Use of reduce without initializers in asset_selection.py

[axellpadilla]

What's the issue?

There are multiple occurrences of reduce being used without an initializer in dagster/python_modules/dagster/dagster/_core/definitions/asset_selection.py.
This can cause an error when an empty selection is used, I had some instances when using for example job_def.selection.resolve where I needed to manually fix this.

TypeError( "reduce() of empty iterable with no initial value")

For example:

dagster/python_modules/dagster/dagster/_core/definitions/asset_selection.py

Lines 882 to 894 in 28bbf98

	reduce(
	operator.or_,
	[
	{asset_key}
	| fetch_connected(
	item=asset_key,
	graph=asset_graph.asset_dep_graph,
	direction="downstream",
	depth=self.depth,
	)
	for asset_key in selection
	],
	),

)

This should be modified to include an initializer to prevent errors with empty sequences:

Expected use:

dagster/python_modules/dagster/dagster/_core/definitions/asset_selection.py

Lines 1109 to 1122 in 28bbf98

	reduce(
	operator.or_,
	[
	{asset_key}
	| fetch_connected(
	item=asset_key,
	graph=asset_graph.asset_dep_graph,
	direction="upstream",
	depth=depth,
	)
	for asset_key in selection
	],
	set(),
	),

What did you expect to happen?

Empty set result like expected use:

dagster/python_modules/dagster/dagster/_core/definitions/asset_selection.py

Lines 1109 to 1122 in 28bbf98

	reduce(
	operator.or_,
	[
	{asset_key}
	| fetch_connected(
	item=asset_key,
	graph=asset_graph.asset_dep_graph,
	direction="upstream",
	depth=depth,
	)
	for asset_key in selection
	],
	set(),
	),

How to reproduce?

Any selection resolved to empty set.

Dagster version

1.9.6

Deployment type

None

Deployment details

No response

Additional information

No response

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