Error message for inf growth constraints

src/muse/constraints.py

@@ -375,6 +375,15 @@ def max_capacity_expansion(
     # Take the most restrictive constraint
     b = np.minimum(np.minimum(add_cap, total_cap), growth_cap)
 
+    # np.inf values are not allowed in the final constraint - raise error
+    # Will happen if user provides "inf" for all three parameters for any technology
+    if np.isinf(b).any():
+        inf_replacements = b.replacement[np.isinf(b)].values
+        raise ValueError(
+            "Capacity growth constraint cannot be infinite. "
+            f"Check growth constraint parameters for technologies: {inf_replacements}"
+        )
+
     if b.region.dims == ():
         capa = 1
     elif "dst_region" in b.dims:

tests/test_constraints.py

@@ -3,7 +3,7 @@
 import numpy as np
 import pandas as pd
 import xarray as xr
-from pytest import approx, fixture
+from pytest import approx, fixture, raises
 
 from muse.timeslices import drop_timeslice
 from muse.utilities import interpolate_capacity, reduce_assets
@@ -499,6 +499,19 @@ def test_max_capacity_expansion_no_limits(
     assert result is None
 
 
+def test_max_capacity_expansion_infinite_limits(
+    market_demand, capacity, search_space, technologies
+):
+    from muse.constraints import max_capacity_expansion
+
+    # If all limits are infinite, a ValueError should be raised
+    technologies["max_capacity_addition"] = np.inf
+    technologies["max_capacity_growth"] = np.inf
+    technologies["total_capacity_limit"] = np.inf
+    with raises(ValueError):
+        max_capacity_expansion(market_demand, capacity, search_space, technologies)
+
+
 def test_max_production(max_production):
     dims = {"replacement", "asset", "commodity", "timeslice"}
     assert set(max_production.capacity.dims) == dims