Using Generated Types

[kevinkhill]

Is this how you would use them? Or is there some cool TS ninja moves I don't know that could simplify this?

[bd82]

I believe the existing interface was designed to support the scenario where all the visit methods return something
of the same BaseType for example converting from CST to AST using some Base ASTNode.

Anyhow this.visit does not do much

• chevrotain/packages/chevrotain/src/parse/cst/cst_visitor.ts

  Lines 46 to 60 in 93c78cd

  	visit: function (cstNode: CstNode | CstNode[], param: any) {
  	// enables writing more concise visitor methods when CstNode has only a single child
  	if (isArray(cstNode)) {
  	// A CST Node's children dictionary can never have empty arrays as values
  	// If a key is defined there will be at least one element in the corresponding value array.
  	cstNode = cstNode[0]
  	}
  	// enables passing optional CstNodes concisely.
  	if (isUndefined(cstNode)) {
  	return undefined
  	}
  	return this[cstNode.name](cstNode.children, param)
  	},

So you can instead call the ProgramNumberLine method directly...

Another approach is that I had some luck defining a variable return type based on the input's type, maybe it is something that
can be expended to the context of CST Visitor

• https://github.com/SAP/app-studio-toolkit/blob/main/packages/vscode-deps-upgrade-tool/src/settings.ts#L24-L27

[kevinkhill]

I keep trying to write one, but I am a novice TS programmer, so I am not well versed in how to sorta make it work... This is my little helper, but I don't really like it. It's more hiding visit than helping it

[bd82]

I will give it a shot, I am not sure it is possible either 😄

[bd82]

Have a look at this Playground snippet

ignore the boilerplate and instead start reading from line 91
focus on the visitByNode method and its usage.

[kevinkhill]

this.programNumberLine(ctx.programNumberLine.children))

had to become this.programNumberLine(ctx.programNumberLine[0].children))

And now I want a fn to help pull that child of, but in a typesafe fashion...🤔

[bd82]

That is why it is likely better to implement a wrapper that could:

• extract the .children
• extract the first element in the CSTNodes array
• maybe even map a CSTNodes array using an one of the visitor handlers as inferred callback (by name prop).

[bd82]

BTW the CST visitor APIs is something that definitively has room for improvement or even a re-write #1039
But there is no plan or timeline for this.