migrate_subnet_limit_to_default

Author: JohnReedV

pallets/subtensor/src/macros/hooks.rs

@@ -135,7 +135,9 @@ mod hooks {
                 // Migrate to fix root counters
                 .saturating_add(migrations::migrate_fix_root_tao_and_alpha_in::migrate_fix_root_tao_and_alpha_in::<T>())
                 // Migrate Immunity Period
-                .saturating_add(migrations::migrate_network_immunity_period::migrate_network_immunity_period::<T>());
+                .saturating_add(migrations::migrate_network_immunity_period::migrate_network_immunity_period::<T>())
+                // Migrate Subnet Limit
+                .saturating_add(migrations::migrate_subnet_limit_to_default::migrate_subnet_limit_to_default::<T>());
 
             weight
         }

pallets/subtensor/src/migrations/migrate_subnet_limit_to_default.rs

@@ -0,0 +1,47 @@
+use super::*;
+use frame_support::{traits::Get, weights::Weight};
+use log;
+use scale_info::prelude::string::String;
+
+pub fn migrate_subnet_limit_to_default<T: Config>() -> Weight {
+    let mig_name: Vec<u8> = b"subnet_limit_to_default".to_vec();
+
+    // 1 read: HasMigrationRun flag
+    let mut total_weight = T::DbWeight::get().reads(1);
+
+    // Run once guard
+    if HasMigrationRun::<T>::get(&mig_name) {
+        log::info!(
+            "Migration '{}' already executed - skipping",
+            String::from_utf8_lossy(&mig_name)
+        );
+        return total_weight;
+    }
+    log::info!("Running migration '{}'", String::from_utf8_lossy(&mig_name));
+
+    // Read current and compute target default
+    let current: u16 = SubnetLimit::<T>::get();
+    let target: u16 = DefaultSubnetLimit::<T>::get();
+
+    if current != target {
+        total_weight = total_weight.saturating_add(T::DbWeight::get().reads_writes(1, 1));
+        SubnetLimit::<T>::put(target);
+        log::info!("SubnetLimit updated: {} -> {}", current, target);
+    } else {
+        total_weight = total_weight.saturating_add(T::DbWeight::get().reads(1));
+        log::info!(
+            "SubnetLimit already equals default ({}), no update performed.",
+            target
+        );
+    }
+
+    // Mark as done
+    HasMigrationRun::<T>::insert(&mig_name, true);
+    total_weight = total_weight.saturating_add(T::DbWeight::get().writes(1));
+
+    log::info!(
+        "Migration '{}' completed",
+        String::from_utf8_lossy(&mig_name)
+    );
+    total_weight
+}

pallets/subtensor/src/migrations/mod.rs

@@ -37,6 +37,7 @@ pub mod migrate_set_registration_enable;
 pub mod migrate_set_subtoken_enabled;
 pub mod migrate_stake_threshold;
 pub mod migrate_subnet_identities_to_v3;
+pub mod migrate_subnet_limit_to_default;
 pub mod migrate_subnet_symbols;
 pub mod migrate_subnet_volume;
 pub mod migrate_to_v1_separate_emission;

pallets/subtensor/src/tests/migration.rs

@@ -1252,3 +1252,52 @@ fn test_migrate_crv3_v2_to_timelocked() {
         assert_eq!(round2, round);
     });
 }
+
+#[test]
+fn test_migrate_subnet_limit_to_default() {
+    new_test_ext(1).execute_with(|| {
+        // ------------------------------
+        // 0. Constants / helpers
+        // ------------------------------
+        const MIG_NAME: &[u8] = b"subnet_limit_to_default";
+
+        // Compute a non-default value safely
+        let default: u16 = DefaultSubnetLimit::<Test>::get();
+        let not_default: u16 = default.wrapping_add(1);
+
+        // ------------------------------
+        // 1. Pre-state: ensure a non-default value is stored
+        // ------------------------------
+        SubnetLimit::<Test>::put(not_default);
+        assert_eq!(
+            SubnetLimit::<Test>::get(),
+            not_default,
+            "precondition failed: SubnetLimit should be non-default before migration"
+        );
+
+        assert!(
+            !HasMigrationRun::<Test>::get(MIG_NAME.to_vec()),
+            "migration flag should be false before run"
+        );
+
+        // ------------------------------
+        // 2. Run migration
+        // ------------------------------
+        let w = crate::migrations::migrate_subnet_limit_to_default::migrate_subnet_limit_to_default::<Test>();
+        assert!(!w.is_zero(), "weight must be non-zero");
+
+        // ------------------------------
+        // 3. Verify results
+        // ------------------------------
+        assert!(
+            HasMigrationRun::<Test>::get(MIG_NAME.to_vec()),
+            "migration flag not set"
+        );
+
+        assert_eq!(
+            SubnetLimit::<Test>::get(),
+            default,
+            "SubnetLimit should be reset to the configured default"
+        );
+    });
+}