Render Mustache tags as typed spans

python/xhtmlmd/__init__.py

@@ -3,10 +3,10 @@
 __all__ = ["to_xhtml", "render", "blocks", "rewrite"]
 
 
-def to_xhtml(markdown: str, *, math: str = "brackets", tagfilter: bool = False, balance: bool = False, callbacks: dict | None = None,
+def to_xhtml(markdown: str, *, math: str = "brackets", mustache: bool = True, tagfilter: bool = False, balance: bool = False, callbacks: dict | None = None,
     max_inline_depth: int | None = None, max_block_depth: int | None = None, max_link_paren_depth: int | None = None) -> str:
     "Render Markdown to an XHTML fragment."
-    return _to_xhtml(markdown, math=math, tagfilter=tagfilter, balance=balance, callbacks=callbacks, max_inline_depth=max_inline_depth,
+    return _to_xhtml(markdown, math=math, mustache=mustache, tagfilter=tagfilter, balance=balance, callbacks=callbacks, max_inline_depth=max_inline_depth,
         max_block_depth=max_block_depth, max_link_paren_depth=max_link_paren_depth)
 
 

src/inline.rs

@@ -193,6 +193,14 @@ fn parse_inner(src: &str, ctx: &InlineContext<'_>, depth: usize) -> Vec<Inline>
     let mut failed = FailedScans::default();
     let mut i = 0;
     while i < src.len() {
+        if ctx.options.mustache && starts(src, i, "{{") {
+            if let Some((item, next)) = mustache(src, i) {
+                scanner.flush_text();
+                scanner.push_inline(item);
+                i = next;
+                continue;
+            }
+        }
         if starts(src, i, "\\[")
             && matches!(ctx.options.math, MathMode::Brackets | MathMode::Dollars)
         {
@@ -420,6 +428,9 @@ fn plain_text_fast_path(src: &str, ctx: &InlineContext<'_>) -> bool {
     if src.contains("==") {
         return false;
     }
+    if ctx.options.mustache && src.contains("{{") {
+        return false;
+    }
     if ctx.options.math == MathMode::Dollars && src.contains('$') {
         return false;
     }
@@ -437,6 +448,24 @@ fn plain_text_fast_path(src: &str, ctx: &InlineContext<'_>) -> bool {
     !can_link_or_span
 }
 
+fn mustache(src: &str, i: usize) -> Option<(Inline, usize)> {
+    let end = src[i + 2..].find("}}")? + i + 4;
+    let body = src[i + 2..end - 2].trim_start();
+    let class = match body.chars().next() {
+        Some('#' | '^' | '/') => "mustache.section",
+        Some('!') => "mustache.comment",
+        Some('>') => "mustache.partial",
+        _ => "mustache.placeholder",
+    };
+    Some((
+        Inline::Span {
+            attrs: Attr::with_class(class),
+            children: vec![Inline::Html(src[i..end].to_string())],
+        },
+        end,
+    ))
+}
+
 struct InlineScanner<'a, 'b> {
     src: &'a str,
     ctx: &'b InlineContext<'b>,

src/lib.rs

@@ -34,6 +34,7 @@ pub enum MathMode {
 #[derive(Clone, Debug)]
 pub struct Options {
     pub math: MathMode,
+    pub mustache: bool,
     pub tagfilter: bool,
     pub balance: bool,
     pub max_inline_depth: usize,
@@ -45,6 +46,7 @@ impl Default for Options {
     fn default() -> Self {
         Self {
             math: MathMode::Brackets,
+            mustache: true,
             tagfilter: false,
             balance: false,
             max_inline_depth: 64,

src/python.rs

@@ -14,6 +14,7 @@ use crate::{MathMode, Options};
     markdown,
     *,
     math = "brackets",
+    mustache = true,
     tagfilter = false,
     balance = false,
     callbacks = None,
@@ -24,6 +25,7 @@ use crate::{MathMode, Options};
 fn to_xhtml(
     markdown: &str,
     math: &str,
+    mustache: bool,
     tagfilter: bool,
     balance: bool,
     callbacks: Option<Bound<'_, PyDict>>,
@@ -33,6 +35,7 @@ fn to_xhtml(
 ) -> PyResult<String> {
     let mut options = Options {
         math: parse_math_mode(math)?,
+        mustache,
         tagfilter,
         balance,
         ..Options::default()

tests/test_python.py

@@ -37,6 +37,21 @@ def test_invalid_math_mode_raises():
     with pytest.raises(ValueError, match="math must be"): to_xhtml("x", math="inline")
 
 
+def test_mustache_placeholders_are_opaque_and_can_be_disabled():
+    src = "{{name.name}} {{#items}} {{/items}} {{^empty}} {{/empty}} {{! comment}} {{> partial}} {{*markdown*}}"
+    html = to_xhtml(src)
+    assert html.count('class="mustache.placeholder"') == 2
+    assert html.count('class="mustache.section"') == 4
+    assert html.count('class="mustache.comment"') == 1
+    assert html.count('class="mustache.partial"') == 1
+    assert '<span class="mustache.placeholder">{{name.name}}</span>' in html
+    assert '<span class="mustache.section">{{#items}}</span>' in html
+    assert '<span class="mustache.comment">{{! comment}}</span>' in html
+    assert '<span class="mustache.partial">{{> partial}}</span>' in html
+    assert "{{*markdown*}}" in html and "<em>markdown</em>" not in html
+    assert_html(to_xhtml("{{*markdown*}}", mustache=False), "<p>{{<em>markdown</em>}}</p>")
+
+
 def test_node_callback_can_override_heading():
     calls = []