UnnecessaryInnerClassSpec.kt

package io.gitlab.arturbosch.detekt.rules.style

import io.gitlab.arturbosch.detekt.api.Config
import io.gitlab.arturbosch.detekt.rules.KotlinCoreEnvironmentTest
import io.gitlab.arturbosch.detekt.test.assertThat
import io.gitlab.arturbosch.detekt.test.lintWithContext
import org.jetbrains.kotlin.cli.jvm.compiler.KotlinCoreEnvironment
import org.junit.jupiter.api.Nested
import org.junit.jupiter.api.Test

@KotlinCoreEnvironmentTest
class UnnecessaryInnerClassSpec(val env: KotlinCoreEnvironment) {
    val subject = UnnecessaryInnerClass(Config.empty)

    @Test
    fun `reports when an inner class does not access members of its outer class`() {
        val code = """
            val fileFoo = "FILE_FOO"
            
            class A {
                val foo = "BAR"
                
                fun printFoo() {
                    println(foo)
                }
                
                inner class B {
                    val fizz = "BUZZ"
                    
                    fun printFizz() {
                        println(fileFoo)
                        println(fizz)
                    }
                }
            }
        """.trimIndent()

        assertThat(subject.lintWithContext(env, code)).hasSize(1)
    }

    @Nested
    inner class `does not report an inner class accessing outer-class members` {
        @Test
        fun `as a default argument for a constructor`() {
            val code = """
                class A {
                    val foo = "BAR"

                    inner class B(val fizz: String = foo)
                }
            """.trimIndent()

            assertThat(subject.lintWithContext(env, code)).isEmpty()
        }

        @Test
        fun `as a property initializer`() {
            val code = """
                class A {
                    val foo = "BAR"

                    inner class B {
                        val fizz = foo
                    }
                }
            """.trimIndent()

            assertThat(subject.lintWithContext(env, code)).isEmpty()
        }

        @Nested
        inner class `in a variable assignment` {
            @Test
            fun `where the outer-class variable is on the left`() {
                val code = """
                    class A {
                        var foo = "BAR"

                        inner class B {
                            val fizz = "BUZZ"
                            init {
                                foo = fizz
                            }
                        }
                    }
                """.trimIndent()

                assertThat(subject.lintWithContext(env, code)).isEmpty()
            }

            @Test
            fun `where the outer-class variable is on the right`() {
                val code = """
                    class A {
                        val foo = "BAR"

                        inner class B {
                            val fizz: String
                            init {
                                fizz = foo
                            }
                        }
                    }
                """.trimIndent()

                assertThat(subject.lintWithContext(env, code)).isEmpty()
            }

            @Test
            fun `where the outer-class variable is in a compound statement`() {
                val code = """
                    class A {
                        val foo = "BAR"

                        inner class B {
                            val fizz: String
                            init {
                                fizz = "FOO" + foo
                            }
                        }
                    }
                """.trimIndent()

                assertThat(subject.lintWithContext(env, code)).isEmpty()
            }
        }

        @Nested
        inner class `in an if-statement` {
            @Test
            fun `where the outer-class variable is the only expression`() {
                val code = """
                    class A(val foo: Boolean) {
                        
                        inner class B {
                            fun printFoo() {
                                if (foo) {
                                    println("FOO")
                                }
                            }
                        }
                    }
                """.trimIndent()

                assertThat(subject.lintWithContext(env, code)).isEmpty()
            }

            @Test
            fun `where the outer-class variable is on the left`() {
                val code = """
                    class A {
                        val foo = "BAR"
                        
                        inner class B {
                            fun printFoo() {
                                if (foo == "BAR") {
                                    println("FOO")
                                }
                            }
                        }
                    }
                """.trimIndent()

                assertThat(subject.lintWithContext(env, code)).isEmpty()
            }

            @Test
            fun `where the outer-class variable is on the right`() {
                val code = """
                    class A {
                        val foo = "BAR"
                        
                        inner class B {
                            fun printFoo() {
                                if ("BAR" == foo) {
                                    println("FOO")
                                }
                            }
                        }
                    }
                """.trimIndent()

                assertThat(subject.lintWithContext(env, code)).isEmpty()
            }

            @Test
            fun `where the outer-class variable is in a compound statement`() {
                val code = """
                    class A {
                        val foo = "BAR"
                        
