feature (vcs): Implement API required for showing changes view diff (IJPL-173924)

It exposes currently selected diffable change in the tree and next/previous nodes. If selection is changed, but previous selection can still be considered selected, the n ew value is not reported

GitOrigin-RevId: b4f649765cb31dae7d3fbba540bf7f673d2944e3

java/java-tests/BUILD.bazel

@@ -46,6 +46,7 @@ jvm_library(
     "//platform/util/diff",
     "//platform/vcs-api:vcs",
     "//platform/vcs-impl/shared",
+    "//platform/vcs-impl/shared:shared_test_lib",
     "//platform/editor-ui-ex:editor-ex",
     "//java/execution/impl",
     "//platform/diff-api:diff",

platform/collaboration-tools/BUILD.bazel

@@ -112,6 +112,7 @@ jvm_library(
     "@lib//:app-cash-turbine-jvm",
     "@lib//:assert_j",
     "//platform/vcs-impl/shared",
+    "//platform/vcs-impl/shared:shared_test_lib",
   ]
 )
 ### auto-generated section `build intellij.platform.collaborationTools` end

platform/dvcs-impl/BUILD.bazel

@@ -65,6 +65,7 @@ jvm_library(
     "//platform/vcs-impl:vcs-impl_test_lib",
     "//platform/project/shared:project",
     "//platform/vcs-impl/shared",
+    "//platform/vcs-impl/shared:shared_test_lib",
     "//platform/kernel/shared:kernel",
     "//platform/core-impl",
     "//platform/platform-impl:ide-impl",

platform/lvcs-impl/BUILD.bazel

@@ -82,6 +82,7 @@ jvm_library(
     "//tools/intellij.tools.ide.metrics.benchmark:ide-metrics-benchmark",
     "//tools/intellij.tools.ide.metrics.benchmark:ide-metrics-benchmark_test_lib",
     "//platform/vcs-impl/shared",
+    "//platform/vcs-impl/shared:shared_test_lib",
     "@lib//:jetbrains-annotations",
     "//platform/projectModel-impl",
   ]

platform/platform-tests/BUILD.bazel

@@ -176,6 +176,7 @@ jvm_library(
     "//platform/locking.impl",
     "//platform/testFramework/junit5/highlighting",
     "//platform/vcs-impl/shared",
+    "//platform/vcs-impl/shared:shared_test_lib",
   ],
   runtime_deps = [
     "//xml/dom-impl",

platform/vcs-api/shared/src/com/intellij/platform/vcs/changes/ChangesUtil.kt

@@ -82,4 +82,7 @@ object ChangesUtil {
            status === FileStatus.MERGED_WITH_BOTH_CONFLICTS ||
            status === FileStatus.MERGED_WITH_PROPERTY_CONFLICTS
   }
+
+  @JvmStatic
+  fun matches(change: Change, path: FilePath): Boolean = path == getAfterPath(change) || path == getBeforePath(change)
 }

platform/vcs-impl/BUILD.bazel

@@ -155,6 +155,7 @@ jvm_library(
     "//libraries/microba",
     "//platform/kernel/shared:kernel",
     "//platform/vcs-impl/shared",
+    "//platform/vcs-impl/shared:shared_test_lib",
     "@lib//:jgoodies-forms",
     "//platform/observable",
     "//platform/platform-impl/concurrency",

platform/vcs-impl/frontend/BUILD.bazel

@@ -38,4 +38,48 @@ jvm_library(
     "//platform/vcs-api/vcs-api-core:vcs-core",
   ]
 )
-### auto-generated section `build intellij.platform.vcs.impl.frontend` end
+
+jvm_library(
+  name = "frontend_test_lib",
+  visibility = ["//visibility:public"],
+  srcs = glob(["testSrc/**/*.kt", "testSrc/**/*.java", "testSrc/**/*.form"], allow_empty = True),
+  associates = [":frontend"],
+  deps = [
+    "@lib//:kotlinx-coroutines-core",
+    "@lib//:kotlin-stdlib",
+    "//platform/core-api:core",
+    "//platform/editor-ui-api:editor-ui",
+    "//platform/projectModel-api:projectModel",
+    "//platform/util:util-ui",
+    "//platform/diagnostic",
+    "//platform/core-ui",
+    "//platform/platform-impl:ide-impl",
+    "//platform/diff-impl",
+    "//platform/util/jdom",
+    "//platform/kernel/shared:kernel",
+    "//platform/lang-core",
+    "//platform/vcs-impl/shared",
+    "//platform/vcs-impl/shared:shared_test_lib",
+    "//platform/project/shared:project",
+    "//platform/util/coroutines",
+    "//libraries/kotlinx/serialization/core",
+    "//libraries/kotlinx/serialization/json",
+    "//platform/recentFiles/frontend",
+    "//platform/analysis-api:analysis",
+    "//platform/vcs-api/shared",
+    "//platform/vcs-api/vcs-api-core:vcs-core",
+    "//platform/vcs-api/vcs-api-core:vcs-core_test_lib",
+    "//platform/testFramework",
+    "//platform/testFramework:testFramework_test_lib",
+  ]
+)
+### auto-generated section `build intellij.platform.vcs.impl.frontend` end
+
+### auto-generated section `test intellij.platform.vcs.impl.frontend` start
+load("@community//build:tests-options.bzl", "jps_test")
+
+jps_test(
+  name = "frontend_test",
+  runtime_deps = [":frontend_test_lib"]
+)
+### auto-generated section `test intellij.platform.vcs.impl.frontend` end

