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Add support for import defer proposal #60757

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Add support for import defer proposal #60757

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de82ce7
Add support for `import defer` proposal
ryzokuken Jul 8, 2024
9e43939
Update AST to unify `type` with other modifiers
nicolo-ribaudo Dec 19, 2024
b1f506b
Add test for comments around `defer`
nicolo-ribaudo Dec 19, 2024
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19 changes: 15 additions & 4 deletions src/compiler/checker.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -9851,7 +9851,7 @@ export function createTypeChecker(host: TypeCheckerHost): TypeChecker {
factory.createImportDeclaration(
/*modifiers*/ undefined,
factory.createImportClause(
/*isTypeOnly*/ false,
/*phaseModifier*/ undefined,
/*name*/ undefined,
factory.createNamedImports([factory.createImportSpecifier(
/*isTypeOnly*/ false,
Expand Down Expand Up @@ -9944,7 +9944,11 @@ export function createTypeChecker(host: TypeCheckerHost): TypeChecker {
addResult(
factory.createImportDeclaration(
/*modifiers*/ undefined,
factory.createImportClause(isTypeOnly, factory.createIdentifier(localName), /*namedBindings*/ undefined),
factory.createImportClause(
/* phaseModifier */ isTypeOnly ? SyntaxKind.TypeKeyword : undefined,
factory.createIdentifier(localName),
/*namedBindings*/ undefined,
),
specifier,
attributes,
),
Expand All @@ -9959,7 +9963,11 @@ export function createTypeChecker(host: TypeCheckerHost): TypeChecker {
addResult(
factory.createImportDeclaration(
/*modifiers*/ undefined,
factory.createImportClause(isTypeOnly, /*name*/ undefined, factory.createNamespaceImport(factory.createIdentifier(localName))),
factory.createImportClause(
/* phaseModifier */ isTypeOnly ? SyntaxKind.TypeKeyword : undefined,
/*name*/ undefined,
factory.createNamespaceImport(factory.createIdentifier(localName)),
),
specifier,
(node as ImportClause).parent.attributes,
),
Expand All @@ -9986,7 +9994,7 @@ export function createTypeChecker(host: TypeCheckerHost): TypeChecker {
factory.createImportDeclaration(
/*modifiers*/ undefined,
factory.createImportClause(
isTypeOnly,
/* phaseModifier */ isTypeOnly ? SyntaxKind.TypeKeyword : undefined,
/*name*/ undefined,
factory.createNamedImports([
factory.createImportSpecifier(
Expand Down Expand Up @@ -52860,6 +52868,9 @@ export function createTypeChecker(host: TypeCheckerHost): TypeChecker {
if (node.isTypeOnly && node.namedBindings?.kind === SyntaxKind.NamedImports) {
return checkGrammarNamedImportsOrExports(node.namedBindings);
}
if (node.phaseModifier === SyntaxKind.DeferKeyword && moduleKind !== ModuleKind.ESNext) {
return grammarErrorOnNode(node, Diagnostics.Deferred_imports_are_only_supported_when_the_module_flag_is_set_to_esnext);
}
return false;
}

Expand Down
12 changes: 12 additions & 0 deletions src/compiler/diagnosticMessages.json
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Original file line number Diff line number Diff line change
Expand Up @@ -8433,5 +8433,17 @@
"String literal import and export names are not supported when the '--module' flag is set to 'es2015' or 'es2020'.": {
"category": "Error",
"code": 18057
},
"Default imports aren't allowed for deferred imports.": {
"category": "Error",
"code": 18058
},
"Named imports aren't allowed for deferred imports.": {
"category": "Error",
"code": 18059
},
"Deferred imports are only supported when the '--module' flag is set to 'esnext'.": {
"category": "Error",
"code": 18060
}
}
6 changes: 5 additions & 1 deletion src/compiler/emitter.ts
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Expand Up @@ -3685,7 +3685,11 @@ export function createPrinter(printerOptions: PrinterOptions = {}, handlers: Pri
}

function emitImportClause(node: ImportClause) {
if (node.isTypeOnly) {
if (node.phaseModifier !== undefined) {
emitTokenWithComment(node.phaseModifier, node.pos, writeKeyword, node);
writeSpace();
}
else if (node.isTypeOnly) {
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I have this in case somebody passes in an object from an old TS version. Is this relevant for TS' API contract, or would removing it not be considered a breaking change?

