hljs: binding: catch hljs errors when specifying language

the language may not exist. do not crash the entire program due to this

src/blog.rs

@@ -120,7 +120,7 @@ impl Post {
 // library updates. Updaing this value invalidates all
 // existing cache and they will be recompiled when someone
 // visits.
-const CACHE_VERSION: &'static str = "0015";
+const CACHE_VERSION: &'static str = "0017";
 
 // The prefix path used for caching remote images
 pub const IMG_CACHE_PREFIX: &'static str = "/imgcache/";

src/hljs.rs

@@ -12,6 +12,11 @@ pub fn highlight_auto(code: &str) -> String {
 }
 
 pub fn highlight(lang: &str, code: &str) -> String {
-    Reflect::get(&hljs_highlight(lang, code), &"value".into())
-        .unwrap().as_string().unwrap()
+    match hljs_highlight(lang, code) {
+        Ok(res) => Reflect::get(&res, &"value".into())
+                        .unwrap().as_string().unwrap(),
+        // This can throw error if `lang` is not supported
+        // or not imported by build.rs (and thus config.json)
+        Err(_) => code.to_owned()
+    }
 }

src/hljs_tpl.rs

@@ -2,6 +2,6 @@
 extern "C" {
     #[wasm_bindgen(js_name = "highlightAuto")]
     fn hljs_highlight_auto(code: &str) -> JsValue;
-    #[wasm_bindgen(js_name = "highlight")]
-    fn hljs_highlight(lang: &str, code: &str) -> JsValue;
+    #[wasm_bindgen(catch, js_name = "highlight")]
+    fn hljs_highlight(lang: &str, code: &str) -> Result<JsValue, JsValue>;
 }