KT-45777: Add tests for top-level functions

Address review + Minor changes
Fix error when building with -Pbootstrap.local=true
Fix tests failing on Windows due to '/' character

libraries/tools/kotlin-gradle-plugin/src/main/kotlin/org/jetbrains/kotlin/gradle/incremental/ClasspathChangesComputer.kt

@@ -68,33 +68,37 @@ object ClasspathChangesComputer {
     /**
      * Maps the unchanged snapshot files of the current build to the unchanged snapshot files of the previous build (selected from all the
      * snapshot files of the previous build).
+     *
+     * Note that the unchanged files of the current build were detected by Gradle, so a mapping must exist for each of them, we only have to
+     * find it.
+     *
+     * IMPORTANT: The alignment algorithm must use the same input normalization that is used for snapshot files in the Gradle task.
+     * Currently, snapshot files are annotated with `@Classpath` and are regular files (not jars), so (only) their contents and order
+     * matter.
      */
     private fun alignUnchangedSnapshotFiles(unchangedCurrentSnapshotFiles: List<File>, previousSnapshotFiles: List<File>): Map<File, File> {
-        var index = 0
+        val sizeToPreviousFiles: Map<Long, List<IndexedValue<File>>> = previousSnapshotFiles.withIndex().groupBy { it.value.length() }
+
+        var startIndexToSearch = 0
         return unchangedCurrentSnapshotFiles.associateWith { unchangedCurrentFile ->
-            var candidates = previousSnapshotFiles.subList(index, previousSnapshotFiles.size).filter { previousFile ->
-                unchangedCurrentFile.lastModified() == previousFile.lastModified() && unchangedCurrentFile.length() == previousFile.length()
+            val candidates = (sizeToPreviousFiles[unchangedCurrentFile.length()] ?: emptyList()).filter { it.index >= startIndexToSearch }
+            val unchangedPreviousFileWithIndex: IndexedValue<File> = if (candidates.size == 1) {
+                // A matching file must exist, so if there is only one candidate, it is the one.
+                candidates.single()
+            } else {
+                // If there are multiple matching files, select the first one. (Even if it doesn't match Gradle's alignment, it is still a
+                // correct alignment.)
+                val unchangedContents = unchangedCurrentFile.readBytes()
+                candidates.firstOrNull { candidate ->
+                    unchangedContents.contentEquals(candidate.value.readBytes())
+                } ?: error("Can't find previous snapshot file of unchanged current snapshot file '${unchangedCurrentFile.path}'")
             }
-            if (candidates.size > 1) {
-                candidates = candidates.filter { candidate ->
-                    unchangedCurrentFile.readBytes().contentEquals(candidate.readBytes())
-                }
-            }
-            check(candidates.isNotEmpty()) {
-                "Can't find previous snapshot file of unchanged current snapshot file '${unchangedCurrentFile.path}'"
-            }
-            // If there are multiple candidates, select the first one. (It doesn't have to match Gradle's alignment as long as it's still a
-            // correct alignment.)
-            val unchangedPreviousFile = candidates.first()
-            while (previousSnapshotFiles[index] != unchangedPreviousFile) {
-                index++
-            }
-            index++
-            unchangedPreviousFile
+            startIndexToSearch = unchangedPreviousFileWithIndex.index + 1
+            unchangedPreviousFileWithIndex.value
         }
     }
 
-    /** Returns `true` if this snapshot file contains a duplicate class with another snapshot file in the given set. */
+    /** Returns `true` if this snapshot file contains a duplicate class with another snapshot file in the given list. */
     @Suppress("unused", "UNUSED_PARAMETER")
     private fun File.containsDuplicatesWith(otherSnapshotFiles: List<File>): Boolean {
         // TODO: Implement and optimize this method
@@ -129,8 +133,8 @@ object ClasspathChangesComputer {
         //   - Add previous class snapshots to incrementalJvmCache.
         //   - Internally, incrementalJvmCache maintains a set of dirty classes to detect removed classes. Add previous classes to this set
         //     to detect removed classes later (see step 2).
-        //   - The final ChangesCollector result will contain all symbols in the previous classes (we actually don't need them, but it's
-        //     part of the API's effects).
+        //   - The ChangesCollector result will contain symbols in the previous classes (we actually don't need them, but it's part of the
+        //     API's effects).
         val unusedChangesCollector = ChangesCollector()
         for (previousSnapshot in previousClassSnapshots) {
             when (previousSnapshot) {
@@ -161,13 +165,11 @@ object ClasspathChangesComputer {
 
