On demand collations.

ext/unicode/unicode.go

@@ -65,6 +65,15 @@ func RegisterCollation(db *sqlite3.Conn, locale, name string) error {
 	return db.CreateCollation(name, collate.New(tag).Compare)
 }
 
+// RegisterCollationsNeeded registers Unicode collation sequences on demand for a database connection.
+func RegisterCollationsNeeded(db *sqlite3.Conn) error {
+	return db.CollationNeeded(func(db *sqlite3.Conn, name string) {
+		if tag, err := language.Parse(name); err == nil {
+			db.CreateCollation(name, collate.New(tag).Compare)
+		}
+	})
+}
+
 func upper(ctx sqlite3.Context, arg ...sqlite3.Value) {
 	if len(arg) == 1 {
 		ctx.ResultRawText(bytes.ToUpper(arg[0].RawText()))

ext/unicode/unicode_test.go

@@ -92,7 +92,7 @@ func TestRegister_collation(t *testing.T) {
 		t.Fatal(err)
 	}
 
-	err = db.Exec(`SELECT icu_load_collation('fr_FR', 'french')`)
+	err = db.Exec(`SELECT icu_load_collation('fr-FR', 'french')`)
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -127,6 +127,57 @@ func TestRegister_collation(t *testing.T) {
 	}
 }
 
+func TestRegisterCollationsNeeded(t *testing.T) {
+	t.Parallel()
+
+	db, err := sqlite3.Open(":memory:")
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer db.Close()
+
+	RegisterCollationsNeeded(db)
+
+	err = db.Exec(`CREATE TABLE words (word VARCHAR(10))`)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	err = db.Exec(`INSERT INTO words (word) VALUES ('côte'), ('cote'), ('coter'), ('coté'), ('cotée'), ('côté')`)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	stmt, _, err := db.Prepare(`SELECT word FROM words ORDER BY word COLLATE fr_FR`)
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer stmt.Close()
+
+	got, want := []string{}, []string{"cote", "coté", "côte", "côté", "cotée", "coter"}
+
+	for stmt.Step() {
+		got = append(got, stmt.ColumnText(0))
+	}
+	if err := stmt.Err(); err != nil {
+		t.Fatal(err)
+	}
+
+	if !reflect.DeepEqual(got, want) {
+		t.Error("not equal")
+	}
+
+	err = stmt.Close()
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	err = db.Close()
+	if err != nil {
+		t.Fatal(err)
+	}
+}
+
 func TestRegister_error(t *testing.T) {
 	t.Parallel()
 

func.go

@@ -33,7 +33,11 @@ func (c *Conn) CollationNeeded(cb func(db *Conn, name string)) error {
 // one or more unknown collating sequences.
 func (c Conn) AnyCollationNeeded() error {
 	r := c.call("sqlite3_anycollseq_init", uint64(c.handle), 0, 0)
-	return c.error(r)
+	if err := c.error(r); err != nil {
+		return err
+	}
+	c.collation = nil
+	return nil
 }
 
 // CreateCollation defines a new collating sequence.