1 files changed, 75 insertions, 0 deletions
diff --git a/js/src/jsapi-tests/testErrorLineOfContext.cpp b/js/src/jsapi-tests/testErrorLineOfContext.cpp
new file mode 100644
index 0000000000..e4e326dbf0
--- /dev/null
+++ b/js/src/jsapi-tests/testErrorLineOfContext.cpp
@@ -0,0 +1,75 @@
+/* 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 "jsfriendapi.h"
+
+#include "js/CompilationAndEvaluation.h"
+#include "js/Exception.h"
+#include "js/SourceText.h"
+#include "jsapi-tests/tests.h"
+#include "vm/ErrorReporting.h"
+
+BEGIN_TEST(testErrorLineOfContext) {
+  static const char16_t fullLineR[] = u"\n  var x = @;  \r  ";
+  CHECK(testLineOfContextHasNoLineTerminator(fullLineR, ' '));
+
+  static const char16_t fullLineN[] = u"\n  var x = @; !\n  ";
+  CHECK(testLineOfContextHasNoLineTerminator(fullLineN, '!'));
+
+  static const char16_t fullLineLS[] = u"\n  var x = @; +\u2028  ";
+  CHECK(testLineOfContextHasNoLineTerminator(fullLineLS, '+'));
+
+  static const char16_t fullLinePS[] = u"\n  var x = @; #\u2029  ";
+  CHECK(testLineOfContextHasNoLineTerminator(fullLinePS, '#'));
+
+  static_assert(js::ErrorMetadata::lineOfContextRadius == 60,
+                "current max count past offset is 60, hits 'X' below");
+
+  static const char16_t truncatedLine[] =
+      u"@ + 4567890123456789012345678901234567890123456789012345678XYZW\n";
+  CHECK(testLineOfContextHasNoLineTerminator(truncatedLine, 'X'));
+
+  return true;
+}
+
+bool eval(const char16_t* chars, size_t len, JS::MutableHandleValue rval) {
+  JS::RealmOptions globalOptions;
+  JS::RootedObject global(
+      cx, JS_NewGlobalObject(cx, getGlobalClass(), nullptr,
+                             JS::FireOnNewGlobalHook, globalOptions));
+  CHECK(global);
+
+  JSAutoRealm ar(cx, global);
+
+  JS::SourceText<char16_t> srcBuf;
+  CHECK(srcBuf.init(cx, chars, len, JS::SourceOwnership::Borrowed));
+
+  JS::CompileOptions options(cx);
+  return JS::Evaluate(cx, options, srcBuf, rval);
+}
+
+template <size_t N>
+bool testLineOfContextHasNoLineTerminator(const char16_t (&chars)[N],
+                                          char16_t expectedLast) {
+  JS::RootedValue rval(cx);
+  CHECK(!eval(chars, N - 1, &rval));
+
+  JS::ExceptionStack exnStack(cx);
+  CHECK(JS::StealPendingExceptionStack(cx, &exnStack));
+
+  JS::ErrorReportBuilder report(cx);
+  CHECK(report.init(cx, exnStack, JS::ErrorReportBuilder::WithSideEffects));
+
+  const auto* errorReport = report.report();
+
+  const char16_t* lineOfContext = errorReport->linebuf();
+  size_t lineOfContextLength = errorReport->linebufLength();
+
+  CHECK(lineOfContext[lineOfContextLength] == '\0');
+  char16_t last = lineOfContext[lineOfContextLength - 1];
+  CHECK(last == expectedLast);
+
+  return true;
+}
+END_TEST(testErrorLineOfContext)