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parse decorators in js (but still generate errors)
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@evanw
evanw committed Apr 2, 2023
1 parent 033c5da commit e9413cc
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Showing 3 changed files with 145 additions and 120 deletions.
240 changes: 139 additions & 101 deletions internal/js_parser/js_parser.go
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Original file line number Diff line number Diff line change
Expand Up @@ -1916,8 +1916,9 @@ func (p *parser) parseStringLiteral() js_ast.Expr {
}

type propertyOpts struct {
decorators []js_ast.Expr
decoratorScope *js_ast.Scope
decorators []js_ast.Expr
decoratorScope *js_ast.Scope
decoratorContext decoratorContextFlags

asyncRange logger.Range
generatorRange logger.Range
Expand Down Expand Up @@ -2317,7 +2318,7 @@ func (p *parser) parseProperty(startLoc logger.Loc, kind js_ast.PropertyKind, op
yield = allowExpr
}

fn, hadBody := p.parseFn(nil, opts.classKeyword, fnOrArrowDataParse{
fn, hadBody := p.parseFn(nil, opts.classKeyword, opts.decoratorContext, fnOrArrowDataParse{
needsAsyncLoc: key.Loc,
asyncRange: opts.asyncRange,
await: await,
Expand Down Expand Up @@ -2810,7 +2811,7 @@ func (p *parser) parseFnExpr(loc logger.Loc, isAsync bool, asyncRange logger.Ran
yield = allowExpr
}

fn, _ := p.parseFn(name, logger.Range{}, fnOrArrowDataParse{
fn, _ := p.parseFn(name, logger.Range{}, 0, fnOrArrowDataParse{
needsAsyncLoc: loc,
asyncRange: asyncRange,
await: await,
Expand Down Expand Up @@ -3454,33 +3455,20 @@ func (p *parser) parsePrefix(level js_ast.L, errors *deferredErrors, flags exprF
return p.parseFnExpr(loc, false /* isAsync */, logger.Range{})

case js_lexer.TClass:
classKeyword := p.lexer.Range()
p.markSyntaxFeature(compat.Class, classKeyword)
p.lexer.Next()
var name *js_ast.LocRef
return p.parseClassExpr(loc, nil)

p.pushScopeForParsePass(js_ast.ScopeClassName, loc)
case js_lexer.TAt:
// Parse decorators before class statements, which are potentially exported
scopeIndex := len(p.scopesInOrder)
decorators := p.parseDecorators(p.currentScope, logger.Range{}, decoratorBeforeClassExpr)

// Parse an optional class name
if p.lexer.Token == js_lexer.TIdentifier {
if nameText := p.lexer.Identifier.String; !p.options.ts.Parse || nameText != "implements" {
if p.fnOrArrowDataParse.await != allowIdent && nameText == "await" {
p.log.AddError(&p.tracker, p.lexer.Range(), "Cannot use \"await\" as an identifier here:")
}
name = &js_ast.LocRef{Loc: p.lexer.Loc(), Ref: p.newSymbol(js_ast.SymbolOther, nameText)}
p.lexer.Next()
}
// "@decorator class {}"
// "@decorator class Foo {}"
if p.lexer.Token != js_lexer.TClass && p.lexer.Token != js_lexer.TExport {
p.logDecoratorWithoutFollowingClassError(loc, scopeIndex)
}

// Even anonymous classes can have TypeScript type parameters
if p.options.ts.Parse {
p.skipTypeScriptTypeParameters(allowInOutVarianceAnnotations | allowConstModifier)
}

class := p.parseClass(classKeyword, name, parseClassOpts{})

p.popScope()
return js_ast.Expr{Loc: loc, Data: &js_ast.EClass{Class: class}}
return p.parseClassExpr(loc, decorators)

case js_lexer.TNew:
p.lexer.Next()
Expand Down Expand Up @@ -5607,7 +5595,12 @@ func (p *parser) parseBinding() js_ast.Binding {
return js_ast.Binding{}
}

