perf: Stop using unnecessary spread operators

[provokateurin]

Closes #696

[Leptopoda]

I think that everywhere where we had a nested ...[] should use a different approach. I don't like that we now rely on indentation for readability.

Either use an external list and conditionally add to it or use a BuiltList like

BuiltList((final b) {
  for ( element in collection ){
    b.add(element);
  }
})

[provokateurin]

But we will need spread operators for those again, right?

[Leptopoda]

Ah my bad. I meant BuiltList.build():

    final body = SettingsList(
      categories: BuiltList<SettingsCategory>.build((final b) {
        for (final category in [...appImplementation.options.categories, null]) {
          final options = appImplementation.options.options.where((final option) => option.category == category);
          final title = category != null ? category.name(context) : AppLocalizations.of(context).optionsCategoryOther;

          if (options.isEmpty) {
            continue;
          }
          final categoryTile = SettingsCategory(
            title: Text(title),
            tiles: BuiltList<SettingsTile>.build((final b) {
              for (final option in options) {
                if (option is ToggleOption) {
                  b.add(
                    CheckBoxSettingsTile(
                      option: option,
                    ),
                  );
                } else if (option is SelectOption) {
                  b.add(
                    DropdownButtonSettingsTile(
                      option: option,
                    ),
                  );
                }
              }
            }).toList(),
          );

          b.add(categoryTile);
        }
      }).toList(),
    );

this also allows us to do the cache values like the appImplementation.options.options.where wich is also not that cheap.

[provokateurin]

Oh that looks neat!

[provokateurin]

But how do we handle conditionals? Just put the if inside a BuiltList as well?

[Leptopoda]

can you show me an example?

I only want the BuiltList approach where we have nested if/for.

[provokateurin]

I feel like using external lists will be easier to comprehend for new people, so I would prefer that approach.

Doing this refactor will be much more work than I anticipated so I will close this PR and maybe comeback later or someone else can do it as well.