ci: Add detekt static analyzer (#18)

* Add detekt static analyzer
* Enable detekt-formatting
* Include in `check` task

Author: petertrr

.github/workflows/build_and_test.yml

@@ -23,6 +23,8 @@ jobs:
         with:
           arguments: build
           gradle-version: wrapper
+          properties: |
+            detektAutoCorrect=false
       - name: Upload test reports
         if: ${{ failure() }}  # runs only if previous step has failed, the entire workflow will still be marked as failed
         uses: actions/upload-artifact@v2

build.gradle.kts

@@ -1,9 +1,11 @@
 import io.github.petertrr.configurePublishing
 import io.github.petertrr.configureVersioning
+import io.gitlab.arturbosch.detekt.Detekt
 import org.jetbrains.kotlin.gradle.targets.jvm.tasks.KotlinJvmTest
 
 plugins {
     alias(libs.plugins.kotlin.multiplatform)
+    alias(libs.plugins.detekt)
     jacoco
 }
 
@@ -52,6 +54,18 @@ tasks.withType<KotlinJvmTest> {
     useJUnitPlatform()
 }
 
+detekt {
+    buildUponDefaultConfig = true
+    config = files("detekt.yml")
+    autoCorrect = (findProperty("detektAutoCorrect") as String?)?.toBoolean() ?: true
+}
+dependencies {
+    detektPlugins(libs.detekt.formatting)
+}
+tasks.withType<Detekt> {
+    tasks.getByName("check").dependsOn(this)
+}
+
 // configure Jacoco-based code coverage reports for JVM tests executions
 jacoco {
     toolVersion = "0.8.7"

detekt.yml

@@ -0,0 +1,9 @@
+style:
+  active: true
+  MaxLineLength:
+    active: true
+    maxLineLength: 180
+formatting:
+  active: true
+  MaximumLineLength:
+    active: false

gradle/libs.versions.toml

@@ -1,10 +1,13 @@
 [versions]
 kotlin = "1.6.0"
 junit = "5.8.1"
+detekt = "1.19.0"
 
 [plugins]
 kotlin-multiplatform = { id = "org.jetbrains.kotlin.multiplatform", version.ref = "kotlin" }
+detekt = { id = "io.gitlab.arturbosch.detekt", version.ref = "detekt" }
 
 [libraries]
 junit-jupiter-api = { module = "org.junit.jupiter:junit-jupiter-api", version.ref = "junit" }
 junit-jupiter-engine = { module = "org.junit.jupiter:junit-jupiter-engine", version.ref = "junit" }
+detekt-formatting = { module = "io.gitlab.arturbosch.detekt:detekt-formatting", version.ref = "detekt" }

src/commonMain/kotlin/io/github/petertrr/diffutils/DiffUtils.kt

@@ -20,6 +20,8 @@
  * Implements the difference and patching engine
  */
 
+@file:Suppress("TooManyFunctions")
+
 package io.github.petertrr.diffutils
 
 import io.github.petertrr.diffutils.algorithm.DiffAlgorithm
@@ -53,9 +55,13 @@ public fun <T> diff(original: List<T>, revised: List<T>, includeEqualParts: Bool
 /**
  * Computes the difference between the original and revised text.
  */
-public fun diff(sourceText: String, targetText: String,
-         progress: DiffAlgorithmListener?): Patch<String> {
-    return diff(sourceText.split("\n"),
+public fun diff(
+    sourceText: String,
+    targetText: String,
+    progress: DiffAlgorithmListener?
+): Patch<String> {
+    return diff(
+        sourceText.split("\n"),
         targetText.split("\n"),
         progress
     )
@@ -73,7 +79,8 @@ public fun diff(sourceText: String, targetText: String,
  * @return The patch describing the difference between the original and revised sequences.
  */
 public fun <T> diff(
-    source: List<T>, target: List<T>,
+    source: List<T>,
+    target: List<T>,
     equalizer: ((T, T) -> Boolean)?
 ): Patch<T> {
     return if (equalizer != null) {
@@ -85,8 +92,10 @@ public fun <T> diff(
 }
 
 public fun <T> diff(
-    original: List<T>, revised: List<T>,
-    algorithm: DiffAlgorithm<T>, progress: DiffAlgorithmListener?
+    original: List<T>,
+    revised: List<T>,
+    algorithm: DiffAlgorithm<T>,
+    progress: DiffAlgorithmListener?
 ): Patch<T> {
     return diff(original, revised, algorithm, progress, false)
 }
@@ -104,8 +113,10 @@ public fun <T> diff(
  * `null`.
  */
 public fun <T> diff(
-    original: List<T>, revised: List<T>,
-    algorithm: DiffAlgorithm<T>, progress: DiffAlgorithmListener?,
+    original: List<T>,
+    revised: List<T>,
+    algorithm: DiffAlgorithm<T>,
+    progress: DiffAlgorithmListener?,
     includeEqualParts: Boolean
 ): Patch<T> {
     return Patch.generate(original, revised, algorithm.computeDiff(original, revised, progress), includeEqualParts)

src/commonMain/kotlin/io/github/petertrr/diffutils/algorithm/Change.kt

@@ -20,9 +20,10 @@ package io.github.petertrr.diffutils.algorithm
 
 import io.github.petertrr.diffutils.patch.DeltaType
 
-public data class Change(val deltaType: DeltaType,
-                         val startOriginal: Int,
-                         val endOriginal: Int,
-                         val startRevised: Int,
-                         val endRevised: Int
+public data class Change(
+    val deltaType: DeltaType,
+    val startOriginal: Int,
+    val endOriginal: Int,
+    val startRevised: Int,
+    val endRevised: Int
 )