platform/vcs-impl/frontend/intellij.platform.vcs.impl.frontend.iml

@@ -30,6 +30,7 @@
     <content url="file://$MODULE_DIR$">
       <sourceFolder url="file://$MODULE_DIR$/resources" type="java-resource" />
       <sourceFolder url="file://$MODULE_DIR$/src" isTestSource="false" />
+      <sourceFolder url="file://$MODULE_DIR$/testSrc" isTestSource="true" />
     </content>
     <orderEntry type="inheritedJdk" />
     <orderEntry type="sourceFolder" forTests="false" />
@@ -55,5 +56,6 @@
     <orderEntry type="module" module-name="intellij.platform.analysis" />
     <orderEntry type="module" module-name="intellij.platform.vcs.shared" />
     <orderEntry type="module" module-name="intellij.platform.vcs.core" />
+    <orderEntry type="module" module-name="intellij.platform.testFramework" scope="TEST" />
   </component>
 </module>

platform/vcs-impl/frontend/src/com/intellij/platform/vcs/impl/frontend/changes/ChangesViewDiffableSelectionHelper.kt

@@ -0,0 +1,110 @@
+// Copyright 2000-2025 JetBrains s.r.o. and contributors. Use of this source code is governed by the Apache 2.0 license.
+package com.intellij.platform.vcs.impl.frontend.changes
+
+import com.intellij.openapi.diagnostic.logger
+import com.intellij.openapi.vcs.FilePath
+import com.intellij.openapi.vcs.changes.Change
+import com.intellij.openapi.vcs.changes.ui.ChangesBrowserNode
+import com.intellij.openapi.vcs.changes.ui.ChangesListView
+import com.intellij.openapi.vcs.changes.ui.VcsTreeModelData
+import com.intellij.platform.vcs.changes.ChangesUtil
+import com.intellij.platform.vcs.impl.shared.changes.ChangesTreePath
+import com.intellij.platform.vcs.impl.shared.rpc.ChangesViewDiffableSelection
+import com.intellij.util.concurrency.annotations.RequiresEdt
+import kotlinx.coroutines.flow.MutableStateFlow
+import kotlinx.coroutines.flow.asStateFlow
+import kotlinx.coroutines.flow.update
+
+private val LOG = logger<ChangesViewDiffableSelectionHelper>()
+
+// TODO support hijacked changes
+internal class ChangesViewDiffableSelectionHelper(private val changesView: ChangesListView) {
+  private val _diffableSelection = MutableStateFlow<ChangesViewDiffableSelection?>(null)
+  val diffableSelection = _diffableSelection.asStateFlow()
+
+  @RequiresEdt
+  fun tryUpdateSelection() {
+    _diffableSelection.update { currentValue ->
+      if (shouldUpdateSelection(currentValue)) getDiffableSelection() else currentValue
+    }
+  }
+
+  @RequiresEdt
+  private fun shouldUpdateSelection(previousSelection: ChangesViewDiffableSelection?): Boolean {
+    if (previousSelection == null) return true
+
+    val currentValueIsSelected = changesView.selectedChangesNodes.any { node ->
+      when (val obj = node.userObject) {
+        is Change -> ChangesUtil.matches(obj, previousSelection.selectedChange.filePath.filePath)
+        is FilePath -> obj == previousSelection.selectedChange.filePath.filePath
+        else -> false
+      }
+    }
+
+    return !currentValueIsSelected
+  }
+
+  @RequiresEdt
+  private fun getDiffableSelection(): ChangesViewDiffableSelection? {
+    val selectedDiffableNode = changesView.selectedChanges.firstOrNull()
+                               ?: changesView.selectedUnversionedFiles.firstOrNull()
+                               ?: return null
+    val selectedNodePath =
+      getPathOrLog(selectedDiffableNode) { LOG.warn("Could not create path for selected node: $it") } ?: return null
+
+
+    val (prevNode, nextNode) = findPreviousAndNextDiffableNodes(selectedDiffableNode)
+
+    return ChangesViewDiffableSelection(
+      selectedChange = selectedNodePath,
+      previousChange = getPathOrLog(prevNode) { LOG.warn("Could not create path for previous node: $it") },
+      nextChange = getPathOrLog(nextNode) { LOG.warn("Could not create path for next node: $it") })
+  }
+
+  private fun getPathOrLog(prevNode: Any?, log: (Any) -> Unit): ChangesTreePath? = prevNode?.let { node ->
+    ChangesTreePath.create(node).also { path -> if (path == null) log(node) }
+  }
+
+  @RequiresEdt
+  private fun findPreviousAndNextDiffableNodes(selectedDiffableNode: Any): Pair<Any?, Any?> {
+    var previousNode: Any? = null
+    var nextNode: Any? = null
+
+    var selectedNodeWasFound = false
+    for (node in VcsTreeModelData.all(changesView).iterateNodes()) {
+      if (nextNode != null) break
+
+      val userObject = node.userObject
+      if (userObject === selectedDiffableNode) {
+        selectedNodeWasFound = true
+      }
+      else {
+        if (isDiffableNode(node)) {
+          if (selectedNodeWasFound) {
+            nextNode = userObject
+          }
+          else {
+            previousNode = userObject
+          }
+        }
+      }
+    }
+
+    return previousNode to nextNode
+  }
+
+  private fun isUnderUnversioned(node: ChangesBrowserNode<*>): Boolean {
+    var current: ChangesBrowserNode<*>? = node.parent
+    while (current != null) {
+      if (current.userObject == ChangesBrowserNode.UNVERSIONED_FILES_TAG) return true
+      current = current.parent
+    }
+    return false
+  }
+
+  private fun isDiffableNode(node: ChangesBrowserNode<*>): Boolean = when (node.userObject) {
+    is Change -> true
+    is FilePath -> isUnderUnversioned(node)
+    else -> false
+  }
+}

platform/vcs-impl/frontend/src/com/intellij/platform/vcs/impl/frontend/changes/FrontendCommitChangesViewWithToolbarPanel.kt

