fix(Core/Spells): Prevent extra attack abilities from chain-proccing (#24806)

Co-authored-by: blinkysc <blinkysc@users.noreply.github.com>
Co-authored-by: trickerer <onlysuffering@gmail.com>

src/server/game/Spells/Auras/SpellAuraEffects.cpp

@@ -1239,6 +1239,29 @@ bool AuraEffect::CheckEffectProc(AuraApplication* aurApp, ProcEventInfo& eventIn
             if (GetCasterGUID() != eventInfo.GetActor()->GetGUID())
                 return false;
             break;
+        case SPELL_AURA_PROC_TRIGGER_SPELL:
+        case SPELL_AURA_PROC_TRIGGER_SPELL_WITH_VALUE:
+        {
+            // Don't proc extra attacks while already processing extra attack spell
+            uint32 triggerSpellId = m_spellInfo->Effects[GetEffIndex()].TriggerSpell;
+            if (SpellInfo const* triggeredSpellInfo = sSpellMgr->GetSpellInfo(triggerSpellId))
+            {
+                if (triggeredSpellInfo->HasEffect(SPELL_EFFECT_ADD_EXTRA_ATTACKS))
+                {
+                    uint32 lastExtraAttackSpell = eventInfo.GetActor()->GetLastExtraAttackSpell();
+
+                    // Patch 1.12.0(?) extra attack abilities can no longer chain proc themselves
+                    if (lastExtraAttackSpell == triggerSpellId)
+                        return false;
+
+                    // Patch 2.2.0 Sword Specialization (Warrior, Rogue) extra attack can no longer proc additional extra attacks
+                    // 3.3.5 Sword Specialization (Warrior), Hack and Slash (Rogue)
+                    if (lastExtraAttackSpell == SPELL_SWORD_SPECIALIZATION || lastExtraAttackSpell == SPELL_HACK_AND_SLASH)
+                        return false;
+                }
+            }
+            break;
+        }
         default:
             break;
     }

src/test/mocks/ProcChanceTestHelper.h

@@ -282,6 +282,45 @@ public:
         return false; // Allow proc
     }
 
+    // =============================================================================
+    // Extra Attack Chain-Proc Prevention - simulates SpellAuraEffects.cpp:1245-1261
+    // =============================================================================
+
+    /**
+     * @brief Configuration for simulating extra attack chain-proc prevention
+     */
+    struct ExtraAttackProcConfig
+    {
+        bool triggeredSpellHasExtraAttacks = false; // triggeredSpellInfo->HasEffect(SPELL_EFFECT_ADD_EXTRA_ATTACKS)
+        uint32 triggerSpellId = 0;                  // m_spellInfo->Effects[GetEffIndex()].TriggerSpell
+        uint32 lastExtraAttackSpell = 0;            // eventInfo.GetActor()->GetLastExtraAttackSpell()
+    };
+
+    /**
+     * @brief Simulate extra attack chain-proc prevention from CheckEffectProc
+     * Returns true if proc should be blocked
+     *
+     * @param config Extra attack proc configuration
+     * @return true if proc should be blocked
+     */
+    static bool ShouldBlockExtraAttackChainProc(ExtraAttackProcConfig const& config)
+    {
+        // Only applies when the triggered spell grants extra attacks
+        if (!config.triggeredSpellHasExtraAttacks)
+            return false;
+
+        // Patch 1.12.0(?) extra attack abilities can no longer chain proc themselves
+        if (config.lastExtraAttackSpell == config.triggerSpellId)
+            return true;
+
+        // Patch 2.2.0 Sword Specialization (Warrior, Rogue) extra attack can no longer proc additional extra attacks
+        // 3.3.5 Sword Specialization (Warrior), Hack and Slash (Rogue)
+        if (config.lastExtraAttackSpell == 16459 || config.lastExtraAttackSpell == 66923)
+            return true;
+
+        return false;
+    }
+
     // =============================================================================
     // DisableEffectsMask - simulates SpellAuras.cpp:2244-2258
     // =============================================================================

