Add a fallback path in `queryPartialDerivationOutputMap` for daemons
that don't support it.
Also upstreams a couple methods from `SSHStore` to `RemoteStore` as this
is needed to handle the fallback path.
When deploying a Hydra instance with current Nix master, most builds
would not run because of errors like this:
queue monitor: error: --- Error --- hydra-queue-runner
error: --- UsageError --- nix-daemon
not a content address because it is not in the form '<prefix>:<rest>': /nix/store/...-somedrv
The last error message is from parseContentAddress, which expects a
colon-separated string, however what we got here is a store path.
Looking at the worker protocol, the following message sent to the Nix
daemon caused the error above:
0x1E -> wopQuerySubstitutablePathInfos
0x01 -> Number of paths
0x16 -> Length of string
"/nix/store/...-somedrv"
0x00 -> Length of string
""
Looking at writeStorePathCAMap, the store path is indeed the first field
that's transmitted. However, readStorePathCAMap expects it to be the
*second* field *on my machine*, since expression evaluation order is a
classic form of unspecified behaviour[1] in C++.
This has been introduced in https://github.com/NixOS/nix/pull/3689,
specifically in commit 66a62b3189.
[1]: https://en.wikipedia.org/wiki/Unspecified_behavior#Order_of_evaluation_of_subexpressions
Signed-off-by: aszlig <aszlig@nix.build>
If we resolve using the known path of a derivation whose output we
didn't have, we previously blew up. Now we just fail gracefully,
returning the map of all outputs unknown.
This means profiles outside of /nix/var/nix/profiles don't get
garbage-collected. It also means we don't need to scan
/nix/var/nix/profiles for GC roots anymore, except for compatibility
with previously existing generations.
Evidentally this was never implemented because Nix switched to using
`buildDerivation` exclusively before `build-remote.pl` was rewritten.
The `nix-copy-ssh` test (already) tests this.
Include a long comment explaining the policy. Perhaps this can be moved
to the manual at some point in the future.
Also bump the daemon protocol minor version, so clients can tell whether
`wopBuildDerivation` supports trustless CA derivation building. I hope
to take advantage of this in a follow-up PR to support trustless remote
building with the minimal sending of derivation closures.
This seems more correct. It also means one can specify the features a
store should support with --store and remote-store=..., which is useful.
I use this to clean up the build remotes test.
Before, processConnection wanted to know a user name and user id, and
`nix-daemon --stdio`, when it isn't proxying to an underlying daemon,
would just assume "root" and 0. But `nix-daemon --stdio` (no proxying)
shouldn't make guesses about who holds the other end of its standard
streams.
Now processConnection takes an "auth hook", so `nix-daemon` can provide
the appropriate policy and daemon.cc doesn't need to know or care what
it is.
Thanks @regnat for catching one of them. The other follows for many of
the same reasons. I'm find fixing others on a need-to-fix basis,
provided their are no regressions.
Some users have their own hashed-mirrors setup, that is used to mirror
things in addition to what’s available on tarballs.nixos.org. Although
this should be feasable to do with a Binary Cache, it’s not always
easy, since you have to remember what "name" each of the tarballs has.
Continuing to support hashed-mirrors is cheap, so it’s best to leave
support in Nix. Note that NIX_HASHED_MIRRORS is also supported in
Nixpkgs through fetchurl.nix.
Note that this excludes tarballs.nixos.org from the default, as in
\#3689. All of these are available on cache.nixos.org.
Since 6185d25e52, this was very
latency-bound since it required a round-trip for every 32 KiB. So for
example copying a 514 MiB closure over a virtual ethernet device with
a articial delay of just 1 ms took 343s. Now it takes 2.7s.
Fixes#3372.
The new interface we offer provides a way of getting all the
DerivationOutputs with the storePaths directly, based on the observation
that it's the most common usecase.
istream->tellg() returns -1 so we can't get the number of bytes
written.
Fixes 'uploaded 's3://nix-cache/nar/00819r9lp5kajr6baxfw5dhhc0cx8ndxaz43qmd2f0gn1hk1ynlp.nar.xz' (-1 bytes) in 11620 ms' messages.
This assumption is broken by CA derivations. Making a PR now to do the
breaking daemon change as soon as possible (if it is already too late,
we can bump protocol intead).
It's a tiny function which is:
- hardly worth abstrating over, and also only used once.