@@ -13,6 +13,7 @@ import com.intellij.platform.vcs.impl.shared.changes.ChangesViewSettings
 import com.intellij.platform.vcs.impl.shared.rpc.BackendChangesViewEvent
 import com.intellij.platform.vcs.impl.shared.rpc.ChangesViewApi
 import com.intellij.platform.vcs.impl.shared.rpc.ChangesViewDiffApi
+import com.intellij.util.asDisposable
 import fleet.rpc.client.durable
 import fleet.util.logging.logger
 import kotlinx.coroutines.CoroutineScope
@@ -21,11 +22,15 @@ import kotlinx.coroutines.flow.launchIn
 import kotlinx.coroutines.flow.onEach
 import kotlinx.coroutines.launch
 
+private val LOG = logger<FrontendCommitChangesViewWithToolbarPanel>()
+
 internal class FrontendCommitChangesViewWithToolbarPanel(
   changesView: ChangesListView,
   cs: CoroutineScope,
   val inclusionModel: ChangesViewDelegatingInclusionModel,
 ) : CommitChangesViewWithToolbarPanel(changesView, cs) {
+  private val diffableSelectionHelper = ChangesViewDiffableSelectionHelper(changesView)
+
   init {
     changesView.setInclusionModel(inclusionModel)
     ChangeListsViewModel.getInstance(project).changeListsState.onEach { scheduleRefresh() }.launchIn(cs)
@@ -35,6 +40,12 @@ internal class FrontendCommitChangesViewWithToolbarPanel(
     cs.launch {
       forwardDiffActionsToBackend()
     }
+    cs.launch {
+      diffableSelectionHelper.diffableSelection.collectLatest {
+        ChangesViewDiffApi.getInstance().notifySelectionUpdated(project.projectId(), it)
+      }
+    }
+    changesView.addSelectionListener({ diffableSelectionHelper.tryUpdateSelection() }, cs.asDisposable())
   }
 
   override fun getModelData(): ModelData {
@@ -85,8 +96,6 @@ internal class FrontendCommitChangesViewWithToolbarPanel(
   }
 
   companion object {
-    private val LOG = logger<FrontendCommitChangesViewWithToolbarPanel>()
-
     fun create(project: Project, cs: CoroutineScope): FrontendCommitChangesViewWithToolbarPanel {
       val tree = LocalChangesListView(project)
       val inclusionModel = ChangesViewDelegatingInclusionModel(project, cs)
@@ -94,4 +103,5 @@ internal class FrontendCommitChangesViewWithToolbarPanel(
       return FrontendCommitChangesViewWithToolbarPanel(tree, cs, inclusionModel)
     }
   }
-}
+}
+

platform/vcs-impl/frontend/testSrc/com/intellij/platform/vcs/impl/frontend/changes/ChangesViewDiffableSelectionHelperTest.kt