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We don't support mixing TS versions between a given Node and the emitter, so that shouldn't be a concern. Inside the compiler we should avoid depending on deprecated functionality.

emitTokenWithComment(SyntaxKind.TypeKeyword, node.pos, writeKeyword, node);
writeSpace();
}
Expand Down
20 changes: 14 additions & 6 deletions src/compiler/factory/nodeFactory.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -135,6 +135,7 @@ import {
ImportClause,
ImportDeclaration,
ImportEqualsDeclaration,
ImportPhaseModifier,
ImportSpecifier,
ImportTypeAssertionContainer,
ImportTypeNode,
Expand Down Expand Up @@ -4723,26 +4724,33 @@ export function createNodeFactory(flags: NodeFactoryFlags, baseFactory: BaseNode
}

// @api
function createImportClause(isTypeOnly: boolean, name: Identifier | undefined, namedBindings: NamedImportBindings | undefined): ImportClause {
function createImportClause(phaseModifier: ImportPhaseModifier | boolean | undefined, name: Identifier | undefined, namedBindings: NamedImportBindings | undefined): ImportClause {
const node = createBaseDeclaration<ImportClause>(SyntaxKind.ImportClause);
node.isTypeOnly = isTypeOnly;
if (typeof phaseModifier === "boolean") {
phaseModifier = phaseModifier ? SyntaxKind.TypeKeyword : undefined;
}
node.isTypeOnly = phaseModifier === SyntaxKind.TypeKeyword;
node.phaseModifier = phaseModifier;
node.name = name;
node.namedBindings = namedBindings;
node.transformFlags |= propagateChildFlags(node.name) |
propagateChildFlags(node.namedBindings);
if (isTypeOnly) {
if (phaseModifier === SyntaxKind.TypeKeyword) {
node.transformFlags |= TransformFlags.ContainsTypeScript;
}
node.transformFlags &= ~TransformFlags.ContainsPossibleTopLevelAwait; // always parsed in an Await context
return node;
}

// @api
function updateImportClause(node: ImportClause, isTypeOnly: boolean, name: Identifier | undefined, namedBindings: NamedImportBindings | undefined) {
return node.isTypeOnly !== isTypeOnly
function updateImportClause(node: ImportClause, phaseModifier: ImportPhaseModifier | boolean | undefined, name: Identifier | undefined, namedBindings: NamedImportBindings | undefined) {
if (typeof phaseModifier === "boolean") {
phaseModifier = phaseModifier ? SyntaxKind.TypeKeyword : undefined;
}
return node.phaseModifier !== phaseModifier
|| node.name !== name
|| node.namedBindings !== namedBindings
? update(createImportClause(isTypeOnly, name, namedBindings), node)
? update(createImportClause(phaseModifier, name, namedBindings), node)
: node;
}

Expand Down
2 changes: 1 addition & 1 deletion src/compiler/factory/utilities.ts
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Expand Up @@ -730,7 +730,7 @@ export function createExternalHelpersImportDeclarationIfNeeded(nodeFactory: Node

