Usage question: Adding a child node

[LukasMachetanz]

Hello again!

Sorry for using this channel again asking a general usage question. But I really appreciated your help the last time.

How can I or how would you add a child node to a given node?

E.g. add static instances = []; to class Test {}.

I know that I can find the class declaration with ts.isClassDeclaration(node) but how would you proceed then?

Do I really have to provide a new class declaration node (like in the code snippet) or is there a more "elegant" way?

if (ts.isClassDeclaration(node) {
   // createInstancesProperty ==> custom fn to create "static instances = [];"
   const extendedMembers = ts.createNodeArray([createInstancesProperty(symbol.name), ...node.members]);
   return ts.createClassDeclaration(node.decorators, node.modifiers, node.name, node.typeParameters, node.heritageClauses, extendedMembers);

}

I am wondering what's the best approach if I would like to do something (on) ...

1. Add a static property to the class || e.g. static instances = [];

2. ts.isConstructorDeclaration

• add content to the constructor if there is one || e.g. ClassName.instances.push(this)
• add the constructor and the content if there is none

3. ts.isMethodDeclaration

4. ts.isPropertyDeclaration

I really enjoy using the visitor pattern approach but I do not know how to use it in combination with my desired tasks 1) and 2).

Any help appreciated. Thanks in advance.

[itsdouges]

Hi! No worries happy to help

In this instance I'm not sure if there is a better way

In general you basically want to do it by a process of elimination until you get to the node you actually want to change, so I might have something in an if statement i want to change

i could check

1. is one of this nodes parents an if statement that i care about
2. is this node the node i care about

then just return a new/updated node

I don't think there's any silver bullet - it's just using the tools in such a way that helps us achieve what we want 😄

[LukasMachetanz]

Okay okay. But how would you tackle the described tasks together then? If I got you correctly my approach regarding returning a new class declaration node wasn’t to bad. At least that’s how I achieved adding the static property to the class.

But in my case (or at least in one of the tasks) it is in general not about changing a specific node; it is more about inserting a child node. Otherwise I would get what you are suggesting.

But how would you now additionally transform/adjust the property declarations of the class? E.g. transforming all numbers to strings. (the use case does actually not really matter)

Do you know what I mean / what my problem is? Referencing the previous code snippet: Just modifying the node (without the visitor pattern and returning a VisitorResult) will not do the trick. At least what I experienced so far.