collection.getFilteredByTag is not a function when populating collection via API

[piyushpaliwal]

Describe the bug

I am trying to implement the solution for previous and next links on my project (#529). My collections are getting populated via an async API call.

After the collection is populated, I am trying to call the function getFilteredByTag but it fails with the error getFilteredByTag is not a function. I may be doing something wrong but can you help identify what could be going wrong in this case?

Screenshots

Environment:

• OS and Version: Ubuntu 18.04 (WSL)
• Eleventy Version: 0.10.0

Additional context

Below is the collection method that I am utilizing to bring data from my ghost installation.

// Get Featured Posts
eleventyConfig.addCollection("featured", async function (collection) {
    collection = await api.posts
        .browse({
            include: "tags,authors",
            limit: "4",
            order: "published_at desc",
            filter: 'featured:true'
        })
        .catch(err => {
            console.error(err);
        });

    collection.forEach(post => {
        post.url = post.primary_tag.slug + stripDomain(post.url);
        post.primary_author.url = stripDomain(post.primary_author.url);
        post.tags.map(tag => tag.url = stripDomain(tag.url));
        post.authors.map(author => author.url = stripDomain(author.url));
        post.published_at = moment(post.published_at).format("Do MMM YYYY");
    });
    const coll = collection.getFilteredByTag("featured");

    for (let i = 0; i < coll.length; i++) {
        const prevPost = coll[i - 1];
        const nextPost = coll[i + 1];

        coll[i].data["prevPost"] = prevPost;
        coll[i].data["nextPost"] = nextPost;
    }
    return coll;
});

[piyushpaliwal]

I have managed to fix this issue by simply adding nextPost and prevPost in the foreach loop like below:

// Get Featured Posts
    eleventyConfig.addCollection("featured", async function (collection) {
        collection = await api.posts
            .browse({
                include: "tags,authors",
                limit: "4",
                order: "published_at desc",
                filter: 'featured:true'
            })
            .catch(err => {
                console.error(err);
            });
        collection.forEach((post, index) => {
            post.url = post.primary_tag.slug + stripDomain(post.url);
            post.primary_author.url = stripDomain(post.primary_author.url);
            post.tags.map(tag => tag.url = stripDomain(tag.url));
            post.authors.map(author => author.url = stripDomain(author.url));
            post.published_at = moment(post.published_at).format("Do MMM YYYY");
            post.prevPost = collection[index - 1];
            post.nextPost = collection[index + 1];
        });
        return collection;
    });

However I would still like to know if collection methods will be available if it is getting populated via an API.

[zachleat]

I think you’ve misunderstood the argument there. I’ve changed the docs to reflect this but it’s more accurate to read it like this:

eleventyConfig.addCollection("featured", async function (collectionApi) {

So what you’re doing there is effectively monkey patching the collections API, which is probably not what you want. Now, you can return any arbitrary object from your collection but we don’t modify those in any way.

https://www.11ty.dev/docs/collections/#return-values

All of that being said, I don’t think collections are the right mechanism here. JavaScript Data Files will probably work much better https://www.11ty.dev/docs/data-js/

[zachleat]

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