enable spack env view regenerate -f

lib/spack/spack/cmd/env.py

@@ -420,6 +420,13 @@ def actions():
 #
 def env_view_setup_parser(subparser):
     """manage a view associated with the environment"""
+    subparser.add_argument(
+        "-f",
+        "--force",
+        action="store_true",
+        dest="force",
+        help="regenerate even if regeneration cannot be done atomically"
+    )
     subparser.add_argument(
         "action", choices=ViewAction.actions(), help="action to take for the environment's view"
     )
@@ -433,7 +440,7 @@ def env_view(args):
 
     if env:
         if args.action == ViewAction.regenerate:
-            env.regenerate_views()
+            env.regenerate_views(force=args.force)
         elif args.action == ViewAction.enable:
             if args.view_path:
                 view_path = args.view_path

lib/spack/spack/environment/environment.py

@@ -604,46 +604,60 @@ def raise_if_invalid_exchange(self):
             msg = "This operating system does not support the 'exchange' atomic update method."
             msg += f"\n  If the view at {self.root} does not already exist on the filesystem,"
             msg += "change its update_method to 'symlink' or 'auto'."
-            msg += f"\n  If the view at {self.root} exists already, either remove it for a"
+            msg += f"\n  If the view at {self.root} exists already, either change the"
-            msg += " non-atomic update or run on a newer OS."
+            msg += " update_method and run `spack env view regenerate --force`"
+            msg += " or run on a newer OS."
             raise RuntimeError(msg)
 
-    def raise_if_symlink_before_exchange(self):
+    def raise_if_symlink_before_exchange(self, force):
         if os.path.islink(self.root):
+            if force:
+                try:
+                    os.unlink(self.root)
+                    return
+                except OSError:
+                    pass
             msg = f"The view at {self.root} cannot be updated with the 'exchange' update method"
             msg += " because it was originally constructed with the 'symlink' method."
-            msg += " Either change the update method to 'symlink' or remove the view for a"
+            msg += " Either change the update method to 'symlink' or"
-            msg += " non-atomic update"
+            msg += " run `spack env view regenerate --force` for a non-atomic update"
             raise RuntimeError(msg)
 
-    def raise_if_exchange_before_symlink(self):
+    def raise_if_exchange_before_symlink(self, force):
         if os.path.isdir(self.root) and not os.path.islink(self.root):
+            if force:
+                try:
+                    shutil.rmtree(self.root)
+                    return
+                except:
+                    pass
             msg = f"The view at {self.root} cannot be updated with the 'symlink' update method"
             msg += " because it was originally constructed with the 'exchange' method."
-            msg += " Either change the update method to 'exchange' or remove the view for a"
+            msg += " Either change the update method to 'exchange' or"
-            msg += " non-atomic update"
+            msg += " run `spack env view regenerate --force` for a non-atomic update"
             raise RuntimeError(msg)
 
-    def use_renameat2(self):
+    def use_renameat2(self, force=False):
         # If it's set explicitly, respect that
         if self.update_method == "exchange":
-            self.raise_if_symlink_before_exchange()
+            self.raise_if_symlink_before_exchange(force)
             self.raise_if_invalid_exchange()
             return True
         if self.update_method == "symlink":
-            self.raise_if_exchange_before_symlink()
+            self.raise_if_exchange_before_symlink(force)
             return False
 
         # If it's set to "auto", detect which it should be
         if os.path.islink(self.root):
             return False
         elif os.path.isdir(self.root):
-            self.raise_if_invalid_exchange()
+            if not spack.util.atomic_update.renameat2():
+                self.raise_if_exchange_before_symlink(force)
             return True
 
         return bool(spack.util.atomic_update.renameat2())
 
-    def regenerate(self, concretized_root_specs):
+    def regenerate(self, concretized_root_specs, force=False):
         specs = self.specs_for_view(concretized_root_specs)
 
         # To ensure there are no conflicts with packages being installed
@@ -656,7 +670,7 @@ def regenerate(self, concretized_root_specs):
         # This allows for atomic swaps when we update the view
 
         # Check which atomic update method we need
-        use_renameat2 = self.use_renameat2()
+        use_renameat2 = self.use_renameat2(force)
 
         # cache the roots because the way we determine which is which does
         # not work while we are updating
@@ -1615,14 +1629,14 @@ def update_default_view(self, viewpath):
         else:
             self.views.pop(name, None)
 
-    def regenerate_views(self):
+    def regenerate_views(self, force=False):
         if not self.views:
             tty.debug("Skip view update, this environment does not" " maintain a view")
             return
 
         concretized_root_specs = [s for _, s in self.concretized_specs()]
         for view in self.views.values():
-            view.regenerate(concretized_root_specs)
+            view.regenerate(concretized_root_specs, force)
 
     def check_views(self):
         """Checks if the environments default view can be activated."""

lib/spack/spack/test/cmd/env.py

@@ -52,7 +52,8 @@
 
 sep = os.sep
 
-if spack.util.atomic_update.renameat2():
+supports_renameat2 = bool(spack.util.atomic_update.renameat2())
+if supports_renameat2:
     use_renameat2 = [True, False]
 else:
     use_renameat2 = [False]
@@ -3303,13 +3304,16 @@ def test_view_update_mismatch(update_method, tmpdir, install_mockery, mock_fetch
     if update_method == "symlink":
         os.makedirs(root)
         checker = "cannot be updated with the 'symlink' update method"
-    elif True in use_renameat2:
+        forceable = True
+    elif supports_renameat2:
         link = str(tmpdir.join("symlink"))
         os.makedirs(link)
         os.symlink(link, root)
         checker = "cannot be updated with the 'exchange' update method"
+        forceable = True
     else:
         checker = "does not support the 'exchange' atomic update method"
+        forceable = False
 
     view = ev.environment.ViewDescriptor(
         base_path=str(tmpdir), root=root, update_method=update_method
@@ -3321,6 +3325,9 @@ def test_view_update_mismatch(update_method, tmpdir, install_mockery, mock_fetch
     with pytest.raises(RuntimeError, match=checker):
         view.regenerate([spec])
 
+    if forceable:
+        view.regenerate([spec], force=True)
+        assert os.path.exists(view.root)
 
 @pytest.mark.parametrize("update_method", ["symlink", "exchange"])
 def test_view_update_fails(update_method, tmpdir, install_mockery, mock_fetch, monkeypatch):