performance.mark("afterIOWrite");

performance.measure("I/O Write", "beforeIOWrite", "afterIOWrite");

}

catch (e) {

if (onError) {

onError(e.message);

}

}

}

function getDefaultLibLocation(): string {

return getDirectoryPath(normalizePath(sys.getExecutingFilePath()));

}

const newLine = getNewLineCharacter(options);

const realpath = sys.realpath && ((path: string) => sys.realpath!(path));

return {

getSourceFile,

getDefaultLibLocation,

getDefaultLibFileName: options => combinePaths(getDefaultLibLocation(), getDefaultLibFileName(options)),

writeFile,

getCurrentDirectory: memoize(() => sys.getCurrentDirectory()),

useCaseSensitiveFileNames: () => sys.useCaseSensitiveFileNames,

getCanonicalFileName,

getNewLine: () => newLine,

fileExists: fileName => sys.fileExists(fileName),

readFile: fileName => sys.readFile(fileName),

trace: (s: string) => sys.write(s + newLine),

directoryExists: directoryName => sys.directoryExists(directoryName),

getEnvironmentVariable: name => sys.getEnvironmentVariable ? sys.getEnvironmentVariable(name) : "",

getDirectories: (path: string) => sys.getDirectories(path),

realpath,

readDirectory: (path, extensions, include, exclude, depth) => sys.readDirectory(path, extensions, include, exclude, depth),

getModifiedTime: sys.getModifiedTime && (path => sys.getModifiedTime!(path)),

setModifiedTime: sys.setModifiedTime && ((path, date) => sys.setModifiedTime!(path, date)),

deleteFile: sys.deleteFile && (path => sys.deleteFile!(path))

};

const diagnostics = [

...program.getConfigFileParsingDiagnostics(),

...program.getOptionsDiagnostics(cancellationToken),

...program.getSyntacticDiagnostics(sourceFile, cancellationToken),

...program.getGlobalDiagnostics(cancellationToken),

...program.getSemanticDiagnostics(sourceFile, cancellationToken)

];

if (program.getCompilerOptions().declaration) {

addRange(diagnostics, program.getDeclarationDiagnostics(sourceFile, cancellationToken));

}

return sortAndDeduplicateDiagnostics(diagnostics);

getCurrentDirectory(): string;

getCanonicalFileName(fileName: string): string;

getNewLine(): string;

let output = "";

for (const diagnostic of diagnostics) {

output += formatDiagnostic(diagnostic, host);

}

return output;

const errorMessage = `${diagnosticCategoryName(diagnostic)} TS${diagnostic.code}: ${flattenDiagnosticMessageText(diagnostic.messageText, host.getNewLine())}${host.getNewLine()}`;

if (diagnostic.file) {

const { line, character } = getLineAndCharacterOfPosition(diagnostic.file, diagnostic.start!); // TODO: GH#18217

const fileName = diagnostic.file.fileName;

const relativeFileName = convertToRelativePath(fileName, host.getCurrentDirectory(), fileName => host.getCanonicalFileName(fileName));

return `${relativeFileName}(${line + 1},${character + 1}): ` + errorMessage;

}

return errorMessage;

Grey = "\u001b[90m",

Red = "\u001b[91m",

Yellow = "\u001b[93m",

Blue = "\u001b[94m",

Cyan = "\u001b[96m"

switch (category) {

case DiagnosticCategory.Error: return ForegroundColorEscapeSequences.Red;

case DiagnosticCategory.Warning: return ForegroundColorEscapeSequences.Yellow;

case DiagnosticCategory.Suggestion: return Debug.fail("Should never get an Info diagnostic on the command line.");

case DiagnosticCategory.Message: return ForegroundColorEscapeSequences.Blue;

}

while (s.length < length) {

s = " " + s;

}

return s;

const { line: firstLine, character: firstLineChar } = getLineAndCharacterOfPosition(file, start);

const { line: lastLine, character: lastLineChar } = getLineAndCharacterOfPosition(file, start + length);

const lastLineInFile = getLineAndCharacterOfPosition(file, file.text.length).line;

const hasMoreThanFiveLines = (lastLine - firstLine) >= 4;

let gutterWidth = (lastLine + 1 + "").length;

if (hasMoreThanFiveLines) {

gutterWidth = Math.max(ellipsis.length, gutterWidth);

}

let context = "";

for (let i = firstLine; i <= lastLine; i++) {

context += host.getNewLine();

// If the error spans over 5 lines, we'll only show the first 2 and last 2 lines,

