Bug 1254174 - Convert uncaught symbol to a descriptive string. r=jorendorff

js/src/jsapi-tests/moz.build

@@ -87,6 +87,7 @@ UNIFIED_SOURCES += [
     'testTypedArrays.cpp',
     'testUbiNode.cpp',
     'testUncaughtError.cpp',
+    'testUncaughtSymbol.cpp',
     'testUTF8.cpp',
     'testWasmLEB128.cpp',
     'testWeakMap.cpp',

js/src/jsapi-tests/testUncaughtSymbol.cpp

@@ -0,0 +1,51 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "jsapi-tests/tests.h"
+
+using JS::CreateError;
+using JS::Rooted;
+using JS::ObjectValue;
+using JS::Value;
+
+static enum {
+    NONE,
+    SYMBOL_ITERATOR,
+    SYMBOL_FOO,
+    SYMBOL_EMPTY,
+} uncaughtType = NONE;
+
+BEGIN_TEST(testUncaughtSymbol)
+{
+    JSErrorReporter old = JS_SetErrorReporter(rt, UncaughtSymbolReporter);
+
+    CHECK(uncaughtType == NONE);
+    exec("throw Symbol.iterator;", __FILE__, __LINE__);
+    CHECK(uncaughtType == SYMBOL_ITERATOR);
+
+    uncaughtType = NONE;
+    exec("throw Symbol('foo');", __FILE__, __LINE__);
+    CHECK(uncaughtType == SYMBOL_FOO);
+
+    uncaughtType = NONE;
+    exec("throw Symbol();", __FILE__, __LINE__);
+    CHECK(uncaughtType == SYMBOL_EMPTY);
+
+    JS_SetErrorReporter(rt, old);
+
+    return true;
+}
+
+static void
+UncaughtSymbolReporter(JSContext* cx, const char* message, JSErrorReport* report)
+{
+    if (strcmp(message, "uncaught exception: Symbol(Symbol.iterator)") == 0)
+        uncaughtType = SYMBOL_ITERATOR;
+    else if (strcmp(message, "uncaught exception: Symbol(foo)") == 0)
+        uncaughtType = SYMBOL_FOO;
+    else if (strcmp(message, "uncaught exception: Symbol()") == 0)
+        uncaughtType = SYMBOL_EMPTY;
+}
+
+END_TEST(testUncaughtSymbol)

js/src/jsexn.cpp

@@ -811,10 +811,17 @@ ErrorReport::init(JSContext* cx, HandleValue exn)
     // Be careful not to invoke ToString if we've already successfully extracted
     // an error report, since the exception might be wrapped in a security
     // wrapper, and ToString-ing it might throw.
-    if (reportp)
+    if (reportp) {
         str = ErrorReportToString(cx, reportp);
-    else
+    } else if (exn.isSymbol()) {
+        RootedValue strVal(cx);
+        if (js::SymbolDescriptiveString(cx, exn.toSymbol(), &strVal))
+            str = strVal.toString();
+        else
+            str = nullptr;
+    } else {
         str = ToString<CanGC>(cx, exn);
+    }
 
     if (!str)
         cx->clearPendingException();