Split --snapshot installer into installer-exact and installer-updated

conda_self/cli/main_reset.py

@@ -20,13 +20,16 @@ class SnapshotData(TypedDict):
     Snapshot to reset the `base` environment to.
     `current` removes all packages except for `conda`, its plugins,
     and their dependencies.
-    `installer` resets the `base` environment to the snapshot provided
-    by the installer.
-    `base-protection` resets the `base` environment to the snapshot saved
+    `installer-exact` restores the `base` environment to exactly what the
+    installer shipped (may downgrade packages you have updated).
+    `installer-updated` keeps the packages the installer shipped at their
+    currently installed versions (no downgrade).
+    `base-protection` restores the `base` environment to the snapshot saved
     by `conda doctor --fix` before protecting base.
 
     If not set, `conda self` will try to reset to the base-protection snapshot
-    first, then to the installer-provided, and finally to the current snapshot.
+    first, then to the installer-provided (preserving updates), and finally
+    to the current snapshot.
     """
 ).lstrip()
 
@@ -57,7 +60,12 @@ def configure_parser(parser: argparse.ArgumentParser) -> None:
     add_output_and_prompt_options(parser)
     parser.add_argument(
         "--snapshot",
-        choices=("current", "installer", "base-protection"),
+        choices=(
+            "current",
+            "installer-exact",
+            "installer-updated",
+            "base-protection",
+        ),
         help=SNAPSHOT_HELP,
     )
     parser.set_defaults(func=execute)
@@ -69,15 +77,19 @@ def execute(args: argparse.Namespace) -> int:
 
     from ..constants import RESET_FILE_BASE_PROTECTION, RESET_FILE_INSTALLER
     from ..query import permanent_dependencies
-    from ..reset import reset
+    from ..reset import names_from_explicit, reset
 
     if not context.quiet:
         print(WHAT_TO_EXPECT)
 
     reset_data: dict[str, SnapshotData] = {
-        "installer": {
+        "installer-exact": {
             "file_path": Path(sys.prefix, "conda-meta", RESET_FILE_INSTALLER),
-            "snapshot_name": "installer-provided",
+            "snapshot_name": "installer-provided (exact)",
+        },
+        "installer-updated": {
+            "file_path": Path(sys.prefix, "conda-meta", RESET_FILE_INSTALLER),
+            "snapshot_name": "installer-provided (with updates)",
         },
         "base-protection": {
             "file_path": Path(sys.prefix, "conda-meta", RESET_FILE_BASE_PROTECTION),
@@ -87,21 +99,23 @@ def execute(args: argparse.Namespace) -> int:
 
     reset_file: Path | None = None
     snapshot_name = ""
-    if not args.snapshot:
-        for snapshot in ("base-protection", "installer"):
-            snapshot_data = reset_data[snapshot]
-            if not snapshot_data["file_path"].exists():
-                continue
-            reset_file = snapshot_data["file_path"]
-            snapshot_name = snapshot_data["snapshot_name"]
-            break
-    elif args.snapshot in reset_data:
-        reset_file = reset_data[args.snapshot]["file_path"]
-        snapshot_name = reset_data[args.snapshot]["snapshot_name"]
+    snapshot_choice = args.snapshot
+
+    if not snapshot_choice:
+        for fallback in ("base-protection", "installer-updated"):
+            snapshot_data = reset_data[fallback]
+            if snapshot_data["file_path"].exists():
+                reset_file = snapshot_data["file_path"]
+                snapshot_name = snapshot_data["snapshot_name"]
+                snapshot_choice = fallback
+                break
+    elif snapshot_choice in reset_data:
+        reset_file = reset_data[snapshot_choice]["file_path"]
+        snapshot_name = reset_data[snapshot_choice]["snapshot_name"]
 
     if reset_file and not reset_file.exists():
         raise FileNotFoundError(
-            f"Failed to reset to `{args.snapshot}`.\n"
+            f"Failed to reset to `{snapshot_choice}`.\n"
             f"Required file {reset_file} not found."
         )
 
