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Keep the code language when stripping CSS classes - #51
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Markdig records a fenced code block's language as class="language-xxx" on the <code> element. The cleanup regex stripped every class attribute, so the only record of the language was destroyed and a round-trip turned ```csharp back into a bare ```. The HTML to Markdown direction already reads the language-* class correctly, so the fix is limited to not throwing it away: the regex now skips class attributes whose value starts with "language-" and continues to strip everything else, which is what Loop needs. Un-skips the round-trip test that documented the bug. Two tests that asserted the old behaviour are updated: one claimed no class attribute survives at all, and the other expected the language to be lost. Non-language stripping is now covered by a custom container, which renders <div class="warning">. Fixes #34 Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com> Copilot-Session: b721ad5f-9add-4f55-b9c8-7e6d7b0fb3e7
This was referenced Aug 28, 2026
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Fixes #34
Markdig records a fenced code block's language as
class="language-xxx"on the<code>element.LoopHtmlConverterthen stripped every class attribute with a blanket regex, which destroyed the only record of the language. A round-trip turned```csharpback into a bare```.The HTML to Markdown direction already reads the
language-*class correctly (that came in with the<pre>fix for #19), so the bug was entirely in the stripping step. The regex now skips class attributes whose value starts withlanguage-and strips everything else, which is what Loop actually needs.Test changes worth a look
Un-skipping the round-trip test made two existing tests fail, both because they asserted the old buggy behaviour:
Convert_StripsCssClassesassertedclass=never appears in the output at all. Replaced with two narrower tests: one that the language class survives, one that a non-language class does not.FencedCode_SurvivesARoundTrip_ExceptTheLanguageexpected the language to be lost. Removed, sinceFencedCode_KeepsItsLanguagenow covers the same input with the correct expectation.For the "non-language classes are still stripped" case I used a custom container (
:::warning), because I wanted a class that Markdig genuinely emits rather than a guess. I verified the actual renderer output first::::warningproduces<div class="warning">before stripping and<div>after, so the assertion cannot pass vacuously.Verification
Full suite: 85 passed, 0 failed, 2 skipped. The two remaining skips are the still-open bugs #32 and #33.
Base branch
This targets
test/23-converter-tests(PR #41) because the converters live inmd2loop.Coreand the test suite only exists on that branch. It needs to merge after #41.