getFirstAncestor with a lambda

Is your feature request related to a problem? Please describe.

I need to get the enclosing method in a class – but this could be a constructor as well. Looks like we’re missing a way to provide a custom lambda for getFirstAncestor, as there is only getFirstAncestorByKind and getFirstAncestorByKindOrThrow.

Describe the solution you’d like

const method = methodBody.getFirstAncestor(ancestor => TypeGuards.isMethodDeclaration(ancestor) || TypeGuards.isConstructorDeclaration(ancestor))

Describe alternatives you’ve considered

The “workaround” is currently this:

  const ancestors = methodBody.getAncestors()
  const method = ancestors.find(ancestor => TypeGuards.isMethodDeclaration(ancestor) || TypeGuards.isConstructorDeclaration(ancestor))

It’s nothing drastic, but this first fetches all ancestors which could be computationally expensive.

[lazarljubenovic]

Exactly. That’s why I meant to remove “getters” which get only by syntax kind – instead, always use a lambda – and that lambda can be a type guard.

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In the concrete example, my idea is to remove this type of call completely.

getFirstAncestorByKind(SyntaxKind.ClassDeclaration)

Instead, only provide a function which accepts a lambda and let me pass in any kind of predicate.

getFirstAncestorBy(ancestor => ancestor.getKind() == SyntaxKind.ClassDeclaration)

Or shorter:

getFirstAncestorBy(ancestor => TypeGuards.isClassDeclaration(ancestor))

Or shorter:

getFirstAncestorBy(TypeGuads.isClassDeclaration)

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The point is, if you look at current thing and the last snippet above, the last one is more flexibile and shorter for the same use case:

getFirstAncestorByKind(SyntaxKind.ClassDeclaration)
getFirstAncestorBy(TypeGuads.isClassDeclaration)

So my suggestion is to remove getFirstAncestorByKind completely as it only bloats the library with a use-case which can already be implemented in just as straight-forward manner and with even less typing.

[dsherret]

@cancerberoSgx I’m going to take a look. I need to re-evaluate the getParentWhile method. There’s already a .getFirstDescendant method.

I definitely don’t want to add it on everything because then the library becomes too bloated. This should be a case-by-case addition. For example, .getParameters() uses the node.parameters array already and there are lots of existing methods on an array that people can use to find things. Additionally, there’s already a .getParameter(...) and .getParameterOrThrow(...) method. There’s also .getMethod(...) method.

I think doing a .filter() on .getDescendants() would be about the same performance. For the best performance, people should use .forEachDescendant((node, traversal) => {}); using the traversal object (see https://dsherret.github.io/ts-simple-ast/navigation/).