                        inner class B {
                            val fizz = "BUZZ"
                            fun printFoo() {
                                if (fizz == "BUZZ" && foo) {
                                    println("FOO")
                                }
                            }
                        }
                    }
                """.trimIndent()

                assertThat(subject.lintWithContext(env, code)).isEmpty()
            }
        }

        @Test
        fun `as a function initializer`() {
            val code = """
                class A {
                    fun printFoo() {
                        println("FOO")
                    }
                    
                    inner class B {
                        fun printFizz() = printFoo()
                    }
                }
            """.trimIndent()

            assertThat(subject.lintWithContext(env, code)).isEmpty()
        }

        @Test
        fun `as a function call`() {
            val code = """
                class A {
                    fun printFoo() {
                        println("FOO")
                    }
                    
                    inner class B {
                        fun printFizz() {
                            printFoo()
                        }
                    }
                }
            """.trimIndent()

            assertThat(subject.lintWithContext(env, code)).isEmpty()
        }

        @Test
        fun `as a function argument`() {
            val code = """
                class A {
                    val foo = "BAR"
                    
                    inner class B {
                        fun printFizz() {
                            println(foo)
                        }
                    }
                }
            """.trimIndent()

            assertThat(subject.lintWithContext(env, code)).isEmpty()
        }

        @Test
        fun `as a default value in a function signature`() {
            val code = """
                class A {
                    val foo = "BAR"
                    
                    inner class B {
                        fun printFizz(fizzVal: String = foo) {
                            println(fizzVal)
                        }
                    }
                }
            """.trimIndent()

            assertThat(subject.lintWithContext(env, code)).isEmpty()
        }

        @Test
        fun `as a safe qualified expression`() {
            val code = """
                class A {
                    var foo: String? = null

                    inner class B {
                        fun fooLength() {
                            foo?.length
                        }
                    }
                }
            """.trimIndent()

            assertThat(subject.lintWithContext(env, code)).isEmpty()
        }

        @Test
        fun `to call a function of the member`() {
            val code = """
                class FooClass {
                    fun printFoo() {
                        println("FOO")
                    }
                }
                
                class A {
                    val foo = FooClass()
                    
                    inner class B {
                        fun printFizz() {
                            foo.printFoo()
                        }
                    }
                }
            """.trimIndent()

            assertThat(subject.lintWithContext(env, code)).isEmpty()
        }

        @Test
        fun `to call a function type variable of the member`() {
            val code = """
                class A {
                    val foo: () -> Unit = {}
                    
                    inner class B {
                        fun bar() {
                            foo()
                        }
                    }
                }
            """.trimIndent()

            assertThat(subject.lintWithContext(env, code)).isEmpty()
        }
    }

    @Nested
    inner class `does not report a double-nested inner class accessing from an outer-class member` {

        @Test
        fun `when the innermost class refers a inner class and the inner class refers the outermost class`() {
            val code = """
                class A {
                    val foo = "BAR"
                    
                    inner class B {
                        val fizz = foo
                        inner class C {
                            fun printFoo() {
                                println(fizz)
                            }
                        }
                    }
                }
            """.trimIndent()

            assertThat(subject.lintWithContext(env, code)).isEmpty()
        }

        @Test
        fun `when the innermost class refers the outermost class`() {
            val code = """
                class A {
                    val foo = "BAR"
                    
                    inner class B {
                        inner class C {
                            fun printFoo() {
                                println(foo)
                            }
                        }
                    }
                }
            """.trimIndent()

            assertThat(subject.lintWithContext(env, code)).isEmpty()
        }
    }

    @Test
    fun `does not report anonymous inner classes`() {
        val code = """
            interface FooInterface {
                fun doFoo()
            }

            class Foo {
                fun runFoo(fi: FooInterface) {
                    fi.doFoo()
                }
                
                fun run() {
                    runFoo(object : FooInterface {
                        override fun doFoo() {
                            println("FOO")
                        }
                    })
                }
            }
        """.trimIndent()

        assertThat(subject.lintWithContext(env, code)).isEmpty()
    }
}