nix/src/libexpr/flake/flake.hh

#pragma once

#include "types.hh"
#include "flakeref.hh"
#include "lockfile.hh"
#include "value.hh"

namespace nix {

class EvalState;

namespace fetchers { struct Tree; }

namespace flake {

struct FlakeInput;

typedef std::map<FlakeId, FlakeInput> FlakeInputs;

/* FlakeInput is the 'Flake'-level parsed form of the "input" entries
 * in the flake file.
 *
 * A FlakeInput is normally constructed by the 'parseFlakeInput'
 * function which parses the input specification in the '.flake' file
 * to create a 'FlakeRef' (a fetcher, the fetcher-specific
 * representation of the input specification, and possibly the fetched
 * local store path result) and then creating this FlakeInput to hold
 * that FlakeRef, along with anything that might override that
 * FlakeRef (like command-line overrides or "follows" specifications).
 *
 * A FlakeInput is also sometimes constructed directly from a FlakeRef
 * instead of starting at the flake-file input specification
 * (e.g. overrides, follows, and implicit inputs).
 *
 * A FlakeInput will usually have one of either "ref" or "follows"
 * set.  If not otherwise specified, a "ref" will be generated to a
 * 'type="indirect"' flake, which is treated as simply the name of a
 * flake to be resolved in the registry.
 */

struct FlakeInput
{
    std::optional<FlakeRef> ref;
    bool isFlake = true;  // true = process flake to get outputs, false = (fetched) static source path
    std::optional<InputPath> follows;
    bool absolute = false; // whether 'follows' is relative to the flake root
    FlakeInputs overrides;
};

struct ConfigFile
{
    using ConfigValue = std::variant<std::string, int64_t, Explicit<bool>, std::vector<std::string>>;

    std::map<std::string, ConfigValue> settings;

    void apply();
};

/* The contents of a flake.nix file. */
struct Flake
{
    FlakeRef originalRef;   // the original flake specification (by the user)
    FlakeRef resolvedRef;   // registry references and caching resolved to the specific underlying flake
    FlakeRef lockedRef;     // the specific local store result of invoking the fetcher
    std::optional<std::string> description;
    std::shared_ptr<const fetchers::Tree> sourceInfo;
    FlakeInputs inputs;
    ConfigFile config; // 'nixConfig' attribute
    ~Flake();
};

Flake getFlake(EvalState & state, const FlakeRef & flakeRef, bool allowLookup);

/* Fingerprint of a locked flake; used as a cache key. */
typedef Hash Fingerprint;

struct LockedFlake
{
    Flake flake;
    LockFile lockFile;

    Fingerprint getFingerprint() const;
};

struct LockFlags
{
    /* Whether to ignore the existing lock file, creating a new one
       from scratch. */
    bool recreateLockFile = false;

    /* Whether to update the lock file at all. If set to false, if any
       change to the lock file is needed (e.g. when an input has been
       added to flake.nix), you get a fatal error. */
    bool updateLockFile = true;

    /* Whether to write the lock file to disk. If set to true, if the
       any changes to the lock file are needed and the flake is not
       writable (i.e. is not a local Git working tree or similar), you
       get a fatal error. If set to false, Nix will use the modified
       lock file in memory only, without writing it to disk. */
    bool writeLockFile = true;

    /* Whether to use the registries to lookup indirect flake
       references like 'nixpkgs'. */
    bool useRegistries = true;

    /* Whether mutable flake references (i.e. those without a Git
       revision or similar) without a corresponding lock are
       allowed. Mutable flake references with a lock are always
       allowed. */
    bool allowMutable = true;

    /* Whether to commit changes to flake.lock. */
    bool commitLockFile = false;

    /* Flake inputs to be overridden. */
    std::map<InputPath, FlakeRef> inputOverrides;

    /* Flake inputs to be updated. This means that any existing lock
       for those inputs will be ignored. */
    std::set<InputPath> inputUpdates;
};

LockedFlake lockFlake(
    EvalState & state,
    const FlakeRef & flakeRef,
    const LockFlags & lockFlags);

void callFlake(
    EvalState & state,
    const LockedFlake & lockedFlake,
    Value & v);

}

void emitTreeAttrs(
    EvalState & state,
    const fetchers::Tree & tree,
    const fetchers::Input & input,
    Value & v, bool emptyRevFallback = false);

}