babel-preset-env does not use package.json browserslist

[sudo-suhas]

babel-preset-env does not yet consume the browserslist config in package.json. There is a PR open for adding this support.

We can see this in action by adding "debug": true to babel-preset-env options in .babelrc

babel-preset-env DEBUG output - Current

babel-preset-env: `DEBUG` option

Using targets:
{}

Modules transform: false

Using plugins:
  check-es2015-constants {}
  transform-es2015-arrow-functions {}
  transform-es2015-block-scoped-functions {}
  transform-es2015-block-scoping {}
  transform-es2015-classes {}
  transform-es2015-computed-properties {}
  transform-es2015-destructuring {}
  transform-es2015-duplicate-keys {}
  transform-es2015-for-of {}
  transform-es2015-function-name {}
  transform-es2015-literals {}
  transform-es2015-object-super {}
  transform-es2015-parameters {}
  transform-es2015-shorthand-properties {}
  transform-es2015-spread {}
  transform-es2015-sticky-regex {}
  transform-es2015-template-literals {}
  transform-es2015-typeof-symbol {}
  transform-es2015-unicode-regex {}
  transform-regenerator {}
  transform-exponentiation-operator {}
  transform-async-to-generator {}
  syntax-trailing-function-commas {}

From babel-preset-env readme:

The default behavior without options runs all transforms (behaves the same as babel-preset-latest).

This can be fixed if we change the babel-preset-env to the following:

{
  "presets": [
    ["env", {
      "modules": false,
      "targets": {
        "browsers": ["> 1%", "last 2 versions", "not ie <= 8"]
      }
    }],
    "stage-2"
  ],
  "plugins": ["transform-runtime"],
  "env": {
    "test": {
      "presets": ["env", "stage-2"],
      "plugins": ["istanbul"]
    }
  }
}

babel-preset-env DEBUG output - Proposed

babel-preset-env: `DEBUG` option

Using targets:
{
  "android": "4.4",
  "chrome": "49",
  "edge": "14",
  "firefox": "53",
  "ie": "10",
  "ios": "10",
  "safari": "10"
}

Modules transform: false

Using plugins:
  check-es2015-constants {"android":"4.4","ie":"10"}
  transform-es2015-arrow-functions {"android":"4.4","ie":"10"}
  transform-es2015-block-scoped-functions {"android":"4.4","ie":"10"}
  transform-es2015-block-scoping {"android":"4.4","ie":"10"}
  transform-es2015-classes {"android":"4.4","ie":"10"}
  transform-es2015-computed-properties {"android":"4.4","ie":"10"}
  transform-es2015-destructuring {"android":"4.4","chrome":"49","edge":"14","ie":"10"}
  transform-es2015-duplicate-keys {"android":"4.4","ie":"10"}
  transform-es2015-for-of {"android":"4.4","chrome":"49","edge":"14","ie":"10"}
  transform-es2015-function-name {"android":"4.4","chrome":"49","edge":"14","ie":"10"}
  transform-es2015-literals {"android":"4.4","ie":"10"}
  transform-es2015-object-super {"android":"4.4","ie":"10"}
  transform-es2015-parameters {"android":"4.4","ie":"10"}
  transform-es2015-shorthand-properties {"android":"4.4","ie":"10"}
  transform-es2015-spread {"android":"4.4","ie":"10"}
  transform-es2015-sticky-regex {"android":"4.4","ie":"10"}
  transform-es2015-template-literals {"android":"4.4","ie":"10"}
  transform-es2015-typeof-symbol {"android":"4.4","ie":"10"}
  transform-es2015-unicode-regex {"android":"4.4","chrome":"49","ie":"10"}
  transform-regenerator {"android":"4.4","chrome":"49","ie":"10"}
  transform-exponentiation-operator {"android":"4.4","chrome":"49","ie":"10","ios":"10","safari":"10"}
  transform-async-to-generator {"android":"4.4","chrome":"49","edge":"14","ie":"10","ios":"10","safari":"10"}
  syntax-trailing-function-commas {"android":"4.4","chrome":"49","ie":"10"

Should I make a pull request with this or do we want the babel-preset-env pull request to go in and then update the dependency?

[LinusBorg]

Thanks for reporting this! Yes, a PR would be very welcome :)

[sudo-suhas]

Great! Created the PR - #763