const externalHelpersImportDeclaration = nodeFactory.createImportDeclaration(
/*modifiers*/ undefined,
nodeFactory.createImportClause(/*isTypeOnly*/ false, /*name*/ undefined, namedBindings),
nodeFactory.createImportClause(/*phaseModifier*/ undefined, /*name*/ undefined, namedBindings),
nodeFactory.createStringLiteral(externalHelpersModuleNameText),
/*attributes*/ undefined,
);
Expand Down
43 changes: 31 additions & 12 deletions src/compiler/parser.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -123,6 +123,7 @@ import {
ImportDeclaration,
ImportEqualsDeclaration,
ImportOrExportSpecifier,
ImportPhaseModifier,
ImportSpecifier,
ImportTypeAssertionContainer,
ImportTypeNode,
Expand Down Expand Up @@ -7190,6 +7191,7 @@ namespace Parser {
// could be legal, it would add complexity for very little gain.
case SyntaxKind.InterfaceKeyword:
case SyntaxKind.TypeKeyword:
case SyntaxKind.DeferKeyword:
return nextTokenIsIdentifierOnSameLine();
case SyntaxKind.ModuleKeyword:
case SyntaxKind.NamespaceKeyword:
Expand Down Expand Up @@ -7221,7 +7223,7 @@ namespace Parser {

case SyntaxKind.ImportKeyword:
nextToken();
return token() === SyntaxKind.StringLiteral || token() === SyntaxKind.AsteriskToken ||
return token() === SyntaxKind.DeferKeyword || token() === SyntaxKind.StringLiteral || token() === SyntaxKind.AsteriskToken ||
token() === SyntaxKind.OpenBraceToken || tokenIsIdentifierOrKeyword(token());
case SyntaxKind.ExportKeyword:
let currentToken = nextToken();
Expand Down Expand Up @@ -7295,6 +7297,7 @@ namespace Parser {
case SyntaxKind.NamespaceKeyword:
case SyntaxKind.TypeKeyword:
case SyntaxKind.GlobalKeyword:
case SyntaxKind.DeferKeyword:
// When these don't start a declaration, they're an identifier in an expression statement
return true;

Expand Down Expand Up @@ -8365,21 +8368,29 @@ namespace Parser {
identifier = parseIdentifier();
}

let isTypeOnly = false;
let phaseModifier: ImportPhaseModifier | undefined;
if (
identifier?.escapedText === "type" &&
(token() !== SyntaxKind.FromKeyword || isIdentifier() && lookAhead(nextTokenIsFromKeywordOrEqualsToken)) &&
(isIdentifier() || tokenAfterImportDefinitelyProducesImportDeclaration())
) {
isTypeOnly = true;
phaseModifier = SyntaxKind.TypeKeyword;
identifier = isIdentifier() ? parseIdentifier() : undefined;
}
else if (identifier?.escapedText === "defer" && token() !== SyntaxKind.FromKeyword) {
phaseModifier = SyntaxKind.DeferKeyword;
identifier = undefined;
if (isIdentifier()) {
parseErrorAtCurrentToken(Diagnostics.Default_imports_aren_t_allowed_for_deferred_imports);
identifier = parseIdentifier();
}
}

if (identifier && !tokenAfterImportedIdentifierDefinitelyProducesImportDeclaration()) {
return parseImportEqualsDeclaration(pos, hasJSDoc, modifiers, identifier, isTypeOnly);
if (identifier && !tokenAfterImportedIdentifierDefinitelyProducesImportDeclaration() && phaseModifier !== SyntaxKind.DeferKeyword) {
return parseImportEqualsDeclaration(pos, hasJSDoc, modifiers, identifier, phaseModifier === SyntaxKind.TypeKeyword);
}

const importClause = tryParseImportClause(identifier, afterImportPos, isTypeOnly);
const importClause = tryParseImportClause(identifier, afterImportPos, phaseModifier, /*skipJsDocLeadingAsterisks*/ undefined);
const moduleSpecifier = parseModuleSpecifier();
const attributes = tryParseImportAttributes();

