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js_parser_lower_class.go
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js_parser_lower_class.go
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package js_parser
import (
"fmt"
"github.com/ije/esbuild-internal/ast"
"github.com/ije/esbuild-internal/compat"
"github.com/ije/esbuild-internal/config"
"github.com/ije/esbuild-internal/helpers"
"github.com/ije/esbuild-internal/js_ast"
"github.com/ije/esbuild-internal/logger"
)
func (p *parser) privateSymbolNeedsToBeLowered(private *js_ast.EPrivateIdentifier) bool {
symbol := &p.symbols[private.Ref.InnerIndex]
return p.options.unsupportedJSFeatures.Has(compat.SymbolFeature(symbol.Kind)) || symbol.Flags.Has(ast.PrivateSymbolMustBeLowered)
}
func (p *parser) lowerPrivateBrandCheck(target js_ast.Expr, loc logger.Loc, private *js_ast.EPrivateIdentifier) js_ast.Expr {
// "#field in this" => "__privateIn(#field, this)"
return p.callRuntime(loc, "__privateIn", []js_ast.Expr{
{Loc: loc, Data: &js_ast.EIdentifier{Ref: private.Ref}},
target,
})
}
func (p *parser) lowerPrivateGet(target js_ast.Expr, loc logger.Loc, private *js_ast.EPrivateIdentifier) js_ast.Expr {
switch p.symbols[private.Ref.InnerIndex].Kind {
case ast.SymbolPrivateMethod, ast.SymbolPrivateStaticMethod:
// "this.#method" => "__privateMethod(this, #method, method_fn)"
fnRef := p.privateGetters[private.Ref]
p.recordUsage(fnRef)
return p.callRuntime(target.Loc, "__privateMethod", []js_ast.Expr{
target,
{Loc: loc, Data: &js_ast.EIdentifier{Ref: private.Ref}},
{Loc: loc, Data: &js_ast.EIdentifier{Ref: fnRef}},
})
case ast.SymbolPrivateGet, ast.SymbolPrivateStaticGet,
ast.SymbolPrivateGetSetPair, ast.SymbolPrivateStaticGetSetPair:
// "this.#getter" => "__privateGet(this, #getter, getter_get)"
fnRef := p.privateGetters[private.Ref]
p.recordUsage(fnRef)
return p.callRuntime(target.Loc, "__privateGet", []js_ast.Expr{
target,
{Loc: loc, Data: &js_ast.EIdentifier{Ref: private.Ref}},
{Loc: loc, Data: &js_ast.EIdentifier{Ref: fnRef}},
})
default:
// "this.#field" => "__privateGet(this, #field)"
return p.callRuntime(target.Loc, "__privateGet", []js_ast.Expr{
target,
{Loc: loc, Data: &js_ast.EIdentifier{Ref: private.Ref}},
})
}
}
func (p *parser) lowerPrivateSet(
target js_ast.Expr,
loc logger.Loc,
private *js_ast.EPrivateIdentifier,
value js_ast.Expr,
) js_ast.Expr {
switch p.symbols[private.Ref.InnerIndex].Kind {
case ast.SymbolPrivateSet, ast.SymbolPrivateStaticSet,
ast.SymbolPrivateGetSetPair, ast.SymbolPrivateStaticGetSetPair:
// "this.#setter = 123" => "__privateSet(this, #setter, 123, setter_set)"
fnRef := p.privateSetters[private.Ref]
p.recordUsage(fnRef)
return p.callRuntime(target.Loc, "__privateSet", []js_ast.Expr{
target,
{Loc: loc, Data: &js_ast.EIdentifier{Ref: private.Ref}},
value,
{Loc: loc, Data: &js_ast.EIdentifier{Ref: fnRef}},
})
default:
// "this.#field = 123" => "__privateSet(this, #field, 123)"
return p.callRuntime(target.Loc, "__privateSet", []js_ast.Expr{
target,
{Loc: loc, Data: &js_ast.EIdentifier{Ref: private.Ref}},
value,
})
}
}
func (p *parser) lowerPrivateSetUnOp(target js_ast.Expr, loc logger.Loc, private *js_ast.EPrivateIdentifier, op js_ast.OpCode) js_ast.Expr {
kind := p.symbols[private.Ref.InnerIndex].Kind
// Determine the setter, if any
var setter js_ast.Expr
switch kind {
case ast.SymbolPrivateSet, ast.SymbolPrivateStaticSet,
ast.SymbolPrivateGetSetPair, ast.SymbolPrivateStaticGetSetPair:
ref := p.privateSetters[private.Ref]
p.recordUsage(ref)
setter = js_ast.Expr{Loc: loc, Data: &js_ast.EIdentifier{Ref: ref}}
}
// Determine the getter, if any
var getter js_ast.Expr
switch kind {
case ast.SymbolPrivateGet, ast.SymbolPrivateStaticGet,
ast.SymbolPrivateGetSetPair, ast.SymbolPrivateStaticGetSetPair:
ref := p.privateGetters[private.Ref]
p.recordUsage(ref)
getter = js_ast.Expr{Loc: loc, Data: &js_ast.EIdentifier{Ref: ref}}
}
// Only include necessary arguments
args := []js_ast.Expr{
target,
{Loc: loc, Data: &js_ast.EIdentifier{Ref: private.Ref}},
}
if setter.Data != nil {
args = append(args, setter)
}
if getter.Data != nil {
if setter.Data == nil {
