• The tsserverlibrary.js entrypoint is now a thin wrapper around the normal typescript.js entrypoint. It's recommended to switch to the latter where possible. If you were relying on being able to load tsserverlibrary.js in a non-CJS context (e.g., as a browser global), tsserverlibrary.js will throw, as it's unable to generically load another script into the page; you should switch to using typescript.js.

• The TypeScript package now targets ES2020 and requires Node 14.17 or newer. Note that Node 14 is EOL at the end of April 2023.
• Occurrences is request handling on tsserver and LanguageService .getOccurrencesAtPosition are removed now that they have been deprecated for a long time. Use documentHighlights request on tsserver and LanguageService.getDocumentHighlights instead.

• TypeScript is now itself implemented using modules (though, the package still contains bundled outputs).
  • The exported API is no longer defined as a "configurable" object, so operations which attempt to modify the package at runtime such as const ts = require("ts"); ts.readJson = ... will throw.
  • The output files have changed significantly; if you are patching TypeScript, you will definitely need to change your patches.
• typescriptServices.js has been removed; this file was identical to typescript.js, the entrypoint for our npm package.
• protocol.d.ts is no longer included in the package; use tsserverlibrary.d.ts's ts.server.protocol namespace instead.
  • Some elements of the protocol are not actually exported by the ts.server.protocol namespace, but were emitted in the old protocol.d.ts file, and may need to be accessed off of the ts namespace instead. See https://github.com/microsoft/vscode/pull/163365 for an potential way to minimize changes to protocol-using codebases.
• The TypeScript package now targets ES2018 and requires Node 12.20 or newer. Prior to 5.0, our package targeted ES5 syntax and the ES2015 library.
• ts.Map, ts.Set, ts.ESMap, ts.Iterator, and associated types have been removed. The native Map, Set, Iterator and associated types should be used instead.
• The ts.Collection and ts.ReadonlyCollection types have been removed. These types were unused in our public API, and were declared with the old Map/Set types (also removed in 5.0).
• The ts.Push type has been removed. This type was only used twice in our API, and its uses have been replaced with arrays for consistency with other parts of our API.
• BuilderProgramHost no longer requires method useCaseSensitiveFileNames since its used from program.
• The TypeScript compiler is now compiled with strictFunctionTypes; to allow this, certain public AST visitor APIs have been modified to better reflect their underlying guarantees, as well as various corrections. The resulting API should be one that is more compatible with projects which also enable strictFunctionTypes (a recommended option enabled by strict).
  • The VisitResult type is no longer undefined by default; if you have written VisitResult<Node>, you may need to rewrite it as VisitResult<Node | undefined> to reflect that your visitor may return undefined.
  • Visitor-using APIs now correctly reflect the type of the output, including whether it passed a given type guard test, and whether or not it may be undefined. In order to get the type you expect, you may need to pass a test parameter to verify your expectations and then check the result for undefined (or, modify your visitor to return a more specific type).
• typingOptions along with its property enableAutoDiscovery which was deprecated for a long time is not supported any more in tsconfig.json and jsconfig.json. Use typeAcquisition in the config instead.
• This release removes many long-deprecated parts of our public API, including (but not limited to):
  • The top-level Node factory functions (deprecated since TS 4.0) such as ts.createIdentifier; use the factory provided in your TransformationContext or ts.factory instead.
  • The isTypeAssertion function (deprecated since TS 4.0); use isTypeAssertionExpression.
  • The overloads of createConstructorTypeNode and updateConstructorTypeNode which do not accept modifiers (deprecated since TS 4.2).
  • The overloads of createImportTypeNode and updateImportTypeNode which do not accept assertions (deprecated since TS 4.6).
  • The overloads of createTypeParameterDeclaration and updateTypeParameterDeclaration which do not accept modifiers (deprecated since TS 4.6).
  • Node properties and factory function overloads which predate the merger of decorators and modifiers (deprecated since TS 4.8).

As part of an optimization on substitution types, SubstitutionType objects no longer contain the substitute property representing the effective substitution (usually an intersection of the base type and the implicit constraint) - instead, they just contain the constraint property.

For more details, read more on the original pull request.

The current direction of decorators in TC39 means that TypeScript will have to handle a break in terms of placement of decorators. Previously, TypeScript assumed decorators would always be placed prior to all keywords/modifiers. For example

Decorators as currently proposed do not support this syntax. Instead, the export keyword must precede the decorator.

Unfortunately, TypeScript's trees are concrete rather than abstract, and our architecture expects syntax tree node fields to be entirely ordered before or after each other. To support both legacy decorators and decorators as proposed, TypeScript will have to gracefully parse, and intersperse, modifiers and decorators.

