[Bug]: Opera mobile equated to Opera desktop in preset-env

[steverep]

💻

• Would you like to work on a fix?

How are you using Babel?

babel-loader (webpack)

Input code

n/a

Configuration file name

babel.config.js

Configuration

{
  "targets": "defaults",
  "presets": ["@babel/preset-env"]
}

Current and expected behavior

When obtaining targets from browserslist, preset-env seems to select the Opera version based on the minimum of "opera" (Opera desktop) and "op_mob" (Opera mobile for Android). This is not appropriate as they have different release cycles and their version numbers are not in sync.

This similar scenario was recently fixed in browserslist version 4.21.9, so that a typical "defaults" query would return a valid op_mob version. However, because of Babel's current treatment, equating the two, a target of Opera 73 is selected (latest Opera for Android) instead of Opera 99 (Opera desktop latest). Since the compatibility data is based on Opera desktop, this causes unnecessary extra transpilation.

Please see browserslist/browserslist#766 (comment) for greater detail.

Environment

core/preset-env 7.22.5
browserslist 4.21.9

Possible solution

Short term fix would be to ignore op_mob in browserslist results.

Longer term, consider adding separate compatibility data for op_mob.

Additional context

No response

[babel-bot]

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[steverep]

The equivalency happens here:

babel/packages/babel-helper-compilation-targets/src/targets.ts

Line 20 in 33dbb85

op_mob: "opera",

Just deleting that would ignore it from browserslist I think, but it's not at all clear if that would have unintended side effects.