@@ -0,0 +1,244 @@
+// Copyright 2000-2025 JetBrains s.r.o. and contributors. Use of this source code is governed by the Apache 2.0 license.
+package com.intellij.platform.vcs.impl.frontend.changes
+
+import com.intellij.openapi.vcs.FilePath
+import com.intellij.openapi.vcs.changes.Change
+import com.intellij.openapi.vcs.changes.LocalChangeListImpl
+import com.intellij.openapi.vcs.changes.ui.ChangesBrowserNode
+import com.intellij.openapi.vcs.changes.ui.VcsTreeModelData
+import com.intellij.platform.vcs.impl.changes.ChangesViewTestBase
+import com.intellij.platform.vcs.impl.shared.changes.ChangesTreePath
+import com.intellij.platform.vcs.impl.shared.rpc.ContentRevisionDto
+import com.intellij.platform.vcs.impl.shared.rpc.FilePathDto
+import com.intellij.testFramework.runInEdtAndWait
+import com.intellij.util.ui.tree.TreeUtil
+
+internal class ChangesViewDiffableSelectionHelperTest : ChangesViewTestBase() {
+  fun `test current change then next unversioned and no previous`() {
+    val changePath = path("a.txt")
+    val unversioned = path("u1.txt")
+
+    val defaultList = defaultChangeList(changePath)
+
+    val model = buildModel(view, listOf(defaultList), listOf(unversioned))
+    updateModelAndSelect(view, model, changePath)
+
+    val helper = ChangesViewDiffableSelectionHelper(view)
+    runInEdtAndWait { helper.tryUpdateSelection() }
+    val selection = helper.diffableSelection.value
+    checkNotNull(selection)
+    assertTreePath(selection.selectedChange, changePath, expectChangeId = true)
+    assertNull(selection.previousChange)
+    assertTreePath(selection.nextChange!!, unversioned, expectChangeId = false)
+  }
+
+  fun `test current change with previous and next changes`() {
+    val p1 = path("c1.txt")
+    val p2 = path("c2.txt")
+    val p3 = path("c3.txt")
+
+    val defaultList = LocalChangeListImpl.Builder(project, "Default").setDefault(true)
+      .setChanges(listOf(change(p1), change(p2), change(p3)))
+      .build()
+
+    val model = buildModel(view, listOf(defaultList), emptyList())
+    updateModelAndSelect(view, model, p2)
+
+    val helper = ChangesViewDiffableSelectionHelper(view)
+    runInEdtAndWait { helper.tryUpdateSelection() }
+    val selection = helper.diffableSelection.value
+    checkNotNull(selection)
+    assertTreePath(selection.selectedChange, p2, expectChangeId = true)
+    assertTreePath(selection.previousChange!!, p1, expectChangeId = true)
+    assertTreePath(selection.nextChange!!, p3, expectChangeId = true)
+  }
+
+  fun `test current unversioned then next unversioned and previous change`() {
+    val c1 = path("c1.txt")
+    val u1 = path("u1.txt")
+    val u2 = path("u2.txt")
+
+    val defaultList = defaultChangeList(c1)
+
+    val model = buildModel(view, listOf(defaultList), listOf(u1, u2))
+    updateModelAndSelect(view, model, u1)
+
+    val helper = ChangesViewDiffableSelectionHelper(view)
+    runInEdtAndWait { helper.tryUpdateSelection() }
+    val selection = helper.diffableSelection.value
+    checkNotNull(selection)
+    assertTreePath(selection.selectedChange, u1, expectChangeId = false)
+    assertTreePath(selection.previousChange!!, c1, expectChangeId = true)
+    assertTreePath(selection.nextChange!!, u2, expectChangeId = false)
+  }
+
+  fun `test only unversioned files present`() {
+    val u1 = path("u1.txt")
+    val u2 = path("u2.txt")
+    val u3 = path("u3.txt")
+
+    val model = buildModel(view, emptyList(), listOf(u1, u2, u3))
+    updateModelAndSelect(view, model, u1)
+
+    val helper = ChangesViewDiffableSelectionHelper(view)
+    runInEdtAndWait { helper.tryUpdateSelection() }
+    val selection = helper.diffableSelection.value
+    checkNotNull(selection)
+    assertTreePath(selection.selectedChange, u1, expectChangeId = false)
+    assertNull(selection.previousChange)
+    assertTreePath(selection.nextChange!!, u2, expectChangeId = false)
+  }
+
+  fun `test only current change`() {
+    val c1 = path("c1.txt")
+    val defaultList = defaultChangeList(c1)
+
+    val model = buildModel(view, listOf(defaultList), emptyList())
+    updateModelAndSelect(view, model, c1)
+
+    val helper = ChangesViewDiffableSelectionHelper(view)
+    runInEdtAndWait { helper.tryUpdateSelection() }
+    val selection = helper.diffableSelection.value
+    checkNotNull(selection)
+    assertTreePath(selection.selectedChange, c1, expectChangeId = true)
+    assertNull(selection.previousChange)
+    assertNull(selection.nextChange)
+  }
+
+  fun `test only current unversioned`() {
+    val u1 = path("u1.txt")
+    val model = buildModel(view, emptyList(), listOf(u1))
+    updateModelAndSelect(view, model, u1)
+
+    val helper = ChangesViewDiffableSelectionHelper(view)
+    runInEdtAndWait { helper.tryUpdateSelection() }
+    val selection = helper.diffableSelection.value
+    checkNotNull(selection)
+    assertTreePath(selection.selectedChange, u1, expectChangeId = false)
+    assertNull(selection.previousChange)
+    assertNull(selection.nextChange)
+  }
+
+  fun `test change selected then selection removed`() {
+    val c1 = path("c1.txt")
+    val c2 = path("c2.txt")
+
+    val defaultList = LocalChangeListImpl.Builder(project, "Default").setDefault(true)
+      .setChanges(listOf(change(c1), change(c2)))
+      .build()
+
+    val model = buildModel(view, listOf(defaultList), emptyList())
+    updateModelAndSelect(view, model, c1)
+
+    val helper = ChangesViewDiffableSelectionHelper(view)
+    runInEdtAndWait { helper.tryUpdateSelection() }
+    assertNotNull(helper.diffableSelection.value)
+
+    runInEdtAndWait {
+      view.clearSelection()
+      helper.tryUpdateSelection()
+    }
+    assertNull(helper.diffableSelection.value)
+  }
+
+
+  fun `test change selected then select changelist node doesn't cause update`() {
+    val c1 = path("c1.txt")
+    val c2 = path("c2.txt")
+
+    val defaultList = LocalChangeListImpl.Builder(project, "Default").setDefault(true)
+      .setChanges(listOf(change(c1), change(c2)))
+      .build()
+
+    val model = buildModel(view, listOf(defaultList), emptyList())
+    updateModelAndSelect(view, model, c1)
+
+    val helper = ChangesViewDiffableSelectionHelper(view)
+    runInEdtAndWait { helper.tryUpdateSelection() }
+    val previous = helper.diffableSelection.value
+
+    // Switch selection to the changelist node
+    runInEdtAndWait {
+      val pathToList = view.findNodePathInTree(defaultList)
+      assertNotNull(pathToList)
+      view.clearSelection()
+      view.addSelectionPath(pathToList)
+      assertEquals(1, view.selectionCount)
+      helper.tryUpdateSelection()
+    }
+
+    val updated = helper.diffableSelection.value
+    assertSame(previous, updated)
+  }
+
+  fun `test unversioned selected then select unversioned root doesn't cause update`() {
+    val u1 = path("u1.txt")
+    val u2 = path("u2.txt")
+
+    val model = buildModel(view, emptyList(), listOf(u1, u2))
+    updateModelAndSelect(view, model, u1)
+
+    val helper = ChangesViewDiffableSelectionHelper(view)
+    runInEdtAndWait { helper.tryUpdateSelection() }
+    val previous = helper.diffableSelection.value
+
+    // Switch selection to Unversioned root node
+    runInEdtAndWait {
+      val unvNode = VcsTreeModelData.findTagNode(view, ChangesBrowserNode.UNVERSIONED_FILES_TAG)
+      checkNotNull(unvNode)
+      val pathToUnv = TreeUtil.getPathFromRoot(unvNode)
+      view.clearSelection()
+      view.addSelectionPath(pathToUnv)
+      assertEquals(1, view.selectionCount)
+      helper.tryUpdateSelection()
+    }
+
+    val updated = helper.diffableSelection.value
+    assertSame(previous, updated)
+  }
+
+  fun `test switch from change to unversioned`() {
+    val c1 = path("c1.txt")
+    val u1 = path("u1.txt")
+
+    val defaultList = defaultChangeList(c1)
+    val model = buildModel(view, listOf(defaultList), listOf(u1))
+    updateModelAndSelect(view, model, c1)
+
+    val helper = ChangesViewDiffableSelectionHelper(view)
+    runInEdtAndWait { helper.tryUpdateSelection() }
+    val previous = helper.diffableSelection.value
+    checkNotNull(previous)
+    assertTreePath(previous.selectedChange, c1, true)
+
+    runInEdtAndWait {
+      val pathToU1 = view.findNodePathInTree(u1)
+      assertNotNull(pathToU1)
+      view.clearSelection()
+      view.addSelectionPath(pathToU1)
+      assertEquals(1, view.selectionCount)
+      helper.tryUpdateSelection()
+    }
+
+    val selection = helper.diffableSelection.value
+    checkNotNull(selection)
+    assertTreePath(selection.selectedChange, u1, false)
+    assertTreePath(selection.previousChange!!, c1, expectChangeId = true)
+    assertNull(selection.nextChange)
+  }
+
+  private fun defaultChangeList(changePath: FilePath): LocalChangeListImpl = LocalChangeListImpl.Builder(project, "Default")
+    .setDefault(true)
+    .setChanges(listOf(change(changePath)))
+    .build()
+
+  private fun change(path: FilePath): Change {
+    val contentRevisionDto = ContentRevisionDto("0", FilePathDto.toDto(path))
+    return Change(null, contentRevisionDto.contentRevision)
+  }
+
+  private fun assertTreePath(path: ChangesTreePath, expected: FilePath, expectChangeId: Boolean) {
+    assertEquals(expected, path.filePath.filePath)
+    if (expectChangeId) assertNotNull(path.changeId) else assertNull(path.changeId)
+  }
+}