         // Step 2:
         //   - Add current class snapshots to incrementalJvmCache. This will overwrite any previous class snapshots that have the same
-        //     `JvmClassName`. The previous class snapshots that are not overwritten will be detected as removed class snapshots and will be
-        //     removed from incrementalJvmCache in step 3.
-        //   - Internally, incrementalJvmCache will mark these classes as non-dirty. That means unchanged/modified classes that were marked
-        //     as dirty in step 1 will now be non-dirty (added classes will also be marked as non-dirty even though they were not marked as
-        //     dirty before). After this, the remaining dirty classes will be removed classes.
-        //   - The intermediate ChangesCollector result will contain all symbols in added classes and changed (added/modified/removed)
-        //     symbols in modified classes. We will collect all symbols in removed classes in step 3.
+        //     `JvmClassName`. The remaining previous class snapshots will be removed in step 3.
+        //   - Internally, incrementalJvmCache will remove current classes from the set of dirty classes. After this, the remaining dirty
+        //     classes will be classes that are present on the previous classpath but not on the current classpath (i.e., removed classes).
+        //   - The intermediate ChangesCollector result will contain symbols in added classes and changed (added/modified/removed) symbols
+        //     in modified classes. We will collect symbols in removed classes in step 3.
         val changesCollector = ChangesCollector()
         for (currentSnapshot in currentClassSnapshots) {
             when (currentSnapshot) {
@@ -195,10 +197,10 @@ object ClasspathChangesComputer {
         }
 
         // Step 3:
-        //   - Detect removed classes: they are the remaining dirty classes.
-        //   - Remove previous class snapshots of removed classes from incrementalJvmCache.
-        //   - The final ChangesCollector result will contain all symbols in added classes, changed (added/modified/removed) symbols in
-        //     modified classes, and all symbols in removed classes.
+        //   - Detect removed classes: They are the remaining dirty classes.
+        //   - Remove class snapshots of removed classes from incrementalJvmCache.
+        //   - The final ChangesCollector result will contain symbols in added classes, changed (added/modified/removed) symbols in modified
+        //     classes, and symbols in removed classes.
         incrementalJvmCache.clearCacheForRemovedClasses(changesCollector)
 
         // Normalize the changes and clean up

libraries/tools/kotlin-gradle-plugin/src/main/kotlin/org/jetbrains/kotlin/gradle/tasks/Tasks.kt

@@ -831,15 +831,25 @@ abstract class KotlinCompile @Inject constructor(
         return if (fileChanges.isEmpty()) {
             ClasspathChanges.Available(LinkedHashSet(), LinkedHashSet())
         } else {
-            val currentClasspathEntrySnapshotFiles = classpathSnapshotProperties.classpathSnapshot.files.toList()
-            val changedCurrentFiles = fileChanges
-                .filter { it.changeType == ChangeType.ADDED || it.changeType == ChangeType.MODIFIED }
-                .map { it.file }.toSet()
-            ClasspathChangesComputer.compute(
-                currentClasspathEntrySnapshotFiles = currentClasspathEntrySnapshotFiles,
-                previousClasspathEntrySnapshotFiles = getPreviousClasspathEntrySnapshotFiles(),
-                unchangedCurrentClasspathEntrySnapshotFiles = currentClasspathEntrySnapshotFiles.filter { it !in changedCurrentFiles }
-            )
+            val previousClasspathEntrySnapshotFiles = getPreviousClasspathEntrySnapshotFiles()
+            if (previousClasspathEntrySnapshotFiles.isEmpty()) {
+                // When this happens, it means that either the previous classpath was empty or there were no source files to compile in the
+                // previous non-incremental run so the task action was skipped and the classpath snapshot directory was not populated (see
+                // AbstractKotlinCompile.executeImpl).
+                // We could improve this handling, but it's fine to return `UnableToCompute` here as it's likely that there are also no
+                // source files to compile/recompile in this incremental run.
+                ClasspathChanges.NotAvailable.UnableToCompute
+            } else {
+                val currentClasspathEntrySnapshotFiles = classpathSnapshotProperties.classpathSnapshot.files.toList()
+                val changedCurrentFiles = fileChanges
+                    .filter { it.changeType == ChangeType.ADDED || it.changeType == ChangeType.MODIFIED }
+                    .map { it.file }.toSet()
+                ClasspathChangesComputer.compute(
+                    currentClasspathEntrySnapshotFiles = currentClasspathEntrySnapshotFiles,
+                    previousClasspathEntrySnapshotFiles = previousClasspathEntrySnapshotFiles,
+                    unchangedCurrentClasspathEntrySnapshotFiles = currentClasspathEntrySnapshotFiles.filter { it !in changedCurrentFiles }
+                )
+            }
         }
     }
 
