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/// <reference path="../factory.ts" />
/// <reference path="../visitor.ts" />
/// <reference path="./destructuring.ts" />
/*@internal*/
namespace ts {
/**
* Indicates whether to emit type metadata in the new format.
*/
const USE_NEW_TYPE_METADATA_FORMAT = false;
const enum TypeScriptSubstitutionFlags {
/** Enables substitutions for decorated classes. */
ClassAliases = 1 << 0,
/** Enables substitutions for namespace exports. */
NamespaceExports = 1 << 1,
/* Enables substitutions for unqualified enum members */
NonQualifiedEnumMembers = 1 << 3
}
const enum ClassFacts {
None = 0,
HasStaticInitializedProperties = 1 << 0,
HasConstructorDecorators = 1 << 1,
HasMemberDecorators = 1 << 2,
IsExportOfNamespace = 1 << 3,
IsNamedExternalExport = 1 << 4,
IsDefaultExternalExport = 1 << 5,
HasExtendsClause = 1 << 6,
UseImmediatelyInvokedFunctionExpression = 1 << 7,
HasAnyDecorators = HasConstructorDecorators | HasMemberDecorators,
NeedsName = HasStaticInitializedProperties | HasMemberDecorators,
MayNeedImmediatelyInvokedFunctionExpression = HasAnyDecorators | HasStaticInitializedProperties,
IsExported = IsExportOfNamespace | IsDefaultExternalExport | IsNamedExternalExport,
}
export function transformTypeScript(context: TransformationContext) {
const {
startLexicalEnvironment,
resumeLexicalEnvironment,
endLexicalEnvironment,
hoistVariableDeclaration,
} = context;
const resolver = context.getEmitResolver();
const compilerOptions = context.getCompilerOptions();
const languageVersion = getEmitScriptTarget(compilerOptions);
const moduleKind = getEmitModuleKind(compilerOptions);
// Save the previous transformation hooks.
const previousOnEmitNode = context.onEmitNode;
const previousOnSubstituteNode = context.onSubstituteNode;
// Set new transformation hooks.
context.onEmitNode = onEmitNode;
context.onSubstituteNode = onSubstituteNode;
// Enable substitution for property/element access to emit const enum values.
context.enableSubstitution(SyntaxKind.PropertyAccessExpression);
context.enableSubstitution(SyntaxKind.ElementAccessExpression);
// These variables contain state that changes as we descend into the tree.
let currentSourceFile: SourceFile;
let currentNamespace: ModuleDeclaration;
let currentNamespaceContainerName: Identifier;
let currentScope: SourceFile | Block | ModuleBlock | CaseBlock;
let currentScopeFirstDeclarationsOfName: UnderscoreEscapedMap<Node>;
/**
* Keeps track of whether expression substitution has been enabled for specific edge cases.
* They are persisted between each SourceFile transformation and should not be reset.
*/
let enabledSubstitutions: TypeScriptSubstitutionFlags;
/**
* A map that keeps track of aliases created for classes with decorators to avoid issues
* with the double-binding behavior of classes.
*/
let classAliases: Identifier[];
/**
* Keeps track of whether we are within any containing namespaces when performing
* just-in-time substitution while printing an expression identifier.
*/
let applicableSubstitutions: TypeScriptSubstitutionFlags;
return transformSourceFile;
/**
* Transform TypeScript-specific syntax in a SourceFile.
*
* @param node A SourceFile node.
*/
function transformSourceFile(node: SourceFile) {
if (node.isDeclarationFile) {
return node;
}
currentSourceFile = node;
const visited = saveStateAndInvoke(node, visitSourceFile);
addEmitHelpers(visited, context.readEmitHelpers());
currentSourceFile = undefined;
return visited;
}
/**
* Visits a node, saving and restoring state variables on the stack.
*
* @param node The node to visit.
*/
function saveStateAndInvoke<T>(node: Node, f: (node: Node) => T): T {
// Save state
const savedCurrentScope = currentScope;
const savedCurrentScopeFirstDeclarationsOfName = currentScopeFirstDeclarationsOfName;
// Handle state changes before visiting a node.
onBeforeVisitNode(node);
const visited = f(node);
// Restore state
if (currentScope !== savedCurrentScope) {
currentScopeFirstDeclarationsOfName = savedCurrentScopeFirstDeclarationsOfName;
}
currentScope = savedCurrentScope;
return visited;
}
/**
* Performs actions that should always occur immediately before visiting a node.
*
* @param node The node to visit.
