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NextAction refactoring to eliminate sentinel arrays and pointers (#1923)

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# Description

This PR aims to refactor the NextAction declaration to achieve two
goals:

## Eliminate C-style sentinel arrays

Currently, a double pointer (`NextAction**`) approach is being used.
This an old pre-C++11 (< 2011) trick before `std::vector<>` became a
thing.
This approach is painful for developers because they constantly need to
declare their `NextAction` arrays as:
```cpp
NextAction::array(0, new NextAction("foo", 1.0f), nullptr)
```
Instead of:
```cpp
{ new NextAction("foo", 1.0f) }
```
The first argument of `NextAction::array` is actually a hack. It is used
to have a named argument so `va_args` can find the remaining arguments.
It is set to 0 everywhere but in fact does nothing. This is very
confusing to people unfamiliar with this antiquated syntax.
The last argument `nullptr` is what we call a sentinel. It's a `nullptr`
because `va_args` is looking for a `nullptr` to stop iterating. It's
also a hack and also leads to confusion.

## Eliminate unnecessary pointers for `NextAction`

Pointers can be used for several reasons, to cite a few:
- Indicate strong, absolute identity.
- Provide strong but transferable ownership (unlike references).
- When a null value is acceptable (`nullptr`).
- When copy is expensive.

`NextAction` meets none of these criteria:
- It has no identity because it is purely behavioural.
- It is never owned by anything as it is passed around and never fetched
from a registry.
- The only situations where it can be `nullptr` are errors that should
in fact throw an `std::invalid_argument` instead.
- They are extremely small objects that embark a single `std::string`
and a single `float`.

Pointers should be avoided when not strictly necessary because they can
quickly lead to undefined behaviour due to unhandled `nullptr`
situations. They also make the syntax heavier due to the necessity to
constantly check for `nullptr`. Finally, they aren't even good for
performance in that situation because shifting a pointer so many times
is likely more expensive than copying such a trivial object.

# End goal

The end goal is to declare `NextAction` arrays this way:
```cpp
{ NextAction("foo", 1.0f) }
```

> [!NOTE]
> Additional note: `NextAction` is nothing but a hacky proxy to an
`Action` constructor. This should eventually be reworked to use handles
instead of strings. This would make copying `NextAction` even cheaper
and remove the need for the extremely heavy stringly typed current
approach. Stringly typed entities are a known anti-pattern so we need to
move on from those.
This commit is contained in:
Nicolas Lebacq
2026-01-06 11:37:39 +00:00
committed by GitHub
parent b13fb7d12a
commit c9cc4324d3
197 changed files with 6795 additions and 4054 deletions
Download Patch File Download Diff File Expand all files Collapse all files

