Merge pull request #89 from michalc/feat/better-exception-handling

feat: slightly more-specific exceptions raised

Author: michalc

README.md

@@ -238,6 +238,25 @@ This means that sqlite-s3-query is not for all use cases of querying SQLite data
 This is not necessarily a permanent decision - it is possible that in future sqlite-s3-query will support unversioned buckets.
 
 
+## Exception hierarchy
+
+- `SQLiteS3QueryError`
+
+   The base class for explicitly raised exceptions.
+
+   - `VersioningNotEnabledError`
+
+      Versioning is not enabled on the bucket.
+
+   - `QueryContextClosedError`
+
+      A results iterable has been attempted to be used after the close of its surrounding query context.
+
+   - `SQLiteError`
+
+      SQLite has detected an error. The first element of the `args` member of the raised exception is the description of the error as provided by SQLite.
+
+
 ## Compatibility
 
 - Linux (tested on Ubuntu 20.04), Windows (tested on Windows Server 2019), or macOS (tested on macOS 11)

sqlite_s3_query.py

@@ -72,11 +72,11 @@ def sqlite_s3_query_multi(url, get_credentials=lambda now: (
     def run(func, *args):
         res = func(*args)
         if res != 0:
-            raise Exception(libsqlite3.sqlite3_errstr(res).decode())
+            raise SQLiteError(libsqlite3.sqlite3_errstr(res).decode())
 
     def run_with_db(db, func, *args):
         if func(*args) != 0:
-            raise Exception(libsqlite3.sqlite3_errmsg(db).decode())
+            raise SQLiteError(libsqlite3.sqlite3_errmsg(db).decode())
 
     @contextmanager
     def make_auth_request(http_client, method, params, headers):
@@ -148,7 +148,7 @@ def get_vfs(http_client):
         try:
             version_id = head_headers['x-amz-version-id']
         except KeyError:
-            raise Exception('The bucket must have versioning enabled')
+            raise VersioningNotEnabledError('The bucket must have versioning enabled')
 
         size = int(head_headers['content-length'])
 
@@ -292,7 +292,7 @@ def get_pp_stmt(statement):
             try:
                 return statements[statement]
             except KeyError:
-                raise Exception('Attempting to use finalized statement') from None
+                raise QueryContextClosedError('Attempting to use finalized statement') from None
 
         def finalize(statement):
             pp_stmt = statements.pop(statement)
@@ -328,7 +328,7 @@ def rows(get_pp_stmt, columns):
             if res == SQLITE_DONE:
                 break
             if res != SQLITE_ROW:
-                raise Exception(libsqlite3.sqlite3_errstr(res).decode())
+                raise SQLiteError(libsqlite3.sqlite3_errstr(res).decode())
 
             yield tuple(
                 extract[libsqlite3.sqlite3_column_type(pp_stmt, i)](pp_stmt, i)
@@ -394,3 +394,19 @@ def query(query_base, sql, params=(), named_params=()):
     ) as query_base:
 
         yield partial(query, query_base)
+
+
+class SQLiteS3QueryError(Exception):
+    pass
+
+
+class VersioningNotEnabledError(SQLiteS3QueryError):
+    pass
+
+
+class SQLiteError(SQLiteS3QueryError):
+    pass
+
+
+class QueryContextClosedError(SQLiteS3QueryError):
+    pass

test.py

@@ -16,7 +16,13 @@
 
 import httpx
 
-from sqlite_s3_query import sqlite_s3_query, sqlite_s3_query_multi
+from sqlite_s3_query import (
+    VersioningNotEnabledError,
+    SQLiteError,
+    QueryContextClosedError,
+    sqlite_s3_query,
+    sqlite_s3_query_multi,
+)
 
 
 class TestSqliteS3Query(unittest.TestCase):
@@ -36,7 +42,7 @@ def test_without_versioning(self):
         ]) as db:
             put_object_without_versioning('bucket-without-versioning', 'my.db', db)
 
-        with self.assertRaisesRegex(Exception, 'The bucket must have versioning enabled'):
+        with self.assertRaisesRegex(VersioningNotEnabledError, 'The bucket must have versioning enabled'):
             sqlite_s3_query('http://localhost:9000/bucket-without-versioning/my.db', get_credentials=lambda now: (
                 'us-east-1',
                 'AKIAIOSFODNN7EXAMPLE',
@@ -98,7 +104,7 @@ def test_select(self):
 
         self.assertEqual(rows, [('some-text-a',)] * 500)
 
