program: make it easer to fill min order size orders (#1799)

* program: make it easer to fill min order size orders

* reduce only tweak

* CHANGELOG

Author: crispheaney

CHANGELOG.md

@@ -15,6 +15,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ### Fixes
 
+- program: make it easier to fill step size orders ([#1799](https://github.com/drift-labs/protocol-v2/pull/1799))
 - program: relax fee tier constraints for maker ([#1876](https://github.com/drift-labs/protocol-v2/pull/1876))
 
 ### Breaking

programs/drift/src/controller/orders.rs

@@ -2172,12 +2172,13 @@ pub fn fulfill_perp_order_with_amm(
     };
 
     // if user position is less than min order size, step size is the threshold
-    let amm_size_threshold =
-        if existing_base_asset_amount.unsigned_abs() > market.amm.min_order_size {
-            market.amm.min_order_size
-        } else {
-            market.amm.order_step_size
-        };
+    let amm_size_threshold = if !user.orders[order_index].reduce_only
+        && existing_base_asset_amount.unsigned_abs() > market.amm.min_order_size
+    {
+        market.amm.min_order_size
+    } else {
+        market.amm.order_step_size
+    };
 
     if base_asset_amount < amm_size_threshold {
         // if is an actual swap (and not amm jit order) then msg!

programs/drift/src/validation/order.rs

@@ -142,7 +142,7 @@ fn validate_limit_order(
         order,
         market.amm.order_step_size,
         market.amm.min_order_size,
-        order.reduce_only,
+        order.reduce_only || order.is_jit_maker(),
     )?;
 
     if order.price == 0 && !order.has_oracle_price_offset() {
@@ -339,7 +339,7 @@ fn validate_base_asset_amount(
     order: &Order,
     step_size: u64,
     min_order_size: u64,
-    reduce_only: bool,
+    reduce_only_or_jit_maker: bool,
 ) -> DriftResult {
     if order.base_asset_amount == 0 {
         msg!("Order base_asset_amount cant be 0");
@@ -355,7 +355,7 @@ fn validate_base_asset_amount(
     )?;
 
     validate!(
-        reduce_only || order.base_asset_amount >= min_order_size,
+        reduce_only_or_jit_maker || order.base_asset_amount >= min_order_size,
         ErrorCode::InvalidOrderMinOrderSize,
         "Order base_asset_amount ({}) < min_order_size ({})",
         order.base_asset_amount,