64
src/strategy/druid/FeralDruidStrategy.cpp
View File

@@ -26,65 +26,65 @@ private:
static ActionNode* survival_instincts([[maybe_unused]] PlayerbotAI* botAI)
{
return new ActionNode("survival instincts",
/*P*/ nullptr,
/*A*/ NextAction::array(0, new NextAction("barkskin"), nullptr),
/*C*/ nullptr);
/*P*/ {},
/*A*/ { NextAction("barkskin") },
/*C*/ {});
}
static ActionNode* thorns([[maybe_unused]] PlayerbotAI* botAI)
{
return new ActionNode("thorns",
/*P*/ NextAction::array(0, new NextAction("caster form"), nullptr),
/*A*/ nullptr,
/*C*/ nullptr);
/*P*/ { NextAction("caster form") },
/*A*/ {},
/*C*/ {});
}
static ActionNode* omen_of_clarity([[maybe_unused]] PlayerbotAI* botAI)
{
return new ActionNode("omen of clarity",
/*P*/ NextAction::array(0, new NextAction("caster form"), nullptr),
/*A*/ nullptr,
/*C*/ nullptr);
/*P*/ { NextAction("caster form") },
/*A*/ {},
/*C*/ {});
}
static ActionNode* cure_poison([[maybe_unused]] PlayerbotAI* botAI)
{
return new ActionNode("cure poison",
/*P*/ NextAction::array(0, new NextAction("caster form"), nullptr),
/*A*/ nullptr,
/*C*/ nullptr);
/*P*/ { NextAction("caster form") },
/*A*/ {},
/*C*/ {});
}
static ActionNode* cure_poison_on_party([[maybe_unused]] PlayerbotAI* botAI)
{
return new ActionNode("cure poison on party",
/*P*/ NextAction::array(0, new NextAction("caster form"), nullptr),
/*A*/ nullptr,
/*C*/ nullptr);
/*P*/ { NextAction("caster form") },
/*A*/ {},
/*C*/ {});
}
static ActionNode* abolish_poison([[maybe_unused]] PlayerbotAI* botAI)
{
return new ActionNode("abolish poison",
/*P*/ NextAction::array(0, new NextAction("caster form"), nullptr),
/*A*/ nullptr,
/*C*/ nullptr);
/*P*/ { NextAction("caster form") },
/*A*/ {},
/*C*/ {});
}
static ActionNode* abolish_poison_on_party([[maybe_unused]] PlayerbotAI* botAI)
{
return new ActionNode("abolish poison on party",
/*P*/ NextAction::array(0, new NextAction("caster form"), nullptr),
/*A*/ nullptr,
/*C*/ nullptr);
/*P*/ { NextAction("caster form") },
/*A*/ {},
/*C*/ {});
}
static ActionNode* prowl([[maybe_unused]] PlayerbotAI* botAI)
{
return new ActionNode("prowl",
/*P*/ NextAction::array(0, new NextAction("cat form"), nullptr),
/*A*/ nullptr,
/*C*/ nullptr);
/*P*/ { NextAction("cat form") },
/*A*/ {},
/*C*/ {});
}
};
@@ -98,20 +98,16 @@ void FeralDruidStrategy::InitTriggers(std::vector<TriggerNode*>& triggers)
{
GenericDruidStrategy::InitTriggers(triggers);
// triggers.push_back(new TriggerNode("not facing target", NextAction::array(0, new NextAction("set facing",
// ACTION_NORMAL + 7), nullptr)));
triggers.push_back(new TriggerNode(
"enemy out of melee", NextAction::array(0, new NextAction("reach melee", ACTION_HIGH + 1), nullptr)));
// triggers.push_back(new TriggerNode("enemy too close for melee", NextAction::array(0, new NextAction("move out of
// enemy contact", ACTION_NORMAL + 8), nullptr)));
"enemy out of melee", { NextAction("reach melee", ACTION_HIGH + 1) }));
triggers.push_back(new TriggerNode(
"critical health", NextAction::array(0, new NextAction("survival instincts", ACTION_EMERGENCY + 1), nullptr)));
"critical health", { NextAction("survival instincts", ACTION_EMERGENCY + 1) }));
triggers.push_back(new TriggerNode(
"omen of clarity", NextAction::array(0, new NextAction("omen of clarity", ACTION_HIGH + 9), nullptr)));
"omen of clarity", { NextAction("omen of clarity", ACTION_HIGH + 9) }));
triggers.push_back(new TriggerNode("player has flag",
NextAction::array(0, new NextAction("dash", ACTION_EMERGENCY + 2), nullptr)));
{ NextAction("dash", ACTION_EMERGENCY + 2) }));
triggers.push_back(new TriggerNode("enemy flagcarrier near",
NextAction::array(0, new NextAction("dash", ACTION_EMERGENCY + 2), nullptr)));
{ NextAction("dash", ACTION_EMERGENCY + 2) }));
triggers.push_back(
new TriggerNode("berserk", NextAction::array(0, new NextAction("berserk", ACTION_HIGH + 6), nullptr)));
new TriggerNode("berserk", { NextAction("berserk", ACTION_HIGH + 6) }));
}