*/
function onBeforeVisitNode(node: Node) {
switch (node.kind) {
case SyntaxKind.SourceFile:
case SyntaxKind.CaseBlock:
case SyntaxKind.ModuleBlock:
case SyntaxKind.Block:
currentScope = <SourceFile | CaseBlock | ModuleBlock | Block>node;
currentScopeFirstDeclarationsOfName = undefined;
break;
case SyntaxKind.ClassDeclaration:
case SyntaxKind.FunctionDeclaration:
if (hasModifier(node, ModifierFlags.Ambient)) {
break;
}
// Record these declarations provided that they have a name.
if ((node as ClassDeclaration | FunctionDeclaration).name) {
recordEmittedDeclarationInScope(node as ClassDeclaration | FunctionDeclaration);
}
else {
// These nodes should always have names unless they are default-exports;
// however, class declaration parsing allows for undefined names, so syntactically invalid
// programs may also have an undefined name.
Debug.assert(node.kind === SyntaxKind.ClassDeclaration || hasModifier(node, ModifierFlags.Default));
}
break;
}
}
/**
* General-purpose node visitor.
*
* @param node The node to visit.
*/
function visitor(node: Node): VisitResult<Node> {
return saveStateAndInvoke(node, visitorWorker);
}
/**
* Visits and possibly transforms any node.
*
* @param node The node to visit.
*/
function visitorWorker(node: Node): VisitResult<Node> {
if (node.transformFlags & TransformFlags.TypeScript) {
// This node is explicitly marked as TypeScript, so we should transform the node.
return visitTypeScript(node);
}
else if (node.transformFlags & TransformFlags.ContainsTypeScript) {
// This node contains TypeScript, so we should visit its children.
return visitEachChild(node, visitor, context);
}
return node;
}
/**
* Specialized visitor that visits the immediate children of a SourceFile.
*
* @param node The node to visit.
*/
function sourceElementVisitor(node: Node): VisitResult<Node> {
return saveStateAndInvoke(node, sourceElementVisitorWorker);
}
/**
* Specialized visitor that visits the immediate children of a SourceFile.
*
* @param node The node to visit.
*/
function sourceElementVisitorWorker(node: Node): VisitResult<Node> {
switch (node.kind) {
case SyntaxKind.ImportDeclaration:
case SyntaxKind.ImportEqualsDeclaration:
case SyntaxKind.ExportAssignment:
case SyntaxKind.ExportDeclaration:
return visitEllidableStatement(<ImportDeclaration | ImportEqualsDeclaration | ExportAssignment | ExportDeclaration>node);
default:
return visitorWorker(node);
}
}
function visitEllidableStatement(node: ImportDeclaration | ImportEqualsDeclaration | ExportAssignment | ExportDeclaration): VisitResult<Node> {
const parsed = getParseTreeNode(node);
if (parsed !== node) {
// If the node has been transformed by a `before` transformer, perform no ellision on it
// As the type information we would attempt to lookup to perform ellision is potentially unavailable for the synthesized nodes
return node;
}
switch (node.kind) {
case SyntaxKind.ImportDeclaration:
return visitImportDeclaration(<ImportDeclaration>node);
case SyntaxKind.ImportEqualsDeclaration:
return visitImportEqualsDeclaration(<ImportEqualsDeclaration>node);
case SyntaxKind.ExportAssignment:
return visitExportAssignment(<ExportAssignment>node);
case SyntaxKind.ExportDeclaration:
return visitExportDeclaration(<ExportDeclaration>node);
default:
Debug.fail("Unhandled ellided statement");
}
}
/**
* Specialized visitor that visits the immediate children of a namespace.
*
* @param node The node to visit.
*/
function namespaceElementVisitor(node: Node): VisitResult<Node> {
return saveStateAndInvoke(node, namespaceElementVisitorWorker);
}
/**
* Specialized visitor that visits the immediate children of a namespace.
*
* @param node The node to visit.
*/
function namespaceElementVisitorWorker(node: Node): VisitResult<Node> {
if (node.kind === SyntaxKind.ExportDeclaration ||
node.kind === SyntaxKind.ImportDeclaration ||
node.kind === SyntaxKind.ImportClause ||
(node.kind === SyntaxKind.ImportEqualsDeclaration &&
(<ImportEqualsDeclaration>node).moduleReference.kind === SyntaxKind.ExternalModuleReference)) {
// do not emit ES6 imports and exports since they are illegal inside a namespace
return undefined;
}
else if (node.transformFlags & TransformFlags.TypeScript || hasModifier(node, ModifierFlags.Export)) {
// This node is explicitly marked as TypeScript, or is exported at the namespace
// level, so we should transform the node.
return visitTypeScript(node);
}
else if (node.transformFlags & TransformFlags.ContainsTypeScript) {
// This node contains TypeScript, so we should visit its children.
return visitEachChild(node, visitor, context);
}
return node;
}
/**
* Specialized visitor that visits the immediate children of a class with TypeScript syntax.
