lix/src/libcmd/command.hh
John Ericson bc23a44c54 Make command infra less stateful and more regular
Already, we had classes like `BuiltPathsCommand` and `StorePathsCommand`
which provided alternative `run` virtual functions providing the
implementation with more arguments. This was a very nice and easy way to
make writing command; just fill in the virtual functions and it is
fairly clear what to do.

However, exception to this pattern were `Installable{,s}Command`. These
two classes instead just had a field where the installables would be
stored, and various side-effecting `prepare` and `load` machinery too
fill them in. Command would wish out those fields.

This isn't so clear to use.

What this commit does is make those command classes like the others,
with richer `run` functions.

Not only does this restore the pattern making commands easier to write,
it has a number of other benefits:

- `prepare` and `load` are gone entirely! One command just hands just
  hands off to the next.

- `useDefaultInstallables` because `defaultInstallables`. This takes
  over `prepare` for the one case that needs it, and provides enough
  flexiblity to handle `nix repl`'s idiosyncratic migration.

- We can use `ref` instead of `std::shared_ptr`. The former must be
  initialized (so it is like Rust's `Box` rather than `Option<Box>`,
  This expresses the invariant that the installable are in fact
  initialized much better.

  This is possible because since we just have local variables not
  fields, we can stop worrying about the not-yet-initialized case.

- Fewer lines of code! (Finally I have a large refactor that makes the
  number go down not up...)

- `nix repl` is now implemented in a clearer way.

The last item deserves further mention. `nix repl` is not like the other
installable commands because instead working from once-loaded
installables, it needs to be able to load them again and again.

To properly support this, we make a new superclass
`RawInstallablesCommand`. This class has the argument parsing and
completion logic, but does *not* hand off parsed installables but
instead just the raw string arguments.

This is exactly what `nix repl` needs, and allows us to instead of
having the logic awkwardly split between `prepare`,
`useDefaultInstallables,` and `load`, have everything right next to each
other. I think this will enable future simplifications of that argument
defaulting logic, but I am saving those for a future PR --- best to keep
code motion and more complicated boolean expression rewriting separate
steps.

The "diagnostic ignored `-Woverloaded-virtual`" pragma helps because C++
doesn't like our many `run` methods. In our case, we don't mind the
shadowing it all --- it is *intentional* that the derived class only
provides a `run` method, and doesn't call any of the overridden `run`
methods.