args = append(args, js_ast.Expr{Loc: loc, Data: js_ast.ENullShared})
}
args = append(args, getter)
}
// "target.#private++" => "__privateWrapper(target, #private, private_set, private_get)._++"
return js_ast.Expr{Loc: loc, Data: &js_ast.EUnary{
Op: op,
Value: js_ast.Expr{Loc: target.Loc, Data: &js_ast.EDot{
Target: p.callRuntime(target.Loc, "__privateWrapper", args),
NameLoc: target.Loc,
Name: "_",
}},
}}
}
func (p *parser) lowerPrivateSetBinOp(target js_ast.Expr, loc logger.Loc, private *js_ast.EPrivateIdentifier, op js_ast.OpCode, value js_ast.Expr) js_ast.Expr {
// "target.#private += 123" => "__privateSet(target, #private, __privateGet(target, #private) + 123)"
targetFunc, targetWrapFunc := p.captureValueWithPossibleSideEffects(target.Loc, 2, target, valueDefinitelyNotMutated)
return targetWrapFunc(p.lowerPrivateSet(targetFunc(), loc, private, js_ast.Expr{Loc: value.Loc, Data: &js_ast.EBinary{
Op: op,
Left: p.lowerPrivateGet(targetFunc(), loc, private),
Right: value,
}}))
}
// Returns valid data if target is an expression of the form "foo.#bar" and if
// the language target is such that private members must be lowered
func (p *parser) extractPrivateIndex(target js_ast.Expr) (js_ast.Expr, logger.Loc, *js_ast.EPrivateIdentifier) {
if index, ok := target.Data.(*js_ast.EIndex); ok {
if private, ok := index.Index.Data.(*js_ast.EPrivateIdentifier); ok && p.privateSymbolNeedsToBeLowered(private) {
return index.Target, index.Index.Loc, private
}
}
return js_ast.Expr{}, logger.Loc{}, nil
}
// Returns a valid property if target is an expression of the form "super.bar"
// or "super[bar]" and if the situation is such that it must be lowered
func (p *parser) extractSuperProperty(target js_ast.Expr) js_ast.Expr {
switch e := target.Data.(type) {
case *js_ast.EDot:
if p.shouldLowerSuperPropertyAccess(e.Target) {
return js_ast.Expr{Loc: e.NameLoc, Data: &js_ast.EString{Value: helpers.StringToUTF16(e.Name)}}
}
case *js_ast.EIndex:
if p.shouldLowerSuperPropertyAccess(e.Target) {
return e.Index
}
}
return js_ast.Expr{}
}
func (p *parser) lowerSuperPropertyOrPrivateInAssign(expr js_ast.Expr) (js_ast.Expr, bool) {
didLower := false
switch e := expr.Data.(type) {
case *js_ast.ESpread:
if value, ok := p.lowerSuperPropertyOrPrivateInAssign(e.Value); ok {
e.Value = value
didLower = true
}
case *js_ast.EDot:
// "[super.foo] = [bar]" => "[__superWrapper(this, 'foo')._] = [bar]"
if p.shouldLowerSuperPropertyAccess(e.Target) {
key := js_ast.Expr{Loc: e.NameLoc, Data: &js_ast.EString{Value: helpers.StringToUTF16(e.Name)}}
expr = p.callSuperPropertyWrapper(expr.Loc, key)
didLower = true
}
case *js_ast.EIndex:
// "[super[foo]] = [bar]" => "[__superWrapper(this, foo)._] = [bar]"
if p.shouldLowerSuperPropertyAccess(e.Target) {
expr = p.callSuperPropertyWrapper(expr.Loc, e.Index)
didLower = true
break
}
// "[a.#b] = [c]" => "[__privateWrapper(a, #b)._] = [c]"
if private, ok := e.Index.Data.(*js_ast.EPrivateIdentifier); ok && p.privateSymbolNeedsToBeLowered(private) {
var target js_ast.Expr
switch p.symbols[private.Ref.InnerIndex].Kind {
case ast.SymbolPrivateSet, ast.SymbolPrivateStaticSet,
ast.SymbolPrivateGetSetPair, ast.SymbolPrivateStaticGetSetPair:
// "this.#setter" => "__privateWrapper(this, #setter, setter_set)"
fnRef := p.privateSetters[private.Ref]
p.recordUsage(fnRef)
target = p.callRuntime(expr.Loc, "__privateWrapper", []js_ast.Expr{
e.Target,
{Loc: expr.Loc, Data: &js_ast.EIdentifier{Ref: private.Ref}},
{Loc: expr.Loc, Data: &js_ast.EIdentifier{Ref: fnRef}},
})
default:
// "this.#field" => "__privateWrapper(this, #field)"
target = p.callRuntime(expr.Loc, "__privateWrapper", []js_ast.Expr{
e.Target,
{Loc: expr.Loc, Data: &js_ast.EIdentifier{Ref: private.Ref}},
})
}
// "__privateWrapper(this, #field)" => "__privateWrapper(this, #field)._"
expr.Data = &js_ast.EDot{Target: target, Name: "_", NameLoc: expr.Loc}
didLower = true
}
case *js_ast.EArray:
for i, item := range e.Items {
if item, ok := p.lowerSuperPropertyOrPrivateInAssign(item); ok {
e.Items[i] = item
didLower = true
}
}
case *js_ast.EObject:
for i, property := range e.Properties {
if property.ValueOrNil.Data != nil {
