This does not yet resolve the coupling between packages and
derivations, but it makes the code more consistent with the
terminology, and it accentuates places where the coupling is
obvious, such as
auto drvPath = packageInfo.queryDrvPath();
if (!drvPath)
throw Error("'%s' is not a derivation", what());
... which isn't wrong, and in my opinion, doesn't even look
wrong, because it just reflects the current logic.
However, I do like that we can now start to see in the code that
this coupling is perhaps a bit arbitrary.
After this rename, we can bring the DerivingPath concept into type
and start to lift this limitation.
these symbols are used a *lot*, so it makes sense to cache them. this
mostly increases clarity of the code (however clear one may wish to call
the parser desugaring here), but it also provides a small performance
benefit.
there's no reason the parser itself should be doing semantic analysis
like bindVars. split this bit apart (retaining the previous name in
EvalState) and have the parser really do *only* parsing, decoupled from
EvalState.
most EvalState and Expr members defined here could be elsewhere, where
they'd be easier to maintain (not being embedded in a file with arcane
syntax) and *somewhat* more faithfully placed according to the path of
the file they're defined in.
most instances of this being used do not refer to the "current"
position, sometimes not even to one reasonably close by. it could also
be called `makePos` instead, but `at` seems clear in context.
ParserState better describes what this struct really is. the parser
really does modify its state (most notably position and symbol tables),
so calling it that rather than obliquely "data" (which implies being
input only) makes sense.
since nix doesn't use the bison `error` terminal anywhere any invocation
of yyerror will immediately cause a failure. since we're *already*
leaking tons of memory whatever little bit bison allocates internally
doesn't much matter any more, and we'll be replacing the parser soon anyway.
coincidentally this now also matches the error behavior of URIs when
they are disabled or ~/ paths in pure eval mode, duplicate attr
detection etc.
Otherwise we get a stray `tests/functional/result`, which can cause
spurious failures later.
(I got a failure because the test temp dir effecting the store dir
changed. This caused a test later because Nix didn't want to remove the
old `result` because it wasn't pointing inside the new Nix store.)
The data was (accidentally?) copied into a std::string,
even though the string is immediately converted into a std::string_view.
The code has been changed to construct a std::string_view directly,
such that one copy less happens.
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.
Robert Hensing
Las Safin