LibUnicode: Handle edge-case script extensions, Common and Inherited

These script extensions have some peculiar behavior in the Unicode spec.
The UCD ScriptExtension file does not contain these scripts. Rather, it
is implied the code points which have these scripts as an extension are
the code points that both:

  1. Have Common or Inherited as their primary script value
  2. Do not have any other script value in their script extension lists

Because these are not explictly listed in the UCD, we must manually form
these script extensions.

1 files changed, 27 insertions, 0 deletions

diff --git a/Userland/Libraries/LibUnicode/CodeGenerators/GenerateUnicodeData.cpp b/Userland/Libraries/LibUnicode/CodeGenerators/GenerateUnicodeData.cpp
index 0446e6cbf2..5d1c289336 100644
--- a/Userland/Libraries/LibUnicode/CodeGenerators/GenerateUnicodeData.cpp
+++ b/Userland/Libraries/LibUnicode/CodeGenerators/GenerateUnicodeData.cpp
@@ -883,6 +883,33 @@ static void normalize_script_extensions(PropList& script_extensions, PropList co
 
         sort_and_merge_code_point_ranges(code_points);
     }
+
+    // Lastly, the Common and Inherited script extensions are special. They must not contain any
+    // code points which appear in other script extensions. The ScriptExtensions UCD file does not
+    // list these extensions, therefore this peculiarity must be handled programatically.
+    // https://www.unicode.org/reports/tr24/#Assignment_ScriptX_Values
+    auto code_point_has_other_extension = [&](StringView key, u32 code_point) {
+        for (auto const& extension : extensions) {
+            if (extension.key == key)
+                continue;
+            if (any_of(extension.value, [&](auto const& r) { return (r.first <= code_point) && (code_point <= r.last); }))
+                return true;
+        }
+
+        return false;
+    };
+
+    auto get_code_points_without_other_extensions = [&](StringView key) {
+        auto code_points = flatten_code_point_ranges(script_list.find(key)->value);
+        code_points.remove_all_matching([&](u32 c) { return code_point_has_other_extension(key, c); });
+        return code_points;
+    };
+
+    auto common_code_points = get_code_points_without_other_extensions("Common"sv);
+    script_extensions.set("Common"sv, form_code_point_ranges(common_code_points));
+
+    auto inherited_code_points = get_code_points_without_other_extensions("Inherited"sv);
+    script_extensions.set("Inherited"sv, form_code_point_ranges(inherited_code_points));
 }
 
 int main(int argc, char** argv)