From 83aa84f12df78a84df9ed50de152140e54d0be5f Mon Sep 17 00:00:00 2001
From: st0012 <stan001212@gmail.com>
Date: Sun, 6 Oct 2019 14:48:07 +0800
Subject: [PATCH] Implement Object#tap

---
 vm/class.go       | 12 ++++++++++++
 vm/object_test.go | 33 +++++++++++++++++++++++++++++++++
 2 files changed, 45 insertions(+)

diff --git a/vm/class.go b/vm/class.go
index 7a683b71a..6e0067cdb 100644
--- a/vm/class.go
+++ b/vm/class.go
@@ -1536,6 +1536,18 @@ var builtinClassCommonInstanceMethods = []*BuiltinMethodObject{
 
 		},
 	},
+	{
+		Name: "tap",
+		Fn: func(receiver Object, sourceLine int, t *Thread, args []Object, blockFrame *normalCallFrame) Object {
+			if blockFrame == nil {
+				return t.vm.InitErrorObject(errors.InternalError, sourceLine, errors.CantYieldWithoutBlockFormat)
+			}
+
+			t.builtinMethodYield(blockFrame, receiver)
+
+			return receiver
+		},
+	},
 	{
 		Name: "thread",
 		Fn: func(receiver Object, sourceLine int, t *Thread, args []Object, blockFrame *normalCallFrame) Object {
diff --git a/vm/object_test.go b/vm/object_test.go
index 0761fb7d4..e772fe502 100644
--- a/vm/object_test.go
+++ b/vm/object_test.go
@@ -19,3 +19,36 @@ func TestObjectClassSuperclass(t *testing.T) {
 		v.checkSP(t, i, 1)
 	}
 }
+
+func TestObjectTapMethod(t *testing.T) {
+	tests := []struct {
+		input    string
+		expected interface{}
+	}{
+		{
+			`
+			a = 1
+			a.tap do |int|
+				int + 1
+			end
+`, 1},
+		{
+			`
+			a = 1
+			b = 2
+			a.tap do |int|
+				b = int + b
+			end
+			b
+`, 3},
+	}
+
+	for i, tt := range tests {
+		v := initTestVM()
+		evaluated := v.testEval(t, tt.input, getFilename())
+		VerifyExpected(t, i, evaluated, tt.expected)
+		v.checkCFP(t, i, 0)
+		v.checkSP(t, i, 1)
+	}
+}
+