Remove deprecated default exports from public entry points (#1759)

[robhogan]

Summary:

Remove the deprecated default-object export from Metro packages. The supported public API is now exclusively named exports, so any consumer importing a Metro package's default - directly, or implicitly via Babel/TypeScript esModuleInterop - will break and must migrate to named imports.

This affects the public entry points of metro, metro-config, metro-cache, metro-core, metro-resolver, metro-source-map, metro-babel-transformer, and metro-transform-worker.

Default imports like these will no longer work:

import metro from 'metro';
metro.runServer(config);

import metroConfig from 'metro-config';
const config = await metroConfig.loadConfig();

const metro = require('metro').default;
metro.runBuild(config, options);

Switch to named imports instead:

import {runServer, runBuild} from 'metro';
import {loadConfig, mergeConfig} from 'metro-config';

runServer(config);

const {runBuild} = require('metro');
runBuild(config, options);

Namespace imports are unaffected and continue to work, since they bind the package's named exports:

import * as metro from 'metro';
metro.runServer(config);

Changelog: [Breaking] Removed the deprecated default export from Metro's public packages; use named (or namespace) imports instead.

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Reviewed By: huntie

Differential Revision: D110062342

[meta-codesync]

@robhogan has exported this pull request. If you are a Meta employee, you can view the originating Diff in D110062342.