Motivation
`PathSet` is not correct because string contexts have other forms
(`Built` and `DrvDeep`) that are not rendered as plain store paths.
Instead of wrongly using `PathSet`, or "stringly typed" using
`StringSet`, use `std::std<StringContextElem>`.
-----
In support of this change, `NixStringContext` is now defined as
`std::std<StringContextElem>` not `std:vector<StringContextElem>`. The
old definition was just used by a `getContext` method which was only
used by the eval cache. It can be deleted altogether since the types are
now unified and the preexisting `copyContext` function already suffices.
Summarizing the previous paragraph:
Old:
- `value/context.hh`: `NixStringContext = std::vector<StringContextElem>`
- `value.hh`: `NixStringContext Value::getContext(...)`
- `value.hh`: `copyContext(...)`
New:
- `value/context.hh`: `NixStringContext = std::set<StringContextElem>`
- `value.hh`: `copyContext(...)`
----
The string representation of string context elements no longer contains
the store dir. The diff of `src/libexpr/tests/value/context.cc` should
make clear what the new representation is, so we recommend reviewing
that file first. This was done for two reasons:
Less API churn:
`Value::mkString` and friends did not take a `Store` before. But if
`NixStringContextElem::{parse, to_string}` *do* take a store (as they
did before), then we cannot have the `Value` functions use them (in
order to work with the fully-structured `NixStringContext`) without
adding that argument.
That would have been a lot of churn of threading the store, and this
diff is already large enough, so the easier and less invasive thing to
do was simply make the element `parse` and `to_string` functions not
take the `Store` reference, and the easiest way to do that was to simply
drop the store dir.
Space usage:
Dropping the `/nix/store/` (or similar) from the internal representation
will safe space in the heap of the Nix programming being interpreted. If
the heap contains many strings with non-trivial contexts, the saving
could add up to something significant.
----
The eval cache version is bumped.
The eval cache serialization uses `NixStringContextElem::{parse,
to_string}`, and since those functions are changed per the above, that
means the on-disk representation is also changed.
This is simply done by changing the name of the used for the eval cache
from `eval-cache-v4` to eval-cache-v5`.
----
To avoid some duplication `EvalCache::mkPathString` is added to abstract
over the simple case of turning a store path to a string with just that
string in the context.
Context
This PR picks up where #7543 left off. That one introduced the fully
structured `NixStringContextElem` data type, but kept `PathSet context`
as an awkward middle ground between internal `char[][]` interpreter heap
string contexts and `NixStringContext` fully parsed string contexts.
The infelicity of `PathSet context` was specifically called out during
Nix team group review, but it was agreeing that fixing it could be left
as future work. This is that future work.
A possible follow-up step would be to get rid of the `char[][]`
evaluator heap representation, too, but it is not yet clear how to do
that. To use `NixStringContextElem` there we would need to get the STL
containers to GC pointers in the GC build, and I am not sure how to do
that.
----
PR #7543 effectively is writing the inverse of a `mkPathString`,
`mkOutputString`, and one more such function for the `DrvDeep` case. I
would like that PR to have property tests ensuring it is actually the
inverse as expected.
This PR sets things up nicely so that reworking that PR to be in that
more elegant and better tested way is possible.
Co-authored-by: Théophane Hufschmitt <7226587+thufschmitt@users.noreply.github.com>
This introduces the SourcePath type from lazy-trees as an abstraction
for accessing files from inputs that may not be materialized in the
real filesystem (e.g. Git repositories). Currently, however, it's just
a wrapper around CanonPath, so it shouldn't change any behaviour. (On
lazy-trees, SourcePath is a <InputAccessor, CanonPath> tuple.)
Documentation on "classic" commands with many sub-commands are
notoriously hard to discover due to lack of overview and anchor links.
Additionally the information on common options and environment variables
is not accessible offline in man pages, and therefore often overlooked
by readers.
With this change, each sub-command of nix-store and nix-env gets its
own page in the manual (listed in the table of contents), and each own
man page.