func (p *parser) parseFn(name *js_ast.LocRef, classKeyword logger.Range, data fnOrArrowDataParse) (fn js_ast.Fn, hadBody bool) {
func (p *parser) parseFn(
name *js_ast.LocRef,
classKeyword logger.Range,
decoratorContext decoratorContextFlags,
data fnOrArrowDataParse,
) (fn js_ast.Fn, hadBody bool) {
fn.Name = name
fn.HasRestArg = false
fn.IsAsync = data.await == allowExpr
Expand Down Expand Up @@ -5703,12 +5696,10 @@ func (p *parser) parseFn(name *js_ast.LocRef, classKeyword logger.Range, data fn
p.fnOrArrowDataParse.needsAsyncLoc = oldFnOrArrowData.needsAsyncLoc
}

decorators = p.parseDecorators(data.decoratorScope)
decorators = p.parseDecorators(data.decoratorScope, classKeyword, decoratorContext|decoratorInFnArgs)

p.fnOrArrowDataParse.await = oldAwait
p.fnOrArrowDataParse.needsAsyncLoc = oldNeedsAsyncLoc
} else if classKeyword.Len > 0 {
p.logInvalidDecoratorError(classKeyword)
}

if !fn.HasRestArg && p.lexer.Token == js_lexer.TDotDotDot {
Expand Down Expand Up @@ -5899,9 +5890,45 @@ func (p *parser) parseClassStmt(loc logger.Loc, opts parseStmtOpts) js_ast.Stmt
return js_ast.Stmt{Loc: loc, Data: &js_ast.SClass{Class: class, IsExport: opts.isExport}}
}

func (p *parser) parseClassExpr(loc logger.Loc, decorators []js_ast.Expr) js_ast.Expr {
classKeyword := p.lexer.Range()
p.markSyntaxFeature(compat.Class, classKeyword)
p.lexer.Next()
var name *js_ast.LocRef

opts := parseClassOpts{
decorators: decorators,
decoratorScope: p.currentScope,
decoratorContext: decoratorInClassExpr,
}
p.pushScopeForParsePass(js_ast.ScopeClassName, loc)

// Parse an optional class name
if p.lexer.Token == js_lexer.TIdentifier {
if nameText := p.lexer.Identifier.String; !p.options.ts.Parse || nameText != "implements" {
if p.fnOrArrowDataParse.await != allowIdent && nameText == "await" {
p.log.AddError(&p.tracker, p.lexer.Range(), "Cannot use \"await\" as an identifier here:")
}
name = &js_ast.LocRef{Loc: p.lexer.Loc(), Ref: p.newSymbol(js_ast.SymbolOther, nameText)}
p.lexer.Next()
}
}

// Even anonymous classes can have TypeScript type parameters
if p.options.ts.Parse {
p.skipTypeScriptTypeParameters(allowInOutVarianceAnnotations | allowConstModifier)
}

class := p.parseClass(classKeyword, name, opts)

p.popScope()
return js_ast.Expr{Loc: loc, Data: &js_ast.EClass{Class: class}}
}

type parseClassOpts struct {
decorators []js_ast.Expr
decoratorScope *js_ast.Scope
decoratorContext decoratorContextFlags
isTypeScriptDeclare bool
}

Expand Down Expand Up @@ -5951,10 +5978,11 @@ func (p *parser) parseClass(classKeyword logger.Range, name *js_ast.LocRef, clas
scopeIndex := p.pushScopeForParsePass(js_ast.ScopeClassBody, bodyLoc)

opts := propertyOpts{
isClass: true,
decoratorScope: classOpts.decoratorScope,
classHasExtends: extendsOrNil.Data != nil,
classKeyword: classKeyword,
isClass: true,
decoratorScope: classOpts.decoratorScope,
decoratorContext: classOpts.decoratorContext,
classHasExtends: extendsOrNil.Data != nil,
classKeyword: classKeyword,
}
hasConstructor := false

Expand All @@ -5966,12 +5994,7 @@ func (p *parser) parseClass(classKeyword logger.Range, name *js_ast.LocRef, clas

// Parse decorators for this property
firstDecoratorLoc := p.lexer.Loc()
if opts.decoratorScope != nil {
opts.decorators = p.parseDecorators(opts.decoratorScope)
} else {
opts.decorators = nil
p.logInvalidDecoratorError(classKeyword)
}
opts.decorators = p.parseDecorators(opts.decoratorScope, classKeyword, opts.decoratorContext)