Expand All @@ -8388,7 +8399,7 @@ namespace Parser {
return withJSDoc(finishNode(node, pos), hasJSDoc);
}

function tryParseImportClause(identifier: Identifier | undefined, pos: number, isTypeOnly: boolean, skipJsDocLeadingAsterisks = false) {
function tryParseImportClause(identifier: Identifier | undefined, pos: number, phaseModifier: undefined | ImportPhaseModifier, skipJsDocLeadingAsterisks = false) {
// ImportDeclaration:
// import ImportClause from ModuleSpecifier ;
// import ModuleSpecifier;
Expand All @@ -8398,7 +8409,7 @@ namespace Parser {
token() === SyntaxKind.AsteriskToken || // import *
token() === SyntaxKind.OpenBraceToken // import {
) {
importClause = parseImportClause(identifier, pos, isTypeOnly, skipJsDocLeadingAsterisks);
importClause = parseImportClause(identifier, pos, phaseModifier, skipJsDocLeadingAsterisks);
parseExpected(SyntaxKind.FromKeyword);
}
return importClause;
Expand Down Expand Up @@ -8464,7 +8475,7 @@ namespace Parser {
return finished;
}

function parseImportClause(identifier: Identifier | undefined, pos: number, isTypeOnly: boolean, skipJsDocLeadingAsterisks: boolean) {
function parseImportClause(identifier: Identifier | undefined, pos: number, phaseModifier: undefined | ImportPhaseModifier, skipJsDocLeadingAsterisks: boolean) {
// ImportClause:
// ImportedDefaultBinding
// NameSpaceImport
Expand All @@ -8480,11 +8491,19 @@ namespace Parser {
parseOptional(SyntaxKind.CommaToken)
) {
if (skipJsDocLeadingAsterisks) scanner.setSkipJsDocLeadingAsterisks(true);
namedBindings = token() === SyntaxKind.AsteriskToken ? parseNamespaceImport() : parseNamedImportsOrExports(SyntaxKind.NamedImports);
if (token() === SyntaxKind.AsteriskToken) {
namedBindings = parseNamespaceImport();
}
else {
if (phaseModifier === SyntaxKind.DeferKeyword) {
parseErrorAtCurrentToken(Diagnostics.Named_imports_aren_t_allowed_for_deferred_imports);
}
namedBindings = parseNamedImportsOrExports(SyntaxKind.NamedImports);
}
if (skipJsDocLeadingAsterisks) scanner.setSkipJsDocLeadingAsterisks(false);
}

return finishNode(factory.createImportClause(isTypeOnly, identifier, namedBindings), pos);
return finishNode(factory.createImportClause(phaseModifier, identifier, namedBindings), pos);
}

function parseModuleReference() {
Expand Down Expand Up @@ -9518,7 +9537,7 @@ namespace Parser {
identifier = parseIdentifier();
}

const importClause = tryParseImportClause(identifier, afterImportTagPos, /*isTypeOnly*/ true, /*skipJsDocLeadingAsterisks*/ true);
const importClause = tryParseImportClause(identifier, afterImportTagPos, SyntaxKind.TypeKeyword, /*skipJsDocLeadingAsterisks*/ true);
const moduleSpecifier = parseModuleSpecifier();
const attributes = tryParseImportAttributes();

