babel: `typescript` preset: incompatible with `+=` operator inside arrow functions, nested in ternary

@pelly You need to check your yarn.lock and manually merge the duplicate elements that you’ve probably got after yarn add d3-array@2.3.3:

-"d3-array@1.2.0 - 2":
-  version "2.5.1"
-  resolved "https://registry.yarnpkg.com/d3-array/-/d3-array-2.5.1.tgz#cc785e1c4b560a34b8c77af9e6709bdf3f2ee117"
-  integrity sha512-cKvAlQZUKhXInw5mosJMtAYsY3dDYwTess/WOFUQTGcr8xV04SZMJs6n6QznsqZC5vJTkvZuCgsH9fo981ysPA==
-
-d3-array@2.3.3:
+d3-array@2.3.3, "d3-array@1.2.0 - 2":
   version "2.3.3"
   resolved "https://registry.yarnpkg.com/d3-array/-/d3-array-2.3.3.tgz#e90c39fbaedccedf59fc30473092f99a0e14efa2"
   integrity sha512-syv3wp0U5aB6toP2zb2OdBkhTy1MWDsCAaYk6OXJZv+G4u7bSWEmYgxLoFyc88RQUhZYGCebW9a9UD1gFi5+MQ==

A safer approach would be to add a static resolution to package.json:

{
  "resolutions": {
    "d3-array": "2.3.3"
  }
}

and re-run yarn.

I had same problem. I’m wondering if ignoring cumsum.js could be a workaround.

// babel.config.js
module.exports = function () {
  return {
    ignore: [new RegExp("d3-array/src/cumsum.js")],
    // other configs...
  }
};

Notes:

• https://github.com/babel/babel/discussions/12231
• https://babeljs.io/docs/en/options#ignore

Released in @babel/parser 7.14.9

My 2 cts observation: it seems the minimal reproduction in REPL can be fixed by changing

0 ? v => (sum += v) : v => 0;

to

0 ? v => (sum += v) : (v => 0);

Similarly, the code in d3-array compiles if we wrap the second arrow function with parentheses:

function cumsum(values, valueof) { 
   var sum = 0, index = 0; 
   return Float64Array.from(values, valueof === undefined 
     ? v => (sum += +v || 0) 
     : (v => (sum += +valueof(v, index++, values) || 0)));
 } 

Adding a resolution to 2.3.3 gave us other compilation errors. For anybody else stumbling on this, we’ve added this in our package.json: "d3-array": "file:./lib/d3-array", then copied the content from the d3-array folder in node_modules to our local folder and changed cumsum.js to this:

export default function cumsum(values, valueof) {
  var sum = 0,
    index = 0
  return Float64Array.from(
    values,
    valueof === undefined
      ? function (v) {
          return (sum += +v || 0)
        }
      : function (v) {
          return (sum += +valueof(v, index++, values) || 0)
        }
  )
}

I am still seeing the same error with babel/parser 7.15.0

I opened https://github.com/babel/babel/issues/13644 since it’s effectively a different bug, so that we don’t spam people interested in the TS one.

Ok, it looks like we fixed it for TypeScript but we have the same bug when using Flow (which is the one used by React Native on .js files)

This also affects d3-array + jest + ts combo.