Fix #8

Author: cmutel

README.md

@@ -59,6 +59,10 @@ You don't need to use library for substitution, that already works natively in B
 
 There is currently no built-in functionality to determine if an edge is functional based on its attributes - instead we rely on the label `functional` being manually specified. You can write a function to iterate over datasets and label the functional edges in whatever fashion you choose.
 
+### Specifying `code` values for allocated products
+
+When writing a multifunctional process, we need to create artificial edges to allocated processes which don't exist yet. You can't therefore specify the `code` of such an edge - but you can tell the system what code the allocated process *should have* upon allocation using the `desired_code` edge attribute. See `dev/basic_example.ipynb` for a simple example.
+
 ### Built-in allocation functions
 
 `multifunctional` includes the following built-in property-based allocation functions:

multifunctional/allocation.py

@@ -58,7 +58,10 @@ def generic_allocation(
             del exc["code"]
 
         try:
-            process_code = exc["mf_allocated_process_code"]
+            if "desired_code" in exc:
+                process_code = exc["desired_code"]
+            else:
+                process_code = exc["mf_allocated_process_code"]
         except KeyError:
             process_code = exc["mf_allocated_process_code"] = uuid4().hex
             change = True

tests/fixtures/basic.py

@@ -15,6 +15,7 @@
             {
                 "functional": True,
                 "type": "production",
+                "desired_code": "my favorite code",
                 "name": "first product - 1",
                 "unit": "kg",
                 "amount": 4,

tests/test_allocation.py

@@ -38,8 +38,8 @@ def check_basic_allocation_results(factor_1, factor_2, database):
         assert nodes[2][key] == value
 
     expected = {
-        "input": nodes[2].key,
-        "output": nodes[2].key,
+        "input": ("basic", "my favorite code"),
+        "output": ("basic", "my favorite code"),
         "amount": 4,
         "type": "production",
         "functional": True,
@@ -51,7 +51,7 @@ def check_basic_allocation_results(factor_1, factor_2, database):
 
     expected = {
         "input": nodes[0].key,
-        "output": nodes[2].key,
+        "output": ("basic", "my favorite code"),
         "amount": factor_1,
         "type": "biosphere",
     }