Markdown code blocks strip leading whitespace

[CAD97]

Example: https://crates.io/crates/slice-dst

The readme for that crate contains the code block

```text
                                             +--------------+
                                             |Node          |
                                       +---->|data: "a"     |
+------------+    +---------------+    |     |children: none|
|Node        |    |Vec<Arc<Node>> |    |     +--------------+
|data: "abc" |    |[0]: +--------------+     |Node          |
|children: +----->|[1]: +------------------->|data: "b"     |
+------------+    |[2]: +--------------+     |children: none|
                  +---------------|    |     +--------------+
                                       |     |Node          |
                                       +---->|data: "c"     |
                                             |children: none|
                                             +--------------+
```

which shows up on crates-io as

+--------------+
                                             |Node          |
                                       +---->|data: "a"     |
+------------+    +---------------+    |     |children: none|
|Node        |    |Vec<Arc<Node>> |    |     +--------------+
|data: "abc" |    |[0]: +--------------+     |Node          |
|children: +----->|[1]: +------------------->|data: "b"     |
+------------+    |[2]: +--------------+     |children: none|
                  +---------------|    |     +--------------+
                                       |     |Node          |
                                       +---->|data: "c"     |
                                             |children: none|
                                             +--------------+

For comparison purposes, lib-rs renders this correctly.

github

crates-io

lib-rs

[jtgeibel]

I was hoping bumping to the latest version of comrak in #2513 would resolve this, but that doesn't appear to be the case. I haven't had a chance trace through the readme logic to see if this is being removed by comrak or some other step in the HTML sanitation process.

[jtgeibel]

I've dug into this a bit more, and it looks like this is a frontend issue with syntax highlighting. The rendered reame looks fine when loaded directly from https://static.crates.io/readmes/slice-dst/slice-dst-1.4.1.html

If I remove the {{highlight-syntax selector="pre > code"}} from

crates.io/app/templates/crate/version.hbs

Line 60 in 6c3efa2

<section local-class="crate-readme" aria-label="Readme" {{highlight-syntax selector="pre > code"}}>

then the issue goes away, although this is obviously a loss of functionality.

[Turbo87]

interesting, I'll have a look!