# What's new in Nix 2.8.0

Numbers:
- Contributors:

git shortlog 69c6fb12eea414382f0b945c0d6c574c43c7c9a3...ad7c99ef20dff74a65d6c8ac2a2c42f538e0a1dd -e -n | rg ":$"
Eelco Dolstra <[e-mail]> (122):
Théophane Hufschmitt <[e-mail]> (16):
John Ericson <[e-mail]> (12):
Théophane Hufschmitt <[e-mail]> (10):
Naïm Favier <[e-mail]> (9):
Daniel Pauls <[e-mail]> (8):
Cole Helbling <[e-mail]> (7):
pennae <[e-mail]> (6):
Artturin <[e-mail]> (5):
Martin Schwaighofer <[e-mail]> (5):
Maximilian Bosch <[e-mail]> (5):
Tom Bereknyei <[e-mail]> (5):
regnat <[e-mail]> (4):
toonn <[e-mail]> (4):
Gabriel Fontes <[e-mail]> (3):
Sergei Trofimovich <[e-mail]> (3):
Alex Ameen <[e-mail]> (2):
Erik Arvstedt <[e-mail]> (2):
Florian Klink <[e-mail]> (2):
Kasper Gałkowski <[e-mail]> (2):
Rehno Lindeque <[e-mail]> (2):
dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com> (2):
Domen Kožar <[e-mail]> (1):
Graham Christensen <[e-mail]> (1):
Hideaki Kawai <[e-mail]> (1):
Joachim Breitner <[e-mail]> (1):
Kevin Amado <[e-mail]> (1):
Robert Helgesson <[e-mail]> (1):
Rok Garbas <[e-mail]> (1):
Sebastian Blunt <[e-mail]> (1):
aszlig <[e-mail]> (1):
polykernel <[e-mail]> (1):
thkoch2001 <[e-mail]> (1):

- Commits

 git rev-list --no-merges --count 69c6fb12eea414382f0b945c0d6c574c43c7c9a3...ad7c99ef20dff74a65d6c8ac2a2c42f538e0a1dd
170

- PRs

git log --oneline $range | grep 'Merge pull request #' | wc -l
73

rev range for
-> 2.8.0: `69c6fb12eea414382f0b945c0d6c574c43c7c9a3...ad7c99ef20dff74a65d6c8ac2a2c42f538e0a1dd`
-> 2.7.0: `ffe155abd36366a870482625543f9bf924a58281...039c9008b13951153052d84c0108a3750db8498f`
-> 2.6.0: `a1cd7e58606a41fcf62bf8637804cf8306f17f62...95bd5da341aec4b99f4719d1b1ab2343ee14fad7`
-> 2.5.0: `a646dfcdd642df404ef1e172abdcddb3aa179d48...158fa6870fef4b20fa55e872bf1c1f2cad408c65`

https://hydra.nixos.org/job/nix/master/metrics.nixpkgs#tabs-charts

* @garbas New experimental command: `nix fmt`, which applies a formatter
defined by the `formatter.<system>` flake output to the Nix
expressions in a flake.

examples in ~/nix/demo

nix fmt --help
nix fmt
cat file.nix

{a=1;b=2;c=3;}

nix fmt ./file.nix

* @garbas Various Nix commands can now read expressions from standard input
using `--file -`.
* DOESNT WORK WITH nix fmt???
* TODO: cat file.nix | nix fmt --file -

echo 'let b = 1; in b' | nix eval --file -

* @tomberek: New experimental builtin function `builtins.fetchClosure` that
copies a closure from a binary cache at evaluation time and rewrites
it to content-addressed form (if it isn't already). Like
`builtins.storePath`, this allows importing pre-built store paths;
the difference is that it doesn't require the user to configure
binary caches and trusted public keys.

This function is only available if you enable the experimental
feature `fetch-closure`.

nix store make-content-addressed nixpkgs#hello

builtins.fetchClosure {
  fromStore = "https://cache.nixos.org";
  fromPath = "/nix/store/h59dfk7dwrn7d2csykh9z9xm2miqmrnz-hello-2.12";
  toPath = "/nix/store/dp3rslbx8fz88cq74mxb5h5z1l4659f0-hello-2.12";
}

* @tomberek: New experimental feature: *impure derivations*. These are
derivations that can produce a different result every time they're
built. Here is an example:

  stdenv.mkDerivation {
    name = "impure";
    __impure = true; # marks this derivation as impure
    buildCommand = "date > $out";
  }

Running `nix build` twice on this expression will build the
derivation twice, producing two different content-addressed store
paths. Like fixed-output derivations, impure derivations have access
to the network. Only fixed-output derivations and impure derivations
can depend on an impure derivation.

##### Additional

* @garbas Docs: Improved uninstall section for macOS
https://github.com/NixOS/nix/pull/6144
* doc: Add detailed uninstall section for macOS

* @tomberek Evaluation
https://github.com/NixOS/nix/pull/6323
* add read-only mode to eval
* performance, scripting
* show larger example? with numbers

* @garbas Better UX (consistency)
* `nix run` is now stricter in what it accepts: members of the `apps`
flake output are now required to be apps (as defined in [the
manual](https://nixos.org/manual/nix/stable/command-ref/new-cli/nix3-run.html#apps)),
and members of `packages` or `legacyPackages` must be derivations
(not apps).
* The `nixosModule` flake output attribute has been renamed consistent
with the `.default` renames in Nix 2.7.

