fix: revert on non-convergence

Author: iamdefinitelyahuman

contracts/pool-templates/base/SwapTemplateBase.vy

@@ -223,11 +223,14 @@ def get_D(xp: uint256[N_COINS], amp: uint256) -> uint256:
         # Equality with the precision of 1
         if D > Dprev:
             if D - Dprev <= 1:
-                break
+                return D
         else:
             if Dprev - D <= 1:
-                break
-    return D
+                return D
+
+    # convergence typically occurs in 4 rounds or less, this should be unreachable!
+    # if it does happen the pool is borked and LPs can withdraw via `remove_liquidity`
+    raise
 
 
 @view
@@ -408,11 +411,11 @@ def get_y(i: int128, j: int128, x: uint256, xp_: uint256[N_COINS]) -> uint256:
         # Equality with the precision of 1
         if y > y_prev:
             if y - y_prev <= 1:
-                break
+                return y
         else:
             if y_prev - y <= 1:
-                break
-    return y
+                return y
+    raise
 
 
 @view
@@ -639,11 +642,11 @@ def get_y_D(A_: uint256, i: int128, xp: uint256[N_COINS], D: uint256) -> uint256
         # Equality with the precision of 1
         if y > y_prev:
             if y - y_prev <= 1:
-                break
+                return y
         else:
             if y_prev - y <= 1:
-                break
-    return y
+                return y
+    raise
 
 
 @view

contracts/pool-templates/meta/SwapTemplateMeta.vy

@@ -297,11 +297,13 @@ def get_D(xp: uint256[N_COINS], amp: uint256) -> uint256:
         # Equality with the precision of 1
         if D > Dprev:
             if D - Dprev <= 1:
-                break
+                return D
         else:
             if Dprev - D <= 1:
-                break
-    return D
+                return D
+    # convergence typically occurs in 4 rounds or less, this should be unreachable!
+    # if it does happen the pool is borked and LPs can withdraw via `remove_liquidity`
+    raise
 
 
 @view
@@ -475,11 +477,11 @@ def get_y(i: int128, j: int128, x: uint256, xp_: uint256[N_COINS]) -> uint256:
         # Equality with the precision of 1
         if y > y_prev:
             if y - y_prev <= 1:
-                break
+                return y
         else:
             if y_prev - y <= 1:
-                break
-    return y
+                return y
+    raise
 
 
 @view
@@ -854,11 +856,11 @@ def get_y_D(A_: uint256, i: int128, xp: uint256[N_COINS], D: uint256) -> uint256
         # Equality with the precision of 1
         if y > y_prev:
             if y - y_prev <= 1:
-                break
+                return y
         else:
             if y_prev - y <= 1:
-                break
-    return y
+                return y
+    raise
 
 
 @view

contracts/pool-templates/y/SwapTemplateY.vy

@@ -264,11 +264,13 @@ def get_D(xp: uint256[N_COINS], amp: uint256) -> uint256:
         # Equality with the precision of 1
         if D > Dprev:
             if D - Dprev <= 1:
-                break
+                return D
         else:
             if Dprev - D <= 1:
-                break
-    return D
+                return D
+    # convergence typically occurs in 4 rounds or less, this should be unreachable!
+    # if it does happen the pool is borked and LPs can withdraw via `remove_liquidity`
+    raise
 
 
 @view
@@ -437,11 +439,11 @@ def get_y(i: int128, j: int128, x: uint256, xp_: uint256[N_COINS]) -> uint256:
         # Equality with the precision of 1
         if y > y_prev:
             if y - y_prev <= 1:
-                break
+                return y
         else:
             if y_prev - y <= 1:
-                break
-    return y
+                return y
+    raise
 
 
 @view
@@ -726,11 +728,11 @@ def get_y_D(A_: uint256, i: int128, xp: uint256[N_COINS], D: uint256) -> uint256
         # Equality with the precision of 1
         if y > y_prev:
             if y - y_prev <= 1:
-                break
+                return y
         else:
             if y_prev - y <= 1:
-                break
-    return y
+                return y
+    raise
 
 
 @view