rollup.Config implements types.BlockType interface

op-node/rollup/types.go

@@ -336,6 +336,10 @@ func (cfg *Config) Check() error {
 	return nil
 }
 
+func (cfg *Config) HasOptimismWithdrawalsRoot(timestamp uint64) bool {
+	return cfg.IsIsthmus(timestamp)
+}
+
 // validateAltDAConfig checks the two approaches to configuring alt-da mode.
 // If the legacy values are set, they are copied to the new location. If both are set, they are check for consistency.
 func validateAltDAConfig(cfg *Config) error {

op-node/rollup/types_test.go

@@ -767,3 +767,37 @@ func TestConfig_IsActivationBlock(t *testing.T) {
 		require.Zero(t, cfg.IsActivationBlock(ts, ts+1))
 	}
 }
+
+func TestConfigImplementsBlockType(t *testing.T) {
+	config := randConfig()
+	isthmusTime := uint64(100)
+	config.IsthmusTime = &isthmusTime
+	tests := []struct {
+		name                       string
+		blockTime                  uint64
+		hasOptimismWithdrawalsRoot bool
+	}{
+		{
+			name:                       "BeforeIsthmus",
+			blockTime:                  uint64(99),
+			hasOptimismWithdrawalsRoot: false,
+		},
+		{
+			name:                       "AtIsthmus",
+			blockTime:                  uint64(100),
+			hasOptimismWithdrawalsRoot: true,
+		},
+		{
+			name:                       "AfterIsthmus",
+			blockTime:                  uint64(200),
+			hasOptimismWithdrawalsRoot: true,
+		},
+	}
+
+	for _, test := range tests {
+		test := test
+		t.Run(fmt.Sprintf("TestHasOptimismWithdrawalsRoot_%s", test.name), func(t *testing.T) {
+			assert.Equal(t, config.HasOptimismWithdrawalsRoot(test.blockTime), test.hasOptimismWithdrawalsRoot)
+		})
+	}
+}