To do this, it exposes a new type alias called ModifierLike which is a Modifier or a Decorator.

Decorators are now placed in the same field as modifiers which is now a NodeArray<ModifierLike> when set, and the entire field is deprecated.

All existing decorators properties have been marked as deprecated and will always be undefined if read. The type has also been changed to undefined so that existing tools know to handle them correctly.

To avoid all deprecation warnings and other issues, TypeScript now exposes four new functions. There are individual predicates for testing whether a node has support modifiers and decorators, along with respective accessor functions for grabbing them.

As an example of how to access modifiers off of a node, you can write

With the note that each call to getModifiers and getDecorators may allocate a new array.

For more information, see changes around

• the restructuring of our tree nodes
• the deprecations
• exposing the predicate functions

• resolveTypeReferenceDirectives (both the services and global ts version) now accept an array of FileReferences as a first argument. If you reimplement resolveTypeReferenceDirectives, you need to handle both the string[] and FileReference[] cases now.

• factory.createImportSpecifier and factory.updateImportSpecifier now take an isTypeOnly parameter:

  - createImportSpecifier(propertyName: Identifier | undefined, name: Identifier): ImportSpecifier; + createImportSpecifier(isTypeOnly: boolean, propertyName: Identifier | undefined, name: Identifier): ImportSpecifier; - updateImportSpecifier(node: ImportSpecifier, propertyName: Identifier | undefined, name: Identifier): ImportSpecifier; + updateImportSpecifier(node: ImportSpecifier, isTypeOnly: boolean, propertyName: Identifier | undefined, name: Identifier): ImportSpecifier;

  You can read more about this change at the implementing PR.

• visitNode's lift Takes a readonly Node[] Instead of a NodeArray<Node>

  The lift function in the visitNode API now takes a readonly Node[]. You can see details of the change here.

• Type Arguments in JavaScript Are Not Parsed as Type Arguments

  Type arguments were already not allowed in JavaScript, but in TypeScript 4.1, the parser will parse them in a more spec-compliant way. So when writing the following code in a JavaScript file:

  f<T>(100)

  TypeScript will parse it as the following JavaScript:

  (f < T) > (100)

  This may impact you if you were leveraging TypeScript's API to parse type constructs in JavaScript files, which may have occurred when trying to parse Flow files.

  See more details here.

• TypeScript provides a set of "factory" functions for producing syntax tree nodes; however, TypeScript 4.0 provides a new node factory API. For TypeScript 4.0 we've made the decision to deprecate these older functions in favor of the new ones. For more details, read up on the relevant pull request for this change.

• TupleTypeNode.elementTypes renamed to TupleTypeNode.elements.

• KeywordTypeNode is no longer used to represent this and null types. null now gets a LiteralTypeNode, this now always gets a ThisTypeNode.

• TypeChecker.typeToTypeNode now correctly produces a LiteralTypeNode for true and false types, which matches the behavior in the parser. Prior to this the checker was incorrectly returning the true and false tokens themselves, which are indistinguishable from expressions when traversing a tree.

• The mutable property disableIncrementalParsing has been removed. It was untested and, at least on GitHub, unused by anyone. Incremental parsing can no longer be disabled.

• the typeArguments property has been removed from the TypeReference interface, and the getTypeArguments method on TypeChecker instances should be used instead. This change was necessary to defer resolution of type arguments in order to support recursive type references.

  As a workaround, you can define a helper function to support multiple versions of TypeScript.

  function getTypeArguments(checker: ts.TypeChecker, typeRef: ts.TypeReference) { return checker.getTypeArguments?.(typeRef) ?? (typeRef as any).typeArguments; }

• SymbolFlags.JSContainer has been renamed to SymbolFlags.Assignment to reflect that Typescript now supports expando assignments to functions.

• The deprecated internal method LanguageService#getSourceFile has been removed. See #24540.
• The deprecated function TypeChecker#getSymbolDisplayBuilder and associated interfaces have been removed. See #25331. The emitter and node builder should be used instead.
• The deprecated functions escapeIdentifier and unescapeIdentifier have been removed. Due to changing how the identifier name API worked in general, they have been identity functions for a few releases, so if you need your code to behave the same way, simply removing the calls should be sufficient. Alternatively, the typesafe escapeLeadingUnderscores and unescapeLeadingUnderscores should be used if the types indicate they are required (as they are used to convert to or from branded __String and string types).
• The TypeChecker#getSuggestionForNonexistentProperty, TypeChecker#getSuggestionForNonexistentSymbol, and TypeChecker#getSuggestionForNonexistentModule methods have been made internal, and are no longer part of our public API. See #25520.

