JPS, tests: Support multimodule mpp tests without steps

jps-plugin/jps-tests/test/org/jetbrains/kotlin/jps/build/AbstractIncrementalJpsTest.kt

@@ -67,8 +67,7 @@ import kotlin.reflect.jvm.javaField
 
 abstract class AbstractIncrementalJpsTest(
     private val allowNoFilesWithSuffixInTestData: Boolean = false,
-    private val checkDumpsCaseInsensitively: Boolean = false,
+    private val checkDumpsCaseInsensitively: Boolean = false
-    private val allowNoBuildLogFileInTestData: Boolean = false
 ) : BaseKotlinJpsBuildTestCase() {
     companion object {
         private val COMPILATION_FAILED = "COMPILATION FAILED"
@@ -305,6 +304,7 @@ abstract class AbstractIncrementalJpsTest(
     protected open fun doTest(testDataPath: String) {
         testDataDir = File(testDataPath)
         workDir = FileUtilRt.createTempDirectory(TEMP_DIRECTORY_TO_USE, "jps-build", null)
+        val buildLogFile = buildLogFinder.findBuildLog(testDataDir)
         Disposer.register(testRootDisposable, Disposable { FileUtilRt.delete(workDir) })
 
         val modulesTxt = configureModules()
@@ -312,19 +312,19 @@ abstract class AbstractIncrementalJpsTest(
 
         initialMake()
 
-        val otherMakeResults = performModificationsAndMake(modulesTxt?.modules?.map { it.name })
+        val otherMakeResults = performModificationsAndMake(
-        val buildLogFile = buildLogFinder.findBuildLog(testDataDir)
+            modulesTxt?.modules?.map { it.name },
-        val logs = createBuildLog(otherMakeResults)
+            hasBuildLog = buildLogFile != null
+        )
 
-        if (buildLogFile != null && buildLogFile.exists()) {
+        buildLogFile?.let {
+            val logs = createBuildLog(otherMakeResults)
             UsefulTestCase.assertSameLinesWithFile(buildLogFile.absolutePath, logs)
-        } else if (!allowNoBuildLogFileInTestData) {
-            throw IllegalStateException("No build log file in $testDataDir")
-        }
 
-        val lastMakeResult = otherMakeResults.last()
+            val lastMakeResult = otherMakeResults.last()
-        rebuildAndCheckOutput(lastMakeResult)
+            rebuildAndCheckOutput(lastMakeResult)
-        clearCachesRebuildAndCheckOutput(lastMakeResult)
+            clearCachesRebuildAndCheckOutput(lastMakeResult)
+        }
     }
 
     private fun createMappingsDump(
@@ -411,15 +411,25 @@ abstract class AbstractIncrementalJpsTest(
     open val testDataSrc: File
         get() = testDataDir
 
-    private fun performModificationsAndMake(moduleNames: Collection<String>?): List<MakeResult> {
+    private fun performModificationsAndMake(
+        moduleNames: Collection<String>?,
+        hasBuildLog: Boolean
+    ): List<MakeResult> {
         val results = arrayListOf<MakeResult>()
         val modifications = getModificationsToPerform(
             testDataSrc,
             moduleNames,
-            allowNoFilesWithSuffixInTestData,
+            allowNoFilesWithSuffixInTestData = allowNoFilesWithSuffixInTestData || !hasBuildLog,
-            TouchPolicy.TIMESTAMP
+            touchPolicy = TouchPolicy.TIMESTAMP
         )
 
+        if (!hasBuildLog) {
+            check(modifications.size == 1 && modifications.single().isEmpty()) {
+                "Bad test data: build steps are provided, but there is no `build.log` file"
+            }
+            return results
+        }
+
         val stepsTxt = File(testDataSrc, "_steps.txt")
         val modificationNames = if (stepsTxt.exists()) stepsTxt.readLines() else null