Fix dry-run iSCSI ID map cascades; add pre-migration existence check

During dry run, "would create" iSCSI objects now populate id_map with
a source-ID placeholder so downstream objects (targets, target-extents)
can remap references without cascading failures.

Adds query_existing_iscsi() and clear_iscsi_config() to migrate.py, and
_prompt_clear_existing_iscsi() to the wizard: if the destination already
has iSCSI config, the user is shown a summary and offered Keep/Remove
before the dry run begins.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

truenas_migrate/cli.py

@@ -57,7 +57,7 @@ from .archive import parse_archive, list_archive_and_exit
 from .client import TrueNASClient, check_dataset_paths, create_missing_datasets, check_iscsi_zvols, create_missing_zvols
 from .colors import log, _bold, _bold_cyan, _bold_red, _bold_yellow, _cyan, _dim, _green, _yellow
 from .csv_source import parse_csv_sources
-from .migrate import migrate_smb_shares, migrate_nfs_shares, migrate_iscsi
+from .migrate import migrate_smb_shares, migrate_nfs_shares, migrate_iscsi, query_existing_iscsi, clear_iscsi_config
 from .summary import Summary
 
 
@@ -214,6 +214,53 @@ def _prompt_iscsi_portals(iscsi: dict) -> None:
     print()
 
 
+def _prompt_clear_existing_iscsi(host: str, port: int, api_key: str) -> None:
+    """
+    Check whether the destination already has iSCSI configuration.
+    If so, summarise what exists and offer to remove it before migration.
+    """
+    async def _check():
+        async with TrueNASClient(host=host, port=port, api_key=api_key, verify_ssl=False) as client:
+            return await query_existing_iscsi(client)
+
+    existing = asyncio.run(_check())
+    counts = {k: len(v) for k, v in existing.items()}
+    total = sum(counts.values())
+    if total == 0:
+        return
+
+    print(f"\n  {_bold_yellow('WARNING:')} Destination already has iSCSI configuration:")
+    labels = [
+        ("extents",       "extent(s)"),
+        ("initiators",    "initiator group(s)"),
+        ("portals",       "portal(s)"),
+        ("targets",       "target(s)"),
+        ("targetextents", "target-extent association(s)"),
+    ]
+    for key, label in labels:
+        n = counts[key]
+        if n:
+            print(f"    • {n} {label}")
+    print()
+    print(f"  {_dim('Keep existing:  new objects will be skipped if conflicts are detected.')}")
+    print(f"  {_dim('Remove existing: ALL iSCSI config will be deleted before migration.')}")
+    print()
+
+    raw = _prompt("  [K]eep existing  /  [R]emove all existing iSCSI config", default="K")
+    if raw.strip().lower().startswith("r"):
+        if _confirm(f"  Remove ALL {total} iSCSI object(s) from {host}?"):
+            async def _clear():
+                async with TrueNASClient(host=host, port=port, api_key=api_key, verify_ssl=False) as client:
+                    await clear_iscsi_config(client)
+            print()
+            asyncio.run(_clear())
+            print(f"  {_bold_cyan('✓')} iSCSI configuration cleared.\n")
+        else:
+            print(f"  {_yellow('–')} Removal cancelled — keeping existing config.\n")
+    else:
+        print(f"  {_dim('Keeping existing iSCSI configuration.')}\n")
+
+
 def _select_shares(shares: list[dict], share_type: str) -> list[dict]:
     """
     Display a numbered list of *shares* and return only those the user selects.
@@ -377,6 +424,10 @@ def interactive_mode() -> None:
         if "iscsi" in migrate and archive_data.get("iscsi", {}).get("portals"):
             _prompt_iscsi_portals(archive_data["iscsi"])
 