@@ -859,10 +869,7 @@ abstract class KotlinCompile @Inject constructor(
         classpathSnapshotDir.deleteRecursively()
         classpathSnapshotDir.mkdirs()
         snapshotFiles.forEachIndexed { index, snapshotFile ->
-            val targetFile = File("$classpathSnapshotDir/$index/${snapshotFile.name}")
-            snapshotFile.copyTo(targetFile, overwrite = true)
-            // Preserve timestamp to find out unchanged files later (see `ClasspathChangesComputer.alignUnchangedSnapshotFiles`)
-            targetFile.setLastModified(snapshotFile.lastModified())
+            snapshotFile.copyTo(File("$classpathSnapshotDir/$index/${snapshotFile.name}"))
         }
     }
 

libraries/tools/kotlin-gradle-plugin/src/test/kotlin/org/jetbrains/kotlin/gradle/incremental/ClasspathChangesComputerTest.kt

@@ -83,12 +83,20 @@ class KotlinClassesClasspathChangesComputerTest : ClasspathChangesComputerTest()
                     LookupSymbol(name = "b3", scope = "com.example.B"),
                     LookupSymbol(name = "b4", scope = "com.example.B"),
                     LookupSymbol(name = "C", scope = "com.example"),
-                    LookupSymbol(name = "D", scope = "com.example")
+                    LookupSymbol(name = "D", scope = "com.example"),
+                    LookupSymbol(name = SAM_LOOKUP_NAME.asString(), scope = "com.example"),
+                    LookupSymbol(name = "topLevelFuncB", scope = "com.example"),
+                    LookupSymbol(name = "topLevelFuncC", scope = "com.example"),
+                    LookupSymbol(name = "topLevelFuncD", scope = "com.example"),
+                    LookupSymbol(name = "topLevelFuncInCKtMovedToDKt", scope = "com.example"),
+                    LookupSymbol(name = "CKt", scope = "com.example"),
                 ),
                 fqNames = setOf(
                     FqName("com.example.B"),
                     FqName("com.example.C"),
-                    FqName("com.example.D")
+                    FqName("com.example.D"),
+                    FqName("com.example"),
+                    FqName("com.example.CKt"),
                 )
             ),
             changes
@@ -169,18 +177,21 @@ private fun snapshotClasspath(classpathSourceDir: File, tmpDir: TemporaryFolder)
             .sortedBy { it }
         val sourceFiles = relativePathsInDir.map { relativePath ->
             if (relativePath.endsWith(".kt")) {
+                val preCompiledClassFilesRoot = classpathEntrySourceDir.path.let {
+                    File(it.substringBeforeLast("src") + "classes" + it.substringAfterLast("src"))
+                }.also { check(it.exists()) }
                 KotlinSourceFile(
                     classpathEntrySourceDir, relativePath,
-                    preCompiledClassFile = ClassFile(
-                        File(classpathEntrySourceDir.path.replace("src/kotlin", "classes/kotlin")),
-                        relativePath.replace(".kt", ".class")
-                    )
+                    preCompiledClassFiles = listOf(
+                        ClassFile(preCompiledClassFilesRoot, relativePath.replace(".kt", ".class")),
+                        ClassFile(preCompiledClassFilesRoot, relativePath.replace(".kt", "Kt.class"))
+                    ).filter { File(it.classRoot, it.unixStyleRelativePath).exists() }
                 )
             } else {
                 SourceFile(classpathEntrySourceDir, relativePath)
             }
         }
-        val classFiles = sourceFiles.map { TestSourceFile(it, tmpDir).compile() }
+        val classFiles = sourceFiles.flatMap { TestSourceFile(it, tmpDir).compileAll() }
         ClasspathEntrySnapshot(
             classSnapshots = classFiles.map { it.unixStyleRelativePath to it.snapshot() }.toMap(LinkedHashMap())
         )

libraries/tools/kotlin-gradle-plugin/src/test/kotlin/org/jetbrains/kotlin/gradle/incremental/ClasspathSnapshotTestCommon.kt

@@ -36,7 +36,12 @@ abstract class ClasspathSnapshotTestCommon {
         fun asFile() = File(baseDir, unixStyleRelativePath)
     }
 
-    class KotlinSourceFile(baseDir: File, relativePath: String, val preCompiledClassFile: ClassFile) : SourceFile(baseDir, relativePath)
+    class KotlinSourceFile(baseDir: File, relativePath: String, val preCompiledClassFiles: List<ClassFile>) :
+        SourceFile(baseDir, relativePath) {
+
+        constructor(baseDir: File, relativePath: String, preCompiledClassFile: ClassFile) :
+                this(baseDir, relativePath, listOf(preCompiledClassFile))
+    }
 
