GsonKotlinTest.kt

package com.bram.demo.test.models.gson

import com.google.gson.GsonBuilder
import org.junit.Assert
import org.junit.Test

class GsonKotlinTest {

    // Data Class + some property has default value = default value doesn't work.
    data class DataClass1(
        val a: String? = "a",
        val b: String?,
        val c: String = "c",
        val d: String
    )

    @Test
    fun testDataClass1() {
        val foo  = GsonBuilder().create().fromJson("""{"b"="foo"}""", DataClass1::class.java)
        Assert.assertEquals(null, foo.a)
        Assert.assertEquals("foo", foo.b)
        Assert.assertEquals(null, foo.c)
        Assert.assertEquals(null, foo.d)
    }

    // Data Class + all property has default value = default values works.
    data class DataClass2(
        val a: String? = "a",
        val b: String? = "b",
        val c: String = "c",
        val d: String = "d"
    )

    @Test
    fun testDataClass2() {
        val foo  = GsonBuilder().create().fromJson("""{"b"="foo"}""", DataClass2::class.java)
        Assert.assertEquals("a", foo.a)
        Assert.assertEquals("foo", foo.b)
        Assert.assertEquals("c", foo.c)
        Assert.assertEquals("d", foo.d)
    }

    // Class + constructor + some property has default value = default values doesn't work.
    class Class1(
        val a: String? = "a",
        val b: String?,
        val c: String = "c",
        val d: String
    )

    @Test
    fun testClass1() {
        val foo  = GsonBuilder().create().fromJson("""{"b"="foo"}""", Class1::class.java)
        Assert.assertEquals(null, foo.a)
        Assert.assertEquals("foo", foo.b)
        Assert.assertEquals(null, foo.c)
        Assert.assertEquals(null, foo.d)
    }

    // Class + no-args constructor = default values works.
    class Class2 {
        val a: String? = "a"
        val b: String? = null
        val c: String = "c"
        var d: String = "d"
    }

    @Test
    fun testClass2() {
        val foo  = GsonBuilder().create().fromJson("""{"b"="foo"}""", Class2::class.java)
        Assert.assertEquals("a", foo.a)
        Assert.assertEquals("foo", foo.b)
        Assert.assertEquals("c", foo.c)
        Assert.assertEquals("d", foo.d)
    }

    // Class + constructor + all property has default value = default values works.
    class Class3(
        val a: String? = "a",
        val b: String? = null,
        val c: String = "c",
        val d: String = "d"
    )

    @Test
    fun testClass3() {
        val foo  = GsonBuilder().create().fromJson("""{"b"="foo"}""", Class3::class.java)
        Assert.assertEquals("a", foo.a)
        Assert.assertEquals("foo", foo.b)
        Assert.assertEquals("c", foo.c)
        Assert.assertEquals("d", foo.d)
    }

    // Data Class + all property has default value = default values works.
    data class DataClassDelegate(
        val a: String? = "a",
        val b: String? = "b",
        val c: String = "c",
        val d: String = "d"
    ) {
        val e: String by lazy {
            if (a.isNullOrEmpty()) {
                "isNull"
            } else {
                "isNotNull"
            }
        }
    }

    @Test
    fun testDataClassDelegate() {
        val foo  = GsonBuilder().create().fromJson("""{"b"="foo"}""", DataClassDelegate::class.java)
        Assert.assertEquals("a", foo.a)
        Assert.assertEquals("foo", foo.b)
        Assert.assertEquals("c", foo.c)
        Assert.assertEquals("d", foo.d)
        Assert.assertEquals("isNotNull", foo.e)

        val dDelegate = DataClassDelegate()
        Assert.assertEquals("a", dDelegate.a)
        Assert.assertEquals("b", dDelegate.b)
        Assert.assertEquals("c", dDelegate.c)
        Assert.assertEquals("d", dDelegate.d)
        Assert.assertEquals("isNotNull", dDelegate.e)

        val json = GsonBuilder().create().toJson(dDelegate)
        Assert.assertEquals("{\"e\$delegate\":{\"_value\":\"isNotNull\"},\"a\":\"a\",\"b\":\"b\",\"c\":\"c\",\"d\":\"d\"}", json)
        try {
            GsonBuilder().create().fromJson(json, DataClassDelegate::class.java)
            Assert.fail()
        } catch (e: RuntimeException) {
            Assert.assertEquals("Unable to invoke no-args constructor for interface kotlin.Lazy. Registering an InstanceCreator with Gson for this type may fix this problem.", e.message)
        }
    }

    // Data Class + all property has default value = default values works.
    class ClassDelegate(
        val a: String? = "a",
        val b: String? = "b",
        val c: String = "c",
        val d: String = "d"
    ) {
        val e: String by lazy {
            if (a.isNullOrEmpty()) {
                "isNull"
            } else {
                "isNotNull"
            }
        }
    }

    @Test
    fun testClassDelegate() {
        val foo  = GsonBuilder().create().fromJson("""{"b"="foo"}""", ClassDelegate::class.java)
        Assert.assertEquals("a", foo.a)
        Assert.assertEquals("foo", foo.b)
        Assert.assertEquals("c", foo.c)
        Assert.assertEquals("d", foo.d)
        Assert.assertEquals("isNotNull", foo.e)

        val delegate = ClassDelegate()
        Assert.assertEquals("a", delegate.a)
        Assert.assertEquals("b", delegate.b)
        Assert.assertEquals("c", delegate.c)
        Assert.assertEquals("d", delegate.d)
        Assert.assertEquals("isNotNull", delegate.e)

        val json = GsonBuilder().create().toJson(delegate)
        Assert.assertEquals("{\"e\$delegate\":{\"_value\":\"isNotNull\"},\"a\":\"a\",\"b\":\"b\",\"c\":\"c\",\"d\":\"d\"}", json)
        try {
            GsonBuilder().create().fromJson(json, ClassDelegate::class.java)
            Assert.fail()
        } catch (e: RuntimeException) {
            Assert.assertEquals("Unable to invoke no-args constructor for interface kotlin.Lazy. Registering an InstanceCreator with Gson for this type may fix this problem.", e.message)
        }
    }

    // Data Class + all property has default value = default values works.
    data class DataClassDelegateTransient(
        val a: String? = "a",
        val b: String? = "b",
        val c: String = "c",
        val d: String = "d"
    ) {
        @delegate:Transient
        val e: String by lazy {
            if (a.isNullOrEmpty()) {
                "isNull"
            } else {
                "isNotNull"
            }
        }
    }

    @Test
    fun testDataClassDelegateTransient() {
        val foo  = GsonBuilder().create().fromJson("""{"b"="foo"}""", DataClassDelegateTransient::class.java)
        Assert.assertEquals("a", foo.a)
        Assert.assertEquals("foo", foo.b)
        Assert.assertEquals("c", foo.c)
        Assert.assertEquals("d", foo.d)
        Assert.assertEquals("isNotNull", foo.e)

        val dDelegateTransient = DataClassDelegateTransient()
        Assert.assertEquals("a", dDelegateTransient.a)
        Assert.assertEquals("b", dDelegateTransient.b)
        Assert.assertEquals("c", dDelegateTransient.c)
        Assert.assertEquals("d", dDelegateTransient.d)
        Assert.assertEquals("isNotNull", dDelegateTransient.e)

        val json = GsonBuilder().create().toJson(dDelegateTransient)
        Assert.assertEquals("{\"a\":\"a\",\"b\":\"b\",\"c\":\"c\",\"d\":\"d\"}", json)

        val dDelegateTransientPlus = GsonBuilder().create().fromJson(json, DataClassDelegateTransient::class.java)
        Assert.assertEquals("a", dDelegateTransientPlus.a)
        Assert.assertEquals("b", dDelegateTransientPlus.b)
        Assert.assertEquals("c", dDelegateTransientPlus.c)
        Assert.assertEquals("d", dDelegateTransientPlus.d)
        Assert.assertEquals("isNotNull", dDelegateTransientPlus.e)
    }

    // Data Class + all property has default value = default values works.
    class ClassDelegateTransient(
        val a: String? = "a",
        val b: String? = "b",
        val c: String = "c",
        val d: String = "d"
    ) {
        @delegate:Transient
        val e: String by lazy {
            if (a.isNullOrEmpty()) {
                "isNull"
            } else {
                "isNotNull"
            }
        }
    }

    @Test
    fun testClassDelegateTransient() {
        val foo  = GsonBuilder().create().fromJson("""{"b"="foo"}""", ClassDelegateTransient::class.java)
        Assert.assertEquals("a", foo.a)
        Assert.assertEquals("foo", foo.b)
        Assert.assertEquals("c", foo.c)
        Assert.assertEquals("d", foo.d)
        Assert.assertEquals("isNotNull", foo.e)

        val delegateTransient = ClassDelegateTransient()
        Assert.assertEquals("a", delegateTransient.a)
        Assert.assertEquals("b", delegateTransient.b)
        Assert.assertEquals("c", delegateTransient.c)
        Assert.assertEquals("d", delegateTransient.d)
        Assert.assertEquals("isNotNull", delegateTransient.e)

        val json = GsonBuilder().create().toJson(delegateTransient)
        Assert.assertEquals("{\"a\":\"a\",\"b\":\"b\",\"c\":\"c\",\"d\":\"d\"}", json)

        val delegateTransientPlus = GsonBuilder().create().fromJson(json, ClassDelegateTransient::class.java)
        Assert.assertEquals("a", delegateTransientPlus.a)
        Assert.assertEquals("b", delegateTransientPlus.b)
        Assert.assertEquals("c", delegateTransientPlus.c)
        Assert.assertEquals("d", delegateTransientPlus.d)
        Assert.assertEquals("isNotNull", delegateTransientPlus.e)
    }
}