Add sort option to Collection glob() loader

[xingwangzhe]

Body

Currently, content collections are generated unsorted(just by file name?).

Proposal: Pre-sort collections at generation time via glob():

const posts = defineCollection({
  loader: glob({ 
    base: "src/content/posts", 
    pattern: "**/*.md",
    sort: { (a, b) => b.data.date - a.data.date) }  // sort once at collection build
  }),
});

Pages then consume pre-sorted data directly:

const posts = await getCollection('posts'); // already sorted

Benefits:

• Reduced computation during page builds
• No repeated sorting logic

Optional, fully backward compatible.

[MoritzLost]

+1 from me, I'm also missing this feature. Though I would like to see this as an option for defineCollection, not just the glob loader. Or at least for both glob() and file().

My use-case is as follows. I have a file photos.json with a list of photos I want to display in order:

[
    "./photos/edinburgh_06.jpg",
    "./photos/edinburgh_09.jpg",
    "./photos/paris_2019_11.jpg",
    "./photos/den_haag_07.jpg",
    "./photos/amsterdam_02.jpg"
]

Then I define a collection based on this file with the file loader:

loader: file(
    'src/content/photos.json',
    {
        parser: (json) => {
            const content = JSON.parse(json);
            return content.map((image: string) => ({
                id: image,
                image,
            }))
        }
    }
)

The problem is that the collection is sorted alphabetically by ID (at least in the moment, looks like this isn't guaranteed). So I would have to manually sort the collection everywhere I want to use it. That's annoying and easy to forget.

As a workaround, I've modified the IDs to make sure they match the order I want:

id: `${String(index).padStart(4, '0')}-${image}`,

But that isn't guaranteed to work, as the sort order of collections isn't guaranteed, either.

This could be improved in several ways, for example:

• Just guarantee that the collection items will be in the same order in which they're returned from the parser.
• Add an optional retainSortOrder parameter to defineCollection() to opt-in to this behaviour.
• Add an optional sort callback to defineCollection() to allow me to define a sort order for the collection that is used whenever getCollection() is called.