[vcs/commit]: Fix files to be included in a commit for hg in rem dev (IJPL-246371)

Merge-request: IJ-MR-212133
Merged-by: Victoria Petrakovich <Victoria.Petrakovich@jetbrains.com>

GitOrigin-RevId: b33a0a595e7ab2da9f81de44d0aa182ec5026010

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

@@ -39,42 +39,80 @@ data class ChangeListDto(
       }
       setDefault(isDefault)
       setId(id)
-    }.setChanges(changes.map { ChangeListChange(it.change, name, id) }).build()
+    }.setChanges(changes.map { it.toChange(name, id) }).build()
   }
 }
 
+/**
+ * A serialized [Change] belonging to a [ChangeListDto].
+ *
+ * The concrete subtype encodes how the backend represents the change, which is what [toChange] reconstructs.
+ * This drives [ChangeId.getId] to produce the same value on both frontend and backend so that commit inclusion
+ * round-trips correctly (see IJPL-246371):
+ * - [ChangelistChangeDto] for VCSes supporting partial changelists (e.g. Git), wrapped into a [ChangeListChange];
+ * - [PlainChangeDto] for the others (e.g. Mercurial, SVN), kept as a plain [Change].
+ */
 @Serializable
 @ApiStatus.Internal
-data class ChangeDto(
-  private val beforeRevision: ContentRevisionDto?,
-  private val afterRevision: ContentRevisionDto?,
-  private val fileStatusId: String,
-  @Transient private val localValue: Change? = null,
-) {
-  val change: Change by lazy {
-    if (localValue != null) return@lazy localValue
+sealed class ChangeDto {
+  protected abstract val beforeRevision: ContentRevisionDto?
+  protected abstract val afterRevision: ContentRevisionDto?
+  protected abstract val fileStatusId: String
+  protected abstract val localValue: Change?
 
-    val fileStatus = PLATFORM_FILE_STATUSES[fileStatusId]
-    Change(beforeRevision?.contentRevision, afterRevision?.contentRevision, fileStatus)
+  /** The plain [Change] carried by this DTO, without any change list wrapping. */
+  val change: Change by lazy {
+    localValue ?: Change(beforeRevision?.contentRevision, afterRevision?.contentRevision, PLATFORM_FILE_STATUSES[fileStatusId])
   }
 
+  /** Reconstructs the change the way the backend represents it inside the change list [listName]/[listId]. */
+  abstract fun toChange(listName: @Nls String, listId: @NonNls String): Change
+
   companion object {
-    fun toDto(change: Change): ChangeDto = ChangeDto(
-      beforeRevision = change.beforeRevision?.toDto(),
-      afterRevision = change.afterRevision?.toDto(),
-      fileStatusId = change.fileStatus.id,
-      localValue = change,
-    )
+    fun toDto(change: Change): ChangeDto {
+      val beforeRevision = change.beforeRevision?.toDto()
+      val afterRevision = change.afterRevision?.toDto()
+      val fileStatusId = change.fileStatus.id
+      return if (change is ChangeListChange) {
+        ChangelistChangeDto(beforeRevision, afterRevision, fileStatusId, localValue = change)
+      }
+      else {
+        PlainChangeDto(beforeRevision, afterRevision, fileStatusId, localValue = change)
+      }
+    }
 
     private fun ContentRevision.toDto() = ContentRevisionDto(
       revisionString = revisionNumber.asString(),
       filePath = FilePathDto.toDto(file),
       localValue = this,
     )
-
   }
 }
 
