Raise FileNotFoundError instead of panic when opening missing files (#93)

Avoid panic when non-existent file is passed into `TIFF.open`

Author: weiji14

python/src/tiff.rs

@@ -3,7 +3,7 @@ use std::sync::Arc;
 use async_tiff::metadata::{PrefetchBuffer, TiffMetadataReader};
 use async_tiff::reader::AsyncFileReader;
 use async_tiff::TIFF;
-use pyo3::exceptions::PyIndexError;
+use pyo3::exceptions::{PyFileNotFoundError, PyIndexError};
 use pyo3::prelude::*;
 use pyo3::types::PyType;
 use pyo3_async_runtimes::tokio::future_into_py;
@@ -32,7 +32,9 @@ impl PyTIFF {
         let reader = store.into_async_file_reader(path);
 
         let cog_reader = future_into_py(py, async move {
-            let metadata_fetch = PrefetchBuffer::new(reader.clone(), prefetch).await.unwrap();
+            let metadata_fetch = PrefetchBuffer::new(reader.clone(), prefetch)
+                .await
+                .map_err(|err| PyFileNotFoundError::new_err(err.to_string()))?;
             let mut metadata_reader = TiffMetadataReader::try_open(&metadata_fetch).await.unwrap();
             let ifds = metadata_reader
                 .read_all_ifds(&metadata_fetch)

python/tests/test_cog.py

@@ -1,5 +1,7 @@
+import pytest
+
 from async_tiff import TIFF, enums
-from async_tiff.store import S3Store
+from async_tiff.store import LocalStore, S3Store
 
 
 async def test_cog_s3():
@@ -23,3 +25,12 @@ async def test_cog_s3():
     gkd = ifd.geo_key_directory
     assert gkd.citation == "WGS 84 / UTM zone 12N"
     assert gkd.projected_type == 32612
+
+
+async def test_cog_missing_file():
+    """
+    Ensure that a FileNotFoundError is raised when passing in a missing file.
+    """
+    store = LocalStore()
+    with pytest.raises(FileNotFoundError):
+        await TIFF.open(path="imaginary_file.tif", store=store)