refactor: add tr_strv_to_utf8_nsstring() (#8174)

* refactor: rename enum types in ip-cache private enum class is_updating_t

this avoids name collisions with YES and NO on macOS

* refactor: rename tr_strv_convert_utf8() to tr_strv_to_utf8_string()

use a name that is symmetrical with the upcoming tr_strv_to_utf8_nsstring()

* feat: add tr_strv_to_utf8_nsstring()

* test: add tests for the new tr_strv_to_utf8_nsstring() methods

tests/libtransmission/CMakeLists.txt

@@ -60,6 +60,12 @@ target_sources(libtransmission-test
         watchdir-test.cc
         web-utils-test.cc)
 
+if(APPLE)
+    target_sources(libtransmission-test
+        PRIVATE
+            utils-apple-test.mm)
+endif()
+
 set_property(
     TARGET libtransmission-test
     PROPERTY FOLDER "tests")

tests/libtransmission/utils-apple-test.mm

@@ -0,0 +1,105 @@
+// This file Copyright © Mnemosyne LLC.
+// It may be used under GPLv2 (SPDX: GPL-2.0-only), GPLv3 (SPDX: GPL-3.0-only),
+// or any future license endorsed by Mnemosyne LLC.
+// License text can be found in the licenses/ folder.
+
+#import <Foundation/Foundation.h>
+
+#include <algorithm>
+#include <string_view>
+
+#include <libtransmission/utils.h>
+
+#include "gtest/gtest.h"
+#include "test-fixtures.h"
+
+using UtilsTest = ::libtransmission::test::TransmissionTest;
+using namespace std::literals;
+
+namespace
+{
+[[nodiscard]] constexpr size_t count_replacement_char(std::string_view const sv)
+{
+    size_t count = 0;
+    constexpr auto needle = "\xEF\xBF\xBD"sv; // U+FFFD replacement
+    auto pos = std::string_view::size_type{};
+
+    while ((pos = sv.find(needle, pos)) != std::string_view::npos)
+    {
+        ++count;
+        pos += std::size(needle);
+    }
+
+    return count;
+}
+
+[[nodiscard]] constexpr bool has_non_ascii(std::string_view const sv)
+{
+    return std::any_of(std::begin(sv), std::end(sv), [](unsigned char ch) { return ch >= 0x80; });
+}
+} // namespace
+
+TEST_F(UtilsTest, trStrvToUtf8NsstringValid)
+{
+    @autoreleasepool
+    {
+        NSString* str = tr_strv_to_utf8_nsstring("hello"sv);
+        EXPECT_TRUE([str isEqualToString:@"hello"]);
+    }
+}
+
+TEST_F(UtilsTest, trStrvToUtf8NsstringInvalid)
+{
+    @autoreleasepool
+    {
+        constexpr auto bad = "\xF4\x33\x81\x82"sv;
+        NSString* str = tr_strv_to_utf8_nsstring(bad);
+        EXPECT_TRUE([str isEqualToString:@""]);
+    }
+}
+
+TEST_F(UtilsTest, trStrvToUtf8NsstringFallback)
+{
+    @autoreleasepool
+    {
+        constexpr auto bad = "\xF4\x33\x81\x82"sv;
+        NSString* const key = @"tr.strv.to.utf8.fallback";
+        NSString* const comment = @"fallback string for tests";
+        NSString* str = tr_strv_to_utf8_nsstring(bad, key, comment);
+        EXPECT_TRUE([str isEqualToString:key]);
+    }
+}
+
+TEST_F(UtilsTest, trStrvToUtf8StringMixedInvalid)
+{
+    constexpr auto input = "hello \xF0\x28\x8C\x28 world"sv;
+    auto const out = tr_strv_to_utf8_string(input);
+    EXPECT_FALSE(out.empty());
+    EXPECT_EQ(out, tr_strv_replace_invalid(out));
+    EXPECT_EQ(out, tr_strv_to_utf8_string(out));
+}
+
+TEST_F(UtilsTest, trStrvToUtf8StringAutodetectImproves)
+{
+    // Shift_JIS-encoded filename from a real-world report in
+    // https://github.com/transmission/transmission/pull/5244#issuecomment-1474442137
+    constexpr auto input =
+        "\x93\xC1\x96\xBD\x8C\x57\x92\xB7\x81\x45\x91\xFC\x96\xEC\x90\x6D"
+        "\x83\x8A\x83\x5E\x81\x5B\x83\x93\x83\x59 (D-ABC 704x396 DivX511).avi"sv;
+
+    auto const replace_only = tr_strv_replace_invalid(input);
+    auto const autodetect = tr_strv_to_utf8_string(input);
+
+    EXPECT_FALSE(autodetect.empty());
+    EXPECT_EQ(autodetect, tr_strv_replace_invalid(autodetect));
+
+    // Autodetect should preserve more readable text than replacement-only.
+    EXPECT_LT(count_replacement_char(autodetect), count_replacement_char(replace_only));
+
+    // If autodetect improves, it should yield valid UTF-8 with real non-ASCII characters.
+    if (count_replacement_char(autodetect) < count_replacement_char(replace_only))
+    {
+        EXPECT_EQ(0U, count_replacement_char(autodetect));
+        EXPECT_TRUE(has_non_ascii(autodetect));
+    }
+}

tests/libtransmission/utils-test.cc

@@ -210,8 +210,8 @@ TEST_F(UtilsTest, strvConvertUtf8Fuzz)
     {
         buf.resize(tr_rand_int(4096U));
         tr_rand_buffer(std::data(buf), std::size(buf));
-        auto const out = tr_strv_convert_utf8({ std::data(buf), std::size(buf) });
-        EXPECT_EQ(out, tr_strv_convert_utf8(out));
+        auto const out = tr_strv_to_utf8_string({ std::data(buf), std::size(buf) });
+        EXPECT_EQ(out, tr_strv_to_utf8_string(out));
     }
 }