if value, ok := p.lowerSuperPropertyOrPrivateInAssign(property.ValueOrNil); ok {
e.Properties[i].ValueOrNil = value
didLower = true
}
}
}
}
return expr, didLower
}
func (p *parser) shouldLowerSuperPropertyAccess(expr js_ast.Expr) bool {
if p.fnOrArrowDataVisit.shouldLowerSuperPropertyAccess {
_, isSuper := expr.Data.(*js_ast.ESuper)
return isSuper
}
return false
}
func (p *parser) callSuperPropertyWrapper(loc logger.Loc, key js_ast.Expr) js_ast.Expr {
ref := *p.fnOnlyDataVisit.innerClassNameRef
p.recordUsage(ref)
class := js_ast.Expr{Loc: loc, Data: &js_ast.EIdentifier{Ref: ref}}
this := js_ast.Expr{Loc: loc, Data: js_ast.EThisShared}
// Handle "this" in lowered static class field initializers
if p.fnOnlyDataVisit.shouldReplaceThisWithInnerClassNameRef {
p.recordUsage(ref)
this.Data = &js_ast.EIdentifier{Ref: ref}
}
if !p.fnOnlyDataVisit.isInStaticClassContext {
// "super.foo" => "__superWrapper(Class.prototype, this, 'foo')._"
// "super[foo]" => "__superWrapper(Class.prototype, this, foo)._"
class.Data = &js_ast.EDot{Target: class, NameLoc: loc, Name: "prototype"}
}
return js_ast.Expr{Loc: loc, Data: &js_ast.EDot{Target: p.callRuntime(loc, "__superWrapper", []js_ast.Expr{
class,
this,
key,
}), Name: "_", NameLoc: loc}}
}
func (p *parser) lowerSuperPropertyGet(loc logger.Loc, key js_ast.Expr) js_ast.Expr {
ref := *p.fnOnlyDataVisit.innerClassNameRef
p.recordUsage(ref)
class := js_ast.Expr{Loc: loc, Data: &js_ast.EIdentifier{Ref: ref}}
this := js_ast.Expr{Loc: loc, Data: js_ast.EThisShared}
// Handle "this" in lowered static class field initializers
if p.fnOnlyDataVisit.shouldReplaceThisWithInnerClassNameRef {
p.recordUsage(ref)
this.Data = &js_ast.EIdentifier{Ref: ref}
}
if !p.fnOnlyDataVisit.isInStaticClassContext {
// "super.foo" => "__superGet(Class.prototype, this, 'foo')"
// "super[foo]" => "__superGet(Class.prototype, this, foo)"
class.Data = &js_ast.EDot{Target: class, NameLoc: loc, Name: "prototype"}
}
return p.callRuntime(loc, "__superGet", []js_ast.Expr{
class,
this,
key,
})
}
func (p *parser) lowerSuperPropertySet(loc logger.Loc, key js_ast.Expr, value js_ast.Expr) js_ast.Expr {
// "super.foo = bar" => "__superSet(Class, this, 'foo', bar)"
// "super[foo] = bar" => "__superSet(Class, this, foo, bar)"
ref := *p.fnOnlyDataVisit.innerClassNameRef
p.recordUsage(ref)
class := js_ast.Expr{Loc: loc, Data: &js_ast.EIdentifier{Ref: ref}}
this := js_ast.Expr{Loc: loc, Data: js_ast.EThisShared}
// Handle "this" in lowered static class field initializers
if p.fnOnlyDataVisit.shouldReplaceThisWithInnerClassNameRef {
p.recordUsage(ref)
this.Data = &js_ast.EIdentifier{Ref: ref}
}
if !p.fnOnlyDataVisit.isInStaticClassContext {
// "super.foo = bar" => "__superSet(Class.prototype, this, 'foo', bar)"
// "super[foo] = bar" => "__superSet(Class.prototype, this, foo, bar)"
class.Data = &js_ast.EDot{Target: class, NameLoc: loc, Name: "prototype"}
}
return p.callRuntime(loc, "__superSet", []js_ast.Expr{
class,
this,
key,
value,
})
}
func (p *parser) lowerSuperPropertySetBinOp(loc logger.Loc, property js_ast.Expr, op js_ast.OpCode, value js_ast.Expr) js_ast.Expr {
// "super.foo += bar" => "__superSet(Class, this, 'foo', __superGet(Class, this, 'foo') + bar)"
// "super[foo] += bar" => "__superSet(Class, this, foo, __superGet(Class, this, foo) + bar)"
// "super[foo()] += bar" => "__superSet(Class, this, _a = foo(), __superGet(Class, this, _a) + bar)"
targetFunc, targetWrapFunc := p.captureValueWithPossibleSideEffects(property.Loc, 2, property, valueDefinitelyNotMutated)
return targetWrapFunc(p.lowerSuperPropertySet(loc, targetFunc(), js_ast.Expr{Loc: value.Loc, Data: &js_ast.EBinary{
Op: op,
Left: p.lowerSuperPropertyGet(loc, targetFunc()),
Right: value,
}}))
}
func (p *parser) maybeLowerSuperPropertyGetInsideCall(call *js_ast.ECall) {
var key js_ast.Expr
switch e := call.Target.Data.(type) {
case *js_ast.EDot:
// Lower "super.prop" if necessary
if !p.shouldLowerSuperPropertyAccess(e.Target) {
return
}
key = js_ast.Expr{Loc: e.NameLoc, Data: &js_ast.EString{Value: helpers.StringToUTF16(e.Name)}}
case *js_ast.EIndex:
// Lower "super[prop]" if necessary