src/commonMain/kotlin/io/github/petertrr/diffutils/algorithm/myers/MyersDiff.kt

@@ -33,7 +33,7 @@ internal class MyersDiff<T>(private val equalizer: (T, T) -> Boolean = { t1, t2
     override fun computeDiff(source: List<T>, target: List<T>, progress: DiffAlgorithmListener?): List<Change> {
         progress?.diffStart()
         val path = buildPath(source, target, progress)
-        val result = buildRevision(path, source, target)
+        val result = buildRevision(path)
         progress?.diffEnd()
         return result
     }
@@ -49,15 +49,15 @@ internal class MyersDiff<T>(private val equalizer: (T, T) -> Boolean = { t1, t2
      */
     private fun buildPath(orig: List<T>, rev: List<T>, progress: DiffAlgorithmListener?): PathNode? {
         // these are local constants
-        val N = orig.size
-        val M = rev.size
-        val MAX = N + M + 1
-        val size = 1 + 2 * MAX
+        val origSize = orig.size
+        val revSize = rev.size
+        val max = origSize + revSize + 1
+        val size = 1 + 2 * max
         val middle = size / 2
         val diagonal: Array<PathNode?> = arrayOfNulls(size)
         diagonal[middle + 1] = PathNode(0, -1, snake = true, bootstrap = true, prev = null)
-        for (d in 0 until MAX) {
-            progress?.diffStep(d, MAX)
+        for (d in 0 until max) {
+            progress?.diffStep(d, max)
             var k = -d
             while (k <= d) {
                 val kmiddle = middle + k
@@ -75,15 +75,15 @@ internal class MyersDiff<T>(private val equalizer: (T, T) -> Boolean = { t1, t2
                 diagonal[kminus] = null // no longer used
                 var j = i - k
                 var node = PathNode(i, j, snake = false, bootstrap = false, prev = prev)
-                while (i < N && j < M && equalizer.invoke(orig[i], rev[j])) {
+                while (i < origSize && j < revSize && equalizer.invoke(orig[i], rev[j])) {
                     i++
                     j++
                 }
                 if (i != node.i) {
                     node = PathNode(i, j, snake = true, bootstrap = false, prev = node)
                 }
                 diagonal[kmiddle] = node
-                if (i >= N && j >= M) {
+                if (i >= origSize && j >= revSize) {
                     return diagonal[kmiddle]
                 }
                 k += 2
@@ -102,7 +102,7 @@ internal class MyersDiff<T>(private val equalizer: (T, T) -> Boolean = { t1, t2
      * @return A list of [Change]s corresponding to the path.
      * @throws IllegalStateException if a patch could not be built from the given path.
      */
-    private fun buildRevision(actualPath: PathNode?, orig: List<T>, rev: List<T>): List<Change> {
+    private fun buildRevision(actualPath: PathNode?): List<Change> {
         var path: PathNode? = actualPath
         val changes: MutableList<Change> = mutableListOf()
         if (path!!.snake) {

src/commonMain/kotlin/io/github/petertrr/diffutils/algorithm/myers/PathNode.kt

@@ -70,4 +70,4 @@ internal class PathNode(
 
     override fun toString() = generateSequence(this) { it.prev }
         .joinToString(prefix = "[", postfix = "]") { "(${it.i}, ${it.j})" }
-}
+}

src/commonMain/kotlin/io/github/petertrr/diffutils/patch/Chunk.kt

@@ -39,7 +39,7 @@ public data class Chunk<T>(
      * the positions of changed lines of chunk in the text
      */
     val changePosition: List<Int>? = null
-    ) {
+) {
     /**
      * Verifies that this chunk's saved text matches the corresponding text in the given sequence.
      *

src/commonMain/kotlin/io/github/petertrr/diffutils/patch/Patch.kt

@@ -25,7 +25,7 @@ import io.github.petertrr.diffutils.algorithm.Change
  *
  * @param T The type of the compared elements in the 'lines'.
  */
-public class Patch<T>(estimatedPatchSize: Int = 10) {
+public class Patch<T> {
     public var deltas: MutableList<Delta<T>> = arrayListOf()
         get() {
             field.sortBy { it.source.position }
@@ -84,15 +84,13 @@ public class Patch<T>(estimatedPatchSize: Int = 10) {
             return Chunk(start, data.subList(start, end))
         }
 
-        public fun <T> generate(original: List<T>, revised: List<T>, _changes: List<Change>, includeEquals: Boolean): Patch<T> {
-            val patch = Patch<T>(_changes.size)
+        public fun <T> generate(original: List<T>, revised: List<T>, changes: List<Change>, includeEquals: Boolean): Patch<T> {
+            val patch = Patch<T>()
             var startOriginal = 0
             var startRevised = 0
-            var changes: List<Change> = _changes
-            if (includeEquals) {
-                changes = _changes.sortedBy { it.startOriginal }
-            }
-            for (change in changes) {
+            changes.run {
+                if (includeEquals) sortedBy { it.startOriginal } else this
+            }.forEach { change ->
                 if (includeEquals && startOriginal < change.startOriginal) {
                     patch.addDelta(
                         EqualDelta(