@@ -112,10 +126,17 @@ def execute(args: argparse.Namespace) -> int:
 
     if not context.quiet:
         print("Resetting 'base' environment...")
-    uninstallable_packages = (
-        permanent_dependencies(add_plugins=True) if not reset_file else set()
-    )
-    reset(uninstallable_packages=uninstallable_packages, snapshot=reset_file)
+
+    if snapshot_choice in ("installer-exact", "base-protection"):
+        reset(snapshot=reset_file)
+    elif snapshot_choice == "installer-updated":
+        assert reset_file is not None
+        keep = permanent_dependencies(add_plugins=True) | names_from_explicit(
+            reset_file
+        )
+        reset(uninstallable_packages=keep)
+    else:
+        reset(uninstallable_packages=permanent_dependencies(add_plugins=True))
 
     if not context.quiet:
         if snapshot_name:

conda_self/health_checks/base_protection.py

@@ -75,9 +75,9 @@ def fix(prefix: str, args: Namespace, confirm: ConfirmCallback) -> int:
     from conda.misc import clone_env
     from conda.models.environment import Environment
 
-    from ..constants import RESET_FILE_BASE_PROTECTION
+    from ..constants import RESET_FILE_BASE_PROTECTION, RESET_FILE_INSTALLER
     from ..query import permanent_dependencies
-    from ..reset import reset
+    from ..reset import names_from_explicit, reset
 
     default_env = DEFAULT_ENV_NAME
     message = "Protected by Base Environment Protection health fix"
@@ -98,8 +98,10 @@ def fix(prefix: str, args: Namespace, confirm: ConfirmCallback) -> int:
         )
     confirm("Proceed?")
 
-    # Get packages to keep in base
-    uninstallable_packages = permanent_dependencies()
+    # Prefer the installer snapshot for resetting base so that
+    # installer-provided packages (e.g. mamba in Miniforge) are preserved.
+    installer_snapshot = base_prefix / "conda-meta" / RESET_FILE_INSTALLER
+    use_snapshot = installer_snapshot.exists()
 
     # Check destination environment
     dest_prefix_data = PrefixData.from_name(default_env)
@@ -136,7 +138,11 @@ def fix(prefix: str, args: Namespace, confirm: ConfirmCallback) -> int:
             verbose=False,
             quiet=True,
         )
-        reset(uninstallable_packages=uninstallable_packages)
+        if use_snapshot:
+            keep = permanent_dependencies() | names_from_explicit(installer_snapshot)
+            reset(uninstallable_packages=keep)
+        else:
+            reset(uninstallable_packages=permanent_dependencies())
 
     # Freeze base
     try:

conda_self/reset.py

@@ -4,17 +4,32 @@
 from typing import TYPE_CHECKING
 
 from boltons.setutils import IndexedSet
+from conda.base.constants import EXPLICIT_MARKER
 from conda.base.context import context
 from conda.core.link import PrefixSetup, UnlinkLinkTransaction
 from conda.core.prefix_data import PrefixData
 from conda.core.solve import diff_for_unlink_link_precs
 from conda.gateways.disk.read import yield_lines
 from conda.misc import get_package_records_from_explicit
+from conda.models.match_spec import MatchSpec
 
 if TYPE_CHECKING:
     from pathlib import Path
 
 
+def names_from_explicit(path: Path) -> set[str]:
+    """Extract package names from a CEP-23 ``@EXPLICIT`` file without fetching.
+
+    Parses each URL line with :class:`~conda.models.match_spec.MatchSpec`,
+    which reads ``name``/``version``/``build`` from the tarball filename and
+    strips any ``#md5=…``/``#sha256=…`` checksum fragment as a comment.  No
+    network access, unlike :func:`conda.misc.get_package_records_from_explicit`.
+    """
+    return {
+        MatchSpec(line).name for line in yield_lines(path) if line != EXPLICIT_MARKER
+    }
+
+
 def reset(
     prefix: str = sys.prefix,
     uninstallable_packages: set[str] = set(),

news/121-installer-updated

@@ -0,0 +1,20 @@
+### Enhancements
+
+* Split `--snapshot installer` into `--snapshot installer-exact` (restores exact installer state, may downgrade) and `--snapshot installer-updated` (keeps installer-shipped packages at currently installed versions, no downgrade). (#121)
+* Auto-fallback now prefers `installer-updated` over `installer-exact` when no `--snapshot` is specified. (#121)
+
+### Bug fixes
+
+* `conda doctor base-protection --fix` no longer downgrades installer-provided packages like `mamba` in Miniforge installs. (#121)
+
+### Deprecations
+
+* <news item>
+
+### Docs
+
+* <news item>
+
+### Other
+
+* <news item>