nix-super/src/libexpr/attr-set.hh

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#pragma once
#include "nixexpr.hh"
#include "symbol-table.hh"
#include <algorithm>
#include <optional>
namespace nix {
class EvalState;
struct Value;
/* Map one attribute name to its value. */
struct Attr
{
Symbol name;
Value * value;
ptr<Pos> pos;
Attr(Symbol name, Value * value, ptr<Pos> pos = ptr(&noPos))
: name(name), value(value), pos(pos) { };
Attr() : pos(&noPos) { };
bool operator < (const Attr & a) const
{
return name < a.name;
}
};
/* Bindings contains all the attributes of an attribute set. It is defined
by its size and its capacity, the capacity being the number of Attr
elements allocated after this structure, while the size corresponds to
the number of elements already inserted in this structure. */
class Bindings
{
public:
typedef uint32_t size_t;
ptr<Pos> pos;
private:
size_t size_, capacity_;
Attr attrs[0];
Bindings(size_t capacity) : pos(&noPos), size_(0), capacity_(capacity) { }
Bindings(const Bindings & bindings) = delete;
public:
size_t size() const { return size_; }
bool empty() const { return !size_; }
typedef Attr * iterator;
void push_back(const Attr & attr)
{
assert(size_ < capacity_);
attrs[size_++] = attr;
}
iterator find(const Symbol & name)
{
Attr key(name, 0);
iterator i = std::lower_bound(begin(), end(), key);
if (i != end() && i->name == name) return i;
return end();
}
Attr * get(const Symbol & name)
{
Attr key(name, 0);
iterator i = std::lower_bound(begin(), end(), key);
if (i != end() && i->name == name) return &*i;
return nullptr;
}
Attr & need(const Symbol & name, const Pos & pos = noPos)
{
auto a = get(name);
if (!a)
throw Error({
Improve error formatting Changes: * The divider lines are gone. These were in practice a bit confusing, in particular with --show-trace or --keep-going, since then there were multiple lines, suggesting a start/end which wasn't the case. * Instead, multi-line error messages are now indented to align with the prefix (e.g. "error: "). * The 'description' field is gone since we weren't really using it. * 'hint' is renamed to 'msg' since it really wasn't a hint. * The error is now printed *before* the location info. * The 'name' field is no longer printed since most of the time it wasn't very useful since it was just the name of the exception (like EvalError). Ideally in the future this would be a unique, easily googleable error ID (like rustc). * "trace:" is now just "…". This assumes error contexts start with something like "while doing X". Example before: error: --- AssertionError ---------------------------------------------------------------------------------------- nix at: (7:7) in file: /home/eelco/Dev/nixpkgs/pkgs/applications/misc/hello/default.nix 6| 7| x = assert false; 1; | ^ 8| assertion 'false' failed ----------------------------------------------------- show-trace ----------------------------------------------------- trace: while evaluating the attribute 'x' of the derivation 'hello-2.10' at: (192:11) in file: /home/eelco/Dev/nixpkgs/pkgs/stdenv/generic/make-derivation.nix 191| // (lib.optionalAttrs (!(attrs ? name) && attrs ? pname && attrs ? version)) { 192| name = "${attrs.pname}-${attrs.version}"; | ^ 193| } // (lib.optionalAttrs (stdenv.hostPlatform != stdenv.buildPlatform && !dontAddHostSuffix && (attrs ? name || (attrs ? pname && attrs ? version)))) { Example after: error: assertion 'false' failed at: (7:7) in file: /home/eelco/Dev/nixpkgs/pkgs/applications/misc/hello/default.nix 6| 7| x = assert false; 1; | ^ 8| … while evaluating the attribute 'x' of the derivation 'hello-2.10' at: (192:11) in file: /home/eelco/Dev/nixpkgs/pkgs/stdenv/generic/make-derivation.nix 191| // (lib.optionalAttrs (!(attrs ? name) && attrs ? pname && attrs ? version)) { 192| name = "${attrs.pname}-${attrs.version}"; | ^ 193| } // (lib.optionalAttrs (stdenv.hostPlatform != stdenv.buildPlatform && !dontAddHostSuffix && (attrs ? name || (attrs ? pname && attrs ? version)))) {
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.msg = hintfmt("attribute '%s' missing", name),
.errPos = pos
});
return *a;
}
iterator begin() { return &attrs[0]; }
iterator end() { return &attrs[size_]; }
Attr & operator[](size_t pos)
{
return attrs[pos];
}
void sort();
size_t capacity() { return capacity_; }
/* Returns the attributes in lexicographically sorted order. */
std::vector<const Attr *> lexicographicOrder() const
{
std::vector<const Attr *> res;
res.reserve(size_);
for (size_t n = 0; n < size_; n++)
res.emplace_back(&attrs[n]);
std::sort(res.begin(), res.end(), [](const Attr * a, const Attr * b) {
return (const string &) a->name < (const string &) b->name;
});
return res;
}
friend class EvalState;
};
/* A wrapper around Bindings that ensures that its always in sorted
order at the end. The only way to consume a BindingsBuilder is to
call finish(), which sorts the bindings. */
class BindingsBuilder
{
Bindings * bindings;
public:
// needed by std::back_inserter
using value_type = Attr;
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EvalState & state;
BindingsBuilder(EvalState & state, Bindings * bindings)
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: bindings(bindings), state(state)
{ }
void insert(Symbol name, Value * value, ptr<Pos> pos = ptr(&noPos))
{
insert(Attr(name, value, pos));
}
void insert(const Attr & attr)
{
push_back(attr);
}
void push_back(const Attr & attr)
{
bindings->push_back(attr);
}
Value & alloc(const Symbol & name, ptr<Pos> pos = ptr(&noPos));
Value & alloc(std::string_view name, ptr<Pos> pos = ptr(&noPos));
Bindings * finish()
{
bindings->sort();
return bindings;
}
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Bindings * alreadySorted()
{
return bindings;
}
};
}