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AK: Print RHS and LHS in EXPECT_EQ if we can

This makes error messages more useful during debugging.

Old:

    START Running test compare_views
    FAIL: ../AK/Tests/TestStringView.cpp:59: EXPECT_EQ(view1, "foobar") failed

New:

    START Running test compare_views
    FAIL: ../AK/Tests/TestStringView.cpp:59: EXPECT_EQ(view1, "foobar") failed: LHS="foo", RHS="foobar"
Ben Wiederhake 5 years ago
parent
commit
53abc626c2
2 changed files with 49 additions and 5 deletions
  1. 4 1
      AK/StdLibExtras.h
  2. 45 4
      AK/TestSuite.h

+ 4 - 1
AK/StdLibExtras.h

@@ -40,7 +40,6 @@ inline constexpr unsigned round_up_to_power_of_two(unsigned value, unsigned powe
 
 namespace AK {
 
-
 template<typename T, typename SizeType = decltype(sizeof(T)), SizeType N>
 constexpr SizeType array_size(T (&)[N])
 {
@@ -501,6 +500,9 @@ template<typename ReferenceType, typename T>
 using CopyConst =
     typename Conditional<IsConst<ReferenceType>::value, typename AddConst<T>::Type, typename RemoveConst<T>::Type>::Type;
 
+template<typename... Ts>
+using Void = void;
+
 }
 
 using AK::AddConst;
@@ -523,3 +525,4 @@ using AK::min;
 using AK::move;
 using AK::RemoveConst;
 using AK::swap;
+using AK::Void;

+ 45 - 4
AK/TestSuite.h

@@ -220,6 +220,35 @@ void TestSuite::run(const NonnullRefPtrVector<TestCase>& tests)
           << m_testtime << " tests, " << m_benchtime << " benchmarks, " << (global_timer.elapsed_milliseconds() - (m_testtime + m_benchtime)) << " other)";
 }
 
+// Use SFINAE to print if we can.
+// This trick is good enough for TestSuite.h, but not flexible enough to be put into LogStream.h.
+template<typename Stream, typename LHS, typename RHS, typename = void>
+struct MaybeStream {
+    static const Stream& call(const Stream& stream, const LHS&, const RHS&)
+    {
+        return stream;
+    }
+};
+template<typename Stream, typename LHS, typename RHS>
+struct MaybeStream<Stream, LHS, RHS, AK::Void<decltype(*reinterpret_cast<const Stream*>(0) << "" << *reinterpret_cast<const LHS*>(0) << "" << *reinterpret_cast<const RHS*>(0) << "")>> {
+    static const Stream& call(const Stream& stream, const LHS& lhs, const RHS& rhs)
+    {
+        return stream << ": LHS=\"" << lhs << "\", RHS=\"" << rhs << "\"";
+    }
+};
+template<typename Stream, typename LHS, typename RHS>
+static const Stream& maybe_print_rhs_lhs(const Stream& stream, const LHS& lhs, const RHS& rhs)
+{
+    return MaybeStream<Stream, LHS, RHS>::call(stream, lhs, rhs);
+}
+template<typename Stream, typename LHS, typename RHS>
+static const Stream& force_print_rhs_lhs(const Stream& stream, const LHS& lhs, const RHS& rhs)
+{
+    using _ = decltype(*reinterpret_cast<const Stream*>(0) << "" << *reinterpret_cast<const LHS*>(0) << "" << *reinterpret_cast<const RHS*>(0) << "");
+    (void)sizeof(_);
+    return MaybeStream<Stream, LHS, RHS>::call(stream, lhs, rhs);
+}
+
 }
 
 using AK::TestCase;
@@ -263,10 +292,22 @@ using AK::TestSuite;
         TestSuite::release();                                       \
     }
 
-#define EXPECT_EQ(a, b)                                                                                           \
-    {                                                                                                             \
-        if ((a) != (b))                                                                                           \
-            warn() << "\033[31;1mFAIL\033[0m: " __FILE__ ":" << __LINE__ << ": EXPECT_EQ(" #a ", " #b ") failed"; \
+#define EXPECT_EQ(a, b)                                                                                                                              \
+    {                                                                                                                                                \
+        auto lhs = (a);                                                                                                                              \
+        auto rhs = (b);                                                                                                                              \
+        if (lhs != rhs)                                                                                                                              \
+            AK::maybe_print_rhs_lhs(warn() << "\033[31;1mFAIL\033[0m: " __FILE__ ":" << __LINE__ << ": EXPECT_EQ(" #a ", " #b ") failed", lhs, rhs); \
+    }
+
+// If you're stuck and `EXPECT_EQ` seems to refuse to print anything useful,
+// try this: It'll spit out a nice compiler error telling you why it doesn't print.
+#define EXPECT_EQ_FORCE(a, b)                                                                                                                        \
+    {                                                                                                                                                \
+        auto lhs = (a);                                                                                                                              \
+        auto rhs = (b);                                                                                                                              \
+        if (lhs != rhs)                                                                                                                              \
+            AK::force_print_rhs_lhs(warn() << "\033[31;1mFAIL\033[0m: " __FILE__ ":" << __LINE__ << ": EXPECT_EQ(" #a ", " #b ") failed", lhs, rhs); \
     }
 
 #define EXPECT(x)                                                                                      \