Enable math extension

This ensures LaTeX/MathJax blocks don't get mangled as seen in
https://github.com/zoni/obsidian-export/issues/14.

changelog.d/14.breaking.md

@@ -0,0 +1 @@
+252.breaking.md

changelog.d/14.fix.md

@@ -0,0 +1,4 @@
+Don't escape square brackets in math expressions
+
+The upgrade to [pulldown-cmark](https://crates.io/crates/pulldown-cmark) 0.11 (see Backwards-incompatible Changes) includes official support for LaTeX-style math expressions.
+With the markdown parser supporting this syntax natively, math expressions are now processed correctly without edge-cases.

changelog.d/252.fix.md

@@ -0,0 +1 @@
+14.fix.md

changelog.d/259.breaking.md

@@ -0,0 +1 @@
+252.breaking.md

src/lib.rs

@@ -483,11 +483,11 @@ impl<'a> Exporter<'a> {
         let frontmatter =
             frontmatter_from_str(&frontmatter).context(FrontMatterDecodeSnafu { path })?;
 
-        let mut parser_options = Options::empty();
+        let parser_options = Options::ENABLE_TABLES
-        parser_options.insert(Options::ENABLE_TABLES);
+            | Options::ENABLE_FOOTNOTES
-        parser_options.insert(Options::ENABLE_FOOTNOTES);
+            | Options::ENABLE_STRIKETHROUGH
-        parser_options.insert(Options::ENABLE_STRIKETHROUGH);
+            | Options::ENABLE_TASKLISTS
-        parser_options.insert(Options::ENABLE_TASKLISTS);
+            | Options::ENABLE_MATH;
 
         let mut ref_parser = RefParser::new();
         let mut events = vec![];

tests/testdata/expected/main-samples/math.md

@@ -0,0 +1,11 @@
+This sentence uses `$` delimiters to show math inline:  $\sqrt{3x-1}+(1+x)^2$
+
+This is the same math expression expressed as a block element:
+$$\sqrt{3x-1}+(1+x)^2$$
+
+<!-- https://github.com/zoni/obsidian-export/issues/14 -->
+
+With square brackets (inline): $[0, 2\pi]$
+
+With square brackets (block):
+$$[0, 2\pi]$$

tests/testdata/input/main-samples/math.md

@@ -0,0 +1,10 @@
+This sentence uses `$` delimiters to show math inline:  $\sqrt{3x-1}+(1+x)^2$
+
+This is the same math expression expressed as a block element:
+$$\sqrt{3x-1}+(1+x)^2$$
+
+<!-- https://github.com/zoni/obsidian-export/issues/14 -->
+With square brackets (inline): $[0, 2\pi]$
+
+With square brackets (block):
+$$[0, 2\pi]$$