if !p.shouldLowerSuperPropertyAccess(e.Target) {
return
}
key = e.Index
default:
return
}
// "super.foo(a, b)" => "__superGet(Class, this, 'foo').call(this, a, b)"
call.Target.Data = &js_ast.EDot{
Target: p.lowerSuperPropertyGet(call.Target.Loc, key),
NameLoc: key.Loc,
Name: "call",
}
thisExpr := js_ast.Expr{Loc: call.Target.Loc, Data: js_ast.EThisShared}
call.Args = append([]js_ast.Expr{thisExpr}, call.Args...)
}
type classLoweringInfo struct {
lowerAllInstanceFields bool
lowerAllStaticFields bool
shimSuperCtorCalls bool
}
func (p *parser) computeClassLoweringInfo(class *js_ast.Class) (result classLoweringInfo) {
// Name keeping for classes is implemented with a static block. So we need to
// lower all static fields if static blocks are unsupported so that the name
// keeping comes first before other static initializers.
if p.options.keepNames && p.options.unsupportedJSFeatures.Has(compat.ClassStaticBlocks) {
result.lowerAllStaticFields = true
}
// TypeScript's "experimentalDecorators" feature replaces all references of
// the class name with the decorated class after class decorators have run.
// This cannot be done by only reassigning to the class symbol in JavaScript
// because it's shadowed by the class name within the class body. Instead,
// we need to hoist all code in static contexts out of the class body so
// that it's no longer shadowed:
//
// const decorate = x => ({ x })
// @decorate
// class Foo {
// static oldFoo = Foo
// static newFoo = () => Foo
// }
// console.log('This must be false:', Foo.x.oldFoo === Foo.x.newFoo())
//
if p.options.ts.Parse && p.options.ts.Config.ExperimentalDecorators == config.True && len(class.Decorators) > 0 {
result.lowerAllStaticFields = true
}
// If something has decorators, just lower everything for now. It's possible
// that we could avoid lowering in certain cases, but doing so is very tricky
// due to the complexity of the decorator specification. The specification is
// also still evolving so trying to optimize it now is also potentially
// premature.
if p.options.unsupportedJSFeatures.Has(compat.Decorators) &&
(!p.options.ts.Parse || p.options.ts.Config.ExperimentalDecorators != config.True) {
for _, prop := range class.Properties {
if len(prop.Decorators) > 0 {
for _, prop := range class.Properties {
if private, ok := prop.Key.Data.(*js_ast.EPrivateIdentifier); ok {
p.symbols[private.Ref.InnerIndex].Flags |= ast.PrivateSymbolMustBeLowered
}
}
result.lowerAllStaticFields = true
result.lowerAllInstanceFields = true
break
}
}
}
// Conservatively lower fields of a given type (instance or static) when any
// member of that type needs to be lowered. This must be done to preserve
// evaluation order. For example:
//
// class Foo {
// #foo = 123
// bar = this.#foo
// }
//
// It would be bad if we transformed that into something like this:
//
// var _foo;
// class Foo {
// constructor() {
// _foo.set(this, 123);
// }
// bar = __privateGet(this, _foo);
// }
// _foo = new WeakMap();
//
// That evaluates "bar" then "foo" instead of "foo" then "bar" like the
// original code. We need to do this instead:
//
// var _foo;
// class Foo {
// constructor() {
// _foo.set(this, 123);
// __publicField(this, "bar", __privateGet(this, _foo));
// }
// }
// _foo = new WeakMap();
//
for _, prop := range class.Properties {
if prop.Kind == js_ast.PropertyClassStaticBlock {
if p.options.unsupportedJSFeatures.Has(compat.ClassStaticBlocks) {
result.lowerAllStaticFields = true
}
continue
}
if private, ok := prop.Key.Data.(*js_ast.EPrivateIdentifier); ok {
if prop.Flags.Has(js_ast.PropertyIsStatic) {
if p.privateSymbolNeedsToBeLowered(private) {
result.lowerAllStaticFields = true
}
} else {
if p.privateSymbolNeedsToBeLowered(private) {
result.lowerAllInstanceFields = true
// We can't transform this:
//
// class Foo {
// #foo = 123
// static bar = new Foo().#foo
// }
//
// into this:
//
// var _foo;
// const _Foo = class {
// constructor() {
// _foo.set(this, 123);
// }
// static bar = __privateGet(new _Foo(), _foo);
// };
// let Foo = _Foo;
// _foo = new WeakMap();
//
// because "_Foo" won't be initialized in the initializer for "bar".