Also, man pages for each subcommand now (again) list common options
and environment variables. While this makes each page quite long and
some common parameters don't apply, this should still make it easier
to navigate as that additional information was not accessible on the
command line at all.
It is now possible to run 'nix-store --<subcommand> --help` to display
help pages for the given subcommand.
Co-authored-by: Valentin Gagarin <valentin.gagarin@tweag.io>
XDG Base Directory is a standard for locations for storing various
files. Nix has a few files which seem to fit in the standard, but
currently use a custom location directly in the user's ~, polluting
it:
- ~/.nix-profile
- ~/.nix-defexpr
- ~/.nix-channels
This commit adds a config option (use-xdg-base-directories) to follow
the XDG spec and instead use the following locations:
- $XDG_STATE_HOME/nix/profile
- $XDG_STATE_HOME/nix/defexpr
- $XDG_STATE_HOME/nix/channels
If $XDG_STATE_HOME is not set, it is assumed to be ~/.local/state.
Co-authored-by: Théophane Hufschmitt <7226587+thufschmitt@users.noreply.github.com>
Co-authored-by: Tim Fenney <kodekata@gmail.com>
Co-authored-by: pasqui23 <pasqui23@users.noreply.github.com>
Co-authored-by: Artturin <Artturin@artturin.com>
Co-authored-by: John Ericson <Ericson2314@Yahoo.com>
This makes the position object used in exceptions abstract, with a
method getSource() to get the source code of the file in which the
error originated. This is needed for lazy trees because source files
don't necessarily exist in the filesystem, and we don't want to make
libutil depend on the InputAccessor type in libfetcher.
Ensures the logger is stopped on exit in legacy commands. Without this,
when using `nix-build --log-format bar` and stopping nix with CTRL+C,
the bar is not cleared from the screen.
this slightly increases the amount of memory used for any given symbol, but this
increase is more than made up for if the symbol is referenced more than once in
the EvalState that holds it. on average every symbol should be referenced at
least twice (once to introduce a binding, once to use it), so we expect no
increase in memory on average.
symbol tables are limited to 2³² entries like position tables, and similar
arguments apply to why overflow is not likely: 2³² symbols would require as many
string instances (at 24 bytes each) and map entries (at 24 bytes or more each,
assuming that the map holds on average at most one item per bucket as the docs
say). a full symbol table would require at least 192GB of memory just for
symbols, which is well out of reach. (an ofborg eval of nixpks today creates
less than a million symbols!)
Pos objects are somewhat wasteful as they duplicate the origin file name and
input type for each object. on files that produce more than one Pos when parsed
this a sizeable waste of memory (one pointer per Pos). the same goes for
ptr<Pos> on 64 bit machines: parsing enough source to require 8 bytes to locate
a position would need at least 8GB of input and 64GB of expression memory. it's
not likely that we'll hit that any time soon, so we can use a uint32_t index to
locate positions instead.
The current `--out-path` flag has two disadvantages when one is only
concerned with querying the names of outputs:
- it requires evaluating every output's `outPath`, which takes
significantly more resources and runs into more failures
- it destroys the information of the order of outputs so we can't tell
which one is the main output
This patch makes the output names always present (replacing paths with
`null` in JSON if `--out-path` isn't given), and adds an `outputName`
field.
help new users find a solution to their problem
./result/bin/nix-env -qa hello
warning: name collision in input Nix expressions, skipping '/home/artturin/.nix-defexpr/channels_root/master'
suggestion: remove 'master' from either the root channels or the user channels
hello-2.12
hello-2.12
This is useful whenever we want to evaluate something to a store path
(e.g. in get-drvs.cc).
Extracted from the lazy-trees branch (where we can require that a
store path must come from a store source tree accessor).
- Make passing the position to `forceValue` mandatory,
this way we remember people that the position is
important for better error messages
- Add pos to all `forceValue` calls
Previously you had to remember to call value->attrs->sort() after
populating value->attrs. Now there is a BindingsBuilder helper that
wraps Bindings and ensures that sort() is called before you can use
it.
