Property assignment dropped with pure_getters=true

[filipesilva]

Bug report or feature request?
Bug report

ES5 or ES6+ input?
ES5

Uglify version (uglifyjs -V)
[email protected]

JavaScript input

// test.js
var MatFab = /*@__PURE__*/ (function () {
  function MatFab(button, anchor) {
    (button || anchor).color = 'accent';
  }
  return MatFab;
}());
var button = {};
MatFab(button);
console.log(button);

The uglifyjs CLI command executed or minify() options used.

uglifyjs -c toplevel,pure_getters=true -b -- test.js

JavaScript output or error produced.

var button = {};

(function() {
    return function(button, anchor) {};
})()(button), console.log(button);

Other information

The (button || anchor).color = 'accent'; statement is dropped when the pure_getters compress is used.

Disabling pure_getters or changing the statement to button.color = 'accent'; will cause it to not be dropped anymore.

I think this is a bug because button.color = 'accent'; and (button || anchor).color = 'accent'; should not have different results. I agree it's a side effect though.

Related to angular/devkit#388

[kzc]

It appears to be a regression from [email protected]. The commit that introduced the issue is 0b0eac1

[alexlamsl]

Thanks to @filipesilva for the detailed report, and @kzc for the bisection - got the cause and fix down much quicker 👍

PR coming up.

[filipesilva]

@alexlamsl awesome, thank you so much!