-        with self.assertRaisesRegex(Exception, 'Attempting to use finalized statement'):
+        with self.assertRaisesRegex(QueryContextClosedError, 'Attempting to use finalized statement'):
             with sqlite_s3_query('http://localhost:9000/my-bucket/my.db', get_credentials=lambda now: (
                 'us-east-1',
                 'AKIAIOSFODNN7EXAMPLE',
@@ -110,7 +116,7 @@ def test_select(self):
                         break
                 next(rows)
 
-        with self.assertRaisesRegex(Exception, 'Attempting to use finalized statement'):
+        with self.assertRaisesRegex(QueryContextClosedError, 'Attempting to use finalized statement'):
             with sqlite_s3_query('http://localhost:9000/my-bucket/my.db', get_credentials=lambda now: (
                 'us-east-1',
                 'AKIAIOSFODNN7EXAMPLE',
@@ -257,7 +263,7 @@ def test_select_multi(self):
                 next(rows_2_it)
                 raise Exception('Multiple open statements')
 
-        with self.assertRaisesRegex(Exception, 'Attempting to use finalized statement'):
+        with self.assertRaisesRegex(QueryContextClosedError, 'Attempting to use finalized statement'):
             with sqlite_s3_query_multi('http://localhost:9000/my-bucket/my.db', get_credentials=lambda now: (
                 'us-east-1',
                 'AKIAIOSFODNN7EXAMPLE',
@@ -393,7 +399,7 @@ def test_non_existant_table(self):
             'wJalrXUtnFEMI/K7MDENG/bPxRfiCYEXAMPLEKEY',
             None,
         ), get_libsqlite3=get_libsqlite3) as query:
-            with self.assertRaisesRegex(Exception, 'no such table: non_table'):
+            with self.assertRaisesRegex(SQLiteError, 'no such table: non_table'):
                 query("SELECT * FROM non_table").__enter__()
 
     def test_empty_object(self):
@@ -405,7 +411,7 @@ def test_empty_object(self):
             'wJalrXUtnFEMI/K7MDENG/bPxRfiCYEXAMPLEKEY',
             None,
         ), get_libsqlite3=get_libsqlite3) as query:
-            with self.assertRaisesRegex(Exception, 'disk I/O error'):
+            with self.assertRaisesRegex(SQLiteError, 'disk I/O error'):
                 query('SELECT 1').__enter__()
 
     def test_bad_db_header(self):
@@ -417,7 +423,7 @@ def test_bad_db_header(self):
             'wJalrXUtnFEMI/K7MDENG/bPxRfiCYEXAMPLEKEY',
             None,
         ), get_libsqlite3=get_libsqlite3) as query:
-            with self.assertRaisesRegex(Exception, 'disk I/O error'):
+            with self.assertRaisesRegex(SQLiteError, 'disk I/O error'):
                 query("SELECT * FROM non_table").__enter__()
 
     def test_bad_db_second_half(self):
@@ -435,7 +441,7 @@ def test_bad_db_second_half(self):
             'wJalrXUtnFEMI/K7MDENG/bPxRfiCYEXAMPLEKEY',
             None,
         ), get_libsqlite3=get_libsqlite3) as query:
-            with self.assertRaisesRegex(Exception, 'database disk image is malformed'):
+            with self.assertRaisesRegex(SQLiteError, 'database disk image is malformed'):
                 with query("SELECT * FROM my_table") as (columns, rows):
                     list(rows)
 
@@ -649,7 +655,7 @@ def iter_bytes(chunk_size=None):
                 'wJalrXUtnFEMI/K7MDENG/bPxRfiCYEXAMPLEKEY',
                 None,
             ), get_http_client=get_http_client, get_libsqlite3=get_libsqlite3) as query:
-                with self.assertRaisesRegex(Exception, 'disk I/O error'):
+                with self.assertRaisesRegex(SQLiteError, 'disk I/O error'):
                     query('SELECT my_col_a FROM my_table').__enter__()
 
     def test_disconnection(self):