I've noticed that when I have an Rmd with runtime: shiny in the YAML, code chunks don't seem to be read from cache. I'm wondering if using the shiny engine for rmarkdown just doesn't support chunk caching, or am I doing something wrong?
Example Rmd file:
---
title: "Cache test"
output: html_document
---
```{r cache=TRUE}
Sys.sleep(10)
```
If you run this 5 times, only the first time will take 10 seconds, and any subsequent run will be fast.
But if you add the runtime: shiny option to the YAML, then every single run will take 10 seconds.
(PS question: any better way to test whether or not code chunks cache is being used?)
i ran into the same problem where, in runtime: shiny, the cache switch was ignored.
Nowadays there is a workaround, using runtime: shiny_prerendered and context="data" with cache=TRUE:
---
title: "Cache test"
output: html_document
runtime: shiny_prerendered
---
```{r,context="data", cache=TRUE}
Sys.sleep(10)
```
this behaves as expected; on the first run, rendering takes 10 seconds; on all subsequent runs, the cached chunk is used.