- doesn't work once we get CA drvs
I rewrote the one callsite to be forwards compatable with CA
derivations, and also potentially more performant: instead of reading in
the derivation it can ust consult the SQLite DB in the common case.
to each Store implementation. The generic regStore implementation will
only be for the ambiguous shorthands, like "" and "auto".
This also could get us close to simplifying the daemon command.
I got it to just become `LocalStore::addToStoreFromDump`, cleanly taking
a store and then doing nothing too fancy with it.
`LocalStore::addToStore(...Path...)` is now just a simple wrapper with a
bare-bones sinkToSource of the right dump command.
This reverts commit a2c27022e9. See
addToStoreSlow(), we don't need to handle this case efficiently
anymore. In fact, we can almost remove the method/hashAlgo arguments
since the non-recursive and/or non-SHA256 are almost not used anymore.
We were calculating the nar hash wrong when the file ingestion method
was flat. I don't think there's anything we can do in that case but dump
the file again, so that's what I do.
As an optomization, we again could reuse the original dump for just the
recursive and non-sha256 case, but I rather do that after this fix, and
after my other PRs which deduplicate this code.
We've added the variant to `DerivationOutput` to support them, but made
`DerivationOutput::path` partial to avoid actually implementing them.
With this chage, we can all collaborate on "just" removing
`DerivationOutput::path` calls to implement CA derivations.
This reduces memory consumption of
nix-instantiate \
-E 'with import <nixpkgs> {}; runCommand "foo" { src = ./blender; } "echo foo"' \
--option nar-buffer-size 10000
(where ./blender is a 1.1 GiB tree) from 1716 to 36 MiB, while still
ensuring that we don't do any write I/O for small source paths (up to
'nar-buffer-size' bytes). The downside is that large paths are now
always written to a temporary location in the store, even if they
produce an already valid store path. Thus, adding large paths might be
slower and run out of disk space. ¯\_(ツ)_/¯ Of course, you can always
restore the old behaviour by setting 'nar-buffer-size' to a very high
value.
Generalize `queryDerivationOutputNames` and `queryDerivationOutputs` by
adding a `queryDerivationOutputMap` that returns the map
`outputName=>outputPath`
(not that this is not equivalent to merging the results of
`queryDerivationOutputs` and `queryDerivationOutputNames` as sets don't
preserve the order, so we would end up with an incorrect mapping).
squash! Add a way to get all the outputs of a derivation with their label
Rename StorePathMap to OutputPathMap
Now the derivation outputs are parsed up front, we can avoid a reparse
by doing it. Also, this just feels a bit better as the `output*` env
vars are more of a `libnixexpr` interface than `libnixstore` interface:
ultimately, it's the derivation outputs that decide whether the
derivation is fixed-output.
Yes, hashed mirrors might go away with #3689, but this bit of code would
be moved rather than deleted, so it's worth doing a cleanup anyways I
think.
When we merge with master, the new lack of string types make this case
impossible (after parsing). Later, when we actually implemenent
CA-derivations, we'll change the types to allow that.
We have a larger problem that passsing computed strings to the first
variable argument of many exception constructors is unsafe because that
first variable argument is interpreted not as a plain string, but format
string, and if it contains '%' boost::format will abort, since there are
no arguments to the format string.
In this particular instance '%' was used as part of an escape code in a
URL, which, when the download failed, caused Nix to abort displaying the
`FileTransferError`.
This was introduced in fa125b9b28, and
then "reverted" in 1cf4801108, except that
revert left the struct around doing nothing useful.
We're removing it all the way now because we want to make a new
`TeeSink` complementing the already-exiting `TeeSource`, that is
actually a completely different concept as far as the class hierarchy is
concerned.
I’m not 100% sure this is wanted since it kind of makes everything
have to know about ca even if they don’t really want to. But it also
make things easier in dealing with looking up ca.
Not implementing anything here, just throwing an error if a derivation
sets `__contentAddressed = true` without
`--experimental-features content-addressed-paths`
(and also with it as there's nothing implemented yet)
This further continues with the dependency inverstion. Also I just went
ahead and exposed `parseDerivation`: it seems like the more proper
building block, and not a bad thing to expose if we are trying to be
less wedded to drv files on disk anywas.
On nix-env -qa -f '<nixpkgs>', this reduces maximum RSS by 20970 KiB
and runtime by 0.8%. This is mostly because we're not parsing the hash
part as a hash anymore (just validating that it consists of base-32
characters).
Also, replace storePathToHash() by StorePath::hashPart().
