fix(3565): preserve trailing commas in declaration-emitted array binding patterns (#3574)

Author: a-tarasyuk

internal/transformers/declarations/transform.go

@@ -64,6 +64,7 @@ type DeclarationTransformer struct {
 	rawReferencedFiles               []ReferencedFilePair
 	rawTypeReferenceDirectives       []*ast.FileReference
 	rawLibReferenceDirectives        []*ast.FileReference
+	bindingNameVisitor               *ast.NodeVisitor
 }
 
 // TODO: Convert to transformers.TransformerFactory signature to allow more automatic composition with other transforms
@@ -94,6 +95,7 @@ func NewDeclarationTransformer(host DeclarationEmitHost, context *printer.EmitCo
 		}
 	}
 	tx.NewTransformer(tx.visit, context)
+	tx.bindingNameVisitor = tx.EmitContext().NewNodeVisitor(tx.visitBindingName)
 	return tx
 }
 
@@ -1943,7 +1945,7 @@ func (tx *DeclarationTransformer) ensureParameter(p *ast.ParameterDeclaration) *
 		p,
 		nil,
 		p.DotDotDotToken,
-		tx.filterBindingPatternInitializers(p.Name()),
+		tx.bindingNameVisitor.VisitNode(p.Name()),
 		questionToken,
 		tx.ensureType(p.AsNode(), true),
 		tx.ensureNoInitializer(p.AsNode()),
@@ -1963,35 +1965,19 @@ func (tx *DeclarationTransformer) ensureNoInitializer(node *ast.Node) *ast.Node
 	return nil
 }
 
-func (tx *DeclarationTransformer) filterBindingPatternInitializers(node *ast.Node) *ast.Node {
-	if node.Kind == ast.KindIdentifier {
+func (tx *DeclarationTransformer) visitBindingName(node *ast.Node) *ast.Node {
+	switch node.Kind {
+	case ast.KindIdentifier, ast.KindOmittedExpression:
 		return node
-	} else {
-		// TODO: visitor to avoid always making new nodes?
-		elements := make([]*ast.Node, 0, len(node.Elements()))
-		for _, elem := range node.Elements() {
-			if elem.Kind == ast.KindOmittedExpression {
-				elements = append(elements, elem)
-				continue
-			}
-			if elem.PropertyName() != nil && ast.IsComputedPropertyName(elem.PropertyName()) && ast.IsEntityNameExpression(elem.PropertyName().Expression()) {
-				tx.checkEntityNameVisibility(elem.PropertyName().Expression(), tx.enclosingDeclaration)
-			}
-			if elem.Name() == nil {
-				elements = append(elements, elem)
-				continue
-			}
-
-			elements = append(elements, tx.Factory().UpdateBindingElement(
-				elem.AsBindingElement(),
-				elem.AsBindingElement().DotDotDotToken,
-				elem.PropertyName(),
-				tx.filterBindingPatternInitializers(elem.Name()),
-				nil,
-			))
+	case ast.KindArrayBindingPattern, ast.KindObjectBindingPattern:
+		return node.VisitEachChild(tx.bindingNameVisitor)
+	case ast.KindBindingElement:
+		if node.PropertyName() != nil && ast.IsComputedPropertyName(node.PropertyName()) && ast.IsEntityNameExpression(node.PropertyName().Expression()) {
+			tx.checkEntityNameVisibility(node.PropertyName().Expression(), tx.enclosingDeclaration)
 		}
-		elemList := tx.Factory().NewNodeList(elements)
-		return tx.Factory().UpdateBindingPattern(node.AsBindingPattern(), elemList)
+		return tx.Factory().UpdateBindingElement(node.AsBindingElement(), node.AsBindingElement().DotDotDotToken, node.PropertyName(), tx.bindingNameVisitor.VisitNode(node.Name()), nil /*initializer*/)
+	default:
+		return node
 	}
 }
 

testdata/baselines/reference/submodule/compiler/declarationEmitDestructuring5.js

@@ -17,8 +17,8 @@ function bar2([, , z, , ,]) { }
 
 
 //// [declarationEmitDestructuring5.d.ts]
-declare function baz([, z, ]: [any, any, any?]): void;
-declare function foo([, b]: [any, any]): void;
-declare function bar([z, , ]: [any, any?, any?]): void;
-declare function bar1([z, , ]?: [number, number, number, number, number]): void;
-declare function bar2([, , z, , ]: [any, any, any, any?, any?]): void;
+declare function baz([, z, ,]: [any, any, any?]): void;
+declare function foo([, b,]: [any, any]): void;
+declare function bar([z, , ,]: [any, any?, any?]): void;
+declare function bar1([z, , ,]?: [number, number, number, number, number]): void;
+declare function bar2([, , z, , ,]: [any, any, any, any?, any?]): void;

testdata/baselines/reference/submoduleTriaged/compiler/declarationEmitDestructuring5.js.diff

@@ -232,10 +232,6 @@ conformance/definiteAssignmentAssertionsWithObjectShortHand.js.diff
 ## https://github.com/microsoft/typescript-go/issues/3564
 conformance/genericFunctionParameters.js.diff
 
-# Declaration emit trailing comma changes in destructuring parameters
-## https://github.com/microsoft/typescript-go/issues/3565
-compiler/declarationEmitDestructuring5.js.diff
-
 # Late-bound computed property [prop] preserved instead of resolved to plain prop
 ## https://github.com/microsoft/typescript-go/issues/3566
 compiler/lateBoundAssignmentCandidateJS2.js.diff