Add 'store add-gc-root' command to manually add indirect roots

src/nix/meson.build

@@ -105,6 +105,7 @@ nix_sources = [config_h] + files(
  'run.cc',
  'search.cc',
  'sigs.cc',
+ 'store-add-gc-root.cc',
  'store-copy-log.cc',
  'store-delete.cc',
  'store-gc.cc',

src/nix/store-add-gc-root.cc

@@ -0,0 +1,70 @@
+#include "command.hh"
+#include "args.hh"
+#include "shared.hh"
+#include "store-cast.hh"
+#include "indirect-root-store.hh"
+#include "common-args.hh"
+
+using namespace nix;
+
+struct CmdAddGCRoot : StoreCommand
+{
+ std::vector<std::string> links;
+ bool checkResults = true;
+
+ CmdAddGCRoot()
+ {
+ expectArgs({
+ .label = "indirect-roots",
+ .handler = {&links},
+ .completer = completePath,
+ });
+
+ addFlag({
+ .longName = "no-check",
+ .description = "Do not test the validity of created roots.",
+ .handler = {&checkResults, false},
+ });
+ }
+
+ std::string description() override
+ {
+ return "Add indirect gc roots through the symlink arguments";
+ }
+
+ std::string doc() override
+ {
+ return
+#include "store-add-gc-root.md"
+ ;
+ }
+
+ Category category() override
+ {
+ return catSecondary;
+ }
+
+ void run(ref<Store> store) override
+ {
+ auto & indirectRootStore = require<IndirectRootStore>(*store);
+
+ for (auto & link : links) {
+ auto indirectPath = absPath(link);
+ if (indirectRootStore.isInStore(indirectPath)) {
+ throw Error("Indirect root '%1%' must not be in the Nix store", link);
+ }
+
+ if (checkResults) {
+ auto path = indirectRootStore.followLinksToStorePath(indirectPath);
+ indirectRootStore.addTempRoot(path);
+ if (!indirectRootStore.isValidPath(path)) {
+ throw Error("Indirect root '%1%' is no a symbolic link to a valid store path", link);
+ }
+ }
+
+ indirectRootStore.addIndirectRoot(indirectPath);
+ }
+ }
+};
+
+static auto rCmdAddGCRoot = registerCommand2<CmdAddGCRoot>({"store", "add-gc-root"});

src/nix/store-add-gc-root.md

@@ -0,0 +1,17 @@
+R""(
+
+# Examples
+
+ ```console
+ $ ln -s /nix/store/xxx foo
+ $ nix store add-gc-root foo
+ $ nix-store -q --roots /nix/store/xxx
+ .../foo -> /nix/store/xxx
+ ```
+
+# Description
+
+This command adds garbage collector root to the paths referenced by the symlinks passed as arguments.
+These are called indirect roots, as the root will disappear as soon as the intermediate symlink gets deleted.
+
+)""

tests/functional/local.mk

@@ -103,6 +103,7 @@ nix_tests = \
  nix-profile.sh \
  suggestions.sh \
  store-info.sh \
+ store-add-gc-root.sh \
  fetchClosure.sh \
  completions.sh \
  impure-derivations.sh \

tests/functional/meson.build

@@ -184,6 +184,7 @@ suites = [
  'debugger.sh',
  'extra-sandbox-profile.sh',
  'help.sh',
+ 'store-add-gc-root.sh',
  ],
  'workdir': meson.current_build_dir(),
  },

tests/functional/store-add-gc-root.sh

@@ -0,0 +1,55 @@
+#!/usr/bin/env bash
+
+source common.sh
+
+TODO_NixOS
+
+clearStore
+
+function delete() { nix-store --delete "$storePath"; }
+function build() { nix build --no-link --print-out-paths -f simple.nix; }
+
+# Check that path can be deleted
+storePath=$(build)
+delete
+
+# Check that add-gc-root prevents deletion,
+# and removing the root make it deletable again.
+storePath=$(build)
+ln -sn "$storePath" myroot
+nix store add-gc-root myroot
+if delete; then false; fi
+rm myroot
+delete
+
+# Create several roots at once
+storePath=$(build)
+ln -sn "$storePath" myroot1
+ln -sn "$storePath" myroot2
+ln -sn "$storePath" myroot3
+nix store add-gc-root myroot1 myroot2 myroot3
+if delete; then false; fi
+rm myroot3 myroot2
+if delete; then false; fi
+rm myroot1
+delete
+
+# Test detection of invalid roots
+# 1. path deleted before root creation
+storePath=$(build)
+delete
+ln -sn "$storePath" myroot
+if nix store add-gc-root myroot; then false; fi
+nix store add-gc-root --no-check myroot
+rm myroot
+
+# 2. invalid path
+ln -sn /invalid-target myroot
+if nix store add-gc-root myroot; then false; fi
+nix store add-gc-root --no-check myroot
+rm myroot
+
+# Fail when trying to setup a direct root
+storePath=$(build)
+if nix store add-gc-root "$storePath"; then false; fi
+