     /** Same as [SourceFile] but with a [TemporaryFolder] to store the results of operations on the [SourceFile]. */
     open class TestSourceFile(val sourceFile: SourceFile, private val tmpDir: TemporaryFolder) {
@@ -73,12 +78,25 @@ abstract class ClasspathSnapshotTestCommon {
         }
 
         private fun compileKotlin(): List<ClassFile> {
-            // TODO: Call Kotlin compiler to generate classes, for example:
-            // org.jetbrains.kotlin.test.MockLibraryUtil.compileKotlin(sourceFile.asFile().path, sourceFile.preCompiledClassFile.classRoot)
-            // However, currently it is not possible (see https://github.com/JetBrains/kotlin/pull/4512#discussion_r679432232), so we use
-            // the precompiled classes in the test data instead.
             sourceFile as KotlinSourceFile
-            return listOf(sourceFile.preCompiledClassFile)
+
+            // TODO: Call Kotlin compiler to generate classes.
+            // If <kotlin-repo>/dist/kotlinc/lib/kotlin-compiler.jar is available (e.g., by running ./gradlew dist), we will be able to
+            // call the Kotlin compiler to generate classes from here. For example:
+//            val classesDir = tmpDir.newFolder()
+//            org.jetbrains.kotlin.test.MockLibraryUtil.compileKotlin(sourceFile.asFile().path, classesDir)
+//            val classFiles = classesDir.walk()
+//                .filter { it.isFile && !it.toRelativeString(classesDir).startsWith("META-INF/") }
+//                .map { ClassFile(classesDir, it.toRelativeString(classesDir)) }
+//                .sortedBy { it.unixStyleRelativePath.substringBefore(".class") }
+//                .toList()
+//            kotlin.test.assertEquals(classFiles.size, sourceFile.preCompiledClassFiles.size)
+//            sourceFile.preCompiledClassFiles.forEach {
+//                File(classesDir, it.unixStyleRelativePath).copyTo(File(it.classRoot, it.unixStyleRelativePath), overwrite = true)
+//            }
+            // However, kotlin-compiler.jar is currently not available in CI builds, so we need to pre-compile the classes, put them in the
+            // test data, and use them here instead.
+            return sourceFile.preCompiledClassFiles
         }
 
         private fun compileJava(): List<ClassFile> {

libraries/tools/kotlin-gradle-plugin/src/testData/ClasspathChangesComputerTest/testMultipleClasses/src/java/previous-classpath/0/com/example/C.java

@@ -1,6 +1,6 @@
 package com.example;
 
-// Will be removed
+// To-be-removed class
 public class C {
     public int c = 0;
 }

libraries/tools/kotlin-gradle-plugin/src/testData/ClasspathChangesComputerTest/testMultipleClasses/src/kotlin/current-classpath/0/com/example/A.kt

@@ -4,3 +4,6 @@ package com.example
 class A {
     val a: Int = 0
 }
+
+// Unchanged top-level function
+fun topLevelFuncA() {}

libraries/tools/kotlin-gradle-plugin/src/testData/ClasspathChangesComputerTest/testMultipleClasses/src/kotlin/current-classpath/0/com/example/B.kt

@@ -7,3 +7,6 @@ public class B {
     //val b3: Int = 0 // Removed field
     val b4: Int = 0 // Added field
 }
+
+// Modified top-level function
+fun topLevelFuncB(): Int = 0

libraries/tools/kotlin-gradle-plugin/src/testData/ClasspathChangesComputerTest/testMultipleClasses/src/kotlin/current-classpath/0/com/example/D.kt

@@ -4,3 +4,9 @@ package com.example
 public class D {
     val d: Int = 0
 }
+
+// Added top-level function
+fun topLevelFuncD() {}
+
+// Moved top-level function
+fun topLevelFuncInCKtMovedToDKt() {}

libraries/tools/kotlin-gradle-plugin/src/testData/ClasspathChangesComputerTest/testMultipleClasses/src/kotlin/previous-classpath/0/com/example/A.kt

@@ -3,3 +3,5 @@ package com.example
 class A {
     val a: Int = 0
 }
+
+fun topLevelFuncA() {}

libraries/tools/kotlin-gradle-plugin/src/testData/ClasspathChangesComputerTest/testMultipleClasses/src/kotlin/previous-classpath/0/com/example/B.kt

@@ -5,3 +5,5 @@ public class B {
     val b2: Int = 0
     val b3: Int = 0
 }
+
+fun topLevelFuncB() {}

libraries/tools/kotlin-gradle-plugin/src/testData/ClasspathChangesComputerTest/testMultipleClasses/src/kotlin/previous-classpath/0/com/example/C.kt

@@ -1,6 +1,12 @@
 package com.example
 
-// Will be removed
+// To-be-removed class
 public class C {
     val c: Int = 0
 }
+
+// To-be-removed top-level function
+fun topLevelFuncC() {}
+
+// To-be-moved top-level function
+fun topLevelFuncInCKtMovedToDKt() {}