sourceType: 'unambiguous' ignores type imports/exports

[jedwards1211]

Bug Report

• I would like to work on a fix!

Current behavior
A clear and concise description of the behavior.

• REPL, Codesandbox, or GitHub Repo helps!

If a file only contains type imports or exports, Babel seems to assume the source type is script. Consequently, a value import inserted by a plugin (babel-plugin-flow-runtime) never gets transpiled by plugin-transform-modules-commonjs.

gajus/flow-runtime#242

I'm not sure if this is intentional or fixable or not? I know sourceType: 'unambiguous' is probably governed by a grammar spec that doesn't deal with type imports or exports. But maybe the unexpected issue I'm running into with this is worth thinking about.

Input Code

// @flow

export type ConnectionStatus = 'connecting' | 'connected' | 'error'

Expected behavior
A clear and concise description of what you expected to happen (or code).

import statements inserted by plugins get transpiled by plugin-transform-modules-commonjs.

Babel Configuration (babel.config.js, .babelrc, package.json#babel, cli command, .eslintrc)

• Filename: babel.config.js

{
  "plugins": [
    ["@babel/plugin-proposal-decorators", {"legacy": true}],
    "babel-plugin-flow-runtime"
  ],
  "presets": [
    ["@babel/preset-env", {"targets": {"node": "current"}}],
    "@babel/preset-flow"
  ],
  "sourceType": "unambiguous"
}

Environment

  System:
    OS: macOS 10.15.3
  Binaries:
    Node: 12.16.2 - ~/.nvm/versions/node/v12.16.2/bin/node
    Yarn: 1.19.1 - /usr/local/bin/yarn
    npm: 6.14.4 - ~/.nvm/versions/node/v12.16.2/bin/npm
  npmPackages:
    @babel/cli: ^7.10.0 => 7.10.0 
    @babel/core: ^7.10.0 => 7.10.0 
    @babel/plugin-proposal-decorators: ^7.10.0 => 7.10.0 
    @babel/preset-env: ^7.10.0 => 7.10.0 
    @babel/preset-flow: ^7.9.0 => 7.9.0 
    babel-plugin-flow-runtime: ^0.19.0 => 0.19.0 

[babel-bot]

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