platform/vcs-impl/shared/BUILD.bazel

@@ -41,4 +41,52 @@ jvm_library(
     "//platform/diagnostic/telemetry",
   ]
 )
-### auto-generated section `build intellij.platform.vcs.impl.shared` end
+
+jvm_library(
+  name = "shared_test_lib",
+  visibility = ["//visibility:public"],
+  srcs = glob(["testSrc/**/*.kt", "testSrc/**/*.java", "testSrc/**/*.form"], allow_empty = True),
+  associates = [":shared"],
+  deps = [
+    "@lib//:kotlin-stdlib",
+    "//platform/core-api:core",
+    "//platform/kernel/shared:kernel",
+    "//platform/project/shared:project",
+    "//platform/platform-api:ide",
+    "//platform/diff-impl",
+    "//platform/projectModel-api:projectModel",
+    "//platform/util:util-ui",
+    "//libraries/kotlinx/serialization/core",
+    "//libraries/kotlinx/serialization/json",
+    "//platform/platform-impl/rpc",
+    "//platform/diagnostic",
+    "@lib//:opentelemetry",
+    "//platform/platform-impl:ide-impl",
+    "//platform/core-ui",
+    "//platform/util/coroutines",
+    "//platform/vcs-api/vcs-api-core:vcs-core",
+    "//platform/vcs-api/vcs-api-core:vcs-core_test_lib",
+    "//platform/editor-ui-api:editor-ui",
+    "//platform/lang-impl",
+    "//platform/util/concurrency",
+    "//platform/util/concurrency:concurrency_test_lib",
+    "//platform/vcs-api/shared",
+    "//libraries/fastutil",
+    "//platform/util/jdom",
+    "//platform/ide-core-impl",
+    "//platform/diagnostic/telemetry",
+    "//platform/diagnostic/telemetry:telemetry_test_lib",
+    "//platform/testFramework",
+    "//platform/testFramework:testFramework_test_lib",
+  ]
+)
+### auto-generated section `build intellij.platform.vcs.impl.shared` end
+
+### auto-generated section `test intellij.platform.vcs.impl.shared` start
+load("@community//build:tests-options.bzl", "jps_test")
+
+jps_test(
+  name = "shared_test",
+  runtime_deps = [":shared_test_lib"]
+)
+### auto-generated section `test intellij.platform.vcs.impl.shared` end

platform/vcs-impl/shared/intellij.platform.vcs.impl.shared.iml

@@ -30,6 +30,7 @@
     <content url="file://$MODULE_DIR$">
       <sourceFolder url="file://$MODULE_DIR$/resources" type="java-resource" />
       <sourceFolder url="file://$MODULE_DIR$/src" isTestSource="false" />
+      <sourceFolder url="file://$MODULE_DIR$/testSrc" isTestSource="true" />
     </content>
     <orderEntry type="inheritedJdk" />
     <orderEntry type="library" name="kotlin-stdlib" level="project" />
@@ -58,5 +59,6 @@
     <orderEntry type="module" module-name="intellij.platform.util.jdom" />
     <orderEntry type="module" module-name="intellij.platform.ide.core.impl" />
     <orderEntry type="module" module-name="intellij.platform.diagnostic.telemetry" />
+    <orderEntry type="module" module-name="intellij.platform.testFramework" scope="TEST" />
   </component>
 </module>

platform/vcs-impl/shared/src/com/intellij/openapi/vcs/changes/ui/ChangesTree.java

