The Firebase documentation claims:

A function calling a transaction (transaction function) might run more than once if a concurrent edit affects a document that the transaction reads.

It is unclear exactly which function will run twice when there is a concurrent edit. In the example below, outerFunc calls the runTranscation method, so a literal interpretation of the documentation would imply that that outerFunc may be called twice.

However, this seems like a strange implementation, and I suspect that the docs mean to say that innerFunc may be called more than once when there is a concurrent edit.

import { runTransaction } from "firebase/firestore";

function outerFunc () {
  console.log('outerFunction');
  try {
    await runTransaction(db, async function innerFunc(transaction) {
      const sfDoc = await transaction.get(sfDocRef);
      if (!sfDoc.exists()) {
        throw "Document does not exist!";
      }

      const newPopulation = sfDoc.data().population + 1;
      transaction.update(sfDocRef, { population: newPopulation });
    });
    console.log("Transaction successfully committed!");
  } catch (e) {
    console.log("Transaction failed: ", e);
  }
}

Could outerFunc be called twice when there is a concurrent edit as the doc imply?