// So we currently lower all static fields in this case too. This
// isn't great and it would be good to find a way to avoid this.
// The inner class name symbol substitution mechanism should probably
// be rethought.
result.lowerAllStaticFields = true
}
}
continue
}
if prop.Kind == js_ast.PropertyAutoAccessor {
if prop.Flags.Has(js_ast.PropertyIsStatic) {
if p.options.unsupportedJSFeatures.Has(compat.ClassPrivateStaticField) {
result.lowerAllStaticFields = true
}
} else {
if p.options.unsupportedJSFeatures.Has(compat.ClassPrivateField) {
result.lowerAllInstanceFields = true
result.lowerAllStaticFields = true
}
}
continue
}
// This doesn't come before the private member check above because
// unsupported private methods must also trigger field lowering:
//
// class Foo {
// bar = this.#foo()
// #foo() {}
// }
//
// It would be bad if we transformed that to something like this:
//
// var _foo, foo_fn;
// class Foo {
// constructor() {
// _foo.add(this);
// }
// bar = __privateMethod(this, _foo, foo_fn).call(this);
// }
// _foo = new WeakSet();
// foo_fn = function() {
// };
//
// In that case the initializer of "bar" would fail to call "#foo" because
// it's only added to the instance in the body of the constructor.
if prop.Kind.IsMethodDefinition() {
// We need to shim "super()" inside the constructor if this is a derived
// class and the constructor has any parameter properties, since those
// use "this" and we can only access "this" after "super()" is called
if class.ExtendsOrNil.Data != nil {
if key, ok := prop.Key.Data.(*js_ast.EString); ok && helpers.UTF16EqualsString(key.Value, "constructor") {
if fn, ok := prop.ValueOrNil.Data.(*js_ast.EFunction); ok {
for _, arg := range fn.Fn.Args {
if arg.IsTypeScriptCtorField {
result.shimSuperCtorCalls = true
break
}
}
}
}
}
continue
}
if prop.Flags.Has(js_ast.PropertyIsStatic) {
// Static fields must be lowered if the target doesn't support them
if p.options.unsupportedJSFeatures.Has(compat.ClassStaticField) {
result.lowerAllStaticFields = true
}
// Convert static fields to assignment statements if the TypeScript
// setting for this is enabled. I don't think this matters for private
// fields because there's no way for this to call a setter in the base
// class, so this isn't done for private fields.
//
// If class static blocks are supported, then we can do this inline
// without needing to move the initializers outside of the class body.
// Otherwise, we need to lower all static class fields.
if p.options.ts.Parse && !class.UseDefineForClassFields && p.options.unsupportedJSFeatures.Has(compat.ClassStaticBlocks) {
result.lowerAllStaticFields = true
}
} else {
if p.options.ts.Parse && !class.UseDefineForClassFields {
// Convert instance fields to assignment statements if the TypeScript
// setting for this is enabled. I don't think this matters for private
// fields because there's no way for this to call a setter in the base
// class, so this isn't done for private fields.
if prop.InitializerOrNil.Data != nil {
// We can skip lowering all instance fields if all instance fields
// disappear completely when lowered. This happens when
// "useDefineForClassFields" is false and there is no initializer.
