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Implement basic cycle detection! (#4)
* Add basic cycle detection uses an ArrayDeque as a stack. currently this is not thread safe and will need to be modified when a concurrent strategy is implemented Adds and removes the `System.identityHashCode()` from a stack. when the hash code is detected in the list of currently processing nodes, a cycle has been detected. Add the hash code to a list of identifiers (in case we encounter many cycles in a single node tree, and then immediately return. This is faster than object comparison and has relatively low memory overhead, but is most likely not optimal * Add cycle detection tests * Add readme bit for cycle detection add another test for small objects
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src/test/kotlin/com/tylerthrailkill/helpers/prettyprint/CycleDetectionTest.kt
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,124 @@ | ||
| package com.tylerthrailkill.helpers.prettyprint | ||
|
|
||
| import org.spekframework.spek2.Spek | ||
| import org.spekframework.spek2.style.specification.describe | ||
|
|
||
| object CycleDetectionTest : Spek({ | ||
| setup() | ||
|
|
||
| describe("pretty printing") { | ||
| context("plain objects with cycles") { | ||
| it("should detect a cycle with plain Unit") { | ||
| val unit = Unit | ||
| val identity = System.identityHashCode(unit) | ||
| prettyPrint(unit) mapsTo """ | ||
| Unit( | ||
| INSTANCE = cyclic reference detected for $identity | ||
| )[${'$'}id=$identity] | ||
| """ | ||
| } | ||
| it("should detect a cycle with two small objects") { | ||
| val sco1 = SmallCyclicalObject1() | ||
| val sco2 = SmallCyclicalObject2(sco1) | ||
| sco1.c = sco2 | ||
| val identity = System.identityHashCode(sco1) | ||
| prettyPrint(sco1) mapsTo """ | ||
| SmallCyclicalObject1( | ||
| c = SmallCyclicalObject2( | ||
| c = cyclic reference detected for $identity | ||
| ) | ||
| )[${'$'}id=$identity] | ||
| """ | ||
| } | ||
| it("should detect no cycle when an element is repeated several times in the same objects fields") { | ||
| val smallObject = SmallObject("a string in small object", 777) | ||
| val nestedLargeObjectNull = NestedLargeObject( | ||
| NestedSmallObject(smallObject), | ||
| smallObject, | ||
| "test string, please don't break", | ||
| null | ||
| ) | ||
| prettyPrint(nestedLargeObjectNull) mapsTo """ | ||
| NestedLargeObject( | ||
| nestedSmallObject = NestedSmallObject( | ||
| smallObject = SmallObject( | ||
| field1 = a string in small object | ||
| field2 = 777 | ||
| ) | ||
| ) | ||
| smallObject = SmallObject( | ||
| field1 = a string in small object | ||
| field2 = 777 | ||
| ) | ||
| testString = test string, please don't break | ||
| bigObject = null | ||
| ) | ||
| """ | ||
| } | ||
| } | ||
| context("maps with cycles") { | ||
| it("should detect a cycle between an object with a map with an object with a cycle") { | ||
| val objectWithMap = ObjectWithMap( | ||
| mutableMapOf(1 to null) | ||
| ) | ||
| val objectContainingObjectWithMap = ObjectContainingObjectWithMap() | ||
| objectContainingObjectWithMap.objectWithMap = objectWithMap | ||
| objectWithMap.map[1] = objectContainingObjectWithMap | ||
| val identity = System.identityHashCode(objectWithMap) | ||
| prettyPrint(objectWithMap) mapsTo """ | ||
| ObjectWithMap( | ||
| map = { | ||
| 1 -> ObjectContainingObjectWithMap( | ||
| objectWithMap = cyclic reference detected for $identity | ||
| ) | ||
| } | ||
| )[${'$'}id=$identity] | ||
| """.trimIndent() | ||
| } | ||
| it("should detect a cycle of a map containing itself") { | ||
| val outerMap: MutableMap<Int, Any?> = mutableMapOf(1 to null) | ||
| val innerMap = mutableMapOf(1 to outerMap) | ||
| outerMap[1] = innerMap | ||
| val identity = System.identityHashCode(outerMap) | ||
| prettyPrint(outerMap) mapsTo """ | ||
| { | ||
| 1 -> { | ||
| 1 -> cyclic reference detected for $identity | ||
| } | ||
| }[${'$'}id=$identity] | ||
| """.trimIndent() | ||
| } | ||
| } | ||
| context("lists with cycles") { | ||
| it("should detect a cycle between an object with a list with an object with a cycle") { | ||
| val objectWithList = ObjectWithList(mutableListOf()) | ||
| val objectContainingObjectWithList = ObjectContainingObjectWithList() | ||
| objectContainingObjectWithList.objectWithList = objectWithList | ||
| objectWithList.list.add(objectContainingObjectWithList) | ||
| val identity = System.identityHashCode(objectWithList) | ||
| prettyPrint(objectWithList) mapsTo """ | ||
| ObjectWithList( | ||
| list = [ | ||
| ObjectContainingObjectWithList( | ||
| objectWithList = cyclic reference detected for $identity | ||
| ) | ||
| ] | ||
| )[${'$'}id=$identity] | ||
| """.trimIndent() | ||
| } | ||
| it("should detect a cycle of a list containing itself") { | ||
| val outerList: MutableList<Any?> = mutableListOf() | ||
| val innerList = mutableListOf(outerList) | ||
| outerList.add(innerList) | ||
| val identity = System.identityHashCode(outerList) | ||
| prettyPrint(outerList) mapsTo """ | ||
| [ | ||
| [ | ||
| cyclic reference detected for $identity | ||
| ] | ||
| ][${'$'}id=$identity] | ||
| """.trimIndent() | ||
| } | ||
| } | ||
| } | ||
| }) |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
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@@ -10,4 +10,4 @@ | |
| <root level="debug"> | ||
| <appender-ref ref="FILE"/> | ||
| </root> | ||
| </configuration> | ||
| </configuration> | ||