Googletest export

Add `Conditional` wrapper to gtest

This follows an initial proposal for an 'EqIff` matcher. `Conditional` was considered more precise as an EqIff() matcher may suffer from `Iff` not being universally understood.

PiperOrigin-RevId: 383407665

Author: Abseil Team

CONTRIBUTORS

@@ -34,6 +34,7 @@ Manuel Klimek <klimek@google.com>
 Mario Tanev <radix@google.com>
 Mark Paskin
 Markus Heule <markus.heule@gmail.com>
+Martijn Vels <mvels@google.com>
 Matthew Simmons <simmonmt@acm.org>
 Mika Raento <mikie@iki.fi>
 Mike Bland <mbland@google.com>

docs/reference/matchers.md

@@ -238,6 +238,7 @@ You can make a matcher from one or more other matchers:
 | `AnyOf(m1, m2, ..., mn)` | `argument` matches at least one of the matchers `m1` to `mn`. |
 | `AnyOfArray({m0, m1, ..., mn})`, `AnyOfArray(a_container)`, `AnyOfArray(begin, end)`, `AnyOfArray(array)`, or `AnyOfArray(array, count)` | The same as `AnyOf()` except that the matchers come from an initializer list, STL-style container, iterator range, or C-style array. |
 | `Not(m)` | `argument` doesn't match matcher `m`. |
+| `Conditional(cond, m1, m2)` | Matches matcher `m1` if `cond` evalutes to true, else matches `m2`.|
 
 ## Adapters for Matchers
 

googlemock/include/gmock/gmock-matchers.h

@@ -1405,6 +1405,30 @@ class AnyOfMatcherImpl : public MatcherInterface<const T&> {
 template <typename... Args>
 using AnyOfMatcher = VariadicMatcher<AnyOfMatcherImpl, Args...>;
 
+// ConditionalMatcher is the implementation of Conditional(cond, m1, m2)
+template <typename MatcherTrue, typename MatcherFalse>
+class ConditionalMatcher {
+ public:
+  ConditionalMatcher(bool condition, MatcherTrue matcher_true,
+                     MatcherFalse matcher_false)
+      : condition_(condition),
+        matcher_true_(std::move(matcher_true)),
+        matcher_false_(std::move(matcher_false)) {}
+
+  template <typename T>
+  operator Matcher<T>() const {  // NOLINT(runtime/explicit)
+    return condition_ ? SafeMatcherCast<T>(matcher_true_)
+                      : SafeMatcherCast<T>(matcher_false_);
+  }
+
+ private:
+  bool condition_;
+  MatcherTrue matcher_true_;
+  MatcherFalse matcher_false_;
+
+  GTEST_DISALLOW_ASSIGN_(ConditionalMatcher);
+};
+
 // Wrapper for implementation of Any/AllOfArray().
 template <template <class> class MatcherImpl, typename T>
 class SomeOfArrayMatcher {
@@ -4926,6 +4950,18 @@ Pair(FirstMatcher first_matcher, SecondMatcher second_matcher) {
 }
 
 namespace no_adl {
+// Conditional() creates a matcher that conditionally uses either the first or
+// second matcher provided. For example, we could create an `equal if, and only
+// if' matcher using the Conditonal wrapper as follows:
+//
+//   EXPECT_THAT(result, Conditional(condition, Eq(expected), Ne(expected)));
+template <typename MatcherTrue, typename MatcherFalse>
+internal::ConditionalMatcher<MatcherTrue, MatcherFalse> Conditional(
+    bool condition, MatcherTrue matcher_true, MatcherFalse matcher_false) {
+  return internal::ConditionalMatcher<MatcherTrue, MatcherFalse>(
+      condition, std::move(matcher_true), std::move(matcher_false));
+}
+
 // FieldsAre(matchers...) matches piecewise the fields of compatible structs.
 // These include those that support `get<I>(obj)`, and when structured bindings
 // are enabled any class that supports them.

googlemock/test/gmock-matchers_test.cc

@@ -2772,6 +2772,34 @@ TEST(AnyOfTest, VariadicMatchesWhenAnyMatches) {
                 "43", "44", "45", "46", "47", "48", "49", "50"));
 }
 
+TEST(ConditionalTest, MatchesFirstIfCondition) {
+  Matcher<std::string> eq_red = Eq("red");
+  Matcher<std::string> ne_red = Ne("red");
+  Matcher<std::string> m = Conditional(true, eq_red, ne_red);
+  EXPECT_TRUE(m.Matches("red"));
+  EXPECT_FALSE(m.Matches("green"));
+
+  StringMatchResultListener listener;
+  StringMatchResultListener expected;
+  EXPECT_FALSE(m.MatchAndExplain("green", &listener));
+  EXPECT_FALSE(eq_red.MatchAndExplain("green", &expected));
+  EXPECT_THAT(listener.str(), Eq(expected.str()));
+}
+
+TEST(ConditionalTest, MatchesSecondIfCondition) {
+  Matcher<std::string> eq_red = Eq("red");
+  Matcher<std::string> ne_red = Ne("red");
+  Matcher<std::string> m = Conditional(false, eq_red, ne_red);
+  EXPECT_FALSE(m.Matches("red"));
+  EXPECT_TRUE(m.Matches("green"));
+
+  StringMatchResultListener listener;
+  StringMatchResultListener expected;
+  EXPECT_FALSE(m.MatchAndExplain("red", &listener));
+  EXPECT_FALSE(ne_red.MatchAndExplain("red", &expected));
+  EXPECT_THAT(listener.str(), Eq(expected.str()));
+}
+
 // Tests the variadic version of the ElementsAreMatcher
 TEST(ElementsAreTest, HugeMatcher) {
   vector<int> test_vector{1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12};