fix(utils_test): u8string triggers linker error with non-C++20 gtest

This is a long standing issue and it's not going to go away, as package
manager prefer that stuff isn't fetched at build time. So we just check
if certain gtest features work with the system-installed version and
work around missing features downstream. Out of the box, with the custom
built ctest, we'll still get all the good stuff. If the system-installed
version is preferred, we probably have some degradation in test output.

README.md

@@ -208,12 +208,7 @@ There are some things to be aware of:
   of GoogleTest. GoogleTest itself recommends that it is being
   downloaded as part of the build. However, you can use the system
   installed version by passing `-DPREFER_SYSTEM_GTEST=ON` to the
-  `cmake` call. Use at your own risk. One known issues with using
-  system-installed versions of GoogleTest is that `utils_test` can
-  fail to compile because it uses C++20 features and GoogleTest is
-  built without `-std=c++20`. The release page has a patch
-  (`dwarfs-system-gtest.patch`) that can be applied to work around
-  this issue.
+  `cmake` call. Use at your own risk.
 
 - For other bundled libraries (namely `fmt`, `parallel-hashmap`,
   `range-v3`), the system installed version is used as long as it

cmake/checks/gtest-u8string.cpp

@@ -0,0 +1,7 @@
+#include <gtest/gtest.h>
+
+#include <string>
+
+TEST(u8string, compare) {
+  EXPECT_EQ(u8"我", u8"我");
+}

cmake/need_gtest.cmake

@@ -24,9 +24,18 @@ if(PREFER_SYSTEM_GTEST)
   add_library(gtest_main ALIAS GTest::gtest_main)
   add_library(gmock ALIAS GTest::gmock)
   add_library(gmock_main ALIAS GTest::gmock_main)
-endif()
 
-if(NOT GTest_FOUND)
+  try_compile(
+    GTEST_SUPPORTS_U8STRING
+    SOURCES ${CMAKE_CURRENT_SOURCE_DIR}/cmake/checks/gtest-u8string.cpp
+    CXX_STANDARD 20
+  )
+
+  if(NOT GTEST_SUPPORTS_U8STRING)
+    message(WARNING "GTest does not support u8string.")
+    target_compile_definitions(GTest::gtest INTERFACE GTEST_NO_U8STRING=1)
+  endif()
+else()
   FetchContent_Declare(
     googletest
     GIT_REPOSITORY ${GOOGLETEST_GIT_REPO}

test/utils_test.cpp

@@ -34,18 +34,25 @@
 
 using namespace dwarfs;
 
+#ifdef GTEST_NO_U8STRING
+#define EXPECT_EQ_U8STR(a, b) EXPECT_TRUE((a) == (b))
+#else
+#define EXPECT_EQ_U8STR(a, b) EXPECT_EQ(a, b)
+#endif
+
 TEST(utils, utf8_display_width) {
-  EXPECT_EQ(0, utf8_display_width(""));
-  EXPECT_EQ(1, utf8_display_width(u8string_to_string(u8"a")));
-  EXPECT_EQ(5, utf8_display_width(u8string_to_string(u8"abcde")));
-  EXPECT_EQ(2, utf8_display_width(u8string_to_string(u8"你")));
-  EXPECT_EQ(4, utf8_display_width(u8string_to_string(u8"我你")));
-  EXPECT_EQ(6, utf8_display_width(u8string_to_string(u8"我爱你")));
-  EXPECT_EQ(5, utf8_display_width(u8string_to_string(u8"☀️ Sun")));
-  EXPECT_EQ(2, utf8_display_width(u8string_to_string(u8"⚽️")));
-  EXPECT_EQ(5, utf8_display_width(u8string_to_string(u8"مرحبًا")));
-  EXPECT_EQ(50, utf8_display_width(u8string_to_string(
-                    u8"unicode/我爱你/☀️ Sun/Γειά σας/مرحبًا/⚽️/Карибського")));
+  EXPECT_EQ_U8STR(0, utf8_display_width(""));
+  EXPECT_EQ_U8STR(1, utf8_display_width(u8string_to_string(u8"a")));
+  EXPECT_EQ_U8STR(5, utf8_display_width(u8string_to_string(u8"abcde")));
+  EXPECT_EQ_U8STR(2, utf8_display_width(u8string_to_string(u8"你")));
+  EXPECT_EQ_U8STR(4, utf8_display_width(u8string_to_string(u8"我你")));
+  EXPECT_EQ_U8STR(6, utf8_display_width(u8string_to_string(u8"我爱你")));
+  EXPECT_EQ_U8STR(5, utf8_display_width(u8string_to_string(u8"☀️ Sun")));
+  EXPECT_EQ_U8STR(2, utf8_display_width(u8string_to_string(u8"⚽️")));
+  EXPECT_EQ_U8STR(5, utf8_display_width(u8string_to_string(u8"مرحبًا")));
+  EXPECT_EQ_U8STR(50,
+                  utf8_display_width(u8string_to_string(
+                      u8"unicode/我爱你/☀️ Sun/Γειά σας/مرحبًا/⚽️/Карибського")));
 }
 
