What does this error means? "use the async read() method on the template instead"

[Julianoe]

Trying to run Eleventy in 2.0 version using a fork of eleventy-garden and I get this error

Original error stack trace: Error: Unfortunately you’re using code that monkey patched some Eleventy internals and it isn’t async-friendly. Change your code to use the async `read()` method on the template instead!
[11ty]     at get frontMatter [as frontMatter] (/USER/eleventy-garden/node_modules/@11ty/eleventy/src/TemplateContent.js:133:13)
[11ty]     at Object.backlinks (/USER/eleventy-garden/notes/notes.11tydata.js:23:56)

the code it is pointing at is the following:

module.exports = {
    layout: "note",
    type: "note",
    // permalink: "{{ page.filePathStem | customSlugifyPath }}/", // if you want subfolder structure to be repercuted
    permalink: "/notes/" + "{{ page.fileSlug | customSlugifyPath }}/",
    eleventyComputed: {
        title: data => data.title || data.page.fileSlug,
        backlinks: (data) => {
            const notes = data.collections.notes;
            const currentFileSlug = data.page.filePathStem.replace('/notes/', '');

            let backlinks = [];

            // Search the other notes for backlinks
            for(const otherNote of notes) {
                const noteContent = otherNote.template.frontMatter.content;

(source)

I'm simply trying to understand what it means. Where can I read about this "async read() method" ?

[leoossa]

To solve this change backlinks to async:

backlinks: async (data) => {

and await to template read:

const template = await otherNote.template.read()
const noteContent = template.content;

Here's the diff for you:

diff --git a/notes/notes.11tydata.js b/notes/notes.11tydata.js
index 8b22ef8..7d410e7 100644
--- a/notes/notes.11tydata.js
+++ b/notes/notes.11tydata.js
@@ -12,7 +12,7 @@ module.exports = {
     type: "note",
     eleventyComputed: {
         title: data => titleCase(data.title || data.page.fileSlug),
-        backlinks: (data) => {
+        backlinks: async (data) => {
             const notes = data.collections.notes;
             const currentFileSlug = data.page.filePathStem.replace('/notes/', '');
 
@@ -20,7 +20,8 @@ module.exports = {
 
             // Search the other notes for backlinks
             for(const otherNote of notes) {
-                const noteContent = otherNote.template.frontMatter.content;
+                const template = await otherNote.template.read()
+                const noteContent = template.content;
 
                 // Get all links from otherNote
                 const outboundLinks = (noteContent.match(wikilinkRegExp) || [])

[Julianoe]

I know it was 3 years ago. But life happened.
I went back to my project to upgrade my website and found this very issue googling for the same error message.
I fixed it thanks to you and now it works. Thanks!