*
* @param node The node to visit.
*/
function classElementVisitor(node: Node): VisitResult<Node> {
return saveStateAndInvoke(node, classElementVisitorWorker);
}
/**
* Specialized visitor that visits the immediate children of a class with TypeScript syntax.
*
* @param node The node to visit.
*/
function classElementVisitorWorker(node: Node): VisitResult<Node> {
switch (node.kind) {
case SyntaxKind.Constructor:
// TypeScript constructors are transformed in `visitClassDeclaration`.
// We elide them here as `visitorWorker` checks transform flags, which could
// erronously include an ES6 constructor without TypeScript syntax.
return undefined;
case SyntaxKind.PropertyDeclaration:
case SyntaxKind.IndexSignature:
case SyntaxKind.GetAccessor:
case SyntaxKind.SetAccessor:
case SyntaxKind.MethodDeclaration:
// Fallback to the default visit behavior.
return visitorWorker(node);
case SyntaxKind.SemicolonClassElement:
return node;
default:
Debug.failBadSyntaxKind(node);
return undefined;
}
}
function modifierVisitor(node: Node): VisitResult<Node> {
if (modifierToFlag(node.kind) & ModifierFlags.TypeScriptModifier) {
return undefined;
}
else if (currentNamespace && node.kind === SyntaxKind.ExportKeyword) {
return undefined;
}
return node;
}
/**
* Branching visitor, visits a TypeScript syntax node.
*
* @param node The node to visit.
*/
function visitTypeScript(node: Node): VisitResult<Node> {
if (hasModifier(node, ModifierFlags.Ambient) && isStatement(node)) {
// TypeScript ambient declarations are elided, but some comments may be preserved.
// See the implementation of `getLeadingComments` in comments.ts for more details.
return createNotEmittedStatement(node);
}
switch (node.kind) {
case SyntaxKind.ExportKeyword:
case SyntaxKind.DefaultKeyword:
// ES6 export and default modifiers are elided when inside a namespace.
return currentNamespace ? undefined : node;
case SyntaxKind.PublicKeyword:
case SyntaxKind.PrivateKeyword:
case SyntaxKind.ProtectedKeyword:
case SyntaxKind.AbstractKeyword:
case SyntaxKind.ConstKeyword:
case SyntaxKind.DeclareKeyword:
case SyntaxKind.ReadonlyKeyword:
// TypeScript accessibility and readonly modifiers are elided.
case SyntaxKind.ArrayType:
case SyntaxKind.TupleType:
case SyntaxKind.TypeLiteral:
case SyntaxKind.TypePredicate:
case SyntaxKind.TypeParameter:
case SyntaxKind.AnyKeyword:
case SyntaxKind.BooleanKeyword:
case SyntaxKind.StringKeyword:
case SyntaxKind.NumberKeyword:
case SyntaxKind.NeverKeyword:
case SyntaxKind.VoidKeyword:
case SyntaxKind.SymbolKeyword:
case SyntaxKind.ConstructorType:
case SyntaxKind.FunctionType:
case SyntaxKind.TypeQuery:
case SyntaxKind.TypeReference:
case SyntaxKind.UnionType:
case SyntaxKind.IntersectionType:
case SyntaxKind.ParenthesizedType:
case SyntaxKind.ThisType:
case SyntaxKind.TypeOperator:
case SyntaxKind.IndexedAccessType:
case SyntaxKind.MappedType:
case SyntaxKind.LiteralType:
// TypeScript type nodes are elided.
case SyntaxKind.IndexSignature:
// TypeScript index signatures are elided.
case SyntaxKind.Decorator:
// TypeScript decorators are elided. They will be emitted as part of visitClassDeclaration.
case SyntaxKind.TypeAliasDeclaration:
// TypeScript type-only declarations are elided.
case SyntaxKind.PropertyDeclaration:
// TypeScript property declarations are elided.
case SyntaxKind.NamespaceExportDeclaration:
// TypeScript namespace export declarations are elided.
return undefined;
case SyntaxKind.Constructor:
return visitConstructor(<ConstructorDeclaration>node);
case SyntaxKind.InterfaceDeclaration:
// TypeScript interfaces are elided, but some comments may be preserved.