result.lowerAllInstanceFields = true
}
} else if p.options.unsupportedJSFeatures.Has(compat.ClassField) {
// Instance fields must be lowered if the target doesn't support them
result.lowerAllInstanceFields = true
}
}
}
// We need to shim "super()" inside the constructor if this is a derived
// class and there are any instance fields that need to be lowered, since
// those use "this" and we can only access "this" after "super()" is called
if result.lowerAllInstanceFields && class.ExtendsOrNil.Data != nil {
result.shimSuperCtorCalls = true
}
return
}
type classKind uint8
const (
classKindExpr classKind = iota
classKindStmt
classKindExportStmt
classKindExportDefaultStmt
)
type lowerClassContext struct {
optionalNameHint string
kind classKind
class *js_ast.Class
classLoc logger.Loc
classExpr js_ast.Expr // Only for "kind == classKindExpr", may be replaced by "nameFunc()"
defaultName ast.LocRef
ctor *js_ast.EFunction
parameterFields []js_ast.Stmt
instanceMembers []js_ast.Stmt
instancePrivateMethods []js_ast.Stmt
autoAccessorCount int
// These expressions are generated after the class body, in this order
computedPropertyChain js_ast.Expr
privateMembers []js_ast.Expr
staticMembers []js_ast.Expr
staticPrivateMethods []js_ast.Expr
// These contain calls to "__decorateClass" for TypeScript experimental decorators
instanceExperimentalDecorators []js_ast.Expr
staticExperimentalDecorators []js_ast.Expr
// These are used for implementing JavaScript decorators
decoratorContextRef ast.Ref
decoratorClassDecorators js_ast.Expr
decoratorPropertyToInitializerMap map[int]int
decoratorCallInstanceMethodExtraInitializers bool
decoratorCallStaticMethodExtraInitializers bool
decoratorStaticNonFieldElements []js_ast.Expr
decoratorInstanceNonFieldElements []js_ast.Expr
decoratorStaticFieldElements []js_ast.Expr
decoratorInstanceFieldElements []js_ast.Expr
// These are used by "lowerMethod"
privateInstanceMethodRef ast.Ref
privateStaticMethodRef ast.Ref
// These are only for class expressions that need to be captured
nameFunc func() js_ast.Expr
wrapFunc func(js_ast.Expr) js_ast.Expr
didCaptureClassExpr bool
}
// Apply all relevant transforms to a class object (either a statement or an
// expression) including:
//
// - Transforming class fields for older environments
// - Transforming static blocks for older environments
// - Transforming TypeScript experimental decorators into JavaScript
// - Transforming TypeScript class fields into assignments for "useDefineForClassFields"
//
// Note that this doesn't transform any nested AST subtrees inside the class
// body (e.g. the contents of initializers, methods, and static blocks). Those
// have already been transformed by "visitClass" by this point. It's done that
// way for performance so that we don't need to do another AST pass.
func (p *parser) lowerClass(stmt js_ast.Stmt, expr js_ast.Expr, result visitClassResult) ([]js_ast.Stmt, js_ast.Expr) {
ctx := lowerClassContext{
decoratorContextRef: ast.InvalidRef,
privateInstanceMethodRef: ast.InvalidRef,
privateStaticMethodRef: ast.InvalidRef,
}
// Unpack the class from the statement or expression
if stmt.Data == nil {
e, _ := expr.Data.(*js_ast.EClass)
ctx.class = &e.Class
ctx.classExpr = expr
ctx.kind = classKindExpr
if ctx.class.Name != nil {
symbol := &p.symbols[ctx.class.Name.Ref.InnerIndex]
ctx.optionalNameHint = symbol.OriginalName
// The inner class name inside the class expression should be the same as
// the class expression name itself
if result.innerClassNameRef != ast.InvalidRef {
p.mergeSymbols(result.innerClassNameRef, ctx.class.Name.Ref)
}
// Remove unused class names when minifying. Check this after we merge in
// the inner class name above since that will adjust the use count.
if p.options.minifySyntax && symbol.UseCountEstimate == 0 {
ctx.class.Name = nil
}
}
if p.nameToKeepIsFor == e {
ctx.optionalNameHint = p.nameToKeep
}
} else if s, ok := stmt.Data.(*js_ast.SClass); ok {
ctx.class = &s.Class
if ctx.class.Name != nil {
ctx.optionalNameHint = p.symbols[ctx.class.Name.Ref.InnerIndex].OriginalName
}
if s.IsExport {
ctx.kind = classKindExportStmt
} else {
ctx.kind = classKindStmt
}
} else {
s, _ := stmt.Data.(*js_ast.SExportDefault)
s2, _ := s.Value.Data.(*js_ast.SClass)
ctx.class = &s2.Class
if ctx.class.Name != nil {
ctx.optionalNameHint = p.symbols[ctx.class.Name.Ref.InnerIndex].OriginalName
}
ctx.defaultName = s.DefaultName
ctx.kind = classKindExportDefaultStmt
}
if stmt.Data == nil {
ctx.classLoc = expr.Loc
} else {
ctx.classLoc = stmt.Loc
}
classLoweringInfo := p.computeClassLoweringInfo(ctx.class)
ctx.enableNameCapture(p, result)
ctx.processProperties(p, classLoweringInfo, result)
ctx.insertInitializersIntoConstructor(p, classLoweringInfo, result)
return ctx.finishAndGenerateCode(p, result)
}
func (ctx *lowerClassContext) enableNameCapture(p *parser, result visitClassResult) {
// Class statements can be missing a name if they are in an
// "export default" statement:
//
// export default class {
// static foo = 123
// }
//
ctx.nameFunc = func() js_ast.Expr {
if ctx.kind == classKindExpr {
// If this is a class expression, capture and store it. We have to
// do this even if it has a name since the name isn't exposed
// outside the class body.