// so we'll skip ahead to the second-to-last line.

if (hasMoreThanFiveLines && firstLine + 1 < i && i < lastLine - 1) {

context += indent + formatColorAndReset(padLeft(ellipsis, gutterWidth), gutterStyleSequence) + gutterSeparator + host.getNewLine();

i = lastLine - 1;

}

const lineStart = getPositionOfLineAndCharacter(file, i, 0);

const lineEnd = i < lastLineInFile ? getPositionOfLineAndCharacter(file, i + 1, 0) : file.text.length;

let lineContent = file.text.slice(lineStart, lineEnd);

lineContent = lineContent.replace(/\s+$/g, ""); // trim from end

lineContent = lineContent.replace("\t", " "); // convert tabs to single spaces

// Output the gutter and the actual contents of the line.

context += indent + formatColorAndReset(padLeft(i + 1 + "", gutterWidth), gutterStyleSequence) + gutterSeparator;

context += lineContent + host.getNewLine();

// Output the gutter and the error span for the line using tildes.

context += indent + formatColorAndReset(padLeft("", gutterWidth), gutterStyleSequence) + gutterSeparator;

context += squiggleColor;

if (i === firstLine) {

// If we're on the last line, then limit it to the last character of the last line.

// Otherwise, we'll just squiggle the rest of the line, giving 'slice' no end position.

const lastCharForLine = i === lastLine ? lastLineChar : undefined;

context += lineContent.slice(0, firstLineChar).replace(/\S/g, " ");

context += lineContent.slice(firstLineChar, lastCharForLine).replace(/./g, "~");

}

else if (i === lastLine) {

context += lineContent.slice(0, lastLineChar).replace(/./g, "~");

}

else {

// Squiggle the entire line.

context += lineContent.replace(/./g, "~");

}

context += resetEscapeSequence;

}

return context;

const { line: firstLine, character: firstLineChar } = getLineAndCharacterOfPosition(file, start); // TODO: GH#18217

const relativeFileName = host ? convertToRelativePath(file.fileName, host.getCurrentDirectory(), fileName => host.getCanonicalFileName(fileName)) : file.fileName;

let output = "";

output += color(relativeFileName, ForegroundColorEscapeSequences.Cyan);

output += ":";

output += color(`${firstLine + 1}`, ForegroundColorEscapeSequences.Yellow);

output += ":";

output += color(`${firstLineChar + 1}`, ForegroundColorEscapeSequences.Yellow);

return output;

let output = "";

for (const diagnostic of diagnostics) {

if (diagnostic.file) {

const { file, start } = diagnostic;

output += formatLocation(file, start!, host); // TODO: GH#18217

output += " - ";

}

output += formatColorAndReset(diagnosticCategoryName(diagnostic), getCategoryFormat(diagnostic.category));

output += formatColorAndReset(` TS${diagnostic.code}: `, ForegroundColorEscapeSequences.Grey);

output += flattenDiagnosticMessageText(diagnostic.messageText, host.getNewLine());

if (diagnostic.file) {

output += host.getNewLine();

output += formatCodeSpan(diagnostic.file, diagnostic.start!, diagnostic.length!, "", getCategoryFormat(diagnostic.category), host); // TODO: GH#18217

if (diagnostic.relatedInformation) {

output += host.getNewLine();

for (const { file, start, length, messageText } of diagnostic.relatedInformation) {

if (file) {

output += host.getNewLine();

output += halfIndent + formatLocation(file, start!, host); // TODO: GH#18217

output += formatCodeSpan(file, start!, length!, indent, ForegroundColorEscapeSequences.Cyan, host); // TODO: GH#18217

}

output += host.getNewLine();

output += indent + flattenDiagnosticMessageText(messageText, host.getNewLine());

}

}

}

output += host.getNewLine();

}

return output;

if (isString(messageText)) {

return messageText;

}

else {

let diagnosticChain = messageText;

let result = "";

let indent = 0;

while (diagnosticChain) {

if (indent) {

result += newLine;

for (let i = 0; i < indent; i++) {

result += " ";

}

}

result += diagnosticChain.messageText;

indent++;

diagnosticChain = diagnosticChain.next;

}

return result;

}

if (names.length === 0) {

return [];

}

const resolutions: T[] = [];

const cache = createMap<T>();

for (const name of names) {

let result: T;

if (cache.has(name)) {

result = cache.get(name)!;

}

else {

cache.set(name, result = loader(name, containingFile));

}

resolutions.push(result);

