This extends the `error: cannot coerce a TYPE to a string` message
to print the value that could not be coerced. This helps with debugging
by making it easier to track down where the value is being produced
from, especially in errors with deep or unhelpful stack traces.
Do this if we want to do `--hash-algo` everywhere, and not `--algo` for
hash commands.
The new `nix hash convert` is updated. Deprecated new CLI commands are
left as-is (`nix hash path` needs to be redone and is also left as-is).
Good to document these formats separately from commands that happen to
use them.
Eventually I would like this and `builtins.derivation` to refer to a
store section on derivations that is authoritative, but that doesn't yet
exist, and will take some time to make. So I think we're just best off
merging this now as is.
Co-authored-by: Valentin Gagarin <valentin.gagarin@tweag.io>
A small step towards https://github.com/NixOS/nix/issues/6507
I believe this incomplete definition is one that can be agreed on.
It would be nice to define more, but considering that the issue
also proposes changes to the design, I believe we should hold off
on those.
As for the wording, we're dealing with some very general and vague
terms, that have to be treated with exactly the right amount of
vagueness to be effective.
I start out with a fairly abstract definition of package.
1. to establish a baseline so we know what we're talking about
2. so that we can go in and clarify that we have an extra, Nix-specific
definition.
"Software" is notoriously ill-defined, so it makes a great qualifier
for package, which we don't really want to pin down either, because
that would just get us lost in discussion.
We can come back to this after we've done 6057 and a few years in a
desert cave.
Then comes the "package attribute set" definition.
I can already hear Valentin say "That's not even Nix's responsibility!"
and on some days I might even agree.
However, in our current reality, we have `nix-env`, `nix-build` and
`nix profile`, which query the `outputName` attribute - among others -
which just don't exist in the derivation.
For those who can't believe what they're reading:
$ nix-build --expr 'with import ./. {}; bind // {outputName = "lib";}' --no-out-link
this path will be fetched (1.16 MiB download, 3.72 MiB unpacked):
/nix/store/rfk6klfx3z972gavxlw6iypnj6j806ma-bind-9.18.21-lib
copying path '/nix/store/rfk6klfx3z972gavxlw6iypnj6j806ma-bind-9.18.21-lib' from 'https://cache.nixos.org'...
/nix/store/rfk6klfx3z972gavxlw6iypnj6j806ma-bind-9.18.21-lib
and let me tell you that bind is not a library.
So anyway, that's also proof of why calling this a "derivation attrset" would be wrong, despite the type attribute.
The Nix team has requested that this output format remain unchanged.
I've added a warning to the man page explaining that `nix-instantiate
--eval` output will not parse correctly in many situations.
channels make everything more stateful, and therefore more complicated
and potentially confusing, but aren't needed for this task, so don't encourage their use.
* deduplicate installation instructions
- reorder sections to present pinned installation more prominently
- remove outdated notes on the macOS installer rework
- update instructions to handle the installer tarball
Co-authored-by: Travis A. Everett <travis.a.everett@gmail.com>
since `up` and `values` are both pointer-aligned the type field will
also be pointer-aligned, wasting 48 bits of space on most machines. we
can get away with removing the type field altogether by encoding some
information into the `with` expr that created the env to begin with,
reducing the GC load for the absolutely massive amount of single-entry
envs we create for lambdas. this reduces memory usage of system eval by
quite a bit (reducing heap size of our system eval from 8.4GB to 8.23GB)
and gives similar savings in eval time.
running `nix eval --raw --impure --expr 'with import <nixpkgs/nixos> {}; system'`
before:
Time (mean ± σ): 5.576 s ± 0.003 s [User: 5.197 s, System: 0.378 s]
Range (min … max): 5.572 s … 5.581 s 10 runs
after:
Time (mean ± σ): 5.408 s ± 0.002 s [User: 5.019 s, System: 0.388 s]
Range (min … max): 5.405 s … 5.411 s 10 runs
a bunch of derivation strings contain no escape sequences. we can
optimize for this fact by first scanning for the end of a derivation
string and simply returning the contents unmodified if no escape
sequences were found. to make this even more efficient we can also use
BackedStringViews to avoid copies, avoiding heap allocations for
transient data.
before:
Benchmark 1: nix eval --raw --impure --expr 'with import <nixpkgs/nixos> {}; system'
Time (mean ± σ): 6.952 s ± 0.015 s [User: 5.294 s, System: 1.452 s]
Range (min … max): 6.926 s … 6.974 s 10 runs
after:
Benchmark 1: nix eval --raw --impure --expr 'with import <nixpkgs/nixos> {}; system'
Time (mean ± σ): 6.907 s ± 0.012 s [User: 5.272 s, System: 1.429 s]
Range (min … max): 6.893 s … 6.926 s 10 runs
This fixes a segfault on infinite function call recursion (rather than
infinite thunk recursion) by tracking the function call depth in
`EvalState`.
Additionally, to avoid printing extremely long stack traces, stack
frames are now deduplicated, with a `(19997 duplicate traces omitted)`
message. This should only really be triggered in infinite recursion
scenarios.
Before:
$ nix-instantiate --eval --expr '(x: x x) (x: x x)'
Segmentation fault: 11
After:
$ nix-instantiate --eval --expr '(x: x x) (x: x x)'
error: stack overflow
at «string»:1:14:
1| (x: x x) (x: x x)
| ^
$ nix-instantiate --eval --expr '(x: x x) (x: x x)' --show-trace
error:
… from call site
at «string»:1:1:
1| (x: x x) (x: x x)
| ^
… while calling anonymous lambda
at «string»:1:2:
1| (x: x x) (x: x x)
| ^
… from call site
at «string»:1:5:
1| (x: x x) (x: x x)
| ^
… while calling anonymous lambda
at «string»:1:11:
1| (x: x x) (x: x x)
| ^
… from call site
at «string»:1:14:
1| (x: x x) (x: x x)
| ^
(19997 duplicate traces omitted)
error: stack overflow
at «string»:1:14:
1| (x: x x) (x: x x)
| ^
Previously, IFDs would be built within the eval store, even though one
is typically using `--eval-store` precisely to *avoid* local builds.
Because the resulting Nix expression must be copied back to the eval
store in order to be imported, this requires the eval store to trust
the build store's signatures.
