Revert "Fix logic around attribute seralization (facebook#26526)"

This reverts commit 4a1cc2d.

Author: kassens

packages/react-dom-bindings/src/server/ReactDOMServerFormatConfig.js

@@ -3926,51 +3926,48 @@ function writeStyleResourceAttributeInJS(
       return;
 
     // Attribute renames
-    case 'className': {
+    case 'className':
       attributeName = 'class';
-      if (__DEV__) {
-        checkAttributeStringCoercion(value, attributeName);
-      }
-      attributeValue = '' + (value: any);
       break;
-    }
+
     // Booleans
-    case 'hidden': {
+    case 'hidden':
       if (value === false) {
         return;
       }
       attributeValue = '';
       break;
-    }
+
     // Santized URLs
     case 'src':
     case 'href': {
-      value = sanitizeURL(value);
       if (__DEV__) {
         checkAttributeStringCoercion(value, attributeName);
       }
-      attributeValue = '' + (value: any);
+      value = sanitizeURL(value);
       break;
     }
     default: {
-      if (
-        // unrecognized event handlers are not SSR'd and we (apparently)
-        // use on* as hueristic for these handler props
-        name.length > 2 &&
-        (name[0] === 'o' || name[0] === 'O') &&
-        (name[1] === 'n' || name[1] === 'N')
-      ) {
-        return;
-      }
       if (!isAttributeNameSafe(name)) {
         return;
       }
-      if (__DEV__) {
-        checkAttributeStringCoercion(value, attributeName);
-      }
-      attributeValue = '' + (value: any);
     }
   }
+
+  if (
+    // shouldIgnoreAttribute
+    // We have already filtered out null/undefined and reserved words.
+    name.length > 2 &&
+    (name[0] === 'o' || name[0] === 'O') &&
+    (name[1] === 'n' || name[1] === 'N')
+  ) {
+    return;
+  }
+
+  if (__DEV__) {
+    checkAttributeStringCoercion(value, attributeName);
+  }
+  attributeValue = '' + (value: any);
   writeChunk(destination, arrayInterstitial);
   writeChunk(
     destination,
@@ -4122,53 +4119,48 @@ function writeStyleResourceAttributeInAttr(
       return;
 
     // Attribute renames
-    case 'className': {
+    case 'className':
       attributeName = 'class';
-      if (__DEV__) {
-        checkAttributeStringCoercion(value, attributeName);
-      }
-      attributeValue = '' + (value: any);
       break;
-    }
 
     // Booleans
-    case 'hidden': {
+    case 'hidden':
       if (value === false) {
         return;
       }
       attributeValue = '';
       break;
-    }
 
     // Santized URLs
     case 'src':
     case 'href': {
-      value = sanitizeURL(value);
       if (__DEV__) {
         checkAttributeStringCoercion(value, attributeName);
       }
-      attributeValue = '' + (value: any);
+      value = sanitizeURL(value);
       break;
     }
     default: {
-      if (
-        // unrecognized event handlers are not SSR'd and we (apparently)
-        // use on* as hueristic for these handler props
-        name.length > 2 &&
-        (name[0] === 'o' || name[0] === 'O') &&
-        (name[1] === 'n' || name[1] === 'N')
-      ) {
-        return;
-      }
       if (!isAttributeNameSafe(name)) {
         return;
       }
-      if (__DEV__) {
-        checkAttributeStringCoercion(value, attributeName);
-      }
-      attributeValue = '' + (value: any);
     }
   }
+
+  if (
+    // shouldIgnoreAttribute
+    // We have already filtered out null/undefined and reserved words.
+    name.length > 2 &&
+    (name[0] === 'o' || name[0] === 'O') &&
+    (name[1] === 'n' || name[1] === 'N')
+  ) {
+    return;
+  }
+
+  if (__DEV__) {
+    checkAttributeStringCoercion(value, attributeName);
+  }
+  attributeValue = '' + (value: any);
   writeChunk(destination, arrayInterstitial);
   writeChunk(
     destination,