Simplify convertToMappedObjectType (microsoft#24360)

Author: Andy

src/services/codefixes/convertToMappedObjectType.ts

@@ -6,89 +6,51 @@ namespace ts.codefix {
 
     type FixableDeclaration = InterfaceDeclaration | TypeAliasDeclaration;
 
-    interface Info {
-        indexSignature: IndexSignatureDeclaration;
-        container: FixableDeclaration;
-        otherMembers: ReadonlyArray<TypeElement>;
-        parameterName: Identifier;
-        parameterType: TypeNode;
-    }
-
     registerCodeFix({
         errorCodes,
         getCodeActions: context => {
             const { sourceFile, span } = context;
-            const info = getFixableSignatureAtPosition(sourceFile, span.start);
-            if (!info) return;
-            const { indexSignature, container, otherMembers, parameterName, parameterType } = info;
-
-            const changes = textChanges.ChangeTracker.with(context, t => doChange(t, sourceFile, indexSignature, container, otherMembers, parameterName, parameterType));
-            return [createCodeFixAction(fixId, changes, [Diagnostics.Convert_0_to_mapped_object_type, idText(container.name)], fixId, [Diagnostics.Convert_0_to_mapped_object_type, idText(container.name)])];
+            const info = getInfo(sourceFile, span.start);
+            if (!info) return undefined;
+            const changes = textChanges.ChangeTracker.with(context, t => doChange(t, sourceFile, info));
+            const name = idText(info.container.name);
+            return [createCodeFixAction(fixId, changes, [Diagnostics.Convert_0_to_mapped_object_type, name], fixId, [Diagnostics.Convert_0_to_mapped_object_type, name])];
         },
         fixIds: [fixId],
         getAllCodeActions: context => codeFixAll(context, errorCodes, (changes, diag) => {
-            const info = getFixableSignatureAtPosition(diag.file, diag.start);
-            if (!info) return;
-            const { indexSignature, container, otherMembers, parameterName, parameterType } = info;
-
-            doChange(changes, context.sourceFile, indexSignature, container, otherMembers, parameterName, parameterType);
+            const info = getInfo(diag.file, diag.start);
+            if (info) doChange(changes, diag.file, info);
         })
     });
 
-    function isFixableParameterName(node: Node): boolean {
-        return node && node.parent && node.parent.parent && node.parent.parent.parent && !isClassDeclaration(node.parent.parent.parent);
-    }
-
-    function getFixableSignatureAtPosition(sourceFile: SourceFile, pos: number): Info | undefined {
+    interface Info { readonly indexSignature: IndexSignatureDeclaration; readonly container: FixableDeclaration; }
+    function getInfo(sourceFile: SourceFile, pos: number): Info | undefined {
         const token = getTokenAtPosition(sourceFile, pos, /*includeJsDocComment*/ false);
-        if (!isFixableParameterName(token)) return undefined;
-
-        const indexSignature = <IndexSignatureDeclaration>token.parent.parent;
-        const container = isInterfaceDeclaration(indexSignature.parent) ? indexSignature.parent : <TypeAliasDeclaration>indexSignature.parent.parent;
-        const members = isInterfaceDeclaration(container) ? container.members : (<TypeLiteralNode>container.type).members;
-        const otherMembers = filter(members, member => !isIndexSignatureDeclaration(member));
-        const parameter = first(indexSignature.parameters);
-
-        return {
-            indexSignature,
-            container,
-            otherMembers,
-            parameterName: <Identifier>parameter.name,
-            parameterType: parameter.type!
-        };
+        const indexSignature = cast(token.parent.parent, isIndexSignatureDeclaration);
+        if (isClassDeclaration(indexSignature.parent)) return undefined;
+        const container = isInterfaceDeclaration(indexSignature.parent) ? indexSignature.parent : cast(indexSignature.parent.parent, isTypeAliasDeclaration);
+        return { indexSignature, container };
     }
 
-    function getInterfaceHeritageClauses(declaration: FixableDeclaration): NodeArray<ExpressionWithTypeArguments> | undefined {
-        if (!isInterfaceDeclaration(declaration)) return undefined;
-
-        const heritageClause = getHeritageClause(declaration.heritageClauses, SyntaxKind.ExtendsKeyword);
-        return heritageClause && heritageClause.types;
+    function createTypeAliasFromInterface(declaration: FixableDeclaration, type: TypeNode): TypeAliasDeclaration {
+        return createTypeAliasDeclaration(declaration.decorators, declaration.modifiers, declaration.name, declaration.typeParameters, type);
     }
 
-    function createTypeAliasFromInterface(indexSignature: IndexSignatureDeclaration, declaration: FixableDeclaration, otherMembers: ReadonlyArray<TypeElement>, parameterName: Identifier, parameterType: TypeNode) {
-        const heritageClauses = getInterfaceHeritageClauses(declaration);
-        const mappedTypeParameter = createTypeParameterDeclaration(parameterName, parameterType);
+    function doChange(changes: textChanges.ChangeTracker, sourceFile: SourceFile, { indexSignature, container }: Info): void {
+        const members = isInterfaceDeclaration(container) ? container.members : (<TypeLiteralNode>container.type).members;
+        const otherMembers = members.filter(member => !isIndexSignatureDeclaration(member));
+        const parameter = first(indexSignature.parameters);
+        const mappedTypeParameter = createTypeParameterDeclaration(cast(parameter.name, isIdentifier), parameter.type);
         const mappedIntersectionType = createMappedTypeNode(
             hasReadonlyModifier(indexSignature) ? createModifier(SyntaxKind.ReadonlyKeyword) : undefined,
             mappedTypeParameter,
             indexSignature.questionToken,
             indexSignature.type);
-
-        return createTypeAliasDeclaration(
-            declaration.decorators,
-            declaration.modifiers,
-            declaration.name,
-            declaration.typeParameters,
-            createIntersectionTypeNode(
-                concatenate(
-                    heritageClauses,
-                    append<TypeNode>([mappedIntersectionType], otherMembers.length ? createTypeLiteralNode(otherMembers) : undefined)
-                )
-            )
-        );
-    }
-
-    function doChange(changes: textChanges.ChangeTracker, sourceFile: SourceFile, indexSignature: IndexSignatureDeclaration, declaration: FixableDeclaration, otherMembers: ReadonlyArray<TypeElement>, parameterName: Identifier, parameterType: TypeNode) {
-        changes.replaceNode(sourceFile, declaration, createTypeAliasFromInterface(indexSignature, declaration, otherMembers, parameterName, parameterType));
+        const intersectionType = createIntersectionTypeNode([
+            ...getAllSuperTypeNodes(container),
+            mappedIntersectionType,
+            ...(otherMembers.length ? [createTypeLiteralNode(otherMembers)] : emptyArray),
+        ]);
+        changes.replaceNode(sourceFile, container, createTypeAliasFromInterface(container, intersectionType));
     }
 }