classExpr := &js_ast.EClass{Class: *ctx.class}
ctx.class = &classExpr.Class
ctx.nameFunc, ctx.wrapFunc = p.captureValueWithPossibleSideEffects(ctx.classLoc, 2, js_ast.Expr{Loc: ctx.classLoc, Data: classExpr}, valueDefinitelyNotMutated)
ctx.classExpr = ctx.nameFunc()
ctx.didCaptureClassExpr = true
name := ctx.nameFunc()
// If we're storing the class expression in a variable, remove the class
// name and rewrite all references to the class name with references to
// the temporary variable holding the class expression. This ensures that
// references to the class expression by name in any expressions that end
// up being pulled outside of the class body still work. For example:
//
// let Bar = class Foo {
// static foo = 123
// static bar = Foo.foo
// }
//
// This might be converted into the following:
//
// var _a;
// let Bar = (_a = class {
// }, _a.foo = 123, _a.bar = _a.foo, _a);
//
if ctx.class.Name != nil {
p.mergeSymbols(ctx.class.Name.Ref, name.Data.(*js_ast.EIdentifier).Ref)
ctx.class.Name = nil
}
return name
} else {
// If anything referenced the inner class name, then we should use that
// name for any automatically-generated initialization code, since it
// will come before the outer class name is initialized.
if result.innerClassNameRef != ast.InvalidRef {
p.recordUsage(result.innerClassNameRef)
return js_ast.Expr{Loc: ctx.class.Name.Loc, Data: &js_ast.EIdentifier{Ref: result.innerClassNameRef}}
}
// Otherwise we should just use the outer class name
if ctx.class.Name == nil {
if ctx.kind == classKindExportDefaultStmt {
ctx.class.Name = &ctx.defaultName
} else {
ctx.class.Name = &ast.LocRef{Loc: ctx.classLoc, Ref: p.generateTempRef(tempRefNoDeclare, "")}
}
}
p.recordUsage(ctx.class.Name.Ref)
return js_ast.Expr{Loc: ctx.class.Name.Loc, Data: &js_ast.EIdentifier{Ref: ctx.class.Name.Ref}}
}
}
}
// Handle lowering of instance and static fields. Move their initializers
// from the class body to either the constructor (instance fields) or after
// the class (static fields).
//
// If this returns true, the return property should be added to the class
// body. Otherwise the property should be omitted from the class body.
func (ctx *lowerClassContext) lowerField(
p *parser,
prop js_ast.Property,
private *js_ast.EPrivateIdentifier,
shouldOmitFieldInitializer bool,
staticFieldToBlockAssign bool,
initializerIndex int,
) (js_ast.Property, bool) {
mustLowerPrivate := private != nil && p.privateSymbolNeedsToBeLowered(private)
// The TypeScript compiler doesn't follow the JavaScript spec for
// uninitialized fields. They are supposed to be set to undefined but the
// TypeScript compiler just omits them entirely.
if !shouldOmitFieldInitializer {
loc := prop.Loc
// Determine where to store the field
var target js_ast.Expr
if prop.Flags.Has(js_ast.PropertyIsStatic) && !staticFieldToBlockAssign {
target = ctx.nameFunc()
} else {
target = js_ast.Expr{Loc: loc, Data: js_ast.EThisShared}
}
// Generate the assignment initializer
var init js_ast.Expr
if prop.InitializerOrNil.Data != nil {
init = prop.InitializerOrNil
} else {
init = js_ast.Expr{Loc: loc, Data: js_ast.EUndefinedShared}
}
// Optionally call registered decorator initializers
if initializerIndex != -1 {
args := []js_ast.Expr{
{Loc: loc, Data: &js_ast.EIdentifier{Ref: ctx.decoratorContextRef}},
{Loc: loc, Data: &js_ast.ENumber{Value: float64((3 + 2*initializerIndex) << 1)}},
}
if _, ok := init.Data.(*js_ast.EUndefined); !ok {
args = append(args, init)
}
init = p.callRuntime(init.Loc, "__runInitializers", args)
p.recordUsage(ctx.decoratorContextRef)
}
// Generate the assignment target
var memberExpr js_ast.Expr
if mustLowerPrivate {
// Generate a new symbol for this private field
ref := p.generateTempRef(tempRefNeedsDeclare, "_"+p.symbols[private.Ref.InnerIndex].OriginalName[1:])
p.symbols[private.Ref.InnerIndex].Link = ref
// Initialize the private field to a new WeakMap
if p.weakMapRef == ast.InvalidRef {
p.weakMapRef = p.newSymbol(ast.SymbolUnbound, "WeakMap")
p.moduleScope.Generated = append(p.moduleScope.Generated, p.weakMapRef)
}
