2023-01-15 18:27:53 +01:00
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# Nix language version history
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The Nix language (“Nix”) has its own versioning mechanism independent from its
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most popular implementation (“C++ Nix”): `builtins.langVersion`. It has been
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increased whenever the language has changed syntactically or semantically in a
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way that would not be introspectable otherwise. In particular, this does not
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include addition (or removal) of `builtins`, as this can be introspected using
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standard attribute set operations.
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Changes to `builtins.langVersion` are best found by viewing the git history of
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C++ Nix using `git log -G 'mkInt\\(v, [0-9]\\)'` for `builtins.langVersion` < 7.
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After that point `git log -G 'v\\.mkInt\\([0-9]+\\)'` should work. To reduce the
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amount of false positives, specify the version number you are interested in
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explicitly.
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## 1
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The first version of the Nix language is its state at the point when
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`builtins.langVersion` was added in [8b8ee53] which was first released
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as part of C++ Nix 1.2.
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## 2
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Nix version 2 changed the behavior of `builtins.storePath`: It would now [try to
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substitute the given path if missing][storePath-substitute], instead of creating
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an evaluation failure. `builtins.langVersion` was increased in [e36229d].
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## 3
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Nix version 3 changed the behavior of the `==` behavior. Strings would now be
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considered [equal even if they had differing string context][equal-no-ctx].
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## 4
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Nix version 4 [added the float type][float] to the language.
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## 5
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The [increase of `builtins.langVersion` to 5][langVersion-5] did not signify a
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language change, but added support for structured attributes to the Nix daemon.
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Eelco Dolstra writes as to what changed:
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> The structured attributes support. Unfortunately that's not so much a language
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> change as a build.cc (i.e. daemon) change, but we don't really have a way to
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> express that...
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2023-06-14 12:47:15 +02:00
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Maybe `builtins.nixVersion` (which was added in version 1) should have been
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used instead. In any case, the [only `langVersion` check][nixpkgs-langVersion-5]
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in nixpkgs verifies a lower bound of 5.
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2023-01-15 18:27:53 +01:00
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## 6
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Nix version 6 added support for [comparing two lists][list-comparison].
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[8b8ee53]: https://github.com/nixos/nix/commit/8b8ee53bc73769bb25d967ba259dabc9b23e2e6f
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[storePath-substitute]: https://github.com/nixos/nix/commit/22d665019a3770148929b7504c73bcdbe025ec12
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[e36229d]: https://github.com/nixos/nix/commit/e36229d27f9ab508e0abf1892f3e8c263d2f8c58
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[equal-no-ctx]: https://github.com/nixos/nix/commit/ee7fe64c0ac00f2be11604a2a6509eb86dc19f0a
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[float]: https://github.com/nixos/nix/commit/14ebde52893263930cdcde1406cc91cc5c42556f
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[langVersion-5]: https://github.com/nixos/nix/commit/8191992c83bf4387b03c5fdaba818dc2b520462d
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[list-comparison]: https://github.com/nixos/nix/commit/09471d2680292af48b2788108de56a8da755d661
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2023-06-14 12:47:15 +02:00
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[nixpkgs-langVersion-5]: https://github.com/NixOS/nixpkgs/blob/d7ac3423d321b8b145ccdd1aed9dfdb280f5e391/pkgs/build-support/closure-info.nix#L11
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