Bug: TypeError in Rollup build: parseRequestedNames doesn't handle array input correctly

[nakjun12]

React version: 18.x.x up to latest
Node version: 16.x.x up to latest

Steps To Reproduce

1. Clone the React repository.
2. Run: yarn install
3. Run either:
   • yarn build-for-devtools-dev
   • yarn build-for-devtools-prod

Link to code example:

• Relevant code: scripts/rollup/build.js (line 72)
• Relevant function: parseRequestedNames

The current behavior:

https://github.com/facebook/react/assets/111031253/80d3b45c-d93d-4ffe-a801-c4494582f14f

When running the commands yarn build-for-devtools-dev or yarn build-for-devtools-prod, a TypeError is thrown: names[i].split is not a function. This is evident in the provided screenshot. The error originates from the parseRequestedNames function in scripts/rollup/build.js.

The problem stems from how the argv.type value is handled. In these specific commands, argv.type is passed as an array (e.g., ['NODE', 'NODE_DEV']), but the code incorrectly wraps it in another array:

const requestedBundleTypes = argv.type
  ? parseRequestedNames([argv.type], 'uppercase') // Incorrect wrapping
  : [];

The parseRequestedNames function then attempts to apply the .split(',') method to each element of names, expecting them to be strings. However, due to the erroneous wrapping, it encounters an array instead, leading to the TypeError.

function parseRequestedNames(names, toCase) {
  let result = [];
  for (let i = 0; i < names.length; i++) {
    let splitNames = names[i].split(',');
    for (let j = 0; j < splitNames.length; j++) {
      let name = splitNames[j].trim();
      if (!name) {
        continue;
      }
      if (toCase === 'uppercase') {
        name = name.toUpperCase();
      } else if (toCase === 'lowercase') {
        name = name.toLowerCase();
      }
      result.push(name);
    }
  }
  return result;
}

The expected behavior:

The yarn build-for-devtools-dev or yarn build-for-devtools-prod commands should run without errors. The argv.type value should be handled correctly even when passed as an array, and bundle type filtering should work as expected.

Additional information:

• The yarn build or yarn build-for-devtools commands work without issues because the argv.type value is passed as a string or undefined.
• The parseRequestedNames function generates requestedBundleTypes and requestedBundleNames arrays based on the provided names (argv.type or argv._). These arrays are used for bundle filtering in the shouldSkipBundle function.