// See the implementation of `getLeadingComments` in comments.ts for more details.
return createNotEmittedStatement(node);
case SyntaxKind.ClassDeclaration:
// This is a class declaration with TypeScript syntax extensions.
//
// TypeScript class syntax extensions include:
// - decorators
// - optional `implements` heritage clause
// - parameter property assignments in the constructor
// - property declarations
// - index signatures
// - method overload signatures
return visitClassDeclaration(<ClassDeclaration>node);
case SyntaxKind.ClassExpression:
// This is a class expression with TypeScript syntax extensions.
//
// TypeScript class syntax extensions include:
// - decorators
// - optional `implements` heritage clause
// - parameter property assignments in the constructor
// - property declarations
// - index signatures
// - method overload signatures
return visitClassExpression(<ClassExpression>node);
case SyntaxKind.HeritageClause:
// This is a heritage clause with TypeScript syntax extensions.
//
// TypeScript heritage clause extensions include:
// - `implements` clause
return visitHeritageClause(<HeritageClause>node);
case SyntaxKind.ExpressionWithTypeArguments:
// TypeScript supports type arguments on an expression in an `extends` heritage clause.
return visitExpressionWithTypeArguments(<ExpressionWithTypeArguments>node);
case SyntaxKind.MethodDeclaration:
// TypeScript method declarations may have decorators, modifiers
// or type annotations.
return visitMethodDeclaration(<MethodDeclaration>node);
case SyntaxKind.GetAccessor:
// Get Accessors can have TypeScript modifiers, decorators, and type annotations.
return visitGetAccessor(<GetAccessorDeclaration>node);
case SyntaxKind.SetAccessor:
// Set Accessors can have TypeScript modifiers and type annotations.
return visitSetAccessor(<SetAccessorDeclaration>node);
case SyntaxKind.FunctionDeclaration:
// Typescript function declarations can have modifiers, decorators, and type annotations.
return visitFunctionDeclaration(<FunctionDeclaration>node);
case SyntaxKind.FunctionExpression:
// TypeScript function expressions can have modifiers and type annotations.
return visitFunctionExpression(<FunctionExpression>node);
case SyntaxKind.ArrowFunction:
// TypeScript arrow functions can have modifiers and type annotations.
return visitArrowFunction(<ArrowFunction>node);
case SyntaxKind.Parameter:
// This is a parameter declaration with TypeScript syntax extensions.
//
// TypeScript parameter declaration syntax extensions include:
// - decorators
// - accessibility modifiers
// - the question mark (?) token for optional parameters
// - type annotations
// - this parameters
return visitParameter(<ParameterDeclaration>node);
case SyntaxKind.ParenthesizedExpression:
// ParenthesizedExpressions are TypeScript if their expression is a
// TypeAssertion or AsExpression
return visitParenthesizedExpression(<ParenthesizedExpression>node);
case SyntaxKind.TypeAssertionExpression:
case SyntaxKind.AsExpression:
// TypeScript type assertions are removed, but their subtrees are preserved.
return visitAssertionExpression(<AssertionExpression>node);
case SyntaxKind.CallExpression:
return visitCallExpression(<CallExpression>node);
case SyntaxKind.NewExpression:
return visitNewExpression(<NewExpression>node);
case SyntaxKind.NonNullExpression:
// TypeScript non-null expressions are removed, but their subtrees are preserved.
return visitNonNullExpression(<NonNullExpression>node);
case SyntaxKind.EnumDeclaration:
// TypeScript enum declarations do not exist in ES6 and must be rewritten.
return visitEnumDeclaration(<EnumDeclaration>node);
case SyntaxKind.VariableStatement:
// TypeScript namespace exports for variable statements must be transformed.
return visitVariableStatement(<VariableStatement>node);
case SyntaxKind.VariableDeclaration:
return visitVariableDeclaration(<VariableDeclaration>node);
case SyntaxKind.ModuleDeclaration:
// TypeScript namespace declarations must be transformed.
return visitModuleDeclaration(<ModuleDeclaration>node);
case SyntaxKind.ImportEqualsDeclaration:
// TypeScript namespace or external module import.
return visitImportEqualsDeclaration(<ImportEqualsDeclaration>node);
default:
Debug.failBadSyntaxKind(node);
return visitEachChild(node, visitor, context);
}
}
function visitSourceFile(node: SourceFile) {
const alwaysStrict = (compilerOptions.alwaysStrict === undefined ? compilerOptions.strict : compilerOptions.alwaysStrict) &&
!(isExternalModule(node) && moduleKind >= ModuleKind.ES2015);
return updateSourceFileNode(
node,
visitLexicalEnvironment(node.statements, sourceElementVisitor, context, /*start*/ 0, alwaysStrict));
}
/**
* Tests whether we should emit a __decorate call for a class declaration.
