THRIFT-6418: Give the browser TApplicationException the symbol-keyed read and write methods

Client: js

Generated JavaScript code reads and writes structs through the keys
Symbol.for("read") and Symbol.for("write"). Since 5fc920d (0.21.0) the
generated client also reads an EXCEPTION reply that way, calling
x[Symbol.for("read")](input) on a new Thrift.TApplicationException.
lib/nodejs gives its TApplicationException both keys, but lib/js did not,
so a browser client threw "TypeError: x[Symbol.for(...)] is not a
function" instead of the TApplicationException the server sent. The two
keys now point at the existing read() and write(), as in lib/nodejs.

The ant JSLint check in lib/js/test/build.xml reads thrift.js as ES3,
where "for" cannot be a property name, so it now runs with the es5
option.

The test that should have caught this could not. test_handler.js took
TException from the top level of the Node.js library, where it is
undefined, so testException("TException") failed inside the test server
with HTTP 500, and the TException test in test.js had been changed to
accept any error. The handler now uses Thrift.TException, and the test
expects the TApplicationException that the server sends for an
undeclared exception. A second test decodes an EXCEPTION reply through
the generated client without a server.

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

Author: Jens-G

lib/js/src/thrift.js

@@ -263,6 +263,12 @@ Thrift.TApplicationException.prototype.write = function(output) {
     output.writeStructEnd();
 };
 
+// Generated code reads and writes every struct through these two keys, which a
+// field named "read" or "write" cannot hide, and it reads an EXCEPTION reply into
+// a TApplicationException the same way.
+Thrift.TApplicationException.prototype[Symbol.for('read')] = Thrift.TApplicationException.prototype.read;
+Thrift.TApplicationException.prototype[Symbol.for('write')] = Thrift.TApplicationException.prototype.write;
+
 /**
  * Returns the application exception code set on the exception.
  * @readonly

lib/js/test/build.xml

@@ -182,7 +182,8 @@
          the following options would probably make sense in the future:
          browser,undef,eqeqeq,plusplus,bitwise,regexp,strict,newcap,immed
     -->
-    <jsl:jslint options="evil,forin,browser,bitwise,regexp,newcap,immed" encoding="UTF-8">
+    <!-- es5: thrift.js uses Symbol.for(), and only ES5 allows "for" as a property name -->
+    <jsl:jslint options="evil,forin,browser,bitwise,regexp,newcap,immed,es5" encoding="UTF-8">
       <formatter type="plain" />
       <fileset dir="../src" includes="thrift.js" />
 

lib/js/test/test.js

@@ -315,16 +315,34 @@ QUnit.module('Exception');
   });
 
   QUnit.test('TException', function(assert) {
-    //ThriftTest does not list TException as a legal exception so it will
-    // generate an exception on the server that does not propagate back to
-    // the client. This test has been modified to equate to "no exception"
+    // ThriftTest does not declare TException, so the server answers with an
+    // EXCEPTION reply, which the client raises as a TApplicationException.
     assert.expect(1);
-    try {
-      client.testException('TException');
-    } catch (e) {
-      //assert.ok(false);
-    }
-    assert.ok(true);
+    assert.throws(
+      function() { client.testException('TException'); },
+      function(e) {
+        return e instanceof Thrift.TApplicationException &&
+               e.message === 'TException' &&
+               e.code === Thrift.TApplicationExceptionType.UNKNOWN;
+      },
+      'testException("TException") raises a TApplicationException'
+    );
+  });
+
+  QUnit.test('EXCEPTION reply without a server', function(assert) {
+    const offlineTransport = new Thrift.Transport('/service');
+    const offlineClient = new ThriftTest.ThriftTestClient(new Thrift.Protocol(offlineTransport));
+    offlineTransport.setRecvBuffer('[1,"testVoid",3,0,{"1":{"str":"boom"},"2":{"i32":6}}]');
+    assert.expect(1);
+    assert.throws(
+      function() { offlineClient.recv_testVoid(); },
+      function(e) {
+        return e instanceof Thrift.TApplicationException &&
+               e.message === 'boom' &&
+               e.code === Thrift.TApplicationExceptionType.INTERNAL_ERROR;
+      },
+      'recv_testVoid raises the TApplicationException of an EXCEPTION reply'
+    );
   });
 
 

lib/js/test/test_handler.js

@@ -23,7 +23,7 @@
 const es6Mode = process.argv.includes('--es6');
 const genFolder = es6Mode ? 'gen-nodejs-es6' : 'gen-nodejs';
 const ttypes = require(`./${genFolder}/ThriftTest_types`);
-const TException = require('../../nodejs/lib/thrift').TException;
+const TException = require('../../nodejs/lib/thrift').Thrift.TException;
 const Int64 = require('node-int64');
 
 exports.ThriftTestHandler = {