Align AST for TSEnumDeclaration with TSInterfaceDeclaration, TSModuleDeclaration, etc

[bradzacher]

For each TSEnumDeclaration, we place its members directly on this AST node.

export interface TSEnumDeclaration extends BaseNode {
  type: AST_NODE_TYPES.TSEnumDeclaration;
  id: Identifier;
  members: TSEnumMember[];
  const?: boolean;
  declare?: boolean;
  modifiers?: Modifier[];
  decorators?: Decorator[];
}

For each TSInterfaceDeclaration, we have a separate TSInterfaceBody node, upon which we place the members.

export interface TSInterfaceDeclaration extends BaseNode {
  type: AST_NODE_TYPES.TSInterfaceDeclaration;
  body: TSInterfaceBody;
  id: Identifier;
  typeParameters?: TSTypeParameterDeclaration;
  extends?: ExpressionWithTypeArguments[];
  implements?: ExpressionWithTypeArguments[];
  decorators?: Decorator[];
  abstract?: boolean;
  declare?: boolean;
}

export interface TSInterfaceBody extends BaseNode {
  type: AST_NODE_TYPES.TSInterfaceBody;
  body: TypeElement[];
}

I'm not sure why there's this inconsistency between the two, but I think we should consider aligning the two.

I'm not sure why TSEnumDeclaration was created without a body, but I think that creating a TSEnumBody node seems like the correct thing to do.
Doing so would align it with not only TSInterfaceDeclaration, but also TSModuleDeclaration, ClassDeclaration and FunctionDeclaration.

[armano2]

hi, @bradzacher reason behind not using *body node for enum was alignment between babel ast for typescript and typescript itself. Enum structure is created in similar way to Object rather than interface.

typescript-eslint/packages/typescript-estree/src/convert.ts

Lines 2471 to 2473 in 835378e

	id: this.convertChild(node.name),
	members: node.members.map(el => this.convertChild(el)),
	});

note

Enum is not behaving in exactly same way as object.
http://www.typescriptlang.org/play/?ssl=10&ssc=1&pln=1&pc=1#code/MYewdgzgLgBAZjAvDA7Gg3AKAKZgK4C2MAogIwwDemMN8SMpANDAPQswDKAFgIYAmIAO4QYULthh4ADlOwAnGAAM4igHTVaAc3pxmbeqUwBfHPiLEATJQ0045ZExsxtyXa3YAVLgEsRv0eKSMvJKKqr0aCjGmEA

[bradzacher]

Enum is not behaving in exactly same way as object.

Sure it's not the same as an object, but in your example, it is equivalent to the following:

const f = 777;
function E1() {
    const f = 1; // Shadows the upper `f`.
    const g = f; // = 1
}
function E2() {
    const f1 = 1;
    const g = f; // This is the upper `f`. = 777
}

Which is kinda my point - it behaves more like a new block scope (see functions, or BlockStatements)

alignment between babel ast for typescript and typescript itself

To me it seems like we should look to mirroring what ESTree does, instead of what babel and TS do. Babel and TS use their AST much differently than ESTree.

[JoshuaKGoldberg]

#8920 was merged into the v8 branch. ✅