*/
function shouldEmitDecorateCallForClass(node: ClassDeclaration) {
if (node.decorators && node.decorators.length > 0) {
return true;
}
const constructor = getFirstConstructorWithBody(node);
if (constructor) {
return forEach(constructor.parameters, shouldEmitDecorateCallForParameter);
}
return false;
}
/**
* Tests whether we should emit a __decorate call for a parameter declaration.
*/
function shouldEmitDecorateCallForParameter(parameter: ParameterDeclaration) {
return parameter.decorators !== undefined && parameter.decorators.length > 0;
}
function getClassFacts(node: ClassDeclaration, staticProperties: ReadonlyArray<PropertyDeclaration>) {
let facts = ClassFacts.None;
if (some(staticProperties)) facts |= ClassFacts.HasStaticInitializedProperties;
if (getClassExtendsHeritageClauseElement(node)) facts |= ClassFacts.HasExtendsClause;
if (shouldEmitDecorateCallForClass(node)) facts |= ClassFacts.HasConstructorDecorators;
if (childIsDecorated(node)) facts |= ClassFacts.HasMemberDecorators;
if (isExportOfNamespace(node)) facts |= ClassFacts.IsExportOfNamespace;
else if (isDefaultExternalModuleExport(node)) facts |= ClassFacts.IsDefaultExternalExport;
else if (isNamedExternalModuleExport(node)) facts |= ClassFacts.IsNamedExternalExport;
if (languageVersion <= ScriptTarget.ES5 && (facts & ClassFacts.MayNeedImmediatelyInvokedFunctionExpression)) facts |= ClassFacts.UseImmediatelyInvokedFunctionExpression;
return facts;
}
/**
* Transforms a class declaration with TypeScript syntax into compatible ES6.
*
* This function will only be called when one of the following conditions are met:
* - The class has decorators.
* - The class has property declarations with initializers.
* - The class contains a constructor that contains parameters with accessibility modifiers.
* - The class is an export in a TypeScript namespace.
*
* @param node The node to transform.
*/
function visitClassDeclaration(node: ClassDeclaration): VisitResult<Statement> {
const staticProperties = getInitializedProperties(node, /*isStatic*/ true);
const facts = getClassFacts(node, staticProperties);
if (facts & ClassFacts.UseImmediatelyInvokedFunctionExpression) {
context.startLexicalEnvironment();
}
const name = node.name || (facts & ClassFacts.NeedsName ? getGeneratedNameForNode(node) : undefined);
const classStatement = facts & ClassFacts.HasConstructorDecorators
? createClassDeclarationHeadWithDecorators(node, name, facts)
: createClassDeclarationHeadWithoutDecorators(node, name, facts);
let statements: Statement[] = [classStatement];
// Emit static property assignment. Because classDeclaration is lexically evaluated,
// it is safe to emit static property assignment after classDeclaration
// From ES6 specification:
// HasLexicalDeclaration (N) : Determines if the argument identifier has a binding in this environment record that was created using
// a lexical declaration such as a LexicalDeclaration or a ClassDeclaration.
if (facts & ClassFacts.HasStaticInitializedProperties) {
addInitializedPropertyStatements(statements, staticProperties, facts & ClassFacts.UseImmediatelyInvokedFunctionExpression ? getInternalName(node) : getLocalName(node));
}
// Write any decorators of the node.
addClassElementDecorationStatements(statements, node, /*isStatic*/ false);
addClassElementDecorationStatements(statements, node, /*isStatic*/ true);
addConstructorDecorationStatement(statements, node);
if (facts & ClassFacts.UseImmediatelyInvokedFunctionExpression) {
// When we emit a TypeScript class down to ES5, we must wrap it in an IIFE so that the
// 'es2015' transformer can properly nest static initializers and decorators. The result
// looks something like:
//
// var C = function () {
// class C {
// }
// C.static_prop = 1;
// return C;
// }();
//
const closingBraceLocation = createTokenRange(skipTrivia(currentSourceFile.text, node.members.end), SyntaxKind.CloseBraceToken);
const localName = getInternalName(node);
// The following partially-emitted expression exists purely to align our sourcemap
// emit with the original emitter.
