Fix canonical_path::parent in the presence of non-ASCII

On Windows, if a canonical_path stores non-ASCII characters, the
counting used in canonical_path::parent was inaccurate and caused path
components to be truncated incorrectly. Fix counting to make
canonical_path::parent work as expected.

canonicalize_path still has encoding-related bugs on Windows. These will
be fixed in future commits.

Author: strager

src/file-canonical.cpp

@@ -115,17 +115,16 @@ canonical_path::canonical_path(std::string &&path) : path_(std::move(path)) {
   }
   std::reverse(this->path_lengths_.begin(), this->path_lengths_.end());
 #elif QLJS_PATHS_WIN32
-  // TODO(strager): path_lengths_ is in UTF-16 code units, but it's interpreted
-  // as UTF-8 code units! Fix by storing a std::wstring in canonical_path
-  // instead of a std::string.
   // TODO(strager): Avoid string conversions and copying.
   std::optional<std::wstring> wpath = mbstring_to_wstring(this->path_.c_str());
   QLJS_ASSERT(wpath.has_value());
   for (;;) {
     HRESULT result = ::PathCchRemoveFileSpec(wpath->data(), wpath->size() + 1);
     switch (result) {
     case S_OK:
-      this->path_lengths_.push_back(std::wcslen(wpath->data()));
+      // TODO(strager): Avoid allocating just to count UTF-8 code units.
+      this->path_lengths_.push_back(
+          std::filesystem::path(wpath->c_str()).u8string().size());
       break;
     case S_FALSE:
       // Path is a root path already.

test/test-file-canonical.cpp

@@ -1033,22 +1033,29 @@ TEST_F(test_file_canonical, parent_of_root_is_root_win32) {
 
 TEST_F(test_file_canonical, parent_of_non_root_removes_component_win32) {
   struct test_case {
-    const std::string_view before;
-    const std::string_view after;
+    const string8_view before;
+    const string8_view after;
   };
 
   for (const test_case& tc : {
-           test_case{R"(C:\hello)", R"(C:\)"},
-           test_case{R"(C:\dir\subdir)", R"(C:\dir)"},
-           test_case{R"(C:\a\b\c\d)", R"(C:\a\b\c)"},
-           test_case{R"(\\?\X:\hello)", R"(\\?\X:\)"},
-           test_case{R"(\\?\X:\dir\subdir)", R"(\\?\X:\dir)"},
-           test_case{R"(\\?\X:\a\b\c\d)", R"(\\?\X:\a\b\c)"},
-           test_case{R"(\\server\share\file)", R"(\\server\share)"},
+           test_case{u8R"(C:\hello)", u8R"(C:\)"},
+           test_case{u8R"(C:\dir\subdir)", u8R"(C:\dir)"},
+           test_case{u8R"(C:\a\b\c\d)", u8R"(C:\a\b\c)"},
+           test_case{u8R"(\\?\X:\hello)", u8R"(\\?\X:\)"},
+           test_case{u8R"(\\?\X:\dir\subdir)", u8R"(\\?\X:\dir)"},
+           test_case{u8R"(\\?\X:\a\b\c\d)", u8R"(\\?\X:\a\b\c)"},
+           test_case{u8R"(\\server\share\file)", u8R"(\\server\share)"},
+           test_case{u8"X:\\parent\u0080dir\\sub\u0080dir",
+                     u8"X:\\parent\u0080dir"},
+           test_case{u8"X:\\parent\u0800dir\\sub\u0800dir",
+                     u8"X:\\parent\u0800dir"},
+           test_case{u8"X:\\parent\U00108000dir\\sub\U00108000dir",
+                     u8"X:\\parent\U00108000dir"},
        }) {
-    canonical_path p(std::string(tc.before));
+    canonical_path p(to_string(tc.before));
     EXPECT_TRUE(p.parent());
-    EXPECT_EQ(p.path(), tc.after) << "before = " << tc.before;
+    EXPECT_EQ(p.path(), to_string(tc.after))
+        << "before = " << out_string8(tc.before);
   }
 }