}

return resolutions;

program: Program | undefined,

rootFileNames: string[],

newOptions: CompilerOptions,

getSourceVersion: (path: Path) => string | undefined,

fileExists: (fileName: string) => boolean,

hasInvalidatedResolution: HasInvalidatedResolution,

hasChangedAutomaticTypeDirectiveNames: boolean,

): boolean {

// If we haven't created a program yet or have changed automatic type directives, then it is not up-to-date

if (!program || hasChangedAutomaticTypeDirectiveNames) {

return false;

}

// If number of files in the program do not match, it is not up-to-date

if (program.getRootFileNames().length !== rootFileNames.length) {

return false;

}

// If any file is not up-to-date, then the whole program is not up-to-date

if (program.getSourceFiles().some(sourceFileNotUptoDate)) {

return false;

}

// If any of the missing file paths are now created

if (program.getMissingFilePaths().some(fileExists)) {

return false;

}

const currentOptions = program.getCompilerOptions();

// If the compilation settings do no match, then the program is not up-to-date

if (!compareDataObjects(currentOptions, newOptions)) {

return false;

}

// If everything matches but the text of config file is changed,

// error locations can change for program options, so update the program

if (currentOptions.configFile && newOptions.configFile) {

return currentOptions.configFile.text === newOptions.configFile.text;

}

return true;

function sourceFileNotUptoDate(sourceFile: SourceFile): boolean {

return sourceFile.version !== getSourceVersion(sourceFile.path) ||

hasInvalidatedResolution(sourceFile.path);

}

return configFileParseResult.options.configFile ?

[...configFileParseResult.options.configFile.parseDiagnostics, ...configFileParseResult.errors] :

configFileParseResult.errors;

// If any of these options change, we can't reuse old source file even if version match

// The change in options like these could result in change in syntax tree change

const oldOptions = program && program.getCompilerOptions();

return oldOptions && (

oldOptions.target !== newOptions.target ||

oldOptions.module !== newOptions.module ||

oldOptions.moduleResolution !== newOptions.moduleResolution ||

oldOptions.noResolve !== newOptions.noResolve ||

oldOptions.jsx !== newOptions.jsx ||

oldOptions.allowJs !== newOptions.allowJs ||

oldOptions.disableSizeLimit !== newOptions.disableSizeLimit ||

oldOptions.baseUrl !== newOptions.baseUrl ||

!equalOwnProperties(oldOptions.paths, newOptions.paths)

);

return {

rootNames,

options,

host,

oldProgram,

configFileParsingDiagnostics

};

const createProgramOptions = isArray(rootNamesOrOptions) ? createCreateProgramOptions(rootNamesOrOptions, _options!, _host, _oldProgram, _configFileParsingDiagnostics) : rootNamesOrOptions; // TODO: GH#18217

const { rootNames, options, configFileParsingDiagnostics, projectReferences } = createProgramOptions;

let { oldProgram } = createProgramOptions;

let program: Program;

let processingDefaultLibFiles: SourceFile[] | undefined;

let processingOtherFiles: SourceFile[] | undefined;

let files: SourceFile[];

let commonSourceDirectory: string;

let diagnosticsProducingTypeChecker: TypeChecker;

let noDiagnosticsTypeChecker: TypeChecker;

let classifiableNames: UnderscoreEscapedMap<true>;

let modifiedFilePaths: Path[] | undefined;

const cachedSemanticDiagnosticsForFile: DiagnosticCache<Diagnostic> = {};

const cachedDeclarationDiagnosticsForFile: DiagnosticCache<DiagnosticWithLocation> = {};

let resolvedTypeReferenceDirectives = createMap<ResolvedTypeReferenceDirective>();

let fileProcessingDiagnostics = createDiagnosticCollection();

// The below settings are to track if a .js file should be add to the program if loaded via searching under node_modules.

// This works as imported modules are discovered recursively in a depth first manner, specifically:

// - For each root file, findSourceFile is called.

// - This calls processImportedModules for each module imported in the source file.

// - This calls resolveModuleNames, and then calls findSourceFile for each resolved module.

// As all these operations happen - and are nested - within the createProgram call, they close over the below variables.