// This property may turn out to be a type in TypeScript, which should be ignored
if property, ok := p.parseProperty(p.saveExprCommentsHere(), js_ast.PropertyNormal, opts, nil); ok {
Expand All @@ -5981,7 +6004,7 @@ func (p *parser) parseClass(classKeyword logger.Range, name *js_ast.LocRef, clas
if key, ok := property.Key.Data.(*js_ast.EString); ok && helpers.UTF16EqualsString(key.Value, "constructor") {
if len(opts.decorators) > 0 {
p.log.AddError(&p.tracker, logger.Range{Loc: firstDecoratorLoc},
"TypeScript does not allow decorators on class constructors")
"Decorators are not allowed on class constructors")
}
if property.Flags.Has(js_ast.PropertyIsMethod) && !property.Flags.Has(js_ast.PropertyIsStatic) && !property.Flags.Has(js_ast.PropertyIsComputed) {
if hasConstructor {
Expand Down Expand Up @@ -6171,7 +6194,7 @@ func (p *parser) parseFnStmt(loc logger.Loc, opts parseStmtOpts, isAsync bool, a
yield = allowExpr
}

fn, hadBody := p.parseFn(name, logger.Range{}, fnOrArrowDataParse{
fn, hadBody := p.parseFn(name, logger.Range{}, 0, fnOrArrowDataParse{
needsAsyncLoc: loc,
asyncRange: asyncRange,
await: await,
Expand Down Expand Up @@ -6234,35 +6257,55 @@ type deferredDecorators struct {
firstAtLoc logger.Loc
}

func (p *parser) parseDecorators(decoratorScope *js_ast.Scope) []js_ast.Expr {
var decorators []js_ast.Expr

if p.options.ts.Parse {
// TypeScript decorators cause us to temporarily revert to the scope that
// encloses the class declaration, since that's where the generated code
// for TypeScript decorators will be inserted.
oldScope := p.currentScope
p.currentScope = decoratorScope
type decoratorContextFlags uint8

for p.lexer.Token == js_lexer.TAt {
p.lexer.Next()
const (
decoratorBeforeClassExpr = 1 << iota
decoratorInClassExpr
decoratorInFnArgs
)

// Parse a new/call expression with "exprFlagDecorator" so we ignore
// EIndex expressions, since they may be part of a computed property:
//
// class Foo {
// @foo ['computed']() {}
// }
//
// This matches the behavior of the TypeScript compiler.
value := p.parseExprWithFlags(js_ast.LNew, exprFlagDecorator)
decorators = append(decorators, value)
func (p *parser) parseDecorators(decoratorScope *js_ast.Scope, classKeyword logger.Range, context decoratorContextFlags) (decorators []js_ast.Expr) {
if p.lexer.Token == js_lexer.TAt {
if p.options.ts.Parse {
if (context & decoratorInClassExpr) != 0 {
p.lexer.AddRangeErrorWithNotes(p.lexer.Range(), "Experimental decorators can only be used with class declarations in TypeScript",
[]logger.MsgData{p.tracker.MsgData(classKeyword, "This is a class expression, not a class declaration:")})
} else if (context & decoratorBeforeClassExpr) != 0 {
p.log.AddError(&p.tracker, p.lexer.Range(), "Experimental decorators cannot be used in expression position in TypeScript")
}
} else {
if (context & decoratorInFnArgs) != 0 {
p.log.AddError(&p.tracker, p.lexer.Range(), "Parameter decorators are not allowed in JavaScript")
} else {
p.log.AddError(&p.tracker, p.lexer.Range(), "JavaScript decorators are not currently supported")
}
}
}

// Avoid "popScope" because this decorator scope is not hierarchical
p.currentScope = oldScope
// TypeScript decorators cause us to temporarily revert to the scope that
// encloses the class declaration, since that's where the generated code
// for TypeScript decorators will be inserted.
oldScope := p.currentScope
p.currentScope = decoratorScope

for p.lexer.Token == js_lexer.TAt {
p.lexer.Next()

// Parse a new/call expression with "exprFlagDecorator" so we ignore
// EIndex expressions, since they may be part of a computed property:
//
// class Foo {
// @foo ['computed']() {}
// }
//
// This matches the behavior of the TypeScript compiler.
value := p.parseExprWithFlags(js_ast.LNew, exprFlagDecorator)
decorators = append(decorators, value)
}

// Avoid "popScope" because this decorator scope is not hierarchical
p.currentScope = oldScope
return decorators
}

