lix/src/libutil/config.hh
Eelco Dolstra 737ed88f35
Modularize config settings
Allow global config settings to be defined in multiple Config
classes. For example, this means that libutil can have settings and
evaluator settings can be moved out of libstore. The Config classes
are registered in a new GlobalConfig class to which config files
etc. are applied.

Relevant to https://github.com/NixOS/nix/issues/2009 in that it
removes the need for ad hoc handling of useCaseHack, which was the
underlying cause of that issue.
2018-05-30 13:28:01 +02:00

262 lines
6 KiB
C++

#include <map>
#include <set>
#include "types.hh"
#pragma once
namespace nix {
class Args;
class AbstractSetting;
class JSONPlaceholder;
class JSONObject;
class AbstractConfig
{
protected:
StringMap unknownSettings;
AbstractConfig(const StringMap & initials = {})
: unknownSettings(initials)
{ }
public:
virtual bool set(const std::string & name, const std::string & value) = 0;
struct SettingInfo
{
std::string value;
std::string description;
};
virtual void getSettings(std::map<std::string, SettingInfo> & res, bool overridenOnly = false) = 0;
void applyConfigFile(const Path & path);
virtual void resetOverriden() = 0;
virtual void toJSON(JSONObject & out) = 0;
virtual void convertToArgs(Args & args, const std::string & category) = 0;
void warnUnknownSettings();
void reapplyUnknownSettings();
};
/* A class to simplify providing configuration settings. The typical
use is to inherit Config and add Setting<T> members:
class MyClass : private Config
{
Setting<int> foo{this, 123, "foo", "the number of foos to use"};
Setting<std::string> bar{this, "blabla", "bar", "the name of the bar"};
MyClass() : Config(readConfigFile("/etc/my-app.conf"))
{
std::cout << foo << "\n"; // will print 123 unless overriden
}
};
*/
class Config : public AbstractConfig
{
friend class AbstractSetting;
public:
struct SettingData
{
bool isAlias;
AbstractSetting * setting;
SettingData(bool isAlias, AbstractSetting * setting)
: isAlias(isAlias), setting(setting)
{ }
};
typedef std::map<std::string, SettingData> Settings;
private:
Settings _settings;
public:
Config(const StringMap & initials = {})
: AbstractConfig(initials)
{ }
bool set(const std::string & name, const std::string & value) override;
void addSetting(AbstractSetting * setting);
void getSettings(std::map<std::string, SettingInfo> & res, bool overridenOnly = false) override;
void resetOverriden() override;
void toJSON(JSONObject & out) override;
void convertToArgs(Args & args, const std::string & category) override;
};
class AbstractSetting
{
friend class Config;
public:
const std::string name;
const std::string description;
const std::set<std::string> aliases;
int created = 123;
bool overriden = false;
protected:
AbstractSetting(
const std::string & name,
const std::string & description,
const std::set<std::string> & aliases);
virtual ~AbstractSetting()
{
// Check against a gcc miscompilation causing our constructor
// not to run (https://gcc.gnu.org/bugzilla/show_bug.cgi?id=80431).
assert(created == 123);
}
virtual void set(const std::string & value) = 0;
virtual std::string to_string() = 0;
virtual void toJSON(JSONPlaceholder & out);
virtual void convertToArg(Args & args, const std::string & category);
bool isOverriden() { return overriden; }
};
/* A setting of type T. */
template<typename T>
class BaseSetting : public AbstractSetting
{
protected:
T value;
public:
BaseSetting(const T & def,
const std::string & name,
const std::string & description,
const std::set<std::string> & aliases = {})
: AbstractSetting(name, description, aliases)
, value(def)
{ }
operator const T &() const { return value; }
operator T &() { return value; }
const T & get() const { return value; }
bool operator ==(const T & v2) const { return value == v2; }
bool operator !=(const T & v2) const { return value != v2; }
void operator =(const T & v) { assign(v); }
virtual void assign(const T & v) { value = v; }
void set(const std::string & str) override;
virtual void override(const T & v)
{
overriden = true;
value = v;
}
std::string to_string() override;
void convertToArg(Args & args, const std::string & category) override;
void toJSON(JSONPlaceholder & out) override;
};
template<typename T>
std::ostream & operator <<(std::ostream & str, const BaseSetting<T> & opt)
{
str << (const T &) opt;
return str;
}
template<typename T>
bool operator ==(const T & v1, const BaseSetting<T> & v2) { return v1 == (const T &) v2; }
template<typename T>
class Setting : public BaseSetting<T>
{
public:
Setting(Config * options,
const T & def,
const std::string & name,
const std::string & description,
const std::set<std::string> & aliases = {})
: BaseSetting<T>(def, name, description, aliases)
{
options->addSetting(this);
}
void operator =(const T & v) { this->assign(v); }
};
/* A special setting for Paths. These are automatically canonicalised
(e.g. "/foo//bar/" becomes "/foo/bar"). */
class PathSetting : public BaseSetting<Path>
{
bool allowEmpty;
public:
PathSetting(Config * options,
bool allowEmpty,
const Path & def,
const std::string & name,
const std::string & description,
const std::set<std::string> & aliases = {})
: BaseSetting<Path>(def, name, description, aliases)
, allowEmpty(allowEmpty)
{
options->addSetting(this);
}
void set(const std::string & str) override;
Path operator +(const char * p) const { return value + p; }
void operator =(const Path & v) { this->assign(v); }
};
struct GlobalConfig : public AbstractConfig
{
typedef std::vector<Config*> ConfigRegistrations;
static ConfigRegistrations * configRegistrations;
bool set(const std::string & name, const std::string & value) override;
void getSettings(std::map<std::string, SettingInfo> & res, bool overridenOnly = false) override;
void resetOverriden() override;
void toJSON(JSONObject & out) override;
void convertToArgs(Args & args, const std::string & category) override;
struct Register
{
Register(Config * config);
};
};
extern GlobalConfig globalConfig;
}