Helps with https://github.com/NixOS/rfcs/pull/134
2023-03-15 16:29:07 -04:00

294 lines
7.1 KiB
C++

#pragma once
#include "installables.hh"
#include "args.hh"
#include "common-eval-args.hh"
#include "path.hh"
#include "flake/lockfile.hh"
#include <optional>
namespace nix {
extern std::string programPath;
extern char * * savedArgv;
class EvalState;
struct Pos;
class Store;
static constexpr Command::Category catSecondary = 100;
static constexpr Command::Category catUtility = 101;
static constexpr Command::Category catNixInstallation = 102;
static constexpr auto installablesCategory = "Options that change the interpretation of [installables](@docroot@/command-ref/new-cli/nix.md#installables)";
struct NixMultiCommand : virtual MultiCommand, virtual Command
{
nlohmann::json toJSON() override;
};
// For the overloaded run methods
#pragma GCC diagnostic ignored "-Woverloaded-virtual"
/* A command that requires a Nix store. */
struct StoreCommand : virtual Command
{
StoreCommand();
void run() override;
ref<Store> getStore();
virtual ref<Store> createStore();
virtual void run(ref<Store>) = 0;
private:
std::shared_ptr<Store> _store;
};
/* A command that copies something between `--from` and `--to`
stores. */
struct CopyCommand : virtual StoreCommand
{
std::string srcUri, dstUri;
CopyCommand();
ref<Store> createStore() override;
ref<Store> getDstStore();
};
struct EvalCommand : virtual StoreCommand, MixEvalArgs
{
bool startReplOnEvalErrors = false;
bool ignoreExceptionsDuringTry = false;
EvalCommand();
~EvalCommand();
ref<Store> getEvalStore();
ref<EvalState> getEvalState();
private:
std::shared_ptr<Store> evalStore;
std::shared_ptr<EvalState> evalState;
};
struct MixFlakeOptions : virtual Args, EvalCommand
{
flake::LockFlags lockFlags;
std::optional<std::string> needsFlakeInputCompletion = {};
MixFlakeOptions();
virtual std::vector<std::string> getFlakesForCompletion()
{ return {}; }
void completeFlakeInput(std::string_view prefix);
void completionHook() override;
};
struct SourceExprCommand : virtual Args, MixFlakeOptions
{
std::optional<Path> file;
std::optional<std::string> expr;
SourceExprCommand();
Installables parseInstallables(
ref<Store> store, std::vector<std::string> ss);
ref<Installable> parseInstallable(
ref<Store> store, const std::string & installable);
virtual Strings getDefaultFlakeAttrPaths();
virtual Strings getDefaultFlakeAttrPathPrefixes();
void completeInstallable(std::string_view prefix);
};
struct MixReadOnlyOption : virtual Args
{
MixReadOnlyOption();
};
/* Like InstallablesCommand but the installables are not loaded */
struct RawInstallablesCommand : virtual Args, SourceExprCommand
{
RawInstallablesCommand();
virtual void run(ref<Store> store, std::vector<std::string> && rawInstallables) = 0;
void run(ref<Store> store) override;
// FIXME make const after CmdRepl's override is fixed up
virtual void applyDefaultInstallables(std::vector<std::string> & rawInstallables);
bool readFromStdIn = false;
std::vector<std::string> getFlakesForCompletion() override;
private:
std::vector<std::string> rawInstallables;
};
/* A command that operates on a list of "installables", which can be
store paths, attribute paths, Nix expressions, etc. */
struct InstallablesCommand : RawInstallablesCommand
{
virtual void run(ref<Store> store, Installables && installables) = 0;
void run(ref<Store> store, std::vector<std::string> && rawInstallables) override;
};
/* A command that operates on exactly one "installable" */
struct InstallableCommand : virtual Args, SourceExprCommand
{
InstallableCommand();
virtual void run(ref<Store> store, ref<Installable> installable) = 0;
void run(ref<Store> store) override;
std::vector<std::string> getFlakesForCompletion() override
{
return {_installable};
}
private:
std::string _installable{"."};
};
struct MixOperateOnOptions : virtual Args
{
OperateOn operateOn = OperateOn::Output;
MixOperateOnOptions();
};
/* A command that operates on zero or more store paths. */
struct BuiltPathsCommand : InstallablesCommand, virtual MixOperateOnOptions
{
private:
bool recursive = false;
bool all = false;
protected:
Realise realiseMode = Realise::Derivation;
public:
BuiltPathsCommand(bool recursive = false);
virtual void run(ref<Store> store, BuiltPaths && paths) = 0;
void run(ref<Store> store, Installables && installables) override;
void applyDefaultInstallables(std::vector<std::string> & rawInstallables) override;
};
struct StorePathsCommand : public BuiltPathsCommand
{
StorePathsCommand(bool recursive = false);
virtual void run(ref<Store> store, StorePaths && storePaths) = 0;
void run(ref<Store> store, BuiltPaths && paths) override;
};
/* A command that operates on exactly one store path. */
struct StorePathCommand : public StorePathsCommand
{
virtual void run(ref<Store> store, const StorePath & storePath) = 0;
void run(ref<Store> store, StorePaths && storePaths) override;
};
/* A helper class for registering commands globally. */
struct RegisterCommand
{
typedef std::map<std::vector<std::string>, std::function<ref<Command>()>> Commands;
static Commands * commands;
RegisterCommand(std::vector<std::string> && name,
std::function<ref<Command>()> command)
{
if (!commands) commands = new Commands;
commands->emplace(name, command);
}
static nix::Commands getCommandsFor(const std::vector<std::string> & prefix);
};
template<class T>
static RegisterCommand registerCommand(const std::string & name)
{
return RegisterCommand({name}, [](){ return make_ref<T>(); });
}
template<class T>
static RegisterCommand registerCommand2(std::vector<std::string> && name)
{
return RegisterCommand(std::move(name), [](){ return make_ref<T>(); });
}
struct MixProfile : virtual StoreCommand
{
std::optional<Path> profile;
MixProfile();
/* If 'profile' is set, make it point at 'storePath'. */
void updateProfile(const StorePath & storePath);
/* If 'profile' is set, make it point at the store path produced
by 'buildables'. */
void updateProfile(const BuiltPaths & buildables);
};
struct MixDefaultProfile : MixProfile
{
MixDefaultProfile();
};
struct MixEnvironment : virtual Args {
StringSet keep, unset;
Strings stringsEnv;
std::vector<char*> vectorEnv;
bool ignoreEnvironment;
MixEnvironment();
/* Modify global environ based on ignoreEnvironment, keep, and unset. It's expected that exec will be called before this class goes out of scope, otherwise environ will become invalid. */
void setEnviron();
};
void completeFlakeRef(ref<Store> store, std::string_view prefix);
void completeFlakeRefWithFragment(
ref<EvalState> evalState,
flake::LockFlags lockFlags,
Strings attrPathPrefixes,
const Strings & defaultFlakeAttrPaths,
std::string_view prefix);
std::string showVersions(const std::set<std::string> & versions);
void printClosureDiff(
ref<Store> store,
const StorePath & beforePath,
const StorePath & afterPath,
std::string_view indent);
}