@@ -522,16 +522,13 @@ public abstract class ChangesTree extends Tree implements UiCompatibleDataProvid
       if (node instanceof DefaultMutableTreeNode mutableTreeNode) {
         Object userObject = mutableTreeNode.getUserObject();
         return (userObject instanceof Change change) ?
-               matches(change, toSelect) :
+               ChangesUtil.matches(change, toSelect) :
                toSelect.equals(VcsTreeModelData.mapUserObjectToFilePath(userObject));
       }
       return false;
     });
   }
 
-  private static boolean matches(@NotNull Change change, @NotNull FilePath toSelect) {
-    return toSelect.equals(ChangesUtil.getAfterPath(change)) || toSelect.equals(ChangesUtil.getBeforePath(change));
-  }
 
   public @NotNull ChangesBrowserNode<?> getRoot() {
     return (ChangesBrowserNode<?>)getModel().getRoot();

platform/vcs-impl/shared/src/com/intellij/platform/vcs/impl/shared/changes/ChangesTreePath.kt

@@ -14,7 +14,7 @@ data class ChangesTreePath(
   val filePath: FilePathDto,
   val changeId: ChangeId?,
 ) {
-  internal companion object {
+  companion object {
     fun create(userObject: Any): ChangesTreePath? {
       val filePath = VcsTreeModelData.mapUserObjectToFilePath(userObject) ?: return null
       return ChangesTreePath(

platform/vcs-impl/shared/src/com/intellij/platform/vcs/impl/shared/rpc/ChangesViewDiffApi.kt

@@ -14,6 +14,8 @@ import org.jetbrains.annotations.ApiStatus
 interface ChangesViewDiffApi : RemoteApi<Unit> {
   suspend fun performDiffAction(projectId: ProjectId, action: ChangesViewDiffAction)
 
+  suspend fun notifySelectionUpdated(projectId: ProjectId, selection: ChangesViewDiffableSelection?)
+
   companion object {
     suspend fun getInstance(): ChangesViewDiffApi = RemoteApiProviderService.resolve(remoteApiDescriptor<ChangesViewDiffApi>())
   }

platform/vcs-impl/shared/src/com/intellij/platform/vcs/impl/shared/rpc/ChangesViewDiffableSelection.kt

@@ -0,0 +1,19 @@
+// Copyright 2000-2025 JetBrains s.r.o. and contributors. Use of this source code is governed by the Apache 2.0 license.
+package com.intellij.platform.vcs.impl.shared.rpc
+
+import com.intellij.platform.vcs.impl.shared.changes.ChangesTreePath
+import kotlinx.serialization.Serializable
+import org.jetbrains.annotations.ApiStatus
+
+/**
+ * Represents the currently selected change in the Changes View
+ * and the changes below and above it, which can be navigated using
+ * "Next/Previous Difference" or "Compare Previous/Next File" action
+ */
+@ApiStatus.Internal
+@Serializable
+data class ChangesViewDiffableSelection(
+  val selectedChange: ChangesTreePath,
+  val previousChange: ChangesTreePath?,
+  val nextChange: ChangesTreePath?,
+)

platform/vcs-impl/shared/testSrc/com/intellij/platform/vcs/impl/changes/ChangesViewTestBase.kt

@@ -0,0 +1,42 @@
+// Copyright 2000-2025 JetBrains s.r.o. and contributors. Use of this source code is governed by the Apache 2.0 license.
+package com.intellij.platform.vcs.impl.changes
+
+import com.intellij.openapi.vcs.FilePath
+import com.intellij.openapi.vcs.actions.VcsContextFactory
+import com.intellij.openapi.vcs.changes.LocalChangeListImpl
+import com.intellij.openapi.vcs.changes.LocalChangesListView
+import com.intellij.openapi.vcs.changes.ui.ChangesTree
+import com.intellij.openapi.vcs.changes.ui.TreeModelBuilder
+import com.intellij.testFramework.LightPlatformTestCase
+import com.intellij.testFramework.runInEdtAndWait
+import javax.swing.tree.DefaultTreeModel
+
+abstract class ChangesViewTestBase : LightPlatformTestCase() {
+  protected lateinit var view: LocalChangesListView
+
+  override fun setUp() {
+    super.setUp()
+    view = LocalChangesListView(project)
+  }
+
+  protected fun updateModelAndSelect(view: LocalChangesListView, model: DefaultTreeModel, toSelect: FilePath) {
+    runInEdtAndWait {
+      view.updateTreeModel(model, ChangesTree.ALWAYS_RESET)
+      assertEquals(0, view.selectionCount)
+      view.selectFile(toSelect)
+      assertEquals(1, view.selectionCount)
+    }
+  }
+
+  protected fun path(fileName: String): FilePath =
+    VcsContextFactory.getInstance().createFilePath("/ChangesViewTest/$fileName", false)
+
+  protected fun buildModel(
+    view: LocalChangesListView,
+    lists: List<LocalChangeListImpl>,
+    unversioned: List<FilePath>,
+  ): DefaultTreeModel = TreeModelBuilder(project, view.grouping)
+    .setChangeLists(lists, false, null)
+    .setUnversioned(unversioned)
+    .build()
+}

platform/vcs-impl/src/com/intellij/vcs/changes/ChangesViewDiffApiImpl.kt

@@ -7,6 +7,7 @@ import com.intellij.openapi.diagnostic.trace
 import com.intellij.openapi.vcs.changes.ChangesViewDiffAction
 import com.intellij.platform.project.ProjectId
 import com.intellij.platform.vcs.impl.shared.rpc.ChangesViewDiffApi
+import com.intellij.platform.vcs.impl.shared.rpc.ChangesViewDiffableSelection
 import com.intellij.vcs.changes.viewModel.getRpcChangesView
 import com.intellij.vcs.rpc.ProjectScopeRpcHelper.projectScoped
 