const outer = createPartiallyEmittedExpression(localName);
outer.end = closingBraceLocation.end;
setEmitFlags(outer, EmitFlags.NoComments);
const statement = createReturn(outer);
statement.pos = closingBraceLocation.pos;
setEmitFlags(statement, EmitFlags.NoComments | EmitFlags.NoTokenSourceMaps);
statements.push(statement);
addRange(statements, context.endLexicalEnvironment());
const iife = createImmediatelyInvokedArrowFunction(statements);
setEmitFlags(iife, EmitFlags.TypeScriptClassWrapper);
const varStatement = createVariableStatement(
/*modifiers*/ undefined,
createVariableDeclarationList([
createVariableDeclaration(
getLocalName(node, /*allowComments*/ false, /*allowSourceMaps*/ false),
/*type*/ undefined,
iife
)
])
);
setOriginalNode(varStatement, node);
setCommentRange(varStatement, node);
setSourceMapRange(varStatement, moveRangePastDecorators(node));
startOnNewLine(varStatement);
statements = [varStatement];
}
// If the class is exported as part of a TypeScript namespace, emit the namespace export.
// Otherwise, if the class was exported at the top level and was decorated, emit an export
// declaration or export default for the class.
if (facts & ClassFacts.IsExportOfNamespace) {
addExportMemberAssignment(statements, node);
}
else if (facts & ClassFacts.UseImmediatelyInvokedFunctionExpression || facts & ClassFacts.HasConstructorDecorators) {
if (facts & ClassFacts.IsDefaultExternalExport) {
statements.push(createExportDefault(getLocalName(node, /*allowComments*/ false, /*allowSourceMaps*/ true)));
}
else if (facts & ClassFacts.IsNamedExternalExport) {
statements.push(createExternalModuleExport(getLocalName(node, /*allowComments*/ false, /*allowSourceMaps*/ true)));
}
}
if (statements.length > 1) {
// Add a DeclarationMarker as a marker for the end of the declaration
statements.push(createEndOfDeclarationMarker(node));
setEmitFlags(classStatement, getEmitFlags(classStatement) | EmitFlags.HasEndOfDeclarationMarker);
}
return singleOrMany(statements);
}
/**
* Transforms a non-decorated class declaration and appends the resulting statements.
*
* @param node A ClassDeclaration node.
* @param name The name of the class.
* @param facts Precomputed facts about the class.
*/
function createClassDeclarationHeadWithoutDecorators(node: ClassDeclaration, name: Identifier, facts: ClassFacts) {
// ${modifiers} class ${name} ${heritageClauses} {
// ${members}
// }
// we do not emit modifiers on the declaration if we are emitting an IIFE
const modifiers = !(facts & ClassFacts.UseImmediatelyInvokedFunctionExpression)
? visitNodes(node.modifiers, modifierVisitor, isModifier)
: undefined;
const classDeclaration = createClassDeclaration(
/*decorators*/ undefined,
modifiers,
name,
/*typeParameters*/ undefined,
visitNodes(node.heritageClauses, visitor, isHeritageClause),
transformClassMembers(node, (facts & ClassFacts.HasExtendsClause) !== 0)
);
// To better align with the old emitter, we should not emit a trailing source map
// entry if the class has static properties.
let emitFlags = getEmitFlags(node);
if (facts & ClassFacts.HasStaticInitializedProperties) {
emitFlags |= EmitFlags.NoTrailingSourceMap;
}
setTextRange(classDeclaration, node);
setOriginalNode(classDeclaration, node);
setEmitFlags(classDeclaration, emitFlags);
return classDeclaration;
}
/**
* Transforms a decorated class declaration and appends the resulting statements. If
* the class requires an alias to avoid issues with double-binding, the alias is returned.
*/
function createClassDeclarationHeadWithDecorators(node: ClassDeclaration, name: Identifier, facts: ClassFacts) {
// When we emit an ES6 class that has a class decorator, we must tailor the
// emit to certain specific cases.
//
// In the simplest case, we emit the class declaration as a let declaration, and
// evaluate decorators after the close of the class body:
//
// [Example 1]
// ---------------------------------------------------------------------
// TypeScript | Javascript
// ---------------------------------------------------------------------
// @dec | let C = class C {
// class C { | }
// } | C = __decorate([dec], C);
// ---------------------------------------------------------------------
// @dec | let C = class C {
// export class C { | }
// } | C = __decorate([dec], C);
// | export { C };
// ---------------------------------------------------------------------
//
// If a class declaration contains a reference to itself *inside* of the class body,
// this introduces two bindings to the class: One outside of the class body, and one
// inside of the class body. If we apply decorators as in [Example 1] above, there
// is the possibility that the decorator `dec` will return a new value for the
// constructor, which would result in the binding inside of the class no longer
// pointing to the same reference as the binding outside of the class.
