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feat(mermaid): integrate diagram rendering into markdown pipeline

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Intercept 'mermaid' code blocks in render.rs and call
mermaid::render_diagram() to convert to inline SVG.

- Use catch_unwind to handle upstream dagre_rust panics gracefully
- Graceful fallback: show raw code with mermaid-error class on failure
- Flowcharts render correctly; some diagram types hit upstream bugs
This commit is contained in:
Timothy DeHerrera
2026-01-28 20:36:45 -07:00
parent abe465723c
commit d417e1c535
2 changed files with 55 additions and 15 deletions
Download Patch File Download Diff File Expand all files Collapse all files

24
src/mermaid.rs
View File

@@ -3,6 +3,7 @@
//! Converts Mermaid diagram definitions to SVG at build-time.
use mermaid_rs_renderer::RenderOptions;
use std::panic;
/// Render a Mermaid diagram to SVG.
///
@@ -11,9 +12,21 @@ use mermaid_rs_renderer::RenderOptions;
///
/// # Returns
/// The rendered SVG string, or an error message on failure.
///
/// # Note
/// Uses catch_unwind to handle panics in upstream dependencies gracefully.
pub fn render_diagram(code: &str) -> Result<String, String> {
let opts = RenderOptions::modern();
mermaid_rs_renderer::render_with_options(code, opts).map_err(|e| e.to_string())
let code = code.to_owned();
let result = panic::catch_unwind(move || {
let opts = RenderOptions::modern();
mermaid_rs_renderer::render_with_options(&code, opts)
});
match result {
Ok(Ok(svg)) => Ok(svg),
Ok(Err(e)) => Err(e.to_string()),
Err(_) => Err("mermaid rendering panicked (upstream bug)".to_string()),
}
}
#[cfg(test)]
@@ -40,4 +53,11 @@ mod tests {
// May succeed with error node or fail gracefully
assert!(result.is_ok() || result.is_err());
}
#[test]
fn test_state_diagram() {
let result =
render_diagram("stateDiagram-v2\n [*] --> Idle\n Idle --> Processing: Start");
assert!(result.is_ok() || result.is_err());
}
}

46
src/render.rs
View File

@@ -46,23 +46,43 @@ pub fn markdown_to_html(markdown: &str) -> String {
Event::End(TagEnd::CodeBlock) => {
// Render the code block with highlighting
let lang_str = code_block_lang.as_deref().unwrap_or("");
html_output.push_str("<pre><code");
if let Some(lang) = Language::from_fence(lang_str) {
// Supported language: apply tree-sitter highlighting
html_output.push_str(&format!(" class=\"language-{}\">", lang_str));
html_output.push_str(&highlight_code(lang, &code_block_content));
} else {
// Unsupported language: render as plain escaped text
if !lang_str.is_empty() {
html_output.push_str(&format!(" class=\"language-{}\">", lang_str));
} else {
html_output.push('>');
// Mermaid diagrams: render to SVG
if lang_str == "mermaid" {
match crate::mermaid::render_diagram(&code_block_content) {
Ok(svg) => {
html_output.push_str("<div class=\"mermaid-diagram\">\n");
html_output.push_str(&svg);
html_output.push_str("\n</div>\n");
}
Err(e) => {
eprintln!("mermaid render error: {e}");
html_output.push_str("<pre class=\"mermaid-error\"><code>");
html_output.push_str(&html_escape(&code_block_content));
html_output.push_str("</code></pre>\n");
}
}
html_output.push_str(&html_escape(&code_block_content));
} else {
// Code blocks: syntax highlighting
html_output.push_str("<pre><code");
if let Some(lang) = Language::from_fence(lang_str) {
// Supported language: apply tree-sitter highlighting
html_output.push_str(&format!(" class=\"language-{}\">", lang_str));
html_output.push_str(&highlight_code(lang, &code_block_content));
} else {
// Unsupported language: render as plain escaped text
if !lang_str.is_empty() {
html_output.push_str(&format!(" class=\"language-{}\">", lang_str));
} else {
html_output.push('>');
}
html_output.push_str(&html_escape(&code_block_content));
}
html_output.push_str("</code></pre>\n");
}
html_output.push_str("</code></pre>\n");
code_block_lang = None;
code_block_content.clear();
}