Use Enum for Provider role field

Author: duckontheweb

docs/api.rst

@@ -86,6 +86,14 @@ TemporalExtent
    :members:
    :undoc-members:
 
+ProviderRole
+~~~~~~~~~~~~
+
+.. autoclass:: pystac.ProviderRole
+   :members:
+   :undoc-members:
+   :show-inheritance:
+
 Provider
 ~~~~~~~~
 

pystac/__init__.py

@@ -32,6 +32,7 @@
     SpatialExtent,
     TemporalExtent,
     Provider,
+    ProviderRole,
     Summaries,
 )
 from pystac.summaries import RangeSummary

pystac/collection.py

@@ -1,5 +1,6 @@
 from copy import deepcopy
 from datetime import datetime as Datetime
+from enum import Enum
 from pystac.errors import STACTypeError
 from typing import (
     Any,
@@ -408,6 +409,18 @@ def from_items(
         return Extent(spatial=spatial, temporal=temporal, extra_fields=extra_fields)
 
 
+class ProviderRole(str, Enum):
+    """Enumerates the allows values of the Provider "role" field."""
+
+    def __str__(self) -> str:
+        return str(self.value)
+
+    LICENSOR = "licensor"
+    PRODUCER = "producer"
+    PROCESSOR = "processor"
+    HOST = "host"
+
+
 class Provider:
     """Provides information about a provider of STAC data. A provider is any of the
     organizations that captured or processed the content of the collection and therefore
@@ -436,7 +449,7 @@ class Provider:
     information such as processing details for processors and producers,
     hosting details for hosts or basic contact information."""
 
-    roles: Optional[List[str]]
+    roles: Optional[List[ProviderRole]]
     """Optional roles of the provider. Any of
     licensor, producer, processor or host."""
 
@@ -452,7 +465,7 @@ def __init__(
         self,
         name: str,
         description: Optional[str] = None,
-        roles: Optional[List[str]] = None,
+        roles: Optional[List[ProviderRole]] = None,
         url: Optional[str] = None,
         extra_fields: Optional[Dict[str, Any]] = None,
     ):

tests/test_item.py

@@ -7,7 +7,7 @@
 import unittest
 
 import pystac
-from pystac import Asset, Item, Provider
+from pystac import Asset, Item, Provider, ProviderRole
 from pystac.validation import validate_dict
 import pystac.serialization.common_properties
 from pystac.item import CommonMetadata
@@ -532,7 +532,7 @@ def test_asset_providers(self) -> None:
             pystac.Provider(
                 name="USGS",
                 url="https://landsat.usgs.gov/",
-                roles=["producer", "licensor"],
+                roles=[ProviderRole.PRODUCER, ProviderRole.LICENSOR],
             )
         ]
 
@@ -546,7 +546,9 @@ def test_asset_providers(self) -> None:
         # Set
         set_value = [
             pystac.Provider(
-                name="John Snow", url="https://cholera.com/", roles=["producer"]
+                name="John Snow",
+                url="https://cholera.com/",
+                roles=[ProviderRole.PRODUCER],
             )
         ]
         cm.set_providers(set_value, item.assets["analytic"])