````markdown
---
title: foo
format: commonmark
keep-md: true
---

```{.python filename="matplotlib.py"}
import matplotlib.pyplot as plt
plt.plot([1,23,2,4])
plt.show()
```
````

This outputs with latest 1.3
````markdown
# foo

``` python
import matplotlib.pyplot as plt
plt.plot([1,23,2,4])
plt.show()
```
````

but it outputs with latest 1.2 release
````markdown
foo
================

<div class="code-with-filename">

**matplotlib.py**

``` python
import matplotlib.pyplot as plt
plt.plot([1,23,2,4])
plt.show()
```

</div>

````



It was lost in https://github.com/quarto-dev/quarto-cli/pull/4118/files#diff-3c9439f2bc27c905f44644b44dee252c2d2729b5da73484cbfc22e814137f98d while introducing `DecoratedCodeBlock` I believe. 

@cscheid is it a regression on purpose ? Or could we port back the old behavior ? 

Previously we did 
````lua
    return pandoc.Div(
      { pandoc.Plain{pandoc.Strong{pandoc.Str(filename)}}, el:clone() },
      pandoc.Attr("", {"code-with-filename"})
    )
````
for non HTML format  and now we just return the content of the code block
https://github.com/quarto-dev/quarto-cli/blob/37ce04581238dc036985fcdab20534aaf78732de/src/resources/filters/customnodes/decoratedcodeblock.lua#L106-L109


(from a discussion in https://github.com/quarto-dev/quarto-cli/issues/5101)


cscheid
2023-04-06T14:31:42Z
cderv
bug regression
v1.3
closed
codefilename not shown anymore for md output
https://github.com/quarto-dev/quarto-cli/issues/5112