add validate_item convenience wrapper (#17)

* add validate_item convenience wrapper

* update cli

* update readme

README.md

@@ -35,7 +35,9 @@ implicitly or explicitly:
 
 #### Implicit
 The `item_model_factory` function creates an appropriate Pydantic model based on the structure of the item by looking
-at the extensions defined by the `stac_extensions` member.
+at the extensions defined by the `stac_extensions` member.  The model can be created once and reused for the life of
+the interpreter.
+
 ```python
 from stac_pydantic import item_model_factory
 
@@ -62,6 +64,14 @@ item = model(**stac_item)
         field required (eo) (type=value_error.missing)
 ```
 
+The `stac_pydantic.validate_item` function provides a convenience wrapper over `item_model_factory` for one-off validation:
+
+```python
+from stac_pydantic import validate_item
+
+assert validate_item(stac_item)
+```
+
 #### Explicit
 Subclass any of the models provided by the library to declare a customized validator:
 

stac_pydantic/__init__.py

@@ -1,4 +1,10 @@
 from .catalog import Catalog
 from .collection import Collection
 from .extensions import Extensions
-from .item import Item, ItemCollection, ItemProperties, item_model_factory
+from .item import (
+    Item,
+    ItemCollection,
+    ItemProperties,
+    item_model_factory,
+    validate_item,
+)

stac_pydantic/item.py

@@ -108,3 +108,16 @@ def item_model_factory(
         )
 
     return create_model("CustomStacItem", **item_fields, __base__=base_class)
+
+
+def validate_item(item: Dict, reraise_exception: bool = False, **kwargs) -> bool:
+    """
+    Wrapper around ``item_model_factory`` for stac item validation
+    """
+    try:
+        item_model_factory(item, **kwargs)(**item)
+    except Exception:
+        if reraise_exception:
+            raise
+        return False
+    return True

stac_pydantic/scripts/cli.py

@@ -2,7 +2,7 @@
 import requests
 from pydantic import ValidationError
 
-from stac_pydantic import item_model_factory
+from stac_pydantic import validate_item as validate
 
 
 @click.group(short_help="Validate STAC")
@@ -19,7 +19,7 @@ def validate_item(infile):
     r.raise_for_status()
     stac_item = r.json()
     try:
-        item_model_factory(stac_item, skip_remote_refs=True)(**stac_item)
+        validate(stac_item, skip_remote_refs=True, reraise_exception=True)
     except ValidationError as e:
         click.echo(str(e))
         return

tests/test_models.py

@@ -13,7 +13,7 @@
 from stac_pydantic.api.search import Search
 from stac_pydantic.extensions import Extensions
 from stac_pydantic.extensions.single_file_stac import SingleFileStac
-from stac_pydantic.item import item_model_factory
+from stac_pydantic.item import item_model_factory, validate_item
 from stac_pydantic.shared import DATETIME_RFC339, Link
 
 from .conftest import dict_match, request
@@ -626,3 +626,16 @@ def test_skip_remote_extension():
 
     # This should work
     item_model_factory(test_item, skip_remote_refs=True)(**test_item)
+
+
+def test_validate_item():
+    test_item = request(EO_EXTENSION)
+    assert validate_item(test_item)
+
+
+def test_validate_item_reraise_exception():
+    test_item = request(EO_EXTENSION)
+    del test_item["properties"]["eo:bands"]
+
+    with pytest.raises(ValidationError):
+        validate_item(test_item, reraise_exception=True)