+        # ── iSCSI pre-migration check ────────────────────────────────────────
+        if "iscsi" in migrate:
+            _prompt_clear_existing_iscsi(host, port, api_key)
+
     # ── Select individual shares (common) ──────────────────────────────────────
     if "smb" in migrate and archive_data["smb_shares"]:
         archive_data["smb_shares"] = _select_shares(archive_data["smb_shares"], "SMB")

truenas_migrate/migrate.py

@@ -239,6 +239,7 @@ async def _migrate_iscsi_extents(
                      _cyan("[DRY RUN]"), _bold_cyan(repr(name)),
                      ext.get("disk") or ext.get("path"))
             summary.iscsi_extents_created += 1
+            id_map[ext["id"]] = ext["id"]  # placeholder — enables downstream dry-run remapping
             if ext.get("type") == "DISK" and ext.get("disk"):
                 summary.zvols_to_check.append(ext["disk"].removeprefix("zvol/"))
             continue
@@ -288,6 +289,7 @@ async def _migrate_iscsi_initiators(
             log.info("   %s would create initiator group %s",
                      _cyan("[DRY RUN]"), _bold_cyan(repr(comment)))
             summary.iscsi_initiators_created += 1
+            id_map[init["id"]] = init["id"]  # placeholder — enables downstream dry-run remapping
             continue
 
         try:
@@ -341,6 +343,7 @@ async def _migrate_iscsi_portals(
             log.info("   %s would create portal %s → %s",
                      _cyan("[DRY RUN]"), _bold_cyan(repr(comment)), ips)
             summary.iscsi_portals_created += 1
+            id_map[portal["id"]] = portal["id"]  # placeholder — enables downstream dry-run remapping
             continue
 
         try:
@@ -404,6 +407,7 @@ async def _migrate_iscsi_targets(
             log.info("   %s would create target %s",
                      _cyan("[DRY RUN]"), _bold_cyan(repr(name)))
             summary.iscsi_targets_created += 1
+            id_map[target["id"]] = target["id"]  # placeholder — enables downstream dry-run remapping
             continue
 
         try:
@@ -480,6 +484,56 @@ async def _migrate_iscsi_targetextents(
                 f"iSCSI target-extent (target={dest_tid}, lun={lunid}): {exc}")
 
 
+# ─────────────────────────────────────────────────────────────────────────────
+# iSCSI pre-migration utilities
+# ─────────────────────────────────────────────────────────────────────────────
+
+async def query_existing_iscsi(client: TrueNASClient) -> dict:
+    """
+    Query all iSCSI object counts from the destination.
+    Returns a dict with keys: extents, initiators, portals, targets, targetextents
+    Each value is a list of objects (may be empty).
+    """
+    result = {}
+    for key, method in [
+        ("extents",       "iscsi.extent.query"),
+        ("initiators",    "iscsi.initiator.query"),
+        ("portals",       "iscsi.portal.query"),
+        ("targets",       "iscsi.target.query"),
+        ("targetextents", "iscsi.targetextent.query"),
+    ]:
+        try:
+            result[key] = await client.call(method) or []
+        except RuntimeError:
+            result[key] = []
+    return result
+
+
+async def clear_iscsi_config(client: TrueNASClient) -> None:
+    """
+    Delete all iSCSI configuration from the destination in safe dependency order:
+    target-extents → targets → portals → initiators → extents.
+    """
+    for method_query, method_delete, label in [
+        ("iscsi.targetextent.query", "iscsi.targetextent.delete", "target-extent"),
+        ("iscsi.target.query",       "iscsi.target.delete",       "target"),
+        ("iscsi.portal.query",       "iscsi.portal.delete",       "portal"),
+        ("iscsi.initiator.query",    "iscsi.initiator.delete",    "initiator"),
+        ("iscsi.extent.query",       "iscsi.extent.delete",       "extent"),
+    ]:
+        try:
+            objects = await client.call(method_query) or []
+        except RuntimeError as exc:
+            log.warning("  Could not query iSCSI %ss: %s", label, exc)
+            continue
+        for obj in objects:
+            try:
+                await client.call(method_delete, [obj["id"]])
+                log.info("  Deleted iSCSI %s id=%s", label, obj["id"])
+            except RuntimeError as exc:
+                log.warning("  Failed to delete iSCSI %s id=%s: %s", label, obj["id"], exc)
+
+
 # ─────────────────────────────────────────────────────────────────────────────
 # Public iSCSI entry point
 # ─────────────────────────────────────────────────────────────────────────────