Expand Down
1 change: 1 addition & 0 deletions src/compiler/scanner.ts
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Expand Up @@ -203,6 +203,7 @@ export const textToKeywordObj: MapLike<KeywordSyntaxKind> = {
true: SyntaxKind.TrueKeyword,
try: SyntaxKind.TryKeyword,
type: SyntaxKind.TypeKeyword,
defer: SyntaxKind.DeferKeyword,
typeof: SyntaxKind.TypeOfKeyword,
undefined: SyntaxKind.UndefinedKeyword,
unique: SyntaxKind.UniqueKeyword,
Expand Down
6 changes: 3 additions & 3 deletions src/compiler/transformers/declarations.ts
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Expand Up @@ -886,7 +886,7 @@ export function transformDeclarations(context: TransformationContext): Transform
decl.modifiers,
factory.updateImportClause(
decl.importClause,
decl.importClause.isTypeOnly,
decl.importClause.phaseModifier,
visibleDefaultBinding,
/*namedBindings*/ undefined,
),
Expand All @@ -902,7 +902,7 @@ export function transformDeclarations(context: TransformationContext): Transform
decl.modifiers,
factory.updateImportClause(
decl.importClause,
decl.importClause.isTypeOnly,
decl.importClause.phaseModifier,
visibleDefaultBinding,
namedBindings,
),
Expand All @@ -918,7 +918,7 @@ export function transformDeclarations(context: TransformationContext): Transform
decl.modifiers,
factory.updateImportClause(
decl.importClause,
decl.importClause.isTypeOnly,
decl.importClause.phaseModifier,
visibleDefaultBinding,
bindingList && bindingList.length ? factory.updateNamedImports(decl.importClause.namedBindings, bindingList) : undefined,
),
Expand Down
2 changes: 1 addition & 1 deletion src/compiler/transformers/jsx.ts
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Expand Up @@ -172,7 +172,7 @@ export function transformJsx(context: TransformationContext): (x: SourceFile | B
for (const [importSource, importSpecifiersMap] of arrayFrom(currentFileState.utilizedImplicitRuntimeImports.entries())) {
if (isExternalModule(node)) {
// Add `import` statement
const importStatement = factory.createImportDeclaration(/*modifiers*/ undefined, factory.createImportClause(/*isTypeOnly*/ false, /*name*/ undefined, factory.createNamedImports(arrayFrom(importSpecifiersMap.values()))), factory.createStringLiteral(importSource), /*attributes*/ undefined);
const importStatement = factory.createImportDeclaration(/*modifiers*/ undefined, factory.createImportClause(/*phaseModifier*/ undefined, /*name*/ undefined, factory.createNamedImports(arrayFrom(importSpecifiersMap.values()))), factory.createStringLiteral(importSource), /*attributes*/ undefined);
setParentRecursive(importStatement, /*incremental*/ false);
statements = insertStatementAfterCustomPrologue(statements.slice(), importStatement);
}
Expand Down
4 changes: 2 additions & 2 deletions src/compiler/transformers/module/esnextAnd2015.ts
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Expand Up @@ -219,7 +219,7 @@ export function transformECMAScriptModule(context: TransformationContext): (x: S
const importStatement = factory.createImportDeclaration(
/*modifiers*/ undefined,
factory.createImportClause(
/*isTypeOnly*/ false,
/*phaseModifier*/ undefined,
/*name*/ undefined,
factory.createNamedImports([
factory.createImportSpecifier(/*isTypeOnly*/ false, factory.createIdentifier("createRequire"), createRequireName),
Expand Down Expand Up @@ -351,7 +351,7 @@ export function transformECMAScriptModule(context: TransformationContext): (x: S
const importDecl = factory.createImportDeclaration(
/*modifiers*/ undefined,
factory.createImportClause(
/*isTypeOnly*/ false,
/*phaseModifier*/ undefined,
/*name*/ undefined,
factory.createNamespaceImport(
synthName,
Expand Down
4 changes: 2 additions & 2 deletions src/compiler/transformers/ts.ts
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Expand Up @@ -2282,11 +2282,11 @@ export function transformTypeScript(context: TransformationContext): Transformer
* @param node The import clause node.
*/
function visitImportClause(node: ImportClause): VisitResult<ImportClause> | undefined {
Debug.assert(!node.isTypeOnly);
Debug.assert(node.phaseModifier !== SyntaxKind.TypeKeyword);
// Elide the import clause if we elide both its name and its named bindings.
const name = shouldEmitAliasDeclaration(node) ? node.name : undefined;
const namedBindings = visitNode(node.namedBindings, visitNamedImportBindings, isNamedImportBindings);
return (name || namedBindings) ? factory.updateImportClause(node, /*isTypeOnly*/ false, name, namedBindings) : undefined;
return (name || namedBindings) ? factory.updateImportClause(node, node.phaseModifier, name, namedBindings) : undefined;
}

/**
Expand Down
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