The build directory has been hardened against interference with the outside world by nesting it inside another directory owned by (and only readable by) the daemon user.
`nix-shell $x` now looks for `$x/shell.nix` when `$x` resolves to a directory.
Although this might be seen as a breaking change, its primarily interactive usage makes it a minor issue.
This adjustment addresses a commonly reported problem.
This also applies to `nix-shell` shebang scripts. Consider the following example:
```shell
#!/usr/bin/env nix-shell
#!nix-shell -i bash
```
This will now load `shell.nix` from the script's directory, if it exists; `default.nix` otherwise.
The old behavior can be opted into by setting the option [`nix-shell-always-looks-for-shell-nix`](@docroot@/command-ref/conf-file.md#conf-nix-shell-always-looks-for-shell-nix) to `false`.
`nix repl` has a `:doc` command that previously only rendered documentation for internally defined functions.
This feature has been extended to also render function documentation comments, in accordance with [RFC 145].
Example:
```
nix-repl> :doc lib.toFunction
Function toFunction
… defined at /home/user/h/nixpkgs/lib/trivial.nix:1072:5
Turns any non-callable values into constant functions. Returns
callable values as is.
Inputs
v
: Any value
Examples
:::{.example}
## lib.trivial.toFunction usage example
| nix-repl> lib.toFunction 1 2
| 1
|
| nix-repl> lib.toFunction (x: x + 1) 2
| 3
:::
```
Known limitations:
- It does not render documentation for "formals", such as `{ /** the value to return */ x, ... }: x`.
- Some extensions to markdown are not yet supported, as you can see in the example above.
We'd like to acknowledge [Yingchi Long (@inclyc)](https://github.com/inclyc) for proposing a proof of concept for this functionality in [#9054](https://github.com/NixOS/nix/pull/9054), as well as [@sternenseemann](https://github.com/sternenseemann) and [Johannes Kirschbauer (@hsjobeki)](https://github.com/hsjobeki) for their contributions, proposals, and their work on [RFC 145].
- Solve `cached failure of attribute X` [#9165](https://github.com/NixOS/nix/issues/9165) [#10513](https://github.com/NixOS/nix/issues/10513) [#10564](https://github.com/NixOS/nix/pull/10564)
This eliminates all "cached failure of attribute X" messages by forcing evaluation of the original value when needed to show the exception to the user. This enhancement improves error reporting by providing the underlying message and stack trace.
- Run the flake regressions test suite [#10603](https://github.com/NixOS/nix/pull/10603)
This update introduces a GitHub action to run a subset of the [flake regressions test suite](https://github.com/NixOS/flake-regressions), which includes 259 flakes with their expected evaluation results. Currently, the action runs the first 25 flakes due to the full test suite's extensive runtime. A manually triggered action may be implemented later to run the entire test suite.
- Support unit prefixes in configuration settings [#10668](https://github.com/NixOS/nix/pull/10668)
Configuration settings in Nix now support unit prefixes, allowing for more intuitive and readable configurations. For example, you can now specify [`--min-free 1G`](@docroot@/command-ref/opt-common.md#opt-min-free) to set the minimum free space to 1 gigabyte.
This enhancement was extracted from [#7851](https://github.com/NixOS/nix/pull/7851) and is also useful for PR [#10661](https://github.com/NixOS/nix/pull/10661).
The [`nix build`](@docroot@/command-ref/new-cli/nix3-build.md) command has been updated to improve the behavior of the [`--keep-going`] flag. Now, when `--keep-going` is used, all hash-mismatch errors of failing fixed-output derivations (FODs) are displayed, similar to the behavior for other build failures. This enhancement ensures that all relevant build errors are shown, making it easier for users to update multiple derivations at once or to diagnose and fix issues.
These changes aim to replace the use of autotools and `make` with Meson for building various components of Nix. Additionally, each library is built in its own derivation, leveraging Meson's "subprojects" feature to allow a single development shell for building all libraries while also supporting separate builds. This approach aims to improve productivity and build modularity, compared to both make and a monolithic Meson-based derivation.
Special thanks to everyone who has contributed to the Meson port, particularly [**@p01arst0rm**](https://github.com/p01arst0rm) and [**@Qyriad**](https://github.com/Qyriad).
2. Nix could sometimes try to commit the evaluation cache SQLite transaction without there being an active transaction, resulting in non-error errors being printed.
A new library, `libnixflake`, has been introduced to better separate the Flakes layer within Nix. This change refactors the codebase to encapsulate Flakes-specific functionality within its own library.
See the commits in the pull request for detailed changes, with the only significant code modifications happening in the initial commit.
This change was alluded to in [RFC 134](https://github.com/nixos/rfcs/blob/master/rfcs/0134-nix-store-layer.md) and is a step towards a more modular and maintainable codebase.
<!-- unfortunately no link target for the specific syntax -->
Relative [path](@docroot@/language/types.md#type-path) literals in `nix-shell` shebang scripts' options are now resolved relative to the [script's location](@docroot@/glossary.md?highlight=base%20directory#gloss-base-directory).
Previously they were resolved relative to the current working directory.
For example, consider the following script in `~/myproject/say-hi`:
Since this release, `nix-shell` resolves `shell.nix` relative to the script's location, and `~/myproject/shell.nix` is used.
```console
$ ./myproject/say-hi
Hello, world!
```
**Opt-out**
This is technically a breaking change, so we have added an option so you can adapt independently of your Nix update.
The old behavior can be opted into by setting the option [`nix-shell-shebang-arguments-relative-to-script`](@docroot@/command-ref/conf-file.md#conf-nix-shell-shebang-arguments-relative-to-script) to `false`.
- Improve handling of tarballs that don't consist of a single top-level directory [#11195](https://github.com/NixOS/nix/pull/11195)
In previous Nix releases, the tarball fetcher (used by `builtins.fetchTarball`) erroneously merged top-level directories into a single directory, and silently discarded top-level files that are not directories. This is no longer the case. The new behaviour is that *only* if the tarball consists of a single directory, the top-level path component of the files in the tarball is removed (similar to `tar`'s `--strip-components=1`).
