Implementation done.

Author: forman

docs/cli.md

@@ -20,6 +20,10 @@ Options:
                          the previous ones.
   -t, --target TARGET    Target Zarr dataset path or URI. Overrides the
                          'target_dir' configuration field.
+  --force-new            Force creation of a new target dataset.  An existing
+                         target dataset (and its lock) will be permanently
+                         deleted before appending of slice datasets begins.
+                         WARNING: the deletion cannot be rolled back.
   --dry-run              Run the tool without creating, changing, or deleting
                          any files.
   --traceback            Show Python traceback on error.

docs/config.md

@@ -240,6 +240,12 @@ The URI or local path of the directory that will be used to temporarily store ro
 Type _object_.
 Options for the filesystem given by the protocol of `temp_dir`.
 
+## `force_new`
+
+Type _boolean_.
+Force creation of a new target dataset.  An existing target dataset (and its lock) will be permanently deleted before appending of slice datasets begins. WARNING: the deletion cannot be rolled back.
+Defaults to `false`.
+
 ## `disable_rollback`
 
 Type _boolean_.

tests/test_api.py

@@ -13,6 +13,7 @@
 from zappend.api import FileObj
 from zappend.api import SliceSource
 from zappend.api import zappend
+from zappend.fsutil.transaction import Transaction
 from .helpers import clear_memory_fs
 from .helpers import make_test_dataset
 
@@ -108,6 +109,39 @@ def test_some_slices_local_output_to_non_existing_dir(self):
             for slice_dir in slices:
                 shutil.rmtree(slice_dir, ignore_errors=True)
 
+    def test_some_slices_local_output_to_existing_dir_force_new(self):
+        target_dir = "memory://target.zarr"
+        slices = [
+            "memory://slice-0.zarr",
+            "memory://slice-1.zarr",
+            "memory://slice-2.zarr",
+            "memory://slice-3.zarr",
+        ]
+        for uri in slices:
+            make_test_dataset(uri=uri)
+
+        # Expect nothing else to happen, even that force_new=True.
+        zappend(slices[:1], target_dir=target_dir, force_new=True)
+        target_ds = xr.open_zarr(target_dir)
+        self.assertEqual({"time": 3, "y": 50, "x": 100}, target_ds.sizes)
+
+        # Expect deletion of existing target_dir
+        zappend(slices[1:], target_dir=target_dir, force_new=True)
+        target_ds = xr.open_zarr(target_dir)
+        self.assertEqual({"time": 9, "y": 50, "x": 100}, target_ds.sizes)
+
+        # Expect no changes, even if force_new=True
+        zappend(slices, target_dir=target_dir, force_new=True, dry_run=True)
+        target_ds = xr.open_zarr(target_dir)
+        self.assertEqual({"time": 9, "y": 50, "x": 100}, target_ds.sizes)
+
+        # Expect a lock file to be deleted to
+        lock_file = Transaction.get_lock_file(FileObj(target_dir))
+        lock_file.write("")
+        self.assertEqual(True, lock_file.exists())
+        zappend(slices, target_dir=target_dir, force_new=True)
+        self.assertEqual(False, lock_file.exists())
+
     def test_some_slices_with_class_slice_source(self):
         target_dir = "memory://target.zarr"
         slices = [make_test_dataset(index=3 * i) for i in range(3)]

tests/test_context.py

@@ -4,8 +4,8 @@
 
 import unittest
 
-import pytest
 import numpy as np
+import pytest
 import xarray as xr
 
 from zappend.context import Context
@@ -35,6 +35,12 @@ def test_with_existing_target(self):
         self.assertEqual(target_dir, ctx.target_dir.uri)
         self.assertIsInstance(ctx.target_metadata, DatasetMetadata)
 
+    def test_force_new(self):
+        ctx = Context({"target_dir": "memory://target.zarr"})
+        self.assertEqual(False, ctx.force_new)
+        ctx = Context({"target_dir": "memory://target.zarr", "force_new": True})
+        self.assertEqual(True, ctx.force_new)
+
     def test_append_dim(self):
         ctx = Context({"target_dir": "memory://target.zarr"})
         self.assertEqual("time", ctx.append_dim)

zappend/cli.py

@@ -13,21 +13,35 @@
     "-c",
     metavar="CONFIG",
     multiple=True,
-    help="Configuration JSON or YAML file."
-    " If multiple are passed, subsequent configurations"
-    " are incremental to the previous ones.",
+    help=(
+        "Configuration JSON or YAML file."
+        " If multiple are passed, subsequent configurations"
+        " are incremental to the previous ones."
+    ),
 )
 @click.option(
     "--target",
     "-t",
     metavar="TARGET",
-    help="Target Zarr dataset path or URI."
-    " Overrides the 'target_dir' configuration field.",
+    help=(
+        "Target Zarr dataset path or URI."
+        " Overrides the 'target_dir' configuration field."
+    ),
+)
+@click.option(
+    "--force-new",
+    is_flag=True,
+    help=(
+        "Force creation of a new target dataset. "
+        " An existing target dataset (and its lock) will be"
+        " permanently deleted before appending of slice datasets"
+        " begins. WARNING: the deletion cannot be rolled back."
+    ),
 )
 @click.option(
     "--dry-run",
     is_flag=True,
-    help="Run the tool without creating, changing," " or deleting any files.",
+    help="Run the tool without creating, changing, or deleting any files.",
 )
 @click.option(
     "--traceback",
@@ -49,6 +63,7 @@ def zappend(
     slices: tuple[str, ...],
     config: tuple[str, ...],
     target: str | None,
+    force_new: bool,
     dry_run: bool,
     traceback: bool,
     version: bool,
@@ -78,7 +93,13 @@ def zappend(
 
     # noinspection PyBroadException
     try:
-        zappend(slices, config=config, target_dir=target, dry_run=dry_run)
+        zappend(
+            slices,
+            config=config,
+            target_dir=target,
+            force_new=force_new,
+            dry_run=dry_run,
+        )
     except BaseException as e:
         if traceback:
             import traceback as tb

zappend/config/schema.py

@@ -676,9 +676,10 @@
         },
         force_new={
             "description": (
-                "If set, an existing target dataset will be deleted at the"
-                " location specified by `target_dir` before appending of slice"
-                " datasets begins. WARNING: This operation cannot be rolled back!"
+                "Force creation of a new target dataset. "
+                " An existing target dataset (and its lock) will be"
+                " permanently deleted before appending of slice datasets"
+                " begins. WARNING: the deletion cannot be rolled back."
             ),
             "type": "boolean",
             "default": False,

zappend/context.py

@@ -189,6 +189,11 @@ def persist_mem_slices(self) -> bool:
         """Whether to persist in-memory slice datasets."""
         return self._config.get("persist_mem_slices", False)
 
+    @property
+    def force_new(self) -> bool:
+        """If set, an existing target dataset will be deleted."""
+        return self._config.get("force_new", False)
+
     @property
     def disable_rollback(self) -> bool:
         """Whether to disable transaction rollbacks."""

zappend/fsutil/transaction.py

@@ -84,15 +84,18 @@ def __init__(
     ):
         transaction_id = f"zappend-{uuid.uuid4()}"
         rollback_dir = temp_dir / transaction_id
-        lock_file = target_dir.parent / (target_dir.filename + LOCK_EXT)
         self._id = transaction_id
         self._rollback_dir = rollback_dir
         self._rollback_file = rollback_dir / ROLLBACK_FILE
         self._target_dir = target_dir
-        self._lock_file = lock_file
+        self._lock_file = self.get_lock_file(target_dir)
         self._disable_rollback = disable_rollback
         self._entered_ctx = False
 
+    @classmethod
+    def get_lock_file(cls, file_obj: FileObj) -> FileObj:
+        return file_obj.parent / (file_obj.filename + LOCK_EXT)
+
     @property
     def target_dir(self) -> FileObj:
         """Target directory that is subject to this transaction."""

zappend/processor.py

@@ -2,26 +2,27 @@
 # Permissions are hereby granted under the terms of the MIT License:
 # https://opensource.org/licenses/MIT.
 
-from typing import Iterable, Any
 import collections.abc
+from typing import Iterable, Any
 
 import numpy as np
 import xarray as xr
 import zarr.attrs
 import zarr.convenience
 
 from .config import ConfigLike
-from .config import exclude_from_config
-from .config import normalize_config
-from .config import validate_config
 from .config import eval_dyn_config_attrs
+from .config import exclude_from_config
 from .config import get_dyn_config_attrs_env
 from .config import has_dyn_config_attrs
+from .config import normalize_config
+from .config import validate_config
 from .context import Context
-from .fsutil.transaction import Transaction
+from .fsutil import FileObj
 from .fsutil.transaction import RollbackCallback
-from .log import logger
+from .fsutil.transaction import Transaction
 from .log import configure_logging
+from .log import logger
 from .profiler import Profiler
 from .rollbackstore import RollbackStore
 from .slice import SliceObj
@@ -53,6 +54,12 @@ def __init__(self, config: ConfigLike = None, **kwargs):
         configure_logging(config.get("logging"))
         self._profiler = Profiler(config.get("profiling"))
         self._config = config
+        if config.get("force_new"):
+            logger.warning(
+                f"Setting 'force_new' is enabled. This will "
+                f" permanently delete existing targets (no rollback)."
+            )
+            delete_target_permanently(config)
 
     def process_slices(self, slices: Iterable[SliceObj]):
         """Process the given `slices`.
@@ -119,6 +126,26 @@ def process_slice(self, slice_obj: SliceObj, slice_index: int = 0):
                     update_target_from_slice(ctx, slice_dataset, rollback_callback)
 
 
+def delete_target_permanently(config: dict[str, Any]):
+    # TODO: I'm not happy with the config being a dict here, because it
+    #   implies and hence duplicates definition of default values.
+    #   Make Processor constructor turn config dict into config object,
+    #   Pass config object to Context and publish via ctx.config property.
+    dry_run = config.get("dry_run", False)
+    target_uri = config.get("target_dir")
+    target_storage_options = config.get("target_storage_options")
+    target_dir = FileObj(target_uri, storage_options=target_storage_options)
+    if target_dir.exists():
+        logger.warning(f"Permanently deleting {target_dir}")
+        if not dry_run:
+            target_dir.delete(recursive=True)
+    target_lock = Transaction.get_lock_file(target_dir)
+    if target_lock.exists():
+        logger.warning(f"Permanently deleting {target_lock}")
+        if not dry_run:
+            target_lock.delete()
+
+
 def create_target_from_slice(
     ctx: Context, slice_ds: xr.Dataset, rollback_cb: RollbackCallback
 ):