fix(webidl): Don't throw when converting a detached buffer source (#12585)

The Web IDL conversion to `BufferSource` and similar types shouldn't
check whether the buffer is detached.

In the case of `TextDecoder`, our implementation would still throw after
the Web IDL conversions because we're creating a new `Uint8Array` from
the buffer source's buffer, which throws if it's detached. This change
also fixes this bug.

2 files changed, 13 insertions, 51 deletions

diff --git a/ext/web/08_text_encoding.js b/ext/web/08_text_encoding.js
index d3f6d45fb..d2922a6d4 100644
--- a/ext/web/08_text_encoding.js
+++ b/ext/web/08_text_encoding.js
@@ -105,14 +105,19 @@
       }
 
       try {
-        if (ArrayBufferIsView(input)) {
-          input = new Uint8Array(
-            input.buffer,
-            input.byteOffset,
-            input.byteLength,
-          );
-        } else {
-          input = new Uint8Array(input);
+        try {
+          if (ArrayBufferIsView(input)) {
+            input = new Uint8Array(
+              input.buffer,
+              input.byteOffset,
+              input.byteLength,
+            );
+          } else {
+            input = new Uint8Array(input);
+          }
+        } catch {
+          // If the buffer is detached, just create a new empty Uint8Array.
+          input = new Uint8Array();
         }
         if (input.buffer instanceof SharedArrayBuffer) {
           // We clone the data into a non-shared ArrayBuffer so we can pass it
diff --git a/ext/webidl/00_webidl.js b/ext/webidl/00_webidl.js
index fa9d14e65..4cbba195c 100644
--- a/ext/webidl/00_webidl.js
+++ b/ext/webidl/00_webidl.js
@@ -441,15 +441,6 @@
     return V instanceof SharedArrayBuffer;
   }
 
-  function isArrayBufferDetached(V) {
-    try {
-      new Uint8Array(V);
-      return false;
-    } catch {
-      return true;
-    }
-  }
-
   converters.ArrayBuffer = (V, opts = {}) => {
     if (!isNonSharedArrayBuffer(V)) {
       if (opts.allowShared && !isSharedArrayBuffer(V)) {
@@ -461,9 +452,6 @@
       }
       throw makeException(TypeError, "is not an ArrayBuffer", opts);
     }
-    if (isArrayBufferDetached(V)) {
-      throw makeException(TypeError, "is a detached ArrayBuffer", opts);
-    }
 
     return V;
   };
@@ -480,13 +468,6 @@
         opts,
       );
     }
-    if (isArrayBufferDetached(V.buffer)) {
-      throw makeException(
-        TypeError,
-        "is backed by a detached ArrayBuffer",
-        opts,
-      );
-    }
 
     return V;
   };
@@ -529,13 +510,6 @@
             opts,
           );
         }
-        if (isArrayBufferDetached(V.buffer)) {
-          throw makeException(
-            TypeError,
-            "is a view on a detached ArrayBuffer",
-            opts,
-          );
-        }
 
         return V;
       };
@@ -561,13 +535,6 @@
       );
     }
 
-    if (isArrayBufferDetached(V.buffer)) {
-      throw makeException(
-        TypeError,
-        "is a view on a detached ArrayBuffer",
-        opts,
-      );
-    }
     return V;
   };
 
@@ -581,13 +548,6 @@
         );
       }
 
-      if (isArrayBufferDetached(V.buffer)) {
-        throw makeException(
-          TypeError,
-          "is a view on a detached ArrayBuffer",
-          opts,
-        );
-      }
       return V;
     }
 
@@ -609,9 +569,6 @@
         opts,
       );
     }
-    if (isArrayBufferDetached(V)) {
-      throw makeException(TypeError, "is a detached ArrayBuffer", opts);
-    }
 
     return V;
   };