This also bans various sneaking of negative numbers from the language
into unsuspecting builtins as was exposed while auditing the
consequences of changing the Nix language integer type to a newtype.
It's unlikely that this change comprehensively ensures correctness when
passing integers out of the Nix language and we should probably add a
checked-narrowing function or something similar, but that's out of scope
for the immediate change.
During the development of this I found a few fun facts about the
language:
- You could overflow integers by converting from unsigned JSON values.
- You could overflow unsigned integers by converting negative numbers
into them when going into Nix config, into fetchTree, and into flake
inputs.
The flake inputs and Nix config cannot actually be tested properly
since they both ban thunks, however, we put in checks anyway because
it's possible these could somehow be used to do such shenanigans some
other way.
Note that Lix has banned Nix language integer overflows since the very
first public beta, but threw a SIGILL about them because we run with
-fsanitize=signed-overflow -fsanitize-undefined-trap-on-error in
production builds. Since the Nix language uses signed integers, overflow
was simply undefined behaviour, and since we defined that to trap, it
did.
Trapping on it was a bad UX, but we didn't even entirely notice
that we had done this at all until it was reported as a bug a couple of
months later (which is, to be fair, that flag working as intended), and
it's got enough production time that, aside from code that is IMHO buggy
(and which is, in any case, not in nixpkgs) such as
https://git.lix.systems/lix-project/lix/issues/445, we don't think
anyone doing anything reasonable actually depends on wrapping overflow.
Even for weird use cases such as doing funny bit crimes, it doesn't make
sense IMO to have wrapping behaviour, since two's complement arithmetic
overflow behaviour is so *aggressively* not what you want for *any* kind
of mathematics/algorithms. The Nix language exists for package
management, a domain where bit crimes are already only dubiously in
scope to begin with, and it makes a lot more sense for that domain for
the integers to never lose precision, either by throwing errors if they
would, or by being arbitrary-precision.
Fixes: https://github.com/NixOS/nix/issues/10968
Original-CL: https://gerrit.lix.systems/c/lix/+/1596
Change-Id: I51f253840c4af2ea5422b8a420aa5fafbf8fae75
- Fix eval cache not being persisted in `nix develop` (since #10570)
- Don't attempt to commit cache transaction if there is no active transaction, which will spew errors in edge cases
- Drive-by: trivial typo fix
This does not yet resolve the coupling between packages and
derivations, but it makes the code more consistent with the
terminology, and it accentuates places where the coupling is
obvious, such as
auto drvPath = packageInfo.queryDrvPath();
if (!drvPath)
throw Error("'%s' is not a derivation", what());
... which isn't wrong, and in my opinion, doesn't even look
wrong, because it just reflects the current logic.
However, I do like that we can now start to see in the code that
this coupling is perhaps a bit arbitrary.
After this rename, we can bring the DerivingPath concept into type
and start to lift this limitation.
As discussed in #7417, it would be good to make more string values work
as installables. That is to say, if an installable refers to a value,
and the value is a string, it used to not work at all, since #7484, it
works somewhat, and this PR make it work some more.
The new cases that are added for `BuiltPath` contexts:
- Fixed input- or content-addressed derivation:
```
nix-repl> hello.out.outPath
"/nix/store/jppfl2bp1zhx8sgs2mgifmsx6dv16mv2-hello-2.12"
nix-repl> :p builtins.getContext hello.out.outPath
{ "/nix/store/c7jrxqjhdda93lhbkanqfs07x2bzazbm-hello-2.12.drv" = { outputs = [ "out" ]; }; }
The string matches the specified single output of that derivation, so
it should also be valid.
- Floating content-addressed derivation:
```
nix-repl> (hello.overrideAttrs (_: { __contentAddressed = true; })).out.outPath
"/1a08j26xqc0zm8agps8anxpjji410yvsx4pcgyn4bfan1ddkx2g0"
nix-repl> :p builtins.getContext (hello.overrideAttrs (_: { __contentAddressed = true; })).out.outPath
{ "/nix/store/qc645pyf9wl37c6qvqzaqkwsm1gp48al-hello-2.12.drv" = { outputs = [ "out" ]; }; }
```
The string is not a path but a placeholder, however it also matches
the context, and because it is a CA derivation we have no better
option. This should also be valid.
We may also want to think about richer attrset based values (also
discussed in that issue and #6507), but this change "completes" our
string-based building blocks, from which the others can be desugared
into or at least described/document/taught in terms of.
Progress towards #7417
Co-authored-by: Robert Hensing <roberth@users.noreply.github.com>
Fixes#8309
This regression was because both `CmdDevelop` and `CmdPrintDevEnv` were
switched to be `InstallableValueCommand` subclasses, but actually
neither should have been.
The `nixpkgsFlakeRef` method should indeed not be on the base
installable class, because "flake refs" and "nixpkgs" are not
installable-wide notions, but that doesn't mean these commands should
only accept installable values.
Instead of having a bunch of optional fields, have a few subclasses
which can have mandatory fields.
Additionally, the new `getExtraPathInfo`, and `nixpkgsFlakeRef`, are
moved to `InstallableValue`.
I did these things because https://github.com/NixOS/rfcs/pull/134 ; with
these things moved to `InstallableValue`, the base `Installable` no
longer depends on libexpr! This is a major step towards that.
Also, add a bunch of doc comments for sake of the internal API docs.
These methods would previously fail on the other `Installable`s, so
moving them to this class is more correct as to where they actually
work.
Additionally, a `InstallableValueCommand` is created to make it easier
(or rather no worse than before) to write commands that just work on
`InstallableValue`s.
Besides being a cleanup to avoid failing default methods, this gets us
closer to https://github.com/NixOS/rfcs/pull/134.