@@ -16,6 +17,11 @@ internal class ChangesViewDiffApiImpl : ChangesViewDiffApi {
     project.getRpcChangesView().diffRequests.emit(action to ClientId.current)
   }
 
+  override suspend fun notifySelectionUpdated(projectId: ProjectId, selection: ChangesViewDiffableSelection?) = projectScoped(projectId) { project ->
+    LOG.trace { "Selection updated for diff: $selection" }
+    project.getRpcChangesView().selectionUpdated(selection)
+  }
+
   companion object {
     private val LOG = logger<ChangesViewDiffApiImpl>()
   }

platform/vcs-impl/src/com/intellij/vcs/changes/viewModel/RpcChangesViewProxy.kt

@@ -12,6 +12,7 @@ import com.intellij.platform.kernel.ids.BackendValueIdType
 import com.intellij.platform.kernel.ids.storeValueGlobally
 import com.intellij.platform.vcs.impl.shared.rpc.BackendChangesViewEvent
 import com.intellij.platform.vcs.impl.shared.rpc.ChangesViewApi
+import com.intellij.platform.vcs.impl.shared.rpc.ChangesViewDiffableSelection
 import com.intellij.ui.split.createComponent
 import kotlinx.coroutines.CoroutineScope
 import kotlinx.coroutines.channels.BufferOverflow
@@ -42,6 +43,8 @@ internal class RpcChangesViewProxy(project: Project, scope: CoroutineScope) : Ch
 
   val inclusionModel = MutableStateFlow<InclusionModel?>(null)
 
+  val diffableSelection = MutableStateFlow<ChangesViewDiffableSelection?>(null)
+
   private var _panel: JComponent? = null
   override val panel: JComponent
     get() = _panel ?: error("Panel is not initialized yet")
@@ -108,6 +111,10 @@ internal class RpcChangesViewProxy(project: Project, scope: CoroutineScope) : Ch
   }
 
   fun refreshPerformed(counter: Int) = refresher.refreshPerformed(counter)
+
+  fun selectionUpdated(selection: ChangesViewDiffableSelection?) {
+    diffableSelection.value = selection
+  }
 }
 
 private val REFRESH_TIMEOUT = 1.minutes
@@ -117,6 +124,7 @@ private class BackendRemoteCommitChangesViewModelRefresher(
   private val requestsSink: MutableSharedFlow<in BackendChangesViewEvent.RefreshRequested>,
 ) {
   private val refreshRequestCounter = AtomicInteger(0)
+
   /**
    * Once backend was notified about refresh applied with the given counter,
    * all the pending callbacks having counter less than or equal to it will be executed.

platform/vcs-impl/testSrc/com/intellij/openapi/vcs/changes/ui/LocalChangesListViewSelectFileTest.kt

@@ -1,23 +1,19 @@
 // Copyright 2000-2025 JetBrains s.r.o. and contributors. Use of this source code is governed by the Apache 2.0 license.
 package com.intellij.openapi.vcs.changes.ui
 
-import com.intellij.openapi.vcs.FilePath
-import com.intellij.openapi.vcs.actions.VcsContextFactory
-import com.intellij.openapi.vcs.changes.*
+import com.intellij.openapi.vcs.changes.Change
+import com.intellij.openapi.vcs.changes.CurrentContentRevision
+import com.intellij.openapi.vcs.changes.LocalChangeListImpl
 import com.intellij.platform.vcs.changes.ChangesUtil
-import com.intellij.testFramework.LightPlatformTestCase
-import com.intellij.testFramework.runInEdtAndWait
+import com.intellij.platform.vcs.impl.changes.ChangesViewTestBase
 import javax.swing.tree.DefaultMutableTreeNode
-import javax.swing.tree.DefaultTreeModel
 
-internal class LocalChangesListViewSelectFileTest : LightPlatformTestCase() {
+internal class LocalChangesListViewSelectFileTest : ChangesViewTestBase() {
   fun `test selects unversioned file path`() {
-    val view = LocalChangesListView(project)
-
-    val unversionedPath = fakePath("unversioned.txt")
+    val unversionedPath = path("unversioned.txt")
     val defaultList = LocalChangeListImpl.Builder(project, "Default")
       .setDefault(true)
-      .setChanges(listOf(Change(null, CurrentContentRevision.create(fakePath("default-change.txt")))))
+      .setChanges(listOf(Change(null, CurrentContentRevision.create(path("default-change.txt")))))
       .build()
 
     val model = buildModel(view, listOf(defaultList), listOf(unversionedPath))
@@ -27,11 +23,9 @@ internal class LocalChangesListViewSelectFileTest : LightPlatformTestCase() {
   }
 
   fun `test selects change by file path`() {
-    val view = LocalChangesListView(project)
-
-    val targetPath = fakePath("added.txt")
+    val targetPath = path("added.txt")
     val targetChange = Change(null, CurrentContentRevision.create(targetPath))
-    val anotherChange = Change(null, CurrentContentRevision.create(fakePath("another.txt")))
+    val anotherChange = Change(null, CurrentContentRevision.create(path("another.txt")))
     val defaultList = LocalChangeListImpl.Builder(project, "Default")
       .setDefault(true)
       .setChanges(listOf(targetChange, anotherChange))
@@ -48,15 +42,13 @@ internal class LocalChangesListViewSelectFileTest : LightPlatformTestCase() {
   }
 
