Allow configurable expand to SensorThings provider (#1879)

* Allow configurable expand to SensorThings provider

* Update license year

Author: webb-ben

docs/source/data-publishing/ogcapi-features.rst

@@ -667,6 +667,10 @@ If ``intralink`` is true for an adjacent STA provider collection within a
 pygeoapi instance, the expanded entity is instead represented by an intra-pygeoapi
 link to the other entity or it's ``uri_field`` if declared.
 
+Additionally there is the optional field ``expand``. This field will overwrite the default
+pygeoapi expand behavior and instead implement the configured expand strategy. This is
+particularly useful if you have Datastreams with many observations.
+
 .. code-block:: yaml
 
    providers:
@@ -677,6 +681,7 @@ link to the other entity or it's ``uri_field`` if declared.
          entity: Datastreams
          time_field: phenomenonTime
          intralink: true
+         expand: Thing/Locations,Observations($select=result,phenomenonTime;$orderby=phenomenonTime desc;$top=1)
 
 If all three entities are configured, the STA provider will represent a complete STA
 endpoint as OGC-API feature collections. The ``Things`` features will include links

pygeoapi/provider/sensorthings.py

@@ -3,7 +3,7 @@
 # Authors: Benjamin Webb <benjamin.miller.webb@gmail.com>
 # Authors: Tom Kralidis <tomkralidis@gmail.com>
 #
-# Copyright (c) 2023 Benjamin Webb
+# Copyright (c) 2024 Benjamin Webb
 # Copyright (c) 2022 Tom Kralidis
 #
 # Permission is hereby granted, free of charge, to any person
@@ -518,6 +518,10 @@ def _generate_mappings(self, provider_def: dict):
             LOGGER.debug('Using default @iot.id for id field')
             self.id_field = '@iot.id'
 
+        # Custom expand
+        if provider_def.get('expand'):
+            EXPAND[self.entity] = provider_def['expand']
+
         # Create intra-links
         self.intralink = provider_def.get('intralink', False)
         if self.intralink and provider_def.get('rel_link'):

tests/test_sensorthings_provider.py

@@ -2,7 +2,7 @@
 #
 # Authors: Benjamin Webb <bwebb@lincolninst.edu>
 #
-# Copyright (c) 2022 Benjamin Webb
+# Copyright (c) 2024 Benjamin Webb
 #
 # Permission is hereby granted, free of charge, to any person
 # obtaining a copy of this software and associated documentation
@@ -138,3 +138,27 @@ def test_get(config):
     assert result['id'] == '9'
     assert result['properties']['name'] == 'Depth Below Surface'
     assert isinstance(result['properties']['Thing'], dict)
+
+
+def test_custom_expand(config):
+    p = SensorThingsProvider(config)
+    fields = p.get_fields()
+    assert 'Observations' in fields
+    assert 'ObservedProperty' in fields
+    assert 'Sensor' in fields
+
+    config['expand'] = 'Thing/Locations'
+    p = SensorThingsProvider(config)
+    fields = p.get_fields()
+    assert len(fields) == 12
+    assert 'Observations' not in fields
+    assert 'ObservedProperty' not in fields
+    assert 'Sensor' not in fields
+
+    config['expand'] = 'Thing/Locations,Observations'
+    p = SensorThingsProvider(config)
+    fields = p.get_fields()
+    assert len(fields) == 14
+    assert 'Observations' in fields
+    assert 'ObservedProperty' not in fields
+    assert 'Sensor' not in fields