// The current resolution depth is tracked by incrementing/decrementing as the depth first search progresses.

const maxNodeModuleJsDepth = typeof options.maxNodeModuleJsDepth === "number" ? options.maxNodeModuleJsDepth : 0;

let currentNodeModulesDepth = 0;

// If a module has some of its imports skipped due to being at the depth limit under node_modules, then track

// this, as it may be imported at a shallower depth later, and then it will need its skipped imports processed.

const modulesWithElidedImports = createMap<boolean>();

// Track source files that are source files found by searching under node_modules, as these shouldn't be compiled.

const sourceFilesFoundSearchingNodeModules = createMap<boolean>();

performance.mark("beforeProgram");

const host = createProgramOptions.host || createCompilerHost(options);

const configParsingHost = parseConfigHostFromCompilerHost(host);

let skipDefaultLib = options.noLib;

const getDefaultLibraryFileName = memoize(() => host.getDefaultLibFileName(options));

const defaultLibraryPath = host.getDefaultLibLocation ? host.getDefaultLibLocation() : getDirectoryPath(getDefaultLibraryFileName());

const programDiagnostics = createDiagnosticCollection();

const currentDirectory = host.getCurrentDirectory();

const supportedExtensions = getSupportedExtensions(options);

// Map storing if there is emit blocking diagnostics for given input

const hasEmitBlockingDiagnostics = createMap<boolean>();

let _compilerOptionsObjectLiteralSyntax: ObjectLiteralExpression | null | undefined;

let _referencesArrayLiteralSyntax: ArrayLiteralExpression | null | undefined;

let moduleResolutionCache: ModuleResolutionCache | undefined;

let resolveModuleNamesWorker: (moduleNames: string[], containingFile: string, reusedNames?: string[]) => ResolvedModuleFull[];

const hasInvalidatedResolution = host.hasInvalidatedResolution || returnFalse;

if (host.resolveModuleNames) {

resolveModuleNamesWorker = (moduleNames, containingFile, reusedNames) => host.resolveModuleNames!(Debug.assertEachDefined(moduleNames), containingFile, reusedNames).map(resolved => {

// An older host may have omitted extension, in which case we should infer it from the file extension of resolvedFileName.

if (!resolved || (resolved as ResolvedModuleFull).extension !== undefined) {

return resolved as ResolvedModuleFull;

}

const withExtension = clone(resolved) as ResolvedModuleFull;

withExtension.extension = extensionFromPath(resolved.resolvedFileName);

return withExtension;

});

}

else {

moduleResolutionCache = createModuleResolutionCache(currentDirectory, x => host.getCanonicalFileName(x));

const loader = (moduleName: string, containingFile: string) => resolveModuleName(moduleName, containingFile, options, host, moduleResolutionCache).resolvedModule!; // TODO: GH#18217

resolveModuleNamesWorker = (moduleNames, containingFile) => loadWithLocalCache<ResolvedModuleFull>(Debug.assertEachDefined(moduleNames), containingFile, loader);

}

let resolveTypeReferenceDirectiveNamesWorker: (typeDirectiveNames: string[], containingFile: string) => ResolvedTypeReferenceDirective[];

if (host.resolveTypeReferenceDirectives) {

resolveTypeReferenceDirectiveNamesWorker = (typeDirectiveNames, containingFile) => host.resolveTypeReferenceDirectives!(Debug.assertEachDefined(typeDirectiveNames), containingFile);

}

else {

const loader = (typesRef: string, containingFile: string) => resolveTypeReferenceDirective(typesRef, containingFile, options, host).resolvedTypeReferenceDirective!; // TODO: GH#18217

resolveTypeReferenceDirectiveNamesWorker = (typeReferenceDirectiveNames, containingFile) => loadWithLocalCache<ResolvedTypeReferenceDirective>(Debug.assertEachDefined(typeReferenceDirectiveNames), containingFile, loader);

}

// Map from a stringified PackageId to the source file with that id.

// Only one source file may have a given packageId. Others become redirects (see createRedirectSourceFile).

// `packageIdToSourceFile` is only used while building the program, while `sourceFileToPackageName` and `isSourceFileTargetOfRedirect` are kept around.

const packageIdToSourceFile = createMap<SourceFile>();

// Maps from a SourceFile's `.path` to the name of the package it was imported with.

let sourceFileToPackageName = createMap<string>();

let redirectTargetsSet = createMap<true>();

const filesByName = createMap<SourceFile | undefined>();

let missingFilePaths: ReadonlyArray<Path> | undefined;

// stores 'filename -> file association' ignoring case

// used to track cases when two file names differ only in casing

const filesByNameIgnoreCase = host.useCaseSensitiveFileNames() ? createMap<SourceFile>() : undefined;

