feat: add assert_asset_exists, assert_href_exists

CHANGELOG.md

@@ -17,7 +17,7 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 - Progress reporting ([#55](https://github.com/stac-utils/stac-asset/pull/55), [#69](https://github.com/stac-utils/stac-asset/pull/69))
 - `ErrorStrategy` ([#69](https://github.com/stac-utils/stac-asset/pull/69))
 - `fail_fast` ([#69](https://github.com/stac-utils/stac-asset/pull/69))
-- `asset_exists` and `Client.href_exists` ([#81](https://github.com/stac-utils/stac-asset/pull/81))
+- `assert_asset_exists`, `asset_exists`, `Client.assert_href_exists`, `Client.href_exists` ([#81](https://github.com/stac-utils/stac-asset/pull/81), [#85](https://github.com/stac-utils/stac-asset/pull/85))
 
 ### Changed
 

src/stac_asset/__init__.py

@@ -15,6 +15,7 @@
 
 
 from ._functions import (
+    assert_asset_exists,
     asset_exists,
     download_asset,
     download_collection,
@@ -53,6 +54,7 @@
     "HttpClient",
     "PlanetaryComputerClient",
     "S3Client",
+    "assert_asset_exists",
     "asset_exists",
     "download_asset",
     "download_collection",

src/stac_asset/_functions.py

@@ -392,30 +392,55 @@ async def download_asset(
     return asset
 
 
-async def asset_exists(
+async def assert_asset_exists(
     asset: Asset,
     config: Optional[Config] = None,
     clients: Optional[List[Client]] = None,
-) -> bool:
-    """Returns true if the asset exists, false if not.
+) -> None:
+    """Asserts that an asset exists.
+
+    Raises the source error if it does not.
 
     Args:
         asset: The asset the check for existence
         config: The download configuration to use for the existence check
         clients: Any pre-configured clients to use for the existence check
 
-    Returns:
-        bool: Whether the assets href exists or not
+    Raises:
+        Exception: An exception from the underlying client.
     """
     if config is None:
         config = Config()
     clients_ = Clients(config, clients=clients)
     href = get_absolute_asset_href(asset, config.alternate_assets)
     if href:
         client = await clients_.get_client(href)
-        return await client.href_exists(href)
+        await client.assert_href_exists(href)
     else:
+        raise ValueError("asset does not have an absolute href")
+
+
+async def asset_exists(
+    asset: Asset,
+    config: Optional[Config] = None,
+    clients: Optional[List[Client]] = None,
+) -> bool:
+    """Returns true if an asset exists.
+
+    Args:
+        asset: The asset the check for existence
+        config: The download configuration to use for the existence check
+        clients: Any pre-configured clients to use for the existence check
+
+    Returns:
+        bool: Whether the asset exists or not
+    """
+    try:
+        await assert_asset_exists(asset, config, clients)
+    except Exception:
         return False
+    else:
+        return True
 
 
 def make_asset_hrefs_relative(

src/stac_asset/client.py

@@ -133,11 +133,26 @@ async def href_exists(self, href: str) -> bool:
             bool: Whether the href exists
         """
         try:
-            async for _ in self.open_href(href):
-                break
+            await self.assert_href_exists(href)
         except Exception:
             return False
-        return True
+        else:
+            return True
+
+    async def assert_href_exists(self, href: str) -> None:
+        """Asserts that a href exists.
+
+        The default implementation naïvely opens the href and reads one chunk.
+        Clients may implement specialized behavior.
+
+        Args:
+            href: The href to open
+
+        Raises:
+            Exception: The underlying error when trying to open the file.
+        """
+        async for _ in self.open_href(href):
+            break
 
     async def close(self) -> None:
         """Close this client."""

src/stac_asset/filesystem_client.py

@@ -50,6 +50,11 @@ async def open_url(
             async for chunk in f:
                 yield chunk
 
+    async def assert_href_exists(self, href: str) -> None:
+        """Asserts that an href exists."""
+        if not os.path.exists(href):
+            raise ValueError(f"href does not exist on the filesystem: {href}")
+
     async def __aenter__(self) -> FilesystemClient:
         return self
 

src/stac_asset/http_client.py

@@ -74,17 +74,13 @@ async def open_url(
             async for chunk, _ in response.content.iter_chunks():
                 yield chunk
 
-    async def href_exists(self, href: str) -> bool:
-        """Returns true if the href exists.
+    async def assert_href_exists(self, href: str) -> None:
+        """Asserts that the href exists.
 
         Uses a HEAD request.
         """
-        try:
-            async with self.session.head(href) as response:
-                # For some reason, mypy can't see that this is a bool
-                return response.status >= 200 and response.status < 300  # type: ignore
-        except Exception:
-            return False
+        async with self.session.head(href) as response:
+            response.raise_for_status()
 
     async def close(self) -> None:
         """Close this http client.

src/stac_asset/planetary_computer_client.py

@@ -99,15 +99,14 @@ async def open_url(
         ):
             yield chunk
 
-    async def href_exists(self, href: str) -> bool:
-        """Returns true if the href exists.
+    async def assert_href_exists(self, href: str) -> None:
+        """Asserts that the href exists.
 
         Uses a HEAD request on a signed url.
         """
         href = await self._maybe_sign_href(href)
         async with self.session.head(href) as response:
-            # For some reason, mypy can't see that this is a bool
-            return response.status >= 200 and response.status < 300  # type: ignore
+            response.raise_for_status()
 
     async def _sign(self, url: URL) -> URL:
         assert url.host

src/stac_asset/s3_client.py

@@ -114,18 +114,13 @@ async def has_credentials(self) -> bool:
         """Returns true if the sessions has credentials."""
         return await self.session.get_credentials() is not None
 
-    async def href_exists(self, href: str) -> bool:
-        """Return true if the href exists.
+    async def assert_href_exists(self, href: str) -> None:
+        """Asserts that the href exists.
 
         Uses ``head_object``
         """
         async with self._create_client() as client:
-            try:
-                await client.head_object(**self._params(URL(href)))
-            except Exception:
-                return False
-            else:
-                return True
+            await client.head_object(**self._params(URL(href)))
 
     def _create_client(self) -> ClientCreatorContext:
         retries = {

tests/test_functions.py

@@ -189,3 +189,9 @@ async def test_queue(tmp_path: Path, item: Item) -> None:
 async def test_asset_exists(item: Item) -> None:
     assert await stac_asset.asset_exists(item.assets["data"])
     assert not await stac_asset.asset_exists(Asset(href="not-a-file"))
+
+
+async def test_asert_asset_exists(item: Item) -> None:
+    await stac_asset.assert_asset_exists(item.assets["data"])
+    with pytest.raises(ValueError):
+        await stac_asset.assert_asset_exists(Asset(href="not-a-file"))