LastModifiedFiles: fix in case of sequential changes in same file

idea/idea-gradle/src/org/jetbrains/kotlin/idea/scripting/gradle/LastModifiedFiles.kt

@@ -11,10 +11,6 @@ import org.jetbrains.kotlin.idea.core.util.readNullable
 import org.jetbrains.kotlin.idea.core.util.readStringList
 import org.jetbrains.kotlin.idea.core.util.writeNullable
 import org.jetbrains.kotlin.idea.core.util.writeStringList
-import org.jetbrains.kotlin.idea.scripting.gradle.roots.GradleBuildRootData
-import org.jetbrains.kotlin.idea.scripting.gradle.roots.GradleBuildRootDataSerializer
-import org.jetbrains.kotlin.idea.scripting.gradle.roots.readKotlinDslScriptModels
-import org.jetbrains.kotlin.idea.scripting.gradle.roots.writeKotlinDslScriptModels
 import java.io.DataInputStream
 import java.io.DataOutput
 
@@ -31,6 +27,11 @@ class LastModifiedFiles(
     private var last: SimultaneouslyChangedFiles = SimultaneouslyChangedFiles(),
     private var previous: SimultaneouslyChangedFiles = SimultaneouslyChangedFiles()
 ) {
+    init {
+        previous.fileIds.removeAll(last.fileIds)
+        if (previous.fileIds.isEmpty()) previous = SimultaneouslyChangedFiles()
+    }
+
     class SimultaneouslyChangedFiles(
         val ts: Long = Long.MIN_VALUE,
         val fileIds: MutableSet<String> = mutableSetOf()
@@ -40,7 +41,10 @@ class LastModifiedFiles(
     fun fileChanged(ts: Long, fileId: String) {
         when {
             ts > last.ts -> {
+                val prevPrev = previous
                 previous = last
+                previous.fileIds.remove(fileId)
+                if (previous.fileIds.isEmpty()) previous = prevPrev
                 last = SimultaneouslyChangedFiles(ts, hashSetOf(fileId))
             }
             ts == last.ts -> last.fileIds.add(fileId)

idea/idea-gradle/tests/org/jetbrains/kotlin/idea/scripting/gradle/LastModifiedFilesTest.kt

@@ -72,4 +72,81 @@ class LastModifiedFilesTest {
         assertEquals(3, files.lastModifiedTimeStampExcept("a"))
         assertEquals(3, files.lastModifiedTimeStampExcept("b"))
     }
+
+    @Test
+    fun testSameFile() {
+        files.fileChanged(1, "x")
+        files.fileChanged(2, "x")
+        assertEquals(Long.MIN_VALUE, files.lastModifiedTimeStampExcept("x"))
+    }
+
+    @Test
+    fun testSameFile1() {
+        files.fileChanged(1, "z")
+        files.fileChanged(2, "x")
+        files.fileChanged(3, "x")
+        assertEquals(1, files.lastModifiedTimeStampExcept("x"))
+        assertEquals(3, files.lastModifiedTimeStampExcept("z"))
+    }
+
+    @Test
+    fun testSameFile2() {
+        files.fileChanged(1, "z")
+        files.fileChanged(1, "x")
+        files.fileChanged(2, "x")
+        assertEquals(1, files.lastModifiedTimeStampExcept("x"))
+        assertEquals(2, files.lastModifiedTimeStampExcept("z"))
+    }
+
+    @Test
+    fun testSameFile3() {
+        files.fileChanged(1, "x")
+        files.fileChanged(1, "y")
+        files.fileChanged(2, "x")
+        assertEquals(1, files.lastModifiedTimeStampExcept("x"))
+        assertEquals(2, files.lastModifiedTimeStampExcept("y"))
+    }
+
+    @Test
+    fun testSameFile4() {
+        files.fileChanged(1, "z")
+        files.fileChanged(2, "x")
+        files.fileChanged(2, "y")
+        files.fileChanged(3, "x")
+        assertEquals(2, files.lastModifiedTimeStampExcept("x"))
+        assertEquals(3, files.lastModifiedTimeStampExcept("y"))
+        assertEquals(3, files.lastModifiedTimeStampExcept("z"))
+    }
+
+    @Test
+    fun testLoadingAfterSameFileBug() {
+        val restored = LastModifiedFiles(
+            LastModifiedFiles.SimultaneouslyChangedFiles(2, mutableSetOf("x")),
+            LastModifiedFiles.SimultaneouslyChangedFiles(1, mutableSetOf("x"))
+        )
+
+        assertEquals(Long.MIN_VALUE, restored.lastModifiedTimeStampExcept("x"))
+    }
+
+    @Test
+    fun testLoadingAfterSameFileBug2() {
+        val restored = LastModifiedFiles(
+            LastModifiedFiles.SimultaneouslyChangedFiles(2, mutableSetOf("x", "y")),
+            LastModifiedFiles.SimultaneouslyChangedFiles(1, mutableSetOf("x"))
+        )
+
+        assertEquals(2, restored.lastModifiedTimeStampExcept("x"))
+        assertEquals(2, restored.lastModifiedTimeStampExcept("y"))
+    }
+
+    @Test
+    fun testLoadingAfterSameFileBug3() {
+        val restored = LastModifiedFiles(
+            LastModifiedFiles.SimultaneouslyChangedFiles(2, mutableSetOf("x", "y")),
+            LastModifiedFiles.SimultaneouslyChangedFiles(1, mutableSetOf("x", "z"))
+        )
+
+        assertEquals(2, restored.lastModifiedTimeStampExcept("x"))
+        assertEquals(2, restored.lastModifiedTimeStampExcept("y"))
+    }
 }