Transforming class member with decorators throws

[shlomiassaf]

TypeScript Version: 2.4.0

Code

Can't use something that runs from "tsc" since it does not support transformers

In a PropertyDeclaration visitor

return ts.updateProperty(
          node,
          node.decorators[0], // assume we have 2 or more decorators...
          node.modifiers,
          node.name,
          node.type,
          node.initializer
        );

Expected behavior:
Should compile.

Actual behavior:
Exception is thrown TypeError: Cannot read property 'kind' of undefined

The exception is throw from here

    export function nodeCanBeDecorated(node: Node): boolean {
        switch (node.kind) {
            case SyntaxKind.ClassDeclaration:
                // classes are valid targets
                return true;

            case SyntaxKind.PropertyDeclaration:
                // property declarations are valid if their parent is a class declaration.
                return node.parent.kind === SyntaxKind.ClassDeclaration;

            case SyntaxKind.GetAccessor:
            case SyntaxKind.SetAccessor:
            case SyntaxKind.MethodDeclaration:
                // if this method has a body and its parent is a class declaration, this is a valid target.
                return (<FunctionLikeDeclaration>node).body !== undefined
                    && node.parent.kind === SyntaxKind.ClassDeclaration;

            case SyntaxKind.Parameter:
                // if the parameter's parent has a body and its grandparent is a class declaration, this is a valid target;
                return (<FunctionLikeDeclaration>node.parent).body !== undefined
                    && (node.parent.kind === SyntaxKind.Constructor
                        || node.parent.kind === SyntaxKind.MethodDeclaration
                        || node.parent.kind === SyntaxKind.SetAccessor)
                    && node.parent.parent.kind === SyntaxKind.ClassDeclaration;
        }

        return false;
    }

Trying to reach node.parent.kind while node.parent is undefined, which is common to all "synthesized" nodes, i.e. transforming nodes.

This is true to all other members... Parameter, MethodDeclaration, GetAccessor and SetAccessor

[shlomiassaf]

I think this PR should fix the problem...

Testing it now.

[tbosch]

This bug also affects Angular / Tsickle as we are now using transformers. Our workaround (see transformer_util.ts):

• setting the parent for synthetic nodes
• not using ts.updateSourceFileNode but instead doing this:

  const sf = getMutableClone(sf);
  sf.statements = statements;
  return sf;
  

/cc @mprobst @evmar @alexeagle

[filipesilva]

@tbosch the related issue #17551 is fixed in 2.5.0 via #18051. Perhaps the workaround in Angular can go away when typescript is detected to be that version of greater.

import { satisfies } from 'semver';
const visitEachChild = satisfies(ts.version, '^2.5.0')
  ? ts.visitEachChild
  : visitEachChildWorkaround;

This issue should be closed since I think #18051 fixes both.

[shlomiassaf]

@filipesilva from what I see #18051 did not solve the issue, or at least did not solve it completely.

See angular/angular#20216

cc @rbuckton