src/test/server/game/Spells/ExtraAttackChainProcTest.cpp

@@ -0,0 +1,149 @@
+/*
+ * This file is part of the AzerothCore Project. See AUTHORS file for Copyright information
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
+ * more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program. If not, see <http://www.gnu.org/licenses/>.
+ */
+
+/**
+ * @file ExtraAttackChainProcTest.cpp
+ * @brief Unit tests for extra attack chain-proc prevention
+ *
+ * Tests the logic from SpellAuraEffects.cpp:1245-1261 (CheckEffectProc):
+ * - Self-chain prevention (same extra attack spell can't proc itself)
+ * - Cross-chain prevention (Sword Specialization / Hack and Slash block all extra attack procs)
+ * - Non-blacklisted extra attack spells allow cross-proccing
+ * - Non-extra-attack procs are unaffected by the guard
+ */
+
+#include "ProcChanceTestHelper.h"
+#include "gtest/gtest.h"
+
+using namespace testing;
+
+// Use existing enum from Unit.h: SPELL_SWORD_SPECIALIZATIONIALIZATION (16459), SPELL_HACK_AND_SLASH (66923)
+constexpr uint32 SPELL_RECKONING       = 32746; // Reckoning (Paladin)
+constexpr uint32 SPELL_HAND_OF_JUSTICE = 15601; // Hand of Justice extra attack
+
+class ExtraAttackChainProcTest : public ::testing::Test
+{
+protected:
+    ProcChanceTestHelper::ExtraAttackProcConfig MakeConfig(
+        bool hasExtraAttacks, uint32 triggerSpellId, uint32 lastExtraAttack)
+    {
+        ProcChanceTestHelper::ExtraAttackProcConfig config;
+        config.triggeredSpellHasExtraAttacks = hasExtraAttacks;
+        config.triggerSpellId = triggerSpellId;
+        config.lastExtraAttackSpell = lastExtraAttack;
+        return config;
+    }
+};
+
+// =============================================================================
+// Normal proc (no extra attack in progress)
+// =============================================================================
+
+TEST_F(ExtraAttackChainProcTest, NormalProc_AllowedWhenNoExtraAttackInProgress)
+{
+    // lastExtraAttackSpell == 0 means no extra attack is executing
+    auto config = MakeConfig(true, SPELL_SWORD_SPECIALIZATION, 0);
+
+    EXPECT_FALSE(ProcChanceTestHelper::ShouldBlockExtraAttackChainProc(config))
+        << "Extra attack proc should be allowed when no extra attack is in progress";
+}
+
+// =============================================================================
+// Self-chain prevention
+// =============================================================================
+
+TEST_F(ExtraAttackChainProcTest, SelfChain_BlockedWhenSameSpell)
+{
+    // Sword Spec trying to proc during its own extra attack
+    auto config = MakeConfig(true, SPELL_SWORD_SPECIALIZATION, SPELL_SWORD_SPECIALIZATION);
+
+    EXPECT_TRUE(ProcChanceTestHelper::ShouldBlockExtraAttackChainProc(config))
+        << "Extra attack spell should not chain-proc itself";
+}
+
+// =============================================================================
+// Cross-chain prevention (blacklisted spells)
+// =============================================================================
+
+TEST_F(ExtraAttackChainProcTest, CrossChain_BlockedBySwordSpecialization)
+{
+    // Reckoning trying to proc during Sword Spec extra attack
+    auto config = MakeConfig(true, SPELL_RECKONING, SPELL_SWORD_SPECIALIZATION);
+
+    EXPECT_TRUE(ProcChanceTestHelper::ShouldBlockExtraAttackChainProc(config))
+        << "Sword Specialization extra attack should block all other extra attack procs";
+}
+
+TEST_F(ExtraAttackChainProcTest, CrossChain_BlockedByHackAndSlash)
+{
+    // Reckoning trying to proc during Hack and Slash extra attack
+    auto config = MakeConfig(true, SPELL_RECKONING, SPELL_HACK_AND_SLASH);
+
+    EXPECT_TRUE(ProcChanceTestHelper::ShouldBlockExtraAttackChainProc(config))
+        << "Hack and Slash extra attack should block all other extra attack procs";
+}
+
+// =============================================================================
+// Non-blacklisted extra attacks allow cross-proccing
+// =============================================================================
+
+TEST_F(ExtraAttackChainProcTest, DifferentExtraAttack_AllowedWhenNotBlacklisted)
+{
+    // Sword Spec trying to proc during Hand of Justice extra attack
+    // Hand of Justice (15601) is not blacklisted, so cross-proc is allowed
+    auto config = MakeConfig(true, SPELL_SWORD_SPECIALIZATION, SPELL_HAND_OF_JUSTICE);
+
+    EXPECT_FALSE(ProcChanceTestHelper::ShouldBlockExtraAttackChainProc(config))
+        << "Non-blacklisted extra attack spells should allow cross-proccing";
+}
+
+// =============================================================================
+// Non-extra-attack procs unaffected
+// =============================================================================
+
+TEST_F(ExtraAttackChainProcTest, NonExtraAttackProc_UnaffectedByExtraAttackState)
+{
+    // A proc that does NOT grant extra attacks should never be blocked,
+    // even during Sword Spec extra attack
+    auto config = MakeConfig(false, 12345, SPELL_SWORD_SPECIALIZATION);
+
+    EXPECT_FALSE(ProcChanceTestHelper::ShouldBlockExtraAttackChainProc(config))
+        << "Non-extra-attack procs should be unaffected by extra attack state";
+}
+
+// =============================================================================
+// Real spell scenarios
+// =============================================================================
+
+TEST_F(ExtraAttackChainProcTest, Reckoning_SelfChainBlocked)
+{
+    // Reckoning (32746) trying to proc during its own extra attack
+    auto config = MakeConfig(true, SPELL_RECKONING, SPELL_RECKONING);
+
+    EXPECT_TRUE(ProcChanceTestHelper::ShouldBlockExtraAttackChainProc(config))
+        << "Reckoning should not chain-proc itself";
+}
+
+TEST_F(ExtraAttackChainProcTest, Reckoning_AllowedDuringHandOfJustice)
+{
+    // Reckoning trying to proc during Hand of Justice extra attack
+    // Hand of Justice is not blacklisted, so Reckoning is allowed
+    auto config = MakeConfig(true, SPELL_RECKONING, SPELL_HAND_OF_JUSTICE);
+
+    EXPECT_FALSE(ProcChanceTestHelper::ShouldBlockExtraAttackChainProc(config))
+        << "Reckoning should be allowed during Hand of Justice extra attack";
+}