   fun `test selects change in multiple change lists`() {
-    val view = LocalChangesListView(project)
-
-    val targetPath = fakePath("default.txt")
+    val targetPath = path("default.txt")
     val change = Change(null, CurrentContentRevision.create(targetPath))
     val workList = LocalChangeListImpl.Builder(project, "Work").setDefault(false)
       .setChanges(
         listOf(
           change,
-          Change(null, CurrentContentRevision.create(fakePath("work-other.txt"))),
+          Change(null, CurrentContentRevision.create(path("work-other.txt"))),
         )
       )
       .build()
@@ -74,25 +66,4 @@ internal class LocalChangesListViewSelectFileTest : LightPlatformTestCase() {
     val changelistNode = view.selectionPath!!.path[1] as DefaultMutableTreeNode
     assertEquals("Selected change must be under the Default changelist node", defaultList, changelistNode.userObject)
   }
-
-  private fun buildModel(
-    view: LocalChangesListView,
-    changeLists: List<ChangeList>,
-    unversionedFiles: List<FilePath>,
-  ): DefaultTreeModel = TreeModelBuilder(project, view.grouping)
-    .setChangeLists(changeLists, false, null)
-    .setUnversioned(unversionedFiles)
-    .build()
-
-  private fun updateModelAndSelect(view: LocalChangesListView, model: DefaultTreeModel, pathToSelect: FilePath) {
-    runInEdtAndWait {
-      view.updateTreeModel(model, ChangesTree.ALWAYS_RESET)
-      assertEquals(0, view.selectionCount)
-      view.selectFile(pathToSelect)
-      assertEquals(1, view.selectionCount)
-    }
-  }
-
-  private fun fakePath(fileName: String): FilePath =
-    VcsContextFactory.getInstance().createFilePath("/LocalChangesListViewSelectFileTest/$fileName", false)
 }

platform/vcs-log/impl/BUILD.bazel

@@ -119,6 +119,7 @@ jvm_library(
     "//platform/util/coroutines",
     "//platform/util/storages",
     "//platform/vcs-impl/shared",
+    "//platform/vcs-impl/shared:shared_test_lib",
     "//libraries/mockito",
     "//platform/bookmarks",
   ]

platform/vcs-tests/BUILD.bazel

@@ -76,6 +76,7 @@ jvm_library(
     "//tools/intellij.tools.ide.metrics.benchmark:ide-metrics-benchmark",
     "//tools/intellij.tools.ide.metrics.benchmark:ide-metrics-benchmark_test_lib",
     "//platform/vcs-impl/shared",
+    "//platform/vcs-impl/shared:shared_test_lib",
     "//platform/core-impl",
   ],
   exports = ["//platform/vcs-tests:vcs-testFramework"]

plugins/git-features-trainer/BUILD.bazel

@@ -74,6 +74,7 @@ jvm_library(
     "//platform/testFramework:testFramework_test_lib",
     "//platform/dvcs-impl/shared",
     "//platform/vcs-impl/shared",
+    "//platform/vcs-impl/shared:shared_test_lib",
   ]
 )
 ### auto-generated section `build intellij.vcs.git.featuresTrainer` end

plugins/git4idea/BUILD.bazel

@@ -145,6 +145,7 @@ jvm_library(
     "//platform/vcs-impl",
     "//platform/vcs-impl:vcs-impl_test_lib",
     "//platform/vcs-impl/shared",
+    "//platform/vcs-impl/shared:shared_test_lib",
     "//platform/lang-api:lang",
     "@lib//:junit4",
     "//platform/lvcs-api:lvcs",

plugins/git4idea/intellij.vcs.git.coverage/BUILD.bazel

@@ -57,6 +57,7 @@ jvm_library(
     "//platform/vcs-log/graph:vcs-log-graph-impl_test_lib",
     "//platform/vcs-api/shared",
     "//platform/vcs-impl/shared",
+    "//platform/vcs-impl/shared:shared_test_lib",
   ]
 )
 ### auto-generated section `build intellij.vcs.git.coverage` end

plugins/git4idea/terminal/BUILD.bazel

@@ -52,6 +52,7 @@ jvm_library(
     "//platform/testFramework",
     "//platform/testFramework:testFramework_test_lib",
     "//platform/vcs-impl/shared",
+    "//platform/vcs-impl/shared:shared_test_lib",
     "//platform/vcs-api/shared",
     "@lib//:assert_j",
     "//libraries/mockito",

plugins/github/github-core/BUILD.bazel

@@ -168,6 +168,7 @@ jvm_library(
     "//platform/dvcs-impl/shared",
     "//platform/ide-core-impl",
     "//platform/vcs-impl/shared",
+    "//platform/vcs-impl/shared:shared_test_lib",
   ]
 )
 ### auto-generated section `build intellij.vcs.github` end

plugins/gitlab/gitlab-core/BUILD.bazel

@@ -139,6 +139,7 @@ jvm_library(
     "//platform/dvcs-impl/shared",
     "//platform/ide-core-impl",
     "//platform/vcs-impl/shared",
+    "//platform/vcs-impl/shared:shared_test_lib",
     "//platform/code-style-api:codeStyle",
   ]
 )

plugins/hg4idea/BUILD.bazel

@@ -81,6 +81,7 @@ jvm_library(
     "//platform/util/coroutines",
     "//platform/dvcs-impl/shared",
     "//platform/vcs-impl/shared",
+    "//platform/vcs-impl/shared:shared_test_lib",
     "//platform/core-impl",
   ]
 )

plugins/kotlin/idea/tests/BUILD.bazel

@@ -58,6 +58,7 @@ jvm_library(
     "//platform/usageView-impl",
     "//platform/vcs-api:vcs",
     "//platform/vcs-impl/shared",
+    "//platform/vcs-impl/shared:shared_test_lib",
     "//platform/workspace/storage",
     "//plugins/kotlin/plugin/k1",
     "//plugins/kotlin/code-insight/api",