TypeGuard for all nodes with a .expression?

[gregjacobs]

Hey David,

Was just working on some AST transforms, and I noticed a pattern that I want to try to take advantage of.

I'm basically trying to replace identifiers such as myVar with this.myVar. I noticed that I basically need to find compiler nodes which have an expression property that contain an Identifier node.

For example, CallExpression, PropertyAccessExpression, IfStatement, and probably many more have an expression property. Was thinking I could transform them with something like this:

// ...traversing nodes
if( TypeGuards.isExpressionableNode( node ) ) {  // <-- does this name make sense?
    if( TypeGuards.isIdentifier( node.getExpression() ) { 
        node.getExpression().replaceWithText( 'this.' + node.getExpression().getText() );
    }
}

Btw, any general thoughts on this? Is there a better way to go about this?

[dsherret]

You're right, this is very common. I'll make all the nodes that have this an ExpressionableNode. Then yes, you will be able to just do TypeGuards.isExpressionableNode(node)

[dsherret]

@gregjacobs I added TypeGuards.hasExpression. This will return true when the node has a .getExpression() method and that method returns a node.

The second check is necessary because .getExpression() could possibly return undefined for certain statements like ReturnStatement (return 5; vs return;) and YieldStatement (yield 5; vs yield;).

I'm running a new release now.

[gregjacobs]

Awesome, thanks man!