We want to be able to write down `foo.drv^bar.drv^baz`:
`foo.drv^bar.drv` is the dynamic derivation (since it is itself a
derivation output, `bar.drv` from `foo.drv`).
To that end, we create `Single{Derivation,BuiltPath}` types, that are
very similar except instead of having multiple outputs (in a set or
map), they have a single one. This is for everything to the left of the
rightmost `^`.
`NixStringContextElem` has an analogous change, and now can reuse
`SingleDerivedPath` at the top level. In fact, if we ever get rid of
`DrvDeep`, `NixStringContextElem` could be replaced with
`SingleDerivedPath` entirely!
Important note: some JSON formats have changed.
We already can *produce* dynamic derivations, but we can't refer to them
directly. Today, we can merely express building or example at the top
imperatively over time by building `foo.drv^bar.drv`, and then with a
second nix invocation doing `<result-from-first>^baz`, but this is not
declarative. The ethos of Nix of being able to write down the full plan
everything you want to do, and then execute than plan with a single
command, and for that we need the new inductive form of these types.
Co-authored-by: Robert Hensing <roberth@users.noreply.github.com>
Co-authored-by: Valentin Gagarin <valentin.gagarin@tweag.io>
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
Special-casing the file name is rather ugly, so we shouldn't do
that. So now any {file,http,https} URL is handled by
TarballInputScheme, except for non-flake inputs (i.e. inputs that have
the attribute `flake = false`).
Over the last year or so I've run into several use cases where I need to
parse and/or serialize URLs for use by `builtins.fetchTree` or
`builtins.getFlake`, largely in order to produce _lockfile-like_ files
for lang2nix frameworks or tools which use `nix` internally to drive
builds.
I've gone through the painstaking process of emulating
`nix::FlakeRef::fromAttrs` and `nix::parseFlakeRef` several times with
mixed success; but these are difficult to create and even harder to
maintain if I hope to stay aligned with changes to the real
parser/serializer.
I understand why adding new `builtins` isn't something we want to do
flagrantly. I'm recommending this addition simply because I keep
encountering use cases where I need to parse/serialize these URIs in
`nix` expressions, and I want a reliable solution.
Co-authored-by: Eelco Dolstra <edolstra@gmail.com>
Co-authored-by: John Ericson <git@JohnEricson.me>
the original change broke many pre-existing anchor links.
also change formatting of the constants listing slightly:
- the type should not be part of the anchor
- add highlight to the "impure only" note
- Better types
- Own header / C++ file pair
- Test factored out methods
- Pass parsed thing around more than strings
Co-authored-by: Robert Hensing <roberth@users.noreply.github.com>
Whereas `ContentAddressWithReferences` is a sum type complex because different
varieties support different notions of reference, and
`ContentAddressMethod` is a nested enum to support that,
`ContentAddress` can be a simple pair of a method and hash.
`ContentAddress` does not need to be a sum type on the outside because
the choice of method doesn't effect what type of hashes we can use.
Co-Authored-By: Cale Gibbard <cgibbard@gmail.com>
If we call `adjustLoc`, the global variable `prev_yylloc` is shared
between threads and racy.
Currently, nix itself does not concurrently parsing files, but this is
helpful for libexpr users. (The parser is thread-safe except this.)
When explicitly requested by the caller, as suggested in the meeting
(https://github.com/NixOS/nix/pull/8090#issuecomment-1531139324)
> @edolstra: { toPath } vs { fromPath } is too implicit
I've opted for the `inputAddressed = true` requirement, because it
we did not agree on renaming the path attributes.
> @roberth: more explicit
> @edolstra: except for the direction; not immediately clear in which direction the rewriting happens
This is in fact the most explicit syntax and a bit redundant, which is
good, because that redundancy lets us deliver an error message that
reminds expression authors that CA provides a better experience to
their users.
This is done in roughly the same way builtin functions are documented.
Also auto-link experimental features for primops, subsuming PR #8371.
Co-authored-by: Eelco Dolstra <edolstra@gmail.com>
Co-authored-by: Robert Hensing <roberth@users.noreply.github.com>
Co-authored-by: Valentin Gagarin <valentin.gagarin@tweag.io>
I got very confused trying to keep all the `first` and `second` straight
reading the code, *especially* as there is also another `(boolean,
string)` pair type also being used.
Named fields is much better.
There are other cleanups that we can do (for example, the existing
TODO), but we can do them later. Doing them now would just make this
harder to review.