//
// As a result, we must instead rewrite all references to the class *inside* of the
// class body to instead point to a local temporary alias for the class:
//
// [Example 2]
// ---------------------------------------------------------------------
// TypeScript | Javascript
// ---------------------------------------------------------------------
// @dec | let C = C_1 = class C {
// class C { | static x() { return C_1.y; }
// static x() { return C.y; } | }
// static y = 1; | C.y = 1;
// } | C = C_1 = __decorate([dec], C);
// | var C_1;
// ---------------------------------------------------------------------
// @dec | let C = class C {
// export class C { | static x() { return C_1.y; }
// static x() { return C.y; } | }
// static y = 1; | C.y = 1;
// } | C = C_1 = __decorate([dec], C);
// | export { C };
// | var C_1;
// ---------------------------------------------------------------------
//
// If a class declaration is the default export of a module, we instead emit
// the export after the decorated declaration:
//
// [Example 3]
// ---------------------------------------------------------------------
// TypeScript | Javascript
// ---------------------------------------------------------------------
// @dec | let default_1 = class {
// export default class { | }
// } | default_1 = __decorate([dec], default_1);
// | export default default_1;
// ---------------------------------------------------------------------
// @dec | let C = class C {
// export default class C { | }
// } | C = __decorate([dec], C);
// | export default C;
// ---------------------------------------------------------------------
//
// If the class declaration is the default export and a reference to itself
// inside of the class body, we must emit both an alias for the class *and*
// move the export after the declaration:
//
// [Example 4]
// ---------------------------------------------------------------------
// TypeScript | Javascript
// ---------------------------------------------------------------------
// @dec | let C = class C {
// export default class C { | static x() { return C_1.y; }
// static x() { return C.y; } | }
// static y = 1; | C.y = 1;
// } | C = C_1 = __decorate([dec], C);
// | export default C;
// | var C_1;
// ---------------------------------------------------------------------
//
const location = moveRangePastDecorators(node);
const classAlias = getClassAliasIfNeeded(node);
const declName = getLocalName(node, /*allowComments*/ false, /*allowSourceMaps*/ true);
// ... = class ${name} ${heritageClauses} {
// ${members}
// }
const heritageClauses = visitNodes(node.heritageClauses, visitor, isHeritageClause);
const members = transformClassMembers(node, (facts & ClassFacts.HasExtendsClause) !== 0);
const classExpression = createClassExpression(/*modifiers*/ undefined, name, /*typeParameters*/ undefined, heritageClauses, members);
setOriginalNode(classExpression, node);
setTextRange(classExpression, location);
// let ${name} = ${classExpression} where name is either declaredName if the class doesn't contain self-reference
// or decoratedClassAlias if the class contain self-reference.
const statement = createVariableStatement(
/*modifiers*/ undefined,
createVariableDeclarationList([
createVariableDeclaration(
declName,
/*type*/ undefined,
classAlias ? createAssignment(classAlias, classExpression) : classExpression
)
], NodeFlags.Let)
);
setOriginalNode(statement, node);
setTextRange(statement, location);
setCommentRange(statement, node);
return statement;
}
/**
* Transforms a class expression with TypeScript syntax into compatible ES6.
*
* This function will only be called when one of the following conditions are met:
* - The class has property declarations with initializers.
* - The class contains a constructor that contains parameters with accessibility modifiers.
*
* @param node The node to transform.
*/
function visitClassExpression(node: ClassExpression): Expression {
const staticProperties = getInitializedProperties(node, /*isStatic*/ true);
const heritageClauses = visitNodes(node.heritageClauses, visitor, isHeritageClause);
const members = transformClassMembers(node, some(heritageClauses, c => c.token === SyntaxKind.ExtendsKeyword));
const classExpression = createClassExpression(
/*modifiers*/ undefined,
node.name,
/*typeParameters*/ undefined,
heritageClauses,
members
);
setOriginalNode(classExpression, node);
setTextRange(classExpression, node);
if (staticProperties.length > 0) {
const expressions: Expression[] = [];
const temp = createTempVariable(hoistVariableDeclaration);
if (resolver.getNodeCheckFlags(node) & NodeCheckFlags.ClassWithConstructorReference) {
// record an alias as the class name is not in scope for statics.
enableSubstitutionForClassAliases();
classAliases[getOriginalNodeId(node)] = getSynthesizedClone(temp);
}
// To preserve the behavior of the old emitter, we explicitly indent
// the body of a class with static initializers.
setEmitFlags(classExpression, EmitFlags.Indented | getEmitFlags(classExpression));
expressions.push(startOnNewLine(createAssignment(temp, classExpression)));
addRange(expressions, generateInitializedPropertyExpressions(staticProperties, temp));
expressions.push(startOnNewLine(temp));
return inlineExpressions(expressions);
}
return classExpression;
}
/**
* Transforms the members of a class.
