[test] Reinstate the assignment to the diagnostic log in the unittest

from r363009

The diagnostic log is now set to "-" which forces it to use STDERR
instead of the filesystem. A new comment is added to explain why
the assignment is needed in the test.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@363199 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/unittests/Frontend/CompilerInstanceTest.cpp b/unittests/Frontend/CompilerInstanceTest.cpp
index 3b3dc527df5c5b11ed47a43f9c8182a19ffbc184..4935853f1383d0396f6fbbbaf68c2db7f56effc5 100644 (file)
--- a/unittests/Frontend/CompilerInstanceTest.cpp
+++ b/unittests/Frontend/CompilerInstanceTest.cpp
@@ -73,6 +73,10 @@ TEST(CompilerInstance, DefaultVFSOverlayFromInvocation) {
 
 TEST(CompilerInstance, AllowDiagnosticLogWithUnownedDiagnosticConsumer) {
   auto DiagOpts = new DiagnosticOptions();
+  // Tell the diagnostics engine to emit the diagnostic log to STDERR. This
+  // ensures that a chained diagnostic consumer is created so that the test can
+  // exercise the unowned diagnostic consumer in a chained consumer.
+  DiagOpts->DiagnosticLogFile = "-";
 
   // Create the diagnostic engine with unowned consumer.
   std::string DiagnosticOutput;