Add support for discussions

Closes #290

tests/test_discussions.py

@@ -0,0 +1,222 @@
+"""Tests for GitHub Discussions backup support."""
+
+import json
+import os
+from unittest.mock import patch
+
+from github_backup import github_backup
+
+
+def test_parse_args_discussions_flag():
+    args = github_backup.parse_args(["--discussions", "testuser"])
+    assert args.include_discussions is True
+
+
+def test_retrieve_discussion_summaries_stops_at_incremental_since(create_args):
+    args = create_args()
+    repository = {"full_name": "owner/repo"}
+
+    page = {
+        "repository": {
+            "hasDiscussionsEnabled": True,
+            "discussions": {
+                "totalCount": 3,
+                "nodes": [
+                    {"number": 3, "title": "new", "updatedAt": "2026-02-01T00:00:00Z"},
+                    {"number": 2, "title": "also new", "updatedAt": "2026-01-10T00:00:00Z"},
+                    {"number": 1, "title": "old", "updatedAt": "2025-12-01T00:00:00Z"},
+                ],
+                "pageInfo": {"hasNextPage": True, "endCursor": "NEXT"},
+            },
+        }
+    }
+
+    with patch(
+        "github_backup.github_backup.retrieve_graphql_data", return_value=page
+    ) as mock_retrieve:
+        summaries, newest, enabled, total = github_backup.retrieve_discussion_summaries(
+            args, repository, since="2026-01-01T00:00:00Z"
+        )
+
+    assert enabled is True
+    assert total == 3
+    assert newest == "2026-02-01T00:00:00Z"
+    assert [item["number"] for item in summaries] == [3, 2]
+    # The old discussion stops pagination, so the next page is not requested.
+    assert mock_retrieve.call_count == 1
+    assert (
+        mock_retrieve.call_args.kwargs["log_context"]
+        == "discussion summaries owner/repo page 1"
+    )
+
+
+def test_retrieve_discussion_summaries_disabled_discussions(create_args):
+    args = create_args()
+    repository = {"full_name": "owner/repo"}
+
+    with patch(
+        "github_backup.github_backup.retrieve_graphql_data",
+        return_value={"repository": {"hasDiscussionsEnabled": False}},
+    ):
+        summaries, newest, enabled, total = github_backup.retrieve_discussion_summaries(
+            args, repository
+        )
+
+    assert summaries == []
+    assert newest is None
+    assert enabled is False
+    assert total == 0
+
+
+def _comment(comment_id, body, replies=None, replies_has_next=False):
+    replies = replies or []
+    return {
+        "id": comment_id,
+        "body": body,
+        "replies": {
+            "totalCount": len(replies) + (1 if replies_has_next else 0),
+            "nodes": replies,
+            "pageInfo": {
+                "hasNextPage": replies_has_next,
+                "endCursor": "REPLIES2" if replies_has_next else None,
+            },
+        },
+    }
+
+
+def _discussion_page(comment_nodes, has_next=False):
+    return {
+        "repository": {
+            "discussion": {
+                "number": 42,
+                "title": "Discussion title",
+                "updatedAt": "