Print recompilation reasons in build report

build-common/src/org/jetbrains/kotlin/incremental/ICReporter.kt

@@ -25,6 +25,20 @@ interface ICReporter {
 
     fun reportCompileIteration(incremental: Boolean, sourceFiles: Collection<File>, exitCode: ExitCode) {}
 
+    fun reportMarkDirtyClass(affectedFiles: Iterable<File>, classFqName: String) {
+        reportMarkDirty(affectedFiles, "dirty class $classFqName")
+    }
+
+    fun reportMarkDirtyMember(affectedFiles: Iterable<File>, scope: String, name: String) {
+        reportMarkDirty(affectedFiles, "dirty member $scope#$name")
+    }
+
+    fun reportMarkDirty(affectedFiles: Iterable<File>, reason: String) {
+        affectedFiles.forEach { file ->
+            reportVerbose { "${pathsAsString(file)} is marked dirty: $reason" }
+        }
+    }
+
     fun pathsAsString(files: Iterable<File>): String =
         files.joinToString { it.canonicalPath }
 

build-common/src/org/jetbrains/kotlin/incremental/buildUtil.kt

@@ -31,8 +31,10 @@ import org.jetbrains.kotlin.modules.TargetId
 import org.jetbrains.kotlin.name.FqName
 import org.jetbrains.kotlin.progress.CompilationCanceledStatus
 import org.jetbrains.kotlin.synthetic.SAM_LOOKUP_NAME
+import org.jetbrains.kotlin.utils.addToStdlib.flattenTo
 import java.io.File
 import java.util.*
+import kotlin.collections.HashSet
 
 const val DELETE_MODULE_FILE_PROPERTY = "kotlin.delete.module.file.after.build"
 
@@ -143,8 +145,7 @@ fun ChangesCollector.getDirtyData(
                 val name = classFqName.shortName().identifier
                 dirtyLookupSymbols.add(LookupSymbol(name, scope))
             }
-        }
-        else if (change is ChangeInfo.MembersChanged) {
+        } else if (change is ChangeInfo.MembersChanged) {
             val fqNames = withSubtypes(change.fqName, caches)
             // need to recompile subtypes because changed member might break override
             dirtyClassesFqNames.addAll(fqNames)
@@ -161,16 +162,16 @@ fun ChangesCollector.getDirtyData(
 }
 
 fun mapLookupSymbolsToFiles(
-        lookupStorage: LookupStorage,
-        lookupSymbols: Iterable<LookupSymbol>,
-        reporter: ICReporter,
-        excludes: Set<File> = emptySet()
+    lookupStorage: LookupStorage,
+    lookupSymbols: Iterable<LookupSymbol>,
+    reporter: ICReporter,
+    excludes: Set<File> = emptySet()
 ): Set<File> {
     val dirtyFiles = HashSet<File>()
 
     for (lookup in lookupSymbols) {
         val affectedFiles = lookupStorage.get(lookup).map(::File).filter { it !in excludes }
-        reporter.report { "${lookup.scope}#${lookup.name} caused recompilation of: ${reporter.pathsAsString(affectedFiles)}" }
+        reporter.reportMarkDirtyMember(affectedFiles, scope = lookup.scope, name = lookup.name)
         dirtyFiles.addAll(affectedFiles)
     }
 
@@ -183,19 +184,22 @@ fun mapClassesFqNamesToFiles(
     reporter: ICReporter,
     excludes: Set<File> = emptySet()
 ): Set<File> {
-    val dirtyFiles = HashSet<File>()
+    val fqNameToAffectedFiles = HashMap<FqName, MutableSet<File>>()
 
     for (cache in caches) {
-        for (dirtyClassFqName in classesFqNames) {
-            val srcFile = cache.getSourceFileIfClass(dirtyClassFqName)
+        for (classFqName in classesFqNames) {
+            val srcFile = cache.getSourceFileIfClass(classFqName)
             if (srcFile == null || srcFile in excludes || srcFile.isJavaFile()) continue
 
-            reporter.report { "Class $dirtyClassFqName caused recompilation of: ${reporter.pathsAsString(srcFile)}" }
-            dirtyFiles.add(srcFile)
+            fqNameToAffectedFiles.getOrPut(classFqName) { HashSet() }.add(srcFile)
         }
     }
 
-    return dirtyFiles
+    for ((classFqName, affectedFiles) in fqNameToAffectedFiles) {
+        reporter.reportMarkDirtyClass(affectedFiles, classFqName.asString())
+    }
+
+    return fqNameToAffectedFiles.values.flattenTo(HashSet())
 }
 
 fun withSubtypes(