Incorrectly high expectations lead to frustration for users who
stick around to experience how useless it is for e.g. a devShell
https://functional.cafe/@arianvp/112976284363120036:
> Flakes doesn't have eval caching. It has command line argument
> caching. It literally just stores the cli argument you passed
> in a sqlite database and yes that's as useless as it sounds
> When I discovered flakes had no expression level caching whatsoever
> I kind of felt lied to and betrayed.
* docs: unify documentation on search paths
- put all the information on search path semantics into `builtins.findFile`
- put all the information on determining the value of `builtins.nixPath` into the
`nix-path` setting
maybe `builtins.nixPath` is a better place for this, but those bits
can still be moved around now that it's all next to each other.
- link to the syntax page for lookup paths from all places that are
concerned with it
- add or clarify examples
- add a test verifying a claim from documentation
* manual: Contributing -> Development, Hacking -> Building
what's currently called "hacking" are really instructions for setting up
a development environment and compiling from source. we have
a contribution guide in the repo (which rightly focuses on GitHub
workflows), and the material in the manual is more about working
on the code itself.
since we'd otherwise have three headings that amount to "Building Nix",
this change also moves the "classic Nix" instructions to the top.
we may want to reorganise this in the future, and bring
contributor-oriented information closer to the code, but for now let's
stick to more accurate names to ease navigation.
* fix NIX_PATH overriding
- test restricted evaluation
- test precedence for setting the search path
Co-authored-by: Robert Hensing <robert@roberthensing.nl>
Co-authored-by: John Ericson <git@JohnEricson.me>
The default value for the setting was evaluated by
calling a method on the object _being currently constructed_,
so we were using it before all fields were initialized.
This has been fixed by making the called method static,
and not using the previously used fields at all.
But functionality hasn't changed!
The fields were usually always zero (by chance?) anyway,
meaning the conditional path was always taken.
Thus the current logic has been kept, the code simplified,
and UB removed.
This was found with the helper of UBSan.
* docs: mention importNative/exec in allow-unsafe-native-code-during-evaluation
Both of these still needs their own actual documentation, but they are
at least now mentioned that they exist and what they're enabled by.
Co-authored-by: Qyriad <qyriad@qyriad.me>
Co-authored-by: Valentin Gagarin <valentin.gagarin@tweag.io>
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)
| ^
`eval-system` option overrides just the value of `builtins.currentSystem`.
This is more useful than overriding `system` since you can build these
derivations on remote builders which can work on the given system.
Co-authored-by: John Ericson <John.Ericson@Obsidian.Systems>
Co-authored-by: Valentin Gagarin <valentin.gagarin@tweag.io>
All OS and IO operations should be moved out, leaving only some misc
portable pure functions.
This is useful to avoid copious CPP when doing things like Windows and
Emscripten ports.
Newly exposed functions to break cycles:
- `restoreSignals`
- `updateWindowSize`
* document "Import From Derivation"
Co-authored-by: Robert Hensing <roberth@users.noreply.github.com>
Co-authored-by: John Ericson <git@JohnEricson.me>
Avoid duplicated code, and also avoid "on the fly" path construction
(which makes it harder to keep track of which paths we use).
The factored out code doesn't create the Nix state dir anymore, but this
is fine because other in nix-env and nix-channel does:
- nix-channel: Line 158 in this commit
- nix-env: Line 1407 in this commit