* `nixosModule` → `nixosModules.default`

As before, the old output will continue to work, but `nix flake check` will
issue a warning about it.
* `nix store make-content-addressable` has been renamed to `nix store
make-content-addressed`.
https://github.com/NixOS/nix/pull/6371
* better error message for nix copy of unbuilt/unavailable build
https://github.com/NixOS/nix/pull/6362
* more output for nix doctor
https://github.com/NixOS/nix/pull/6330
* nix {run,shell}: Print a better error message if the store is not local

* @tomberek Completions & Suggestions
https://github.com/NixOS/nix/pull/6128
* Shell completion improvements
* respect `--override-flake`
* tilde expansion with flake fragments
* follow symlinks
* completions for `--update-input`
https://github.com/NixOS/nix/pull/6216
* Add some suggestions to the evaluator
https://github.com/NixOS/nix/pull/6244
* nix-env: Add a suggestion for when there's a name collision in channels

- Outro from Eelco
- What he is excited

1) video
2) touch base with eelco for roadmap.
3) How can we help
4) NixUX -> NixCore ?
* decision/execution/deletion cycle
* go hunt for inconsistencies?
*
5) NixUX is the focus for now

## 2.9.0
Here are the release notes:

### nix build has a new --print-out-paths flag to print the resulting output paths. This matches the default behaviour of nix-build.

nix build nixpkgs#curl --print-out-paths
[tom@tframe:~]$ nix build nixpkgs#curl --print-out-paths
/nix/store/vcdb1dq99vhh7yya9js6clzvf68w706w-curl-7.83.1-bin
/nix/store/x8wsdqg5hzgh4amkah5kav7nd1q946sw-curl-7.83.1-man

"This is for scripting purposes."

### Debugger

### nix repl has a new build-and-link (:bl) command that builds a derivation while creating GC root symlinks.

nix repl nixpkgs
:bl legacyPackages.x86_64-linux.hello

"This repl command allows one to both build a derivation and generate a symlink in the current directory which will also protect that build output from garbage collection."

### builtins.fetchTree (and flake inputs) can now be used to fetch plain files over the http(s) and file protocols in addition to directory tarballs.

builtins.fetchTree "https://raw.githubusercontent.com/NixOS/nix/master/default.nix"

"Previously, fetchTree had to operate over a tarball or git repository - something that could be a directory tree. This change allows one to fetch a bare file. It can be helpful when one may want to decompress something in a custom way, or to literally fetch a raw file iteslf. This also paves the way to fetch .patch files and apply them."

## 2.10.0

### nix repl now takes installables on the command line, unifying the usage with other commands that use --file and --expr. Primary breaking change is for the common usage of
* @tomberek
- `nix repl '<nixpkgs>' which can be recovered with nix repl --file '<nixpkgs>' or nix repl --expr 'import <nixpkgs>{}'.`
This is currently guarded by the repl-flake experimental feature.

An important note here is that behavior is unified so anything that worked with nix flake before will work here as well.

nix repl --extra-experimental-features repl-flake flake:nixpkgs
nix repl --extra-experimental-features repl-flake --expr '{a=1;}'
nix repl --extra-experimental-features repl-flake --file default.nix
nix repl --extra-experimental-features repl-flake github:NixOS/nixpkgs

### A new function builtins.traceVerbose is available. It is similar to builtins.trace if the trace-verbose setting is set to true, and it is a no-op otherwise.
* @djacu

[tom@tframe:~/nix]$ nix eval --expr 'builtins.traceVerbose "warning: hello!" 1'
1

[tom@tframe:~/nix]$ nix eval --expr 'builtins.traceVerbose "warning: hello!" 1' --option trace-verbose true
trace: warning: hello!
1

- maybe have a flake that has a bunch of traces that are useful for debugging

### nix search has a new flag --exclude to filter out packages.
* @djacu

nix search nixpkgs requests
nix search nixpkgs requests --exclude python
nix search nixpkgs requests --exclude 'python|perl'

### nix-portable
* @tomberek
On Linux, if /nix doesn’t exist and cannot be created and you’re not running as root, Nix will automatically use ~/.local/share/nix/root as a chroot store. This enables non-root users to download the statically linked Nix binary and have it work out of the box, e.g.
- note, will not work on Darwin
- grab a VM of Debian/Arch/etc and show how a user can try out Nix easily
- does this work for users with wheel priviledges?
- log in to a machine without priviledges

ls ~/.local/share/nix/root/nix/store

conceptually: `nix --store /home/tom/.local/share/nix/root`

### ~/nix run nixpkgs#hello
warning: '/nix' does not exists, so Nix will use '/home/ubuntu/.local/share/nix/root' as a chroot store
Hello, world!