 TEST(utils, uft8_truncate) {
@@ -58,22 +65,22 @@ TEST(utils, uft8_truncate) {
   // -----------------123456789012345--
   auto const str = u8"我爱你/مرحبًا/⚽️";
 
-  EXPECT_EQ(str, u8trunc(str, 15));
+  EXPECT_EQ_U8STR(str, u8trunc(str, 15));
   // ----------123456789012345--
-  EXPECT_EQ(u8"我爱你/مرحبًا/", u8trunc(str, 14));
-  EXPECT_EQ(u8"我爱你/مرحبًا/", u8trunc(str, 13));
-  EXPECT_EQ(u8"我爱你/مرحبًا", u8trunc(str, 12));
-  EXPECT_EQ(u8"我爱你/مرحبً", u8trunc(str, 11));
-  EXPECT_EQ(u8"我爱你/مرح", u8trunc(str, 10));
-  EXPECT_EQ(u8"我爱你/مر", u8trunc(str, 9));
-  EXPECT_EQ(u8"我爱你/م", u8trunc(str, 8));
-  EXPECT_EQ(u8"我爱你/", u8trunc(str, 7));
-  EXPECT_EQ(u8"我爱你", u8trunc(str, 6));
-  EXPECT_EQ(u8"我爱", u8trunc(str, 5));
-  EXPECT_EQ(u8"我爱", u8trunc(str, 4));
-  EXPECT_EQ(u8"我", u8trunc(str, 3));
-  EXPECT_EQ(u8"我", u8trunc(str, 2));
-  EXPECT_EQ(u8"", u8trunc(str, 1));
+  EXPECT_EQ_U8STR(u8"我爱你/مرحبًا/", u8trunc(str, 14));
+  EXPECT_EQ_U8STR(u8"我爱你/مرحبًا/", u8trunc(str, 13));
+  EXPECT_EQ_U8STR(u8"我爱你/مرحبًا", u8trunc(str, 12));
+  EXPECT_EQ_U8STR(u8"我爱你/مرحبً", u8trunc(str, 11));
+  EXPECT_EQ_U8STR(u8"我爱你/مرح", u8trunc(str, 10));
+  EXPECT_EQ_U8STR(u8"我爱你/مر", u8trunc(str, 9));
+  EXPECT_EQ_U8STR(u8"我爱你/م", u8trunc(str, 8));
+  EXPECT_EQ_U8STR(u8"我爱你/", u8trunc(str, 7));
+  EXPECT_EQ_U8STR(u8"我爱你", u8trunc(str, 6));
+  EXPECT_EQ_U8STR(u8"我爱", u8trunc(str, 5));
+  EXPECT_EQ_U8STR(u8"我爱", u8trunc(str, 4));
+  EXPECT_EQ_U8STR(u8"我", u8trunc(str, 3));
+  EXPECT_EQ_U8STR(u8"我", u8trunc(str, 2));
+  EXPECT_EQ_U8STR(u8"", u8trunc(str, 1));
 }
 
 TEST(utils, shorten_path_ascii) {
@@ -183,7 +190,7 @@ TEST(utils, shorten_path_utf8) {
     for (size_t max_len = 0; max_len < expected.size(); ++max_len) {
       std::string path = u8string_to_string(path_u8);
       shorten_path_string(path, '/', max_len);
-      EXPECT_EQ(u8string_to_string(expected[max_len]), path);
+      EXPECT_EQ_U8STR(u8string_to_string(expected[max_len]), path);
     }
   }
 }