Can't get this to work with a simple example

[kasbah]

I took this simple example from this blog post but I couldn't get it to run:

// transform.ts
import * as ts from 'typescript';

export default function(/*opts?: Opts*/) {
  const visitor: ts.Visitor = (node: ts.Node): ts.VisitResult => {
    if (ts.isCallExpression(node) && node.expression.getText(sf) == 'safely') {
      // we have found an expression of the form safely(...)
      // we can now replace or update it

      // get the argument to safely
      const target = node.arguments[0];
      // check to make sure it is a property access, like "a.b"
      if (ts.isPropertyAccessExpression(target)) {
        // return a binary expression with a && a.b
        return ts.createBinary(
          target.expression, // the left hand operand is the object
          ts.SyntaxKind.AmpersandAmpersandToken, // the && operator
          target,
        ); // the right hand operand is the full expression
      }
    }
    // otherwise continue visiting all the nodes
    return ts.visitEachChild(node, visitor, ctx);
  };
  return (ctx: ts.TransformationContext): ts.Transformer => {
    return (sf: ts.SourceFile) => ts.visitNode(sf, visitor(ctx, sf));
  };
}

// example.ts
const a = {b: 1}
const c = safely(a.b)

tsconfig.json

{
  "compilerOptions": {
   "customTransformers": {
      "before": [
        "./transform.ts"
      ]
    }
  }
}

I ran:

ttsc example.ts

Result:

var a = { b: 1 };
var c = safely(a.b);

Expected:

var a = { b: 1 };
var c = a && a.b;

[cevek]

Currently transformers work only with js files in commonjs style. But soon I'll implement supporting ts files Second problem that you give a wrapper function, but transformers must be without this one

export default function(/*opts?: Opts*/)

Work transformer version

//transform.js
'use strict';
var ts = require('typescript');
function visitor(ctx, sf, opts) {
    var visitor = function(node) {
        if (ts.isCallExpression(node) && ts.getTextOfNodeFromSourceText(sf.text, node.expression)) {
            var target = node.arguments[0];
            if (ts.isPropertyAccessExpression(target)) {
                return ts.createBinary(
                    target.expression, // the left hand operand is the object
                    ts.SyntaxKind.AmpersandAmpersandToken, // the && operator
                    target
                );
            }
        }
        return ts.visitEachChild(node, visitor, ctx);
    };
    return visitor;
}
module.exports = function(ctx) {
    return function(sf) {
        return ts.visitNode(sf, visitor(ctx, sf, {}));
    };
};

[kasbah]

Thanks for your help. I copied your transform.js and changed tsconfig.json to:

{
  "compilerOptions": {
   "customTransformers": {
      "before": [
        "./transform.js"
      ]
    }
  }
}

But the ttsc transformation is still as above. In fact, I noticed even if I change ./transform.js to a non-existent file it runs the same.

[cevek]

I've publish new version(1.0.5) that can works with transformers written in ts Also I've attach an example project Read readme.md

[kasbah]

Nice, I tried the example and it does work for me when I run ttsc on its own. However, if I run ttsc test.ts it doesn't work as expected (seems to be like running tsc -- the transform is not applied).

(Also, I noticed you committed an out of date example/test.js)

[cevek]

When you run tsc test.ts tsc doesn't use your tsconfig.json

[kasbah]

Ah, thanks. That's kind of confusing behaviour but I haven't used tsc very much. It might make sense for ttsc file.ts to still use the transform section of the config because right now it's just like calling tsc file.ts?

[cevek]

Yeah, you right, maybe in the next version I'll add this feature

[kasbah]

Thanks again for this project and your help. I feel like with the addition of an example this is resolved.