Using a solution chunk as a chained setup chunk hides the solution in the UI

[gadenbuie]

In the example below, the second exercise uses the solution to the first exercise as its setup chunk, via the chunk option exercise.setup = "first-solution". As a result, the Solution button is not included in the UI since the solution code isn't added to the HTML.

---
title: "Tutorial"
output: learnr::tutorial
runtime: shiny_prerendered
---

```{r setup, include=FALSE}
library(learnr)
knitr::opts_chunk$set(echo = FALSE)
```

## Topic 1

```{r first, exercise = TRUE}
x <- 1
x + 1
```

```{r first-solution}
x <- 2
x + 1
```

```{r second, exercise = TRUE, exercise.setup="first-solution"}
x + 2
```

```{r second-solution}
x + 2
```

The HTML output for the first exercise in the above is missing the code for the solution.

<div class="tutorial-exercise" data-label="first" data-completion="1" data-diagnostics="1" data-startover="1" data-lines="0">
<pre class="text"><code>x &lt;- 1
x + 1</code></pre>
<script type="application/json" data-ui-opts="1">{"engine":"r","has_checker":false,"caption":"<span data-i18n=\"text.enginecap\" data-i18n-opts=\"{&quot;engine&quot;:&quot;R&quot;}\">R Code<\/span>"}</script>
</div>
<div class="tutorial-exercise-support" data-label="first-solution" data-completion="1" data-diagnostics="1" data-startover="1" data-lines="0">

</div>

The problem doesn't occur if a new chunk is created duplicating the solution chunk:

```{r first-solution2, ref.label="first-solution"}

```

```{r second, exercise = TRUE, exercise.setup="first-solution2"}
x + 2
```

[gadenbuie]

I think the solution here is to remove the complexity around the knitr hooks. Instead of individually writing the tutorial support chunks, we should have the exercise chunk write all of the HTML for the exercise and then we'll disable any kind of output from the support chunks. In addition to simplifying the logic, this would let us re-use chunks between exercises.

Alternatively, if we decouple hints and solutions and let the shiny app control whether the solution button is present (and what that solution is), then we wouldn't even need to write the solution chunk html into the document.

[luk-brue]

I really appreciate that you are working on this, because in the context of chained setup chunks, it would avoid unnecessary duplication of a solution. My current strategy for the tutorials I am working on (GitHub repo) is to duplicate the solution chunk and make it a chained setup chunk for the next exercise. So currently I need:

• a chained setup chunk for the next exercise building on the solution
• a user-viewable solution chunk

Good news might be, that it might probably be possible to address the issue without breaking old tutorials, because the duplication strategy is not broken.