Expand Down Expand Up @@ -6636,45 +6679,40 @@ func (p *parser) parseStmt(opts parseStmtOpts) js_ast.Stmt {

case js_lexer.TAt:
// Parse decorators before class statements, which are potentially exported
if p.options.ts.Parse {
scopeIndex := len(p.scopesInOrder)
decorators := p.parseDecorators(p.currentScope)
scopeIndex := len(p.scopesInOrder)
decorators := p.parseDecorators(p.currentScope, logger.Range{}, 0)

// If this turns out to be a "declare class" statement, we need to undo the
// scopes that were potentially pushed while parsing the decorator arguments.
// That can look like any one of the following:
//
// "@decorator declare class Foo {}"
// "@decorator declare abstract class Foo {}"
// "@decorator export declare class Foo {}"
// "@decorator export declare abstract class Foo {}"
//
opts.decorators = &deferredDecorators{
firstAtLoc: loc,
values: decorators,
scopeIndex: scopeIndex,
}

// "@decorator class Foo {}"
// "@decorator abstract class Foo {}"
// "@decorator declare class Foo {}"
// "@decorator declare abstract class Foo {}"
// "@decorator export class Foo {}"
// "@decorator export abstract class Foo {}"
// "@decorator export declare class Foo {}"
// "@decorator export declare abstract class Foo {}"
// "@decorator export default class Foo {}"
// "@decorator export default abstract class Foo {}"
if p.lexer.Token != js_lexer.TClass && p.lexer.Token != js_lexer.TExport &&
!p.lexer.IsContextualKeyword("abstract") && !p.lexer.IsContextualKeyword("declare") {
p.logDecoratorWithoutFollowingClassError(opts.decorators.firstAtLoc, opts.decorators.scopeIndex)
}
// If this turns out to be a "declare class" statement, we need to undo the
// scopes that were potentially pushed while parsing the decorator arguments.
// That can look like any one of the following:
//
// "@decorator declare class Foo {}"
// "@decorator declare abstract class Foo {}"
// "@decorator export declare class Foo {}"
// "@decorator export declare abstract class Foo {}"
//
opts.decorators = &deferredDecorators{
firstAtLoc: loc,
values: decorators,
scopeIndex: scopeIndex,
}

return p.parseStmt(opts)
// "@decorator class Foo {}"
// "@decorator abstract class Foo {}"
// "@decorator declare class Foo {}"
// "@decorator declare abstract class Foo {}"
// "@decorator export class Foo {}"
// "@decorator export abstract class Foo {}"
// "@decorator export declare class Foo {}"
// "@decorator export declare abstract class Foo {}"
// "@decorator export default class Foo {}"
// "@decorator export default abstract class Foo {}"
if p.lexer.Token != js_lexer.TClass && p.lexer.Token != js_lexer.TExport &&
(!p.options.ts.Parse || (!p.lexer.IsContextualKeyword("abstract") && !p.lexer.IsContextualKeyword("declare"))) {
p.logDecoratorWithoutFollowingClassError(opts.decorators.firstAtLoc, opts.decorators.scopeIndex)
}

p.lexer.Unexpected()
return js_ast.Stmt{}
return p.parseStmt(opts)

case js_lexer.TClass:
if opts.lexicalDecl != lexicalDeclAllowAll {
Expand Down
13 changes: 0 additions & 13 deletions internal/js_parser/ts_parser.go
View file
Original file line number Diff line number Diff line change
Expand Up @@ -1236,19 +1236,6 @@ func (p *parser) skipTypeScriptTypeStmt(opts parseStmtOpts) {
p.lexer.ExpectOrInsertSemicolon()
}

func (p *parser) logInvalidDecoratorError(classKeyword logger.Range) {
if p.options.ts.Parse && p.lexer.Token == js_lexer.TAt {
// Forbid decorators inside class expressions
p.lexer.AddRangeErrorWithNotes(p.lexer.Range(), "Decorators can only be used with class declarations in TypeScript",
[]logger.MsgData{p.tracker.MsgData(classKeyword, "This is a class expression, not a class declaration:")})

// Parse and discard decorators for error recovery
scopeIndex := len(p.scopesInOrder)
p.parseDecorators(p.currentScope)
p.discardScopesUpTo(scopeIndex)
}
}

func (p *parser) parseTypeScriptEnumStmt(loc logger.Loc, opts parseStmtOpts) js_ast.Stmt {
p.lexer.Expect(js_lexer.TEnum)
nameLoc := p.lexer.Loc()
Expand Down
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