// A parallel array to projectReferences storing the results of reading in the referenced tsconfig files

let resolvedProjectReferences: (ResolvedProjectReference | undefined)[] | undefined = projectReferences ? [] : undefined;

const projectReferenceRedirects: Map<string> = createMap();

const shouldCreateNewSourceFile = shouldProgramCreateNewSourceFiles(oldProgram, options);

const structuralIsReused = tryReuseStructureFromOldProgram();

if (structuralIsReused !== StructureIsReused.Completely) {

processingDefaultLibFiles = [];

processingOtherFiles = [];

if (projectReferences) {

for (const ref of projectReferences) {

const parsedRef = parseProjectReferenceConfigFile(ref);

resolvedProjectReferences!.push(parsedRef);

if (parsedRef) {

if (parsedRef.commandLine.options.outFile) {

const dtsOutfile = changeExtension(parsedRef.commandLine.options.outFile, ".d.ts");

processSourceFile(dtsOutfile, /*isDefaultLib*/ false, /*ignoreNoDefaultLib*/ false, /*packageId*/ undefined);

}

addProjectReferenceRedirects(parsedRef.commandLine, projectReferenceRedirects);

}

}

}

forEach(rootNames, name => processRootFile(name, /*isDefaultLib*/ false, /*ignoreNoDefaultLib*/ false));

// load type declarations specified via 'types' argument or implicitly from types/ and node_modules/@types folders

const typeReferences: string[] = getAutomaticTypeDirectiveNames(options, host);

if (typeReferences.length) {

// This containingFilename needs to match with the one used in managed-side

const containingDirectory = options.configFilePath ? getDirectoryPath(options.configFilePath) : host.getCurrentDirectory();

const containingFilename = combinePaths(containingDirectory, "__inferred type names__.ts");

const resolutions = resolveTypeReferenceDirectiveNamesWorker(typeReferences, containingFilename);

for (let i = 0; i < typeReferences.length; i++) {

processTypeReferenceDirective(typeReferences[i], resolutions[i]);

}

}

// Do not process the default library if:

// - The '--noLib' flag is used.

// - A 'no-default-lib' reference comment is encountered in

// processing the root files.

if (!skipDefaultLib) {

// If '--lib' is not specified, include default library file according to '--target'

// otherwise, using options specified in '--lib' instead of '--target' default library file

const defaultLibraryFileName = getDefaultLibraryFileName();

if (!options.lib && defaultLibraryFileName) {

processRootFile(defaultLibraryFileName, /*isDefaultLib*/ true, /*ignoreNoDefaultLib*/ false);

}

else {

forEach(options.lib, libFileName => {

processRootFile(combinePaths(defaultLibraryPath, libFileName), /*isDefaultLib*/ true, /*ignoreNoDefaultLib*/ false);

});

}

}

missingFilePaths = arrayFrom(filesByName.keys(), p => <Path>p).filter(p => !filesByName.get(p));

files = stableSort(processingDefaultLibFiles, compareDefaultLibFiles).concat(processingOtherFiles);

processingDefaultLibFiles = undefined;

processingOtherFiles = undefined;

}

Debug.assert(!!missingFilePaths);

// Release any files we have acquired in the old program but are

// not part of the new program.

if (oldProgram && host.onReleaseOldSourceFile) {

const oldSourceFiles = oldProgram.getSourceFiles();

for (const oldSourceFile of oldSourceFiles) {

if (!getSourceFile(oldSourceFile.path) || shouldCreateNewSourceFile) {

host.onReleaseOldSourceFile(oldSourceFile, oldProgram.getCompilerOptions());

}

}

}

// unconditionally set oldProgram to undefined to prevent it from being captured in closure

oldProgram = undefined;

program = {

getRootFileNames: () => rootNames,

getSourceFile,

getSourceFileByPath,

getSourceFiles: () => files,

getMissingFilePaths: () => missingFilePaths!, // TODO: GH#18217

getCompilerOptions: () => options,

getSyntacticDiagnostics,

getOptionsDiagnostics,

getGlobalDiagnostics,

getSemanticDiagnostics,

getSuggestionDiagnostics,

getDeclarationDiagnostics,

getTypeChecker,

getClassifiableNames,

getDiagnosticsProducingTypeChecker,

getCommonSourceDirectory,

emit,

getCurrentDirectory: () => currentDirectory,

getNodeCount: () => getDiagnosticsProducingTypeChecker().getNodeCount(),

getIdentifierCount: () => getDiagnosticsProducingTypeChecker().getIdentifierCount(),

getSymbolCount: () => getDiagnosticsProducingTypeChecker().getSymbolCount(),