Simplify tails.

conn.go

@@ -172,9 +172,6 @@ func (c *Conn) PrepareFlags(sql string, flags PrepareFlag) (stmt *Stmt, tail str
 	if len(sql) > _MAX_LENGTH {
 		return nil, "", TOOBIG
 	}
-	if emptyStatement(sql) {
-		return nil, "", nil
-	}
 
 	defer c.arena.mark()()
 	stmtPtr := c.arena.new(ptrlen)
@@ -187,8 +184,9 @@ func (c *Conn) PrepareFlags(sql string, flags PrepareFlag) (stmt *Stmt, tail str
 
 	stmt = &Stmt{c: c}
 	stmt.handle = util.ReadUint32(c.mod, stmtPtr)
-	i := util.ReadUint32(c.mod, tailPtr)
-	tail = sql[i-sqlPtr:]
+	if sql := sql[util.ReadUint32(c.mod, tailPtr)-sqlPtr:]; sql != "" {
+		tail = sql
+	}
 
 	if err := c.error(r, sql); err != nil {
 		return nil, "", err

driver/driver.go

@@ -247,17 +247,8 @@ func (c *conn) PrepareContext(ctx context.Context, query string) (driver.Stmt, e
 		return nil, err
 	}
 	if tail != "" {
-		// Check if the tail contains any SQL.
-		st, _, err := c.Conn.Prepare(tail)
-		if err != nil {
-			s.Close()
-			return nil, err
-		}
-		if st != nil {
-			s.Close()
-			st.Close()
-			return nil, util.TailErr
-		}
+		s.Close()
+		return nil, util.TailErr
 	}
 	return &stmt{s, c.Conn}, nil
 }

driver/driver_test.go

@@ -186,12 +186,6 @@ func Test_Prepare(t *testing.T) {
 	}
 	defer db.Close()
 
-	stmt, err := db.Prepare(`SELECT 1; -- HERE`)
-	if err != nil {
-		t.Error(err)
-	}
-	defer stmt.Close()
-
 	var serr *sqlite3.Error
 	_, err = db.Prepare(`SELECT`)
 	if err == nil {
@@ -207,18 +201,14 @@ func Test_Prepare(t *testing.T) {
 		t.Error("got message:", got)
 	}
 
+	_, err = db.Prepare(`SELECT 1; `)
+	if err.Error() != string(util.TailErr) {
+		t.Error("want tailErr")
+	}
+
 	_, err = db.Prepare(`SELECT 1; SELECT`)
-	if err == nil {
-		t.Error("want error")
-	}
-	if !errors.As(err, &serr) {
-		t.Fatalf("got %T, want sqlite3.Error", err)
-	}
-	if rc := serr.Code(); rc != sqlite3.ERROR {
-		t.Errorf("got %d, want sqlite3.ERROR", rc)
-	}
-	if got := err.Error(); got != `sqlite3: SQL logic error: incomplete input` {
-		t.Error("got message:", got)
+	if err.Error() != string(util.TailErr) {
+		t.Error("want tailErr")
 	}
 
 	_, err = db.Prepare(`SELECT 1; SELECT 2`)

stmt.go

@@ -501,18 +501,3 @@ func (s *Stmt) ColumnValue(col int) Value {
 		handle: uint32(r),
 	}
 }
-
-// Return true if stmt is an empty SQL statement.
-// This is used as an optimization.
-// It's OK to always return false here.
-func emptyStatement(stmt string) bool {
-	for _, b := range []byte(stmt) {
-		switch b {
-		case ' ', '\n', '\r', '\t', '\v', '\f':
-		case ';':
-		default:
-			return false
-		}
-	}
-	return true
-}

stmt_test.go

@@ -1,58 +0,0 @@
-package sqlite3
-
-import "testing"
-
-func Test_emptyStatement(t *testing.T) {
-	t.Parallel()
-
-	tests := []struct {
-		name string
-		stmt string
-		want bool
-	}{
-		{"empty", "", true},
-		{"space", " ", true},
-		{"separator", ";\n ", true},
-		{"begin", "BEGIN", false},
-		{"select", "SELECT 1;", false},
-	}
-	for _, tt := range tests {
-		t.Run(tt.name, func(t *testing.T) {
-			if got := emptyStatement(tt.stmt); got != tt.want {
-				t.Errorf("got %v, want %v", got, tt.want)
-			}
-		})
-	}
-}
-
-func Fuzz_emptyStatement(f *testing.F) {
-	f.Add("")
-	f.Add(" ")
-	f.Add(";\n ")
-	f.Add("; ;\v")
-	f.Add("BEGIN")
-	f.Add("SELECT 1;")
-
-	db, err := Open(":memory:")
-	if err != nil {
-		f.Fatal(err)
-	}
-	defer db.Close()
-
-	f.Fuzz(func(t *testing.T, sql string) {
-		// If empty, SQLite parses it as empty.
-		if emptyStatement(sql) {
-			stmt, tail, err := db.Prepare(sql)
-			if err != nil {
-				t.Errorf("%q, %v", sql, err)
-			}
-			if stmt != nil {
-				t.Errorf("%q, %v", sql, stmt)
-			}
-			if tail != "" {
-				t.Errorf("%q", sql)
-			}
-			stmt.Close()
-		}
-	})
-}