ctx.privateMembers = append(ctx.privateMembers, js_ast.Assign(
js_ast.Expr{Loc: prop.Key.Loc, Data: &js_ast.EIdentifier{Ref: ref}},
js_ast.Expr{Loc: prop.Key.Loc, Data: &js_ast.ENew{Target: js_ast.Expr{Loc: prop.Key.Loc, Data: &js_ast.EIdentifier{Ref: p.weakMapRef}}}},
))
p.recordUsage(ref)
// Add every newly-constructed instance into this map
key := js_ast.Expr{Loc: prop.Key.Loc, Data: &js_ast.EIdentifier{Ref: ref}}
args := []js_ast.Expr{target, key}
if _, ok := init.Data.(*js_ast.EUndefined); !ok {
args = append(args, init)
}
memberExpr = p.callRuntime(loc, "__privateAdd", args)
p.recordUsage(ref)
} else if private == nil && ctx.class.UseDefineForClassFields {
args := []js_ast.Expr{target, prop.Key}
if _, ok := init.Data.(*js_ast.EUndefined); !ok {
args = append(args, init)
}
memberExpr = js_ast.Expr{Loc: loc, Data: &js_ast.ECall{
Target: p.importFromRuntime(loc, "__publicField"),
Args: args,
}}
} else {
if key, ok := prop.Key.Data.(*js_ast.EString); ok && !prop.Flags.Has(js_ast.PropertyIsComputed) && !prop.Flags.Has(js_ast.PropertyPreferQuotedKey) {
target = js_ast.Expr{Loc: loc, Data: &js_ast.EDot{
Target: target,
Name: helpers.UTF16ToString(key.Value),
NameLoc: prop.Key.Loc,
}}
} else {
target = js_ast.Expr{Loc: loc, Data: &js_ast.EIndex{
Target: target,
Index: prop.Key,
}}
}
memberExpr = js_ast.Assign(target, init)
}
// Run extra initializers
if initializerIndex != -1 {
var value js_ast.Expr
if prop.Flags.Has(js_ast.PropertyIsStatic) {
value = ctx.nameFunc()
} else {
value = js_ast.Expr{Loc: loc, Data: js_ast.EThisShared}
}
memberExpr = js_ast.JoinWithComma(memberExpr, p.callRuntime(loc, "__runInitializers", []js_ast.Expr{
{Loc: loc, Data: &js_ast.EIdentifier{Ref: ctx.decoratorContextRef}},
{Loc: loc, Data: &js_ast.ENumber{Value: float64(((4 + 2*initializerIndex) << 1) | 1)}},
value,
}))
p.recordUsage(ctx.decoratorContextRef)
}
if prop.Flags.Has(js_ast.PropertyIsStatic) {
// Move this property to an assignment after the class ends
if staticFieldToBlockAssign {
// Use inline assignment in a static block instead of lowering
return js_ast.Property{
Loc: loc,
Kind: js_ast.PropertyClassStaticBlock,
ClassStaticBlock: &js_ast.ClassStaticBlock{
Loc: loc,
Block: js_ast.SBlock{Stmts: []js_ast.Stmt{
{Loc: loc, Data: &js_ast.SExpr{Value: memberExpr}}},
},
},
}, true
} else {
// Move this property to an assignment after the class ends
ctx.staticMembers = append(ctx.staticMembers, memberExpr)
}
} else {
// Move this property to an assignment inside the class constructor
ctx.instanceMembers = append(ctx.instanceMembers, js_ast.Stmt{Loc: loc, Data: &js_ast.SExpr{Value: memberExpr}})
}
}
if private == nil || mustLowerPrivate {
// Remove the field from the class body
return js_ast.Property{}, false
}
// Keep the private field but remove the initializer
prop.InitializerOrNil = js_ast.Expr{}
return prop, true
}
func (ctx *lowerClassContext) lowerPrivateMethod(p *parser, prop js_ast.Property, private *js_ast.EPrivateIdentifier) {
// All private methods can share the same WeakSet
var ref *ast.Ref
if prop.Flags.Has(js_ast.PropertyIsStatic) {
ref = &ctx.privateStaticMethodRef
} else {
ref = &ctx.privateInstanceMethodRef
}
if *ref == ast.InvalidRef {
// Generate a new symbol to store the WeakSet
var name string
if prop.Flags.Has(js_ast.PropertyIsStatic) {
name = "_static"
} else {
name = "_instances"
}
if ctx.optionalNameHint != "" {
name = fmt.Sprintf("_%s%s", ctx.optionalNameHint, name)
}
*ref = p.generateTempRef(tempRefNeedsDeclare, name)
// Generate the initializer
if p.weakSetRef == ast.InvalidRef {
p.weakSetRef = p.newSymbol(ast.SymbolUnbound, "WeakSet")
p.moduleScope.Generated = append(p.moduleScope.Generated, p.weakSetRef)
}
ctx.privateMembers = append(ctx.privateMembers, js_ast.Assign(
js_ast.Expr{Loc: ctx.classLoc, Data: &js_ast.EIdentifier{Ref: *ref}},
js_ast.Expr{Loc: ctx.classLoc, Data: &js_ast.ENew{Target: js_ast.Expr{Loc: ctx.classLoc, Data: &js_ast.EIdentifier{Ref: p.weakSetRef}}}},
))
p.recordUsage(*ref)
p.recordUsage(p.weakSetRef)
// Determine what to store in the WeakSet
var target js_ast.Expr