異字体セレクタを含む入力への対応: 文字列から異字体セレクタを取り除くメソッドを定義

core/src/util.rs

@@ -1,3 +1,4 @@
 pub mod converter;
+pub(crate) mod extension;
 pub mod sequence_matcher;
 mod trimmer;

core/src/util/extension.rs

@@ -0,0 +1,62 @@
+pub(crate) trait CharExt {
+    fn is_variation_selector(&self) -> bool;
+}
+
+impl CharExt for char {
+    /// 異字体セレクタかどうかを判別します
+    fn is_variation_selector(&self) -> bool {
+        matches!(self, '\u{FE00}'..='\u{FE0F}' | '\u{E0100}'..='\u{E01EF}')
+    }
+}
+
+pub(crate) trait StrExt {
+    fn strip_variation_selectors(&self) -> String;
+}
+
+impl StrExt for str {
+    /// 文字列から異字体セレクタを取り除きます
+    fn strip_variation_selectors(&self) -> String {
+        self.chars()
+            .filter(|c| !c.is_variation_selector())
+            .collect()
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use crate::util::extension::{CharExt, StrExt};
+
+    #[test]
+    fn is_variation_selector() {
+        assert_eq!('あ'.is_variation_selector(), false);
+        assert_eq!('亜'.is_variation_selector(), false);
+
+        assert_eq!('\u{FDFF}'.is_variation_selector(), false);
+        assert_eq!('\u{FE00}'.is_variation_selector(), true);
+
+        assert_eq!('\u{FE0F}'.is_variation_selector(), true);
+        assert_eq!('\u{FE10}'.is_variation_selector(), false);
+
+        assert_eq!('\u{E00FF}'.is_variation_selector(), false);
+        assert_eq!('\u{E0100}'.is_variation_selector(), true);
+
+        assert_eq!('\u{E01EF}'.is_variation_selector(), true);
+        assert_eq!('\u{E01F0}'.is_variation_selector(), false);
+    }
+
+    #[test]
+    fn strip_variation_selectors_逢坂() {
+        let normal = "\u{9022}\u{5742}"; // 逢坂
+        let variant = "\u{9022}\u{E0101}\u{5742}"; // 逢󠄁坂
+        assert_ne!(normal, variant);
+        assert_eq!(normal, variant.strip_variation_selectors());
+    }
+
+    #[test]
+    fn strip_variation_selectors_茨城() {
+        let normal = "\u{8328}\u{57CE}";
+        let variant = "\u{8328}\u{E0100}\u{57CE}";
+        assert_ne!(normal, variant);
+        assert_eq!(normal, variant.strip_variation_selectors());
+    }
+}