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nix/doc/manual/source/release-notes/rl-2.30.md
Eelco Dolstra f5312492c1 Add manual release notes
2025-07-07 14:53:11 +02:00

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Release 2.30.0 (2025-07-07)

  • Reduce the size of value from 24 to 16 bytes #13407

    This shaves off a very significant amount of memory used for evaluation (~20% percent reduction in maximum heap size and ~17% in total bytes).

  • builtins.sort uses PeekSort #12623

    Previously it used libstdc++'s std::stable_sort(). However, that implementation is not reliable if the user-supplied comparison function is not a strict weak ordering.

  • nix repl prints which variables were loaded #11406

    Instead of Added <n> variables it now prints the first 10 variables that were added to the global scope.

  • nix flake archive: add --no-check-sigs option #13277

    This is useful when using nix flake archive with the destination set to a remote store.

  • Emit warnings for IFDs with trace-import-from-derivation option #13279

    While we have the setting allow-import-from-derivation to deny import-from-derivation (IFD), sometimes users would like to observe IFDs during CI processes to gradually phase out the idiom. The new setting trace-import-from-derivation, when set, logs a simple warning to the console.

  • build-dir no longer defaults to $TMPDIR

    The directory in which temporary build directories are created no longer defaults to TMPDIR or /tmp, to avoid builders making their directories world-accessible. This behavior allowed escaping the build sandbox and can cause build impurities even when not used maliciously. We now default to builds in NIX_STATE_DIR (which is /nix/var/nix/builds in the default configuration).

  • Deprecate manually making structured attrs with __json = ...; #13220

    The proper way to create a derivation using structured attrs in the Nix language is by using __structuredAttrs = true with builtins.derivation. However, by exploiting how structured attrs are implementated, it has also been possible to create them by setting the __json environment variable to a serialized JSON string. This sneaky alternative method is now deprecated, and may be disallowed in future versions of Nix.

  • Add stack sampling evaluation profiler #13220

    Nix evaluator now supports stack sampling evaluation profiling via --eval-profiler flamegraph setting. It collects collapsed call stack information to output file specified by --eval-profile-file (nix.profile by default) in a format directly consumable by flamegraph.pl and compatible tools like speedscope. Sampling frequency can be configured via --eval-profiler-frequency (99 Hz by default).

    Unlike existing --trace-function-calls this profiler includes the name of the function being called when it's available.

  • json-log-path setting #13003

    New setting json-log-path that sends a copy of all Nix log messages (in JSON format) to a file or Unix domain socket.

  • Rename nix profile install to nix profile add #13224

    The command nix profile install has been renamed to nix profile add (though the former is still available as an alias). This is because the verb "add" is a better antonym for the verb "remove" (i.e. nix profile remove). Nix also does not have install hooks or general behavior often associated with "installing".

  • Non-flake inputs now contain a sourceInfo attribute #13164 #13170

    Flakes have always had a sourceInfo attribute which describes the source of the flake. The sourceInfo.outPath is often identical to the flake's outPath. However, it can differ when the flake is located in a subdirectory of its source.

    Non-flake inputs (i.e. inputs with flake = false) can also be located at some path within a wider source. This usually happens when defining a relative path input within the same source as the parent flake, e.g. inputs.foo.url = ./some-file.nix. Such relative inputs will now inherit their parent's sourceInfo.

    This also means it is now possible to use ?dir=subdir on non-flake inputs.

    This iterates on the work done in 2.26 to improve relative path support (#10089), and resolves a regression introduced in 2.28 relating to nested relative path inputs (#13164).

  • Revert incomplete closure mixed download and build feature #77 #12628 #13176

    Since Nix 1.3 (299141ecbd in 2013) Nix has attempted to mix together upstream fresh builds and downstream substitutions when remote substuters contain an "incomplete closure" (have some store objects, but not the store objects they reference). This feature is now removed.

    Worst case, removing this feature could cause more building downstream, but it should not cause outright failures, since this is not happening for opaque store objects that we don't know how to build if we decide not to substitute. In practice, however, we doubt even the more building is very likely to happen. Remote stores that are missing dependencies in arbitrary ways (e.g. corruption) don't seem to be very common.

    On the contrary, when remote stores fail to implement the closure property, it is usually an intentional choice on the part of the remote store, because it wishes to serve as an "overlay" store over another store, such as https://cache.nixos.org. If an "incomplete closure" is encountered in that situation, the right fix is not to do some sort of "franken-building" as this feature implemented, but instead to make sure both substituters are enabled in the settings.

    (In the future, we should make it easier for remote stores to indicate this to clients, to catch settings that won't work in general before a missing dependency is actually encountered.)

Contributors

This release was made possible by the following 32 contributors: