Guard against methods-terms as sub-categories

definitions/variable/sdg-indicators/sdg.yaml

@@ -98,12 +98,12 @@
     sdg: 2
     unit: kcal/cap/day
     weight: Population
-- Price|Agriculture|Livestock|Index:
+- Price|Agriculture|Livestock [Index]:
     description: Weighted average price index of livestock
     sdg: 2
     unit: Index (2020 = 1)
     skip-region-aggregation: true
-#     weight: Agricultural Production|Non-Energy
+    shape: Price|Agriculture|Livestock|Index
 - Health|Premature Deaths|PM2.5:
     description: Number of premature deaths associated with increased health risks from
       exposure to air pollution of fine particles with a diameter of 2.5 μm or less (PM2.5)

tests/test_reserved_terms.py

@@ -0,0 +1,17 @@
+from nomenclature import DataStructureDefinition
+
+
+def test_variable_ops_as_square_brackets():
+    # Check that variables use square brackets for operations
+    # https://github.com/IAMconsortium/common-definitions/issues/55
+
+    dsd = DataStructureDefinition("definitions/", dimensions=["variable"])
+
+    error = []
+    for variable, attrs in dsd.variable.items():
+        if reserved_terms := [r for r in ["Index", "Share"] if "|" + r in variable]:
+            error.append(f"Variable '{variable}' -> '[{''.join(reserved_terms)}]'")
+    if error:
+        raise ValueError(
+            f"Found reserved terms in the following variables:\n{'\n - '.join(error)}"
+        )