*
* @param node The current class.
* @param hasExtendsClause A value indicating whether the class has an extends clause.
*/
function transformClassMembers(node: ClassDeclaration | ClassExpression, hasExtendsClause: boolean) {
const members: ClassElement[] = [];
const constructor = transformConstructor(node, hasExtendsClause);
if (constructor) {
members.push(constructor);
}
addRange(members, visitNodes(node.members, classElementVisitor, isClassElement));
return setTextRange(createNodeArray(members), /*location*/ node.members);
}
/**
* Transforms (or creates) a constructor for a class.
*
* @param node The current class.
* @param hasExtendsClause A value indicating whether the class has an extends clause.
*/
function transformConstructor(node: ClassDeclaration | ClassExpression, hasExtendsClause: boolean) {
// Check if we have property assignment inside class declaration.
// If there is a property assignment, we need to emit constructor whether users define it or not
// If there is no property assignment, we can omit constructor if users do not define it
const hasInstancePropertyWithInitializer = forEach(node.members, isInstanceInitializedProperty);
const hasParameterPropertyAssignments = node.transformFlags & TransformFlags.ContainsParameterPropertyAssignments;
const constructor = getFirstConstructorWithBody(node);
// If the class does not contain nodes that require a synthesized constructor,
// accept the current constructor if it exists.
if (!hasInstancePropertyWithInitializer && !hasParameterPropertyAssignments) {
return visitEachChild(constructor, visitor, context);
}
const parameters = transformConstructorParameters(constructor);
const body = transformConstructorBody(node, constructor, hasExtendsClause);
// constructor(${parameters}) {
// ${body}
// }
return startOnNewLine(
setOriginalNode(
setTextRange(
createConstructor(
/*decorators*/ undefined,
/*modifiers*/ undefined,
parameters,
body
),
constructor || node
),
constructor
)
);
}
/**
* Transforms (or creates) the parameters for the constructor of a class with
* parameter property assignments or instance property initializers.
*
* @param constructor The constructor declaration.
* @param hasExtendsClause A value indicating whether the class has an extends clause.
*/
function transformConstructorParameters(constructor: ConstructorDeclaration) {
// The ES2015 spec specifies in 14.5.14. Runtime Semantics: ClassDefinitionEvaluation:
// If constructor is empty, then
// If ClassHeritag_eopt is present and protoParent is not null, then
// Let constructor be the result of parsing the source text
// constructor(...args) { super (...args);}
// using the syntactic grammar with the goal symbol MethodDefinition[~Yield].
// Else,
// Let constructor be the result of parsing the source text
// constructor( ){ }
// using the syntactic grammar with the goal symbol MethodDefinition[~Yield].
//
// While we could emit the '...args' rest parameter, certain later tools in the pipeline might
// downlevel the '...args' portion less efficiently by naively copying the contents of 'arguments' to an array.
// Instead, we'll avoid using a rest parameter and spread into the super call as
// 'super(...arguments)' instead of 'super(...args)', as you can see in "transformConstructorBody".
return visitParameterList(constructor && constructor.parameters, visitor, context)
|| <ParameterDeclaration[]>[];
}
/**
* Transforms (or creates) a constructor body for a class with parameter property
* assignments or instance property initializers.
*
* @param node The current class.
* @param constructor The current class constructor.
* @param hasExtendsClause A value indicating whether the class has an extends clause.
*/
function transformConstructorBody(node: ClassExpression | ClassDeclaration, constructor: ConstructorDeclaration, hasExtendsClause: boolean) {
let statements: Statement[] = [];
let indexOfFirstStatement = 0;
resumeLexicalEnvironment();
if (constructor) {
indexOfFirstStatement = addPrologueDirectivesAndInitialSuperCall(constructor, statements);
// Add parameters with property assignments. Transforms this:
//
// constructor (public x, public y) {
// }
//
// Into this:
//
// constructor (x, y) {
// this.x = x;
// this.y = y;
// }
//