[unittest] teach gTest to print entries of DenseMap as pairs

sam-mccall · sam-mccall · commit fe8a168161a3 · 2023-06-28T11:29:52.000+02:00
When an assertion like the following fails: EXPECT_THAT(map, ElementsAre(Pair("p", "nullable")))); Error message before: Actual: { 40-byte object <E8-A5 9C-7F 25-37 00-00 58-7E 51-51 D0-7F 00-00 00-00 00-00 00-00 00-00 01-00 00-00 00-00 00-00 00-DA C7-7F 25-37 00-00> } After: Actual: { ("p", "nonnull") } It is not ideal that we need to refer directly to DenseMapPair inside the internal namespace, but I believe the practical maintenance risk is low. This change is covered by DenseMap's unittests, as we've covered SmallString etc in the past. Differential Revision: https://reviews.llvm.org/D153930
diff --git a/llvm/unittests/ADT/DenseMapTest.cpp b/llvm/unittests/ADT/DenseMapTest.cpp
@@ -9,6 +9,7 @@
 #include "llvm/ADT/DenseMap.h"
 #include "llvm/ADT/DenseMapInfo.h"
 #include "llvm/ADT/DenseMapInfoVariant.h"
+#include "llvm/ADT/StringRef.h"
 #include "gmock/gmock.h"
 #include "gtest/gtest.h"
 #include <map>
@@ -756,4 +757,12 @@ TEST(DenseMapCustomTest, VariantSupport) {
   // operator==.
   EXPECT_FALSE(DenseMapInfo<variant>::isEqual(Keys[2], Keys[2]));
 }
+
+// Test that gTest prints map entries as pairs instead of opaque objects.
+// See third-party/unittest/googletest/internal/custom/gtest-printers.h
+TEST(DenseMapCustomTest, PairPrinting) {
+  DenseMap<int, StringRef> Map = {{1, "one"}, {2, "two"}};
+  EXPECT_EQ(R"({ (1, "one"), (2, "two") })", ::testing::PrintToString(Map));
+}
+
 } // namespace
diff --git a/third-party/unittest/googletest/include/gtest/internal/custom/gtest-printers.h b/third-party/unittest/googletest/include/gtest/internal/custom/gtest-printers.h
@@ -40,6 +40,7 @@
 #define GTEST_INCLUDE_GTEST_INTERNAL_CUSTOM_GTEST_PRINTERS_H_
 
 #if !GTEST_NO_LLVM_SUPPORT
+#include "llvm/ADT/DenseMap.h"
 #include "llvm/ADT/SmallString.h"
 #include "llvm/ADT/StringRef.h"
 #include <ostream>
@@ -63,6 +64,17 @@ inline void PrintTo(const SmallString<N> &S, std::ostream *OS) {
 inline void PrintTo(const SmallVectorImpl<char> &S, std::ostream *OS) {
   *OS << ::testing::PrintToString(std::string(S.data(), S.size()));
 }
+
+// DenseMap's entries inherit from std::pair, and should act like pairs.
+// However gTest's provided `PrintTo(pair<K,V>)` template won't deduce K and V
+// because of the needed derived-to-base conversion.
+namespace detail {
+template <typename K, typename V>
+inline void PrintTo(const DenseMapPair<K, V> &Pair, std::ostream *OS) {
+  *OS << ::testing::PrintToString(static_cast<const std::pair<K, V> &>(Pair));
+}
+} // namespace detail
+
 } // namespace llvm
 #endif // !GTEST_NO_LLVM_SUPPORT
 
