Add test for seek to end + defer_seek (#901)

* Add test for seek to end + defer_seek

* Disable helptext

* Fix test

* Re-enable helptext

* Add upper pin for google-api-core

Author: ddelange

.github/workflows/python-package.yml

@@ -23,10 +23,7 @@ jobs:
           - {python-version: '3.9', os: windows-2025}
           - {python-version: '3.14', os: windows-2025}
 
-          # deprecate macos-15-intel when python 3.9 becomes the minimum supported version
-          # ref https://github.blog/changelog/2025-09-19-github-actions-macos-13-runner-image-is-closing-down/
-          # ref  https://github.com/actions/python-versions/blob/d026dedcb/versions-manifest.json#L9969-L10016
-          - {python-version: '3.9', os: macos-15-intel}
+          - {python-version: '3.9', os: macos-15}
           - {python-version: '3.14', os: macos-15}
 
     steps:

pyproject.toml

@@ -34,7 +34,7 @@ dependencies = ["wrapt"]
 
 [project.optional-dependencies]
 s3 = ["boto3>=1.9.17"]
-gcs = ["google-cloud-storage>=2.6.0"]
+gcs = ["google-cloud-storage>=2.6.0", "google-api-core<2.28;python_version<'3.10'"] # https://github.com/googleapis/python-api-core/pull/832#issuecomment-3470137771
 azure = ["azure-storage-blob", "azure-common", "azure-core"]
 http = ["requests"]
 webhdfs = ["requests"]

smart_open/s3.py

@@ -531,7 +531,12 @@ def seek(self, offset, whence=constants.WHENCE_START):
         # If we can figure out that we've read past the EOF, then we can save
         # an extra API call.
         #
-        if self._content_length is None:
+        if start is None and stop == 0 and self._content_length is None:
+            # seek(0, WHENCE_END) seeks straight to EOF: make a minimal request to populate _content_length
+            self._open_body(start=0, stop=0)
+            self.close()
+            reached_eof = True
+        elif self._content_length is None:
             reached_eof = False
         elif start is not None and start >= self._content_length:
             reached_eof = True

tests/test_s3.py

@@ -313,6 +313,22 @@ def test_seek_end(self):
             self.assertEqual(seek, len(self.body) - 4)
             self.assertEqual(fin.read(), b'you?')
 
+    def test_seek_end_tell_without_defer_seek(self):
+        """Does seek(0, SEEK_END) + tell() work correctly without defer_seek?"""
+        with self.assertApiCalls(GetObject=1):  # One call during __init__
+            fin = smart_open.s3.Reader(BUCKET_NAME, KEY_NAME, defer_seek=False)
+            pos = fin.seek(0, whence=smart_open.constants.WHENCE_END)
+            self.assertEqual(pos, len(self.body))
+            self.assertEqual(fin.tell(), len(self.body))
+
+    def test_seek_end_tell_with_defer_seek(self):
+        """Does seek(0, SEEK_END) + tell() work correctly with defer_seek=True?"""
+        with self.assertApiCalls(GetObject=1):  # One call on first seek
+            fin = smart_open.s3.Reader(BUCKET_NAME, KEY_NAME, defer_seek=True)
+            pos = fin.seek(0, whence=smart_open.constants.WHENCE_END)
+            self.assertEqual(pos, len(self.body))
+            self.assertEqual(fin.tell(), len(self.body))
+
     def test_seek_past_end(self):
         with self.assertApiCalls(GetObject=1), patch_invalid_range_response(str(len(self.body))):
             fin = smart_open.s3.Reader(BUCKET_NAME, KEY_NAME, defer_seek=True)