• getJsxIntrinsicTagNames has been removed and replaced with getJsxIntrinsicTagNamesAt, which requires a node to use as the location to look up the valid intrinsic names at (to handle locally-scoped JSX namespaces).

• Some services methods (getCompletionEntryDetails and getCompletionEntrySymbols) have additional parameters. Plugins that wrap the language service must pass these parameters along to the original implementation. See #19507

• Symbol.name, Symbol.getName(), and Identifier.text are all now of type __String. This is a special branded string to help track where strings are appropriately escaped and prevent their misuse. escapeIdentifier and unescapeIdentifier has been renamed to escapeLeadingUnderscores and unescapeLeadingUnderscores and had their types updated accordingly. Deprecated versions of escapeIdentifier and unescapeIdentifier still exist with the old name and type signature, however they will be removed in a future version. See #16915.

• The following types/namespaces are now string enums: ts.Extension, ts.ScriptElementKind, ts.HighlightSpanKind, ts.ClassificationTypeNames, protocol.CommandTypes, protocol.IndentStyle, protocol.JsxEmit, protocol.ModuleKind, protocol.ModuleResolutionKind, protocol.NewLineKind, and protocol.ScriptTarget. Also, ts.CommandNames is now an alias for protocol.CommandTypes. See #15966 and #16425.

• The type EnumLiteralType was removed and LiteralType is used instead. LiteralType also replaces .text with a .value which may be either a number or string. See String valued members in enums.

• Declaration does not have a name property. TypeScript now recognize assignments in .js files as declarations in certain contexts, e.g. func.prototype.method = function() {..} will be a declaration of member method on func. As a result Declaration is not guaranteed to have a name property as before. A new type was introduced NamedDeclaration to take the place of Declaration, and Declaration moved to be the base type of both NamedDeclaration and BinaryExpression. Casting to NamedDeclaration should be safe for non .js declarations. See #15594 for more details.

• ts.Map<T> is now a native Map<string, T> or a shim. This affects the SymbolTable type, exposed by Symbol.members, Symbol.exports, and Symbol.globalExports.

• ParseConfigHost now requires a new member readFile to support configuration inheritance.

• LanguageService.getSourceFile has been removed; LanguageService.getProgram().getSourceFile should be used instead.

• ts.parseConfigFile has been renamed to ts.parseJsonConfigFileContent

• return type of CompilerHost.resolveModuleNames was changed from string[] to ResolvedModule[]. Extra optional property isExternalLibraryImport in ResolvedModule interface denotes if Program should apply some particular set of policies to the resolved file. For example if Node resolver has resolved non-relative module name to the file in 'node_modules', then this file:

  • should be a 'd.ts' file
  • should be an external module
  • should not contain tripleslash references.

  Rationale: files containing external typings should not pollute global scope (to avoid conflicts between different versions of the same package). Also such files should never be added to the list of compiled files (otherwise compiled .ts file might overwrite actual .js file with implementation of the package)

• TypeChecker.emitFiles is no longer available; use Program.emit instead.
• Getting diagnostics are now all centralized on Program,
  • for Syntactic diagnostics for a single file use: Program.getSyntacticDiagnostics(sourceFile)
  • for Syntactic diagnostics for all files use: Program.getSyntacticDiagnostics()
  • for Semantic diagnostics for a single file use: Program.getSemanticDiagnostics(sourceFile)
  • for Semantic diagnostics for all files use: Program.getSemanticDiagnostics()
  • for compiler options and global diagnostics use: Program.getGlobalDiagnostics()

Tip: use ts.getPreEmitDiagnostics(program) to get syntactic, semantic, and global diagnostics for all files

Here are the details:

• CompilerHost.getDefaultLibFilename => CompilerHost.getDefaultLibFileName
• SourceFile.filename => SourceFile.fileName
• FileReference.filename => FileReference.fileName
• LanguageServiceHost.getDefaultLibFilename => LanguageServiceHost.getDefaultLibFileName
• LanguageServiceShimHost.getDefaultLibFilename => LanguageServiceShimHost.getDefaultLibFileName

The full list of APIs can be found in this commit

See Pull Request #2051 for more details.

TextChange.start and TextChange.length became properties instead of methods.

SourceFile.getLineAndCharacterFromPosition became SourceFile.getLineAndCharacterOfPosition

We did some cleanup to the public interfaces, here is the full list of changes:

• Commit 2ee134c6b3c0ec
• Commit 35dde28d44122c
• Commit c9ef4db99ac93bb1c166a

• Commit b4e5d5b0b460cc88a10db

The two files exposed helpers in the past that were not part of the supported TypeScript API. If you were using any of these APIs please file an issue to re-expose them; requests for exposing helper APIs will be triaged on a case-by-case basis.

For more information please see the full change.