find_graph_dependents method of Database results not reproducible

[tngTUDOR]

Current

In a scenario context with:

• multiple databases ni a project, for example a background database and a foreground database,
• the foreground database has inputs from the background database

calling the find_graph_dependents method of the foreground database does not provide the right depencies, unless calling process method.

I have observed this when creating databases as follows:

• create foreground database -> db
• register the database -> db.register()
• create & save new nodes -> db.new_node(...).save()
• create background database -> db_bg
• register the database -> db_bg.register()
• create & save new nodes -> db_bg.new_node(...).save()
• create & save edges from foreground db to background db

using the following deps:

• bw2data 4.3
• bwcalc 2.0
• bw2io 0.9.3

Expected

There is a difference in writing a full database with the write() method and adding nodes .
Is calling the "process" method of the database object a requirement ? Or maybe there is somewhere in the "save" method of activities and exchanges that this is being overlooked ?

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# %%
import bw2data as bd
import bw2calc as bc
import bw2io as bi

# %%
print(bd.__version__)
print(bc.__version__)
print(bi.__version__)

# (4, 3)
# 2.0
# 0.9.3

# %%
bi.remote.install_project("ecoinvent-3.10-biosphere", "bk-project", overwrite_existing=True)

# %%
bd.projects.set_current("bk-project")

# %%
bd.databases

# %%
db = bd.Database('bike')
db.register()

# %%
bd.databases

# %%
# First activity: the bike
data = {
    'code': 'bike',
    'name': 'bike production',
    'location': 'DK',
    'unit': 'bike'
}
bike = db.new_node(**data)
bike.save()


# %%
bike.id 

# 123372841738444800


# %%
db_bg = bd.Database('materials')
db_bg.register()

# %%
# First input
data = {
    'code': 'ng',
    'name': 'natural gas production',
    'location': 'NO',
    'unit': 'MJ'
}

ng = db_bg.new_node(**data)
ng.save()

# Second input
data = {
    'code': 'cf',
    'name': 'carbon fibre production',
    'location': 'DE',
    'unit': 'kg'
}

cf = db_bg.new_node(**data)
cf.save()

# %%
bd.databases

# %%
# We add the exchange to the bike activity, from the carbon fiber prod

bike.new_edge(
    amount=2.5, 
    type='technosphere',
    input=cf
).save()

# %%
# Verify by printing the exchanges of the bike
a_bike = db.get('bike')
for e in a_bike.exchanges():
    print(e)

# %%
# Add another exchange to the carbon fiber production
cf.new_edge(
    amount=237.3,  # plus 58 kWh of electricity, in ecoinvent 3.8 
    uncertainty_type=5, 
    minimum=200, 
    maximum=300, 
    type='technosphere',
    input=ng,
).save()


# %%
# dependent dbs
db.find_graph_dependents()

# {'bike'}

# %%
db.metadata['depends']

# [ ]

# %%
db.process()

# %%
db.find_graph_dependents()

# {'bike', 'materials'}


# %%
db.metadata['depends']

# ['materials']