E.g. instead of
error: --- BuildError ----------------------------------------------- nix
builder for '/nix/store/03nk0a3n8h2948k4lqfgnnmym7knkcma-foo.drv' failed with exit code 1
error: --- Error ---------------------------------------------------- nix
build of '/nix/store/03nk0a3n8h2948k4lqfgnnmym7knkcma-foo.drv' failed
we now get
error: --- Error ---------------------------------------------------- nix
builder for '/nix/store/03nk0a3n8h2948k4lqfgnnmym7knkcma-foo.drv' failed with exit code 1
Originally, the test was only checking for different “real” storeDir.
That’s an easy case to handle, but the much harder one is if different
virtual store dirs are used. To do this, we need the SubstitutionGoal
to know about the ca, so it can recalculate the path to copy it over.
An important note here is that the store path passed to copyStorePath
needs to be one for srcStore - so that queryPathInfo works properly.
This also adds an error message when the store path from queryPathInfo
is different from the one we requested.
Substituters can substitute from one store dir to another with a
little bit of help. The store api just needs to have a CA so it can
recompute the store path based on the new store dir. We can only do
this for fixed output derivations with no references, though.
This function was used in only one place, where it could easily be
replaced by readDerivation() since it's not
performance-critical. (This function appears to have been modelled
after queryDerivationOutputs(), which exists only to make the garbage
collector faster.)
Make the printing of the build logs systematically go through the
logger, and replicate the behavior of `no-build-output` by having two
different loggers (one that prints the build logs and one that doesn't)
bool coerces anything >0 to true, but in the future we may have other
file ingestion methods. This shows a better error message when the
“recursive” byte isn’t 1.
Instead, `Hash` uses `std::optional<HashType>`. In the future, we may
also make `Hash` itself require a known hash type, encoraging people to
use `std::optional<Hash>` instead.
The idea is it's always more flexible to consumer a `Source` than a
plain string, and it might even reduce memory consumption.
I also looked at `addToStoreFromDump` with its `// FIXME: remove?`, but
the worked needed for that is far more up for interpretation, so I
punted for now.
For remote stores the log messages are already forwarded as structured
STDERR_RESULT messages so the old format is duplicate information. But
still included with -vvv since it could be useful for debugging
problems.
$ nix build -L /nix/store/nl71b2niws857ffiaggyrkjwgx9jjzc0-foo.drv --store ssh-ng://localhost
Hello World!
foo> Hello World!
[1/0/1 built] building foo
Fixes#3556
The commit 3cc1125595 adds a `grantpt`
call on the builder pseudo terminal fd. This call is actually only
required for MacOS, but it however requires a RW access to /dev/pts
which is only RO bindmounted in the Bazel Linux sandbox. So, Nix can
not be actually run in the Bazel Linux sandbox for unneeded reasons.
Motivation: maintain project-level configuration files.
Document the whole situation a bit better so that it corresponds to the
implementation, and add NIX_USER_CONF_FILES that allows overriding
which user files Nix will load during startup.
Temporarily add user-write permission to build directory so that it
can be moved out of the sandbox to the store with a .check suffix.
This is necessary because the build directory has already had its
permissions set read-only, but write permission is required
to update the directory's parent link to move it out of the sandbox.
Updated the related --check "derivation may not be deterministic"
messages to consistently use the real store paths.
Added test for non-root sandbox nix-build --check -K to demonstrate
issue and help prevent regressions.
With --check and the --keep-failed (-K) flag, the temporary directory
was being retained regardless of whether the build was successful and
reproducible. This removes the temporary directory, as expected, on
a reproducible check build.
Added tests to verify that temporary build directories are not
retained unnecessarily, particularly when using --check with
--keep-failed.
This provides a pluggable mechanism for defining new fetchers. It adds
a builtin function 'fetchTree' that generalizes existing fetchers like
'fetchGit', 'fetchMercurial' and 'fetchTarball'. 'fetchTree' takes a
set of attributes, e.g.
fetchTree {
type = "git";
url = "https://example.org/repo.git";
ref = "some-branch";
rev = "abcdef...";
}
The existing fetchers are just wrappers around this. Note that the
input attributes to fetchTree are the same as flake input
specifications and flake lock file entries.
All fetchers share a common cache stored in
~/.cache/nix/fetcher-cache-v1.sqlite. This replaces the ad hoc caching
mechanisms in fetchGit and download.cc (e.g. ~/.cache/nix/{tarballs,git-revs*}).
This also adds support for Git worktrees (c169ea5904).
When encountering an unsupported protocol, there's no need to retry.