+/** A change from a VCS without partial changelist support; reconstructed as a plain [Change]. */
+@Serializable
+@ApiStatus.Internal
+data class PlainChangeDto(
+  override val beforeRevision: ContentRevisionDto?,
+  override val afterRevision: ContentRevisionDto?,
+  override val fileStatusId: String,
+  @Transient override val localValue: Change? = null,
+) : ChangeDto() {
+  override fun toChange(listName: String, listId: String): Change = change
+}
+
+/** A change from a VCS with partial changelist support; reconstructed as a [ChangeListChange]. */
+@Serializable
+@ApiStatus.Internal
+data class ChangelistChangeDto(
+  override val beforeRevision: ContentRevisionDto?,
+  override val afterRevision: ContentRevisionDto?,
+  override val fileStatusId: String,
+  @Transient override val localValue: ChangeListChange? = null,
+) : ChangeDto() {
+  override fun toChange(listName: String, listId: String): ChangeListChange = ChangeListChange(change, listName, listId)
+}
+
 private val PLATFORM_FILE_STATUSES: Map<String, FileStatus> by lazy {
   FileStatusFactory.getInstance().globalFileStatuses.associateBy { it.id }
 }

platform/vcs-tests/testSrc/com/intellij/openapi/vcs/changes/ChangeListDtoChangeIdRoundTripTest.kt

@@ -0,0 +1,64 @@
+// Copyright 2000-2026 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
+
+import com.intellij.openapi.vcs.LocalFilePath
+import com.intellij.platform.vcs.impl.shared.rpc.ChangeDto
+import com.intellij.platform.vcs.impl.shared.rpc.ChangeId
+import com.intellij.platform.vcs.impl.shared.rpc.ChangeListDto
+import com.intellij.testFramework.fixtures.BasePlatformTestCase
+
+/**
+ * Verifies that the [ChangeId] a change gets on the frontend (after being reconstructed from [ChangeListDto]) matches
+ * the [ChangeId] the backend keys its cache with, for VCSes both with and without partial changelist support.
+ *
+ * Regression test: previously [ChangeListDto] unconditionally wrapped every change into [ChangeListChange], producing
+ * a `ChangeListChangeId`. For a VCS without partial changelist support (e.g. Mercurial, SVN) the backend keeps the
+ * plain [Change] and thus keys the cache by a `NonChangeListChangeId`, so the ids did not match, the backend inclusion
+ * stayed empty, and the Commit button reported "Select files to commit".
+ *
+ * @see ChangeListDto.getChangeList (frontend reconstruction / wrapping decision)
+ * @see com.intellij.vcs.changes.ChangesViewChangeIdProvider (backend cache, keyed by [ChangeId.getId])
+ */
+internal class ChangeListDtoChangeIdRoundTripTest : BasePlatformTestCase() {
+  fun `test ChangeId matches for VCS without partial changelist support`() {
+    assertFrontendChangeIdMatchesBackend(partialChangelistsSupported = false)
+  }
+
+  fun `test ChangeId matches for VCS with partial changelist support`() {
+    assertFrontendChangeIdMatchesBackend(partialChangelistsSupported = true)
+  }
+
+  private fun assertFrontendChangeIdMatchesBackend(partialChangelistsSupported: Boolean) {
+    val listName = "Test List"
+    val listId = "test-list-id"
+    val filePath = LocalFilePath("/root/file.txt", false)
+    val change = Change(
+      SimpleContentRevision("base", filePath, "1"),
+      SimpleContentRevision("content", filePath, "2"),
+    )
+
+    // How the backend represents the change and keys the ChangeId cache, see ChangeListWorker.getChangesMapping:
+    // it wraps into a ChangeListChange only for VCSes that support partial changelists.
+    val backendChange: Change =
+      if (partialChangelistsSupported) ChangeListChange(change, listName, listId) else change
+    val backendId = ChangeId.getId(backendChange)
+
+    // How the frontend reconstructs the change from the serialized DTO, see ChangeListDto.getChangeList.
+    // The backend serializes its own representation of the change (backendChange), so ChangeDto.toDto picks the
+    // matching DTO subtype based on whether the change is wrapped into a ChangeListChange.
+    val dto = ChangeListDto(
+      name = listName,
+      comment = null,
+      id = listId,
+      isDefault = false,
+      changes = listOf(ChangeDto.toDto(backendChange)),
+    )
+    val frontendChange = dto.getChangeList(project).changes.single()
+    val frontendId = ChangeId.getId(frontendChange)
+
+    assertEquals(
+      "Frontend and backend must compute the same ChangeId (partialChangelistsSupported=$partialChangelistsSupported)",
+      backendId, frontendId,
+    )
+  }
+}