Fix potential null error in JsValue::as_debug_string() (#4192)

CHANGELOG.md

@@ -25,6 +25,9 @@
 * Fixed `#[should_panic]` not working with `#[wasm_bindgen_test(unsupported = ...)]`.
   [#4196](https://github.com/rustwasm/wasm-bindgen/pull/4196)
 
+* Fixed potential `null` error when using `JsValue::as_debug_string()`.
+  [#4192](https://github.com/rustwasm/wasm-bindgen/pull/4192)
+
 --------------------------------------------------------------------------------
 
 ## [0.2.95](https://github.com/rustwasm/wasm-bindgen/compare/0.2.94...0.2.95)

crates/cli-support/src/js/mod.rs

@@ -1958,7 +1958,6 @@ __wbg_set_wasm(wasm);"
                 if (!(instance instanceof klass)) {
                     throw new Error(`expected instance of ${klass.name}`);
                 }
-                return instance.ptr;
             }
             ",
         );
@@ -3986,7 +3985,7 @@ __wbg_set_wasm(wasm);"
                 // Test for built-in
                 const builtInMatches = /\\[object ([^\\]]+)\\]/.exec(toString.call(val));
                 let className;
-                if (builtInMatches.length > 1) {
+                if (builtInMatches && builtInMatches.length > 1) {
                     className = builtInMatches[1];
                 } else {
                     // Failed to match the standard '[object ClassName]'

crates/cli/tests/reference/web-sys.js

@@ -90,7 +90,7 @@ function debugString(val) {
     // Test for built-in
     const builtInMatches = /\[object ([^\]]+)\]/.exec(toString.call(val));
     let className;
-    if (builtInMatches.length > 1) {
+    if (builtInMatches && builtInMatches.length > 1) {
         className = builtInMatches[1];
     } else {
         // Failed to match the standard '[object ClassName]'