fish-shell/src/autoload.h

// The classes responsible for autoloading functions and completions.
#ifndef FISH_AUTOLOAD_H
#define FISH_AUTOLOAD_H

#include <pthread.h>
#include <time.h>

#include <set>
#include <unordered_set>

#include "common.h"
#include "env.h"
#include "lru.h"
#include "wutil.h"

/// Record of an attempt to access a file.
struct file_access_attempt_t {
    /// If filled, the file ID of the checked file.
    /// Otherwise the file did not exist or was otherwise inaccessible.
    /// Note that this will never contain kInvalidFileID.
    maybe_t<file_id_t> file_id;

    /// When we last checked the file.
    time_t last_checked;

    /// Whether or not we believe we can access this file.
    bool accessible() const { return file_id.has_value(); }
};
file_access_attempt_t access_file(const wcstring &path, int mode);

struct autoload_function_t {
    explicit autoload_function_t(bool placeholder)
        : access(), is_loaded(false), is_placeholder(placeholder) {}

    /// The last access attempt recorded
    file_access_attempt_t access;
    /// Have we actually loaded this function?
    bool is_loaded;
    /// Whether we are a placeholder that stands in for "no such function". If this is true, then
    /// is_loaded must be false.
    bool is_placeholder;
};

class environment_t;

/// Class representing a path from which we can autoload and the autoloaded contents.
class autoload_t : public lru_cache_t<autoload_t, autoload_function_t> {
   private:
    /// Lock for thread safety.
    std::mutex lock;
    /// The environment variable name.
    const wcstring env_var_name;
    /// The paths from which to autoload, or missing if none.
    maybe_t<wcstring_list_t> paths;
    /// A table containing all the files that are currently being loaded.
    /// This is here to help prevent recursion.
    std::unordered_set<wcstring> is_loading_set;

    void remove_all_functions() { this->evict_all_nodes(); }

    bool locate_file_and_maybe_load_it(const wcstring &cmd, bool really_load, bool reload,
                                       const wcstring_list_t &path_list);

    autoload_function_t *get_autoloaded_function_with_creation(const wcstring &cmd,
                                                               bool allow_eviction);

   public:
    // CRTP override
    void entry_was_evicted(wcstring key, autoload_function_t node);

    // Create an autoload_t for the given environment variable name.
    explicit autoload_t(wcstring env_var_name_var);

    /// Autoload the specified file, if it exists in the specified path. Do not load it multiple
    /// times unless its timestamp changes or parse_util_unload is called.
    /// @param cmd the filename to search for. The suffix '.fish' is always added to this name
    /// @param reload wheter to recheck file timestamps on already loaded files
    int load(const wcstring &cmd, bool reload);

    /// Check whether we have tried loading the given command. Does not do any I/O.
    bool has_tried_loading(const wcstring &cmd);

    /// Tell the autoloader that the specified file, in the specified path, is no longer loaded.
    /// Returns non-zero if the file was removed, zero if the file had not yet been loaded
    int unload(const wcstring &cmd);

    /// Check whether the given command could be loaded, but do not load it.
    bool can_load(const wcstring &cmd, const environment_t &vars);

    /// Invalidates all entries. Uesd when the underlying path variable changes.
    void invalidate();
};
#endif