Chances are, it won't suddenly be supported between retry attempts;
error instead. Otherwise, you see something like the following:
$ nix-env -i -f git://git@github.com/foo/bar
warning: unable to download 'git://git@github.com/foo/bar': Unsupported protocol (1); retrying in 335 ms
warning: unable to download 'git://git@github.com/foo/bar': Unsupported protocol (1); retrying in 604 ms
warning: unable to download 'git://git@github.com/foo/bar': Unsupported protocol (1); retrying in 1340 ms
warning: unable to download 'git://git@github.com/foo/bar': Unsupported protocol (1); retrying in 2685 ms
With this change, you now see:
$ nix-env -i -f git://git@github.com/foo/bar
error: unable to download 'git://git@github.com/foo/bar': Unsupported protocol (1)
Sadly 10.15 changed /bin/sh to a shim which executes bash, this means it
can't be used anymore without also opening up the sandbox to allow bash.
Failed to exec /bin/bash as variant for /bin/sh (1: Operation not permitted).
This is used to determine the dependency tree of impure libraries so nix
knows what paths to open in the sandbox. With the less restrictive
defaults it isn't needed anymore.
See documentattion in header and comments in implementation for details.
This is actually done in preparation for floating ca derivations, not
multi-output fixed ca derivations, but the distinction doesn't yet
mattter.
Thanks @cole-h for finding and fixing a bunch of typos.
If you do a fetchTree on a Git repository, whether the result contains
a revCount attribute should not depend on whether that repository
happens to be a shallow clone or not. That would complicate caching a
lot and would be semantically messy. So applying fetchTree/fetchGit to
a shallow repository is now an error unless you pass the attribute
'shallow = true'. If 'shallow = true', we don't return revCount, even
if the repository is not actually shallow.
Note that Nix itself is not doing shallow clones at the moment. But it
could do so as an optimisation if the user specifies 'shallow = true'.
Issue #2988.
Today's fixed output derivations and regular derivations differ in a few
ways which are largely orthogonal. This replaces `isFixedOutput` with a
`type` that returns an enum of possible combinations.
In
nix-instantiate --dry-run '<nixpkgs/nixos/release-combined.nix>' -A nixos.tests.simple.x86_64-linux
this reduces time spent in unparse() from 9.15% to 4.31%. The main
culprit was appending characters one at a time to the destination
string. Even though the string has enough capacity, push_back() still
needs to check this on every call.
Worktrees[1] are a feature of git which allow you to check out a ref in
a different directory.
While playing around with flakes I realized that git repositories in a
worktree checkout break when trying to build a flake:
```
$ git worktree add ../nixpkgs-flakes nixpkgs-flakes
$ cd ../nixpkgs-flakes
$ nix build .#hello
error: opening directory '/home/ma27/Projects/nixpkgs-flakes/.git/refs/heads': Not a directory
```
This issue has been fixed by determining with `git rev-parse --git-common-dir`
where the actual `.git` directory is.
Please note that this issue only exists on the `flakes` branch, fetching
worktree checkouts with Nix master seems to work fine.
[1] https://git-scm.com/docs/git-worktree
The ssh client is lazily started by the first worker thread, that
requires a ssh connection. To avoid the ssh client to be killed, when
the worker process is stopped, do not set PR_SET_PDEATHSIG.
Brings the functionality of ssh-ng:// in sync with the legacy ssh://
implementation. Specifying the remote store uri enables various useful
things. eg.
$ nix copy --to ssh-ng://cache?remote-store=file://mnt/cache --all
When computing a lock file, we now respect the lock files of flake
inputs. This is important for usability / reproducibility. For
example, the 'nixops' flake depends on the 'nixops-aws' and
'nixops-hetzner' repositories. So when the 'nixops' flake is used in
another flake, we want the versions of 'nixops-aws' and
'nixops-hetzner' locked by the the 'nixops' flake because those
presumably have been tested.
This can lead to a proliferation of versions of flakes like 'nixpkgs'
(since every flake's lock file could depend on a different version of
'nixpkgs'). This is not a major issue when using Nixpkgs overlays or
NixOS modules, since then the top-level flake composes those
overlays/modules into *its* version of Nixpkgs and all other versions
are ignored. Lock file computation has been made a bit more lazy so it
won't try to fetch all those versions of 'nixpkgs'.
However, in case it's necessary to minimize flake versions, there now
are two input attributes that allow this. First, you can copy an input
from another flake, as follows:
inputs.nixpkgs.follows = "dwarffs/nixpkgs";
This states that the calling flake's 'nixpkgs' input shall be the same
as the 'nixpkgs' input of the 'dwarffs' input.
Second, you can override inputs of inputs:
inputs.nixpkgs.url = github:edolstra/nixpkgs/<hash>;
inputs.nixops.inputs.nixpkgs.url = github:edolstra/nixpkgs/<hash>;
or equivalently, using 'follows':
inputs.nixpkgs.url = github:edolstra/nixpkgs/<hash>;
inputs.nixops.inputs.nixpkgs.follows = "nixpkgs";
This states that the 'nixpkgs' input of the 'nixops' input shall be
the same as the calling flake's 'nixpkgs' input.
Finally, at '-v' Nix now prints the changes to the lock file, e.g.
$ nix flake update ~/Misc/eelco-configurations/hagbard
inputs of flake 'git+file:///home/eelco/Misc/eelco-configurations?subdir=hagbard' changed:
updated 'nixpkgs': 'github:edolstra/nixpkgs/7845bf5f4b3013df1cf036e9c9c3a55a30331db9' -> 'github:edolstra/nixpkgs/03f3def66a104a221aac8b751eeb7075374848fd'
removed 'nixops'
removed 'nixops/nixops-aws'
removed 'nixops/nixops-hetzner'
removed 'nixops/nixpkgs'
Fixes
error: derivation '/nix/store/klivma7r7h5lndb99f7xxmlh5whyayvg-zlib-1.2.11.drv' has incorrect output '/nix/store/fv98nnx5ykgbq8sqabilkgkbc4169q05-zlib-1.2.11-dev', should be '/nix/store/adm7pilzlj3z5k249s8b4wv3scprhzi1-zlib-1.2.11-dev'
Having a colon in the path may cause issues, and having the hash
function indicated isn't actually necessary. We now verify the path
format in the tests to prevent regressions.
Before, we would get:
[deploy@bastion:~]$ nix-store -r /nix/store/grfnl76cahwls0igd2by2pqv0dimi8h2-nixos-system-eris-19.09.20191213.03f3def.drv
these derivations will be built:
/nix/store/3ka4ihvwh6wsyhpd2qa9f59506mnxvx1-initrd-linux-4.19.88.drv
/nix/store/ssxwmll7v21did1c8j027q0m8w6pg41i-unit-prometheus-alertmanager-irc-notifier.service.drv
/nix/store/mvyvkj46ay7pp7b1znqbkck2mq98k0qd-unit-script-network-local-commands-start.drv
/nix/store/vsl1y9mz38qfk6pyirjwnfzfggz5akg6-unit-network-local-commands.service.drv
/nix/store/wi5ighfwwb83fdmav6z6n2fw6npm9ffl-unit-prometheus-hydra-exporter.service.drv
/nix/store/x0qkv535n75pbl3xn6nn1w7qkrg9wwyg-unit-prometheus-packet-sd.service.drv
/nix/store/lv491znsjxdf51xnfxh9ld7r1zg14d52-unit-script-packet-sd-env-key-pre-start.drv
/nix/store/nw4nzlca49agsajvpibx7zg5b873gk9f-unit-script-packet-sd-env-key-start.drv
/nix/store/x674wwabdwjrkhnykair4c8mpxa9532w-unit-packet-sd-env-key.service.drv
/nix/store/ywivz64ilb1ywlv652pkixw3vxzfvgv8-unit-wireguard-wg0.service.drv
/nix/store/v3b648293g3zl8pnn0m1345nvmyd8dwb-unit-script-acme-selfsigned-status.nixos.org-start.drv
/nix/store/zci5d3zvr6fgdicz6k7jjka6lmx0v3g4-unit-acme-selfsigned-status.nixos.org.service.drv
/nix/store/f6pwvnm63d0kw5df0v7sipd1rkhqxk5g-system-units.drv
/nix/store/iax8071knxk9c7krpm9jqg0lcrawf4lc-etc.drv
/nix/store/grfnl76cahwls0igd2by2pqv0dimi8h2-nixos-system-eris-19.09.20191213.03f3def.drv
error: invalid file name 'closure-init-0' in 'exportReferencesGraph'
This was tough to debug, I didn't figure out which one was broken until I did:
nix-store -r /nix/store/grfnl76cahwls0igd2by2pqv0dimi8h2-nixos-system-eris-19.09.20191213.03f3def.drv 2>&1 | grep nix/store | xargs -n1 nix-store -r
and then looking at the remaining build graph:
$ nix-store -r /nix/store/grfnl76cahwls0igd2by2pqv0dimi8h2-nixos-system-eris-19.09.20191213.03f3def.drv
these derivations will be built:
/nix/store/3ka4ihvwh6wsyhpd2qa9f59506mnxvx1-initrd-linux-4.19.88.drv
/nix/store/grfnl76cahwls0igd2by2pqv0dimi8h2-nixos-system-eris-19.09.20191213.03f3def.drv
error: invalid file name 'closure-init-0' in 'exportReferencesGraph'
and knowing the initrd build is before the system, then:
$ nix show-derivation /nix/store/3ka4ihvwh6wsyhpd2qa9f59506mnxvx1-initrd-linux-4.19.88.drv
{
"/nix/store/3ka4ihvwh6wsyhpd2qa9f59506mnxvx1-initrd-linux-4.19.88.drv": {
[...]
"exportReferencesGraph": "closure-init-0 /nix/store/...-stage-1-init.sh closure-mdadm.conf-1 /nix/store/...-mdadm.conf closure-ubuntu.conf-2 ...",
[...]
}
}
I then searched the repo for "in 'exportReferencesGraph'", found this
recently updated regex, and realized it was missing a "-".
Before:
$ nix-channel --update
unpacking channels...
warning: SQLite database '/nix/var/nix/db/db.sqlite' is busy (SQLITE_PROTOCOL)
warning: SQLite database '/nix/var/nix/db/db.sqlite' is busy (SQLITE_PROTOCOL)
warning: SQLite database '/nix/var/nix/db/db.sqlite' is busy (SQLITE_PROTOCOL)
warning: SQLite database '/nix/var/nix/db/db.sqlite' is busy (SQLITE_PROTOCOL)
warning: SQLite database '/nix/var/nix/db/db.sqlite' is busy (SQLITE_PROTOCOL)
After:
$ inst/bin/nix-channel --update
unpacking channels...
created 1 symlinks in user environment
I've seen complaints that "sandbox" caused problems under WSL but I'm
having no problems. I think recent changes could have fixed the issue.
This allows overriding the priority of substituters, e.g.
$ nix-store --store ~/my-nix/ -r /nix/store/df3m4da96d84ljzxx4mygfshm1p0r2n3-geeqie-1.4 \
--substituters 'http://cache.nixos.org?priority=100 daemon?priority=10'
Fixes#3264.
If the `throw` is reached, this means that execvp into `ssh` wasn’t
successful. We can hint at a usual problem, which is a missing `ssh`
executable.
Test with:
```
env PATH= ./result/bin/nix-copy-closure --builders '' unusedhost
```
and the bash version with
```
env PATH= ./result/bin/nix-copy-closure --builders '' localhost
```
Most functions now take a StorePath argument rather than a Path (which
is just an alias for std::string). The StorePath constructor ensures
that the path is syntactically correct (i.e. it looks like
<store-dir>/<base32-hash>-<name>). Similarly, functions like
buildPaths() now take a StorePathWithOutputs, rather than abusing Path
by adding a '!<outputs>' suffix.
Note that the StorePath type is implemented in Rust. This involves
some hackery to allow Rust values to be used directly in C++, via a
helper type whose destructor calls the Rust type's drop()
function. The main issue is the dynamic nature of C++ move semantics:
after we have moved a Rust value, we should not call the drop function
on the original value. So when we move a value, we set the original
value to bitwise zero, and the destructor only calls drop() if the
value is not bitwise zero. This should be sufficient for most types.
Also lots of minor cleanups to the C++ API to make it more modern
(e.g. using std::optional and std::string_view in some places).
Also, fetchGit now runs in O(1) memory since we pipe the output of
'git archive' directly into unpackTarball() (rather than first reading
it all into memory).
We can now convert Rust Errors to C++ exceptions. At the Rust->C++ FFI
boundary, Result<T, Error> will cause Error to be converted to and
thrown as a C++ exception.
E.g.
$ nix-build '<nixpkgs>' -A hello --experimental-features no-url-literals
error: URL literals are disabled, at /nix/store/vsjamkzh15r3c779q2711az826hqgvzr-nixpkgs-20.03pre194957.bef773ed53f/nixpkgs/pkgs/top-level/all-packages.nix:1236:11
Helps with implementing https://github.com/NixOS/rfcs/pull/45.
Jonas Chevalier
Robert Hensing
Maximilian Bosch
edef
Yorick