From 947387a6ba0ed910a06489eb1b83c4ed0d015029 Mon Sep 17 00:00:00 2001
From: Brent Anderson <brent@knock.app>
Date: Wed, 18 Mar 2026 10:58:23 -0500
Subject: [PATCH] fix: catch panics in NIF to prevent BEAM crash

Wraps the css inlining logic in `std::panic::catch_unwind` so any
unexpected Rust panic is converted to a RustlerError instead of
aborting the BEAM VM.
---
 native/css_inline_nif/src/lib.rs | 36 ++++++++++++++++++++------------
 1 file changed, 23 insertions(+), 13 deletions(-)

diff --git a/native/css_inline_nif/src/lib.rs b/native/css_inline_nif/src/lib.rs
index d3e7ca6..0579c49 100644
--- a/native/css_inline_nif/src/lib.rs
+++ b/native/css_inline_nif/src/lib.rs
@@ -33,21 +33,31 @@ struct Options {
 ///   since BEAM-managed data must live on the BEAM heap.
 #[rustler::nif(schedule = "DirtyCpu")]
 fn inline_css(html: &str, opts: Options) -> Result<Vec<u8>, RustlerError> {
-    let estimated_size = (html.len() as f64 * 1.5) as usize;
-    let mut buffer: Vec<u8> = Vec::with_capacity(estimated_size);
-    let inliner = CSSInliner::options()
-        .inline_style_tags(opts.inline_style_tags)
-        .keep_style_tags(opts.keep_style_tags)
-        .keep_link_tags(opts.keep_link_tags)
-        .load_remote_stylesheets(opts.load_remote_stylesheets)
-        .minify_css(opts.minify_css)
-        .build();
+    std::panic::catch_unwind(|| {
+        let estimated_size = (html.len() as f64 * 1.5) as usize;
+        let mut buffer: Vec<u8> = Vec::with_capacity(estimated_size);
+        let inliner = CSSInliner::options()
+            .inline_style_tags(opts.inline_style_tags)
+            .keep_style_tags(opts.keep_style_tags)
+            .keep_link_tags(opts.keep_link_tags)
+            .load_remote_stylesheets(opts.load_remote_stylesheets)
+            .minify_css(opts.minify_css)
+            .build();
 
-    inliner
-        .inline_to(html, &mut buffer)
-        .map_err(|e| RustlerError::Term(Box::new(format!("CSS inlining failed: {}", e))))?;
+        inliner
+            .inline_to(html, &mut buffer)
+            .map_err(|e| RustlerError::Term(Box::new(format!("CSS inlining failed: {}", e))))?;
 
-    Ok(buffer)
+        Ok(buffer)
+    })
+    .map_err(|e| {
+        let msg = e
+            .downcast_ref::<String>()
+            .map(|s| s.as_str())
+            .or_else(|| e.downcast_ref::<&str>().copied())
+            .unwrap_or("unknown panic");
+        RustlerError::Term(Box::new(format!("NIF panic: {}", msg)))
+    })?
 }
 
 rustler::init!("Elixir.CSSInline.Native");