Using cached remote context

[jg10-mastodon-social]

My understanding is that this library will fetch a remote context every time a document with a remote context is parsed.

This can lead to the context server replying with 429 Too many requests, and parsing failing.

A workaround is to download a local copy of the context in question and replace it before parsing through string operations, e.g.

fileName <- "activitystreams.jsonld"
context <- readChar(fileName, file.info(fileName)$size)
contents <- sub('"https://www.w3.org/ns/activitystreams"', context, contents)