Allow specifying locale in `lexicographicSortSchema`

[vhenzl]

I use lexicographicSortSchema() to get a stable output when generating TS types from GraphQL schema and recently I discovered a problem when a field called chemicalName is misplaced and causing a diff.

The reason is that one of my machines has non-English, Czech locale and in Czech alphabet, the digraph Ch is handled as a single letter and sorted between H and I.

Example

const items = ['xx', 'aa', 'dd', 'cx', 'ch', 'cc'];

items.sort((a, b) => a.localeCompare(b, 'en'));
// ["aa", "cc", "ch", "cx", "dd", "xx"]

items.sort((a, b) => a.localeCompare(b, 'cs'));
// ["aa", "cc", "cx", "dd", "ch", "xx"]

Would be great if lexicographicSortSchema() could accept locales and possibly also options parameters for localeCompare to be able to force a particular (English) locale for the schema sorting independently on the machine's locale.

[IvanGoncharov]

@vhenzl Thanks for taking the time to open this issue.
Since we sort only identifiers and GraphQL restricts them to A-Za-z0-9_ I think supporting custom locales is overkill and complicates APIs.
As a solution to different default locales, we can write a super simple function that compares characters based on position in ASCII tables.
What do you think?

[vhenzl]

Hi @IvanGoncharov! First of all, sorry for the late answer. And thanks for looking into it.

You are probably right, supporting locales is likely overkill. Using a simple character comparison would for sure work for my use case. My objective here is to get a stable order regardless of system locale, but not necessarily alphabetically/lexicographically correct order. Which I guess should suit most of the graphql users; but possibly not all.

Since the alphabet is restricted to English letters, only digraphs (trigraphs?) and letter case are interesting in terms of sorting. There is a handful of languages that sort digraphs in special ways, most other languages threat them as combinations of separate letters.

With a simple character comparison, words with digraphs would be placed differently than they should be in the given language. However, for someone to be really affected by that, it would mean that names in the sorted GraphQL schema are in that non-English language (who doesn't use English for programming?) and that the order really matters for the given use case (maybe something like a table of contents). So to cut a long story short, the chances that it would affect someone negatively are IMO minimal.

I'm not so sure about different order for letter cases tho, because it would affect all languages:

function ascii(x, y) {
  if(x > y) return 1; 
  if(x < y) return -1; 
  return 0
}

function asciiUpperCase(xx, yy) {
  const x = xx.toUpperCase(); 
  const y = yy.toUpperCase(); 
  if(x > y) return 1; 
  if(x < y) return -1; 
  return 0
}

const a = ['c', 'b', 'a', 'Ab', 'ab', 'AB', 'aB', '10', '5', 'C', 'B', 'A'];

[...a].sort(asciiUpperCase) 
// ["10", "5", "a", "A", "Ab", "ab", "AB", "aB", "b", "B", "c", "C"]

[...a].sort(ascii) // same as [...a].sort() 
// ["10", "5", "A", "AB", "Ab", "B", "C", "a", "aB", "ab", "b", "c"]

[...a].sort((x, y) => x.localeCompare(y, 'cs')) // same as 'en' locale
// ["10", "5", "a", "A", "ab", "aB", "Ab", "AB", "b", "B", "c", "C"]

So names using camelCase would be sorted differently then they are now.

---

As for the #2876 PR, I'm not sure I understand what is findBreakingChanges.js about, but it seems that you are sorting only fields. But the problem here applies to all names (types, inputs,…), not just fields. So I believe that sortBy function in lexicographicSortSchema.js should be modified. Before I noticed your PR, I was about to create my own with something like this:

function sortBy<T>(
  array: $ReadOnlyArray<T>,
  mapToKey: (T) => string,
): Array<T> {
  return array.slice().sort((obj1, obj2) => {
    const key1 = mapToKey(obj1).toUpperCase();
    const key2 = mapToKey(obj2).toUpperCase();
    if (key1 > key2) {
      return 1;
    }
    if (key1 < key2) {
      return -1;
    }
    return 0;
  });
}

I tried the change locally on my project and it works just fine. Using toUpperCase gives me the same order (apart from names with the ch digraph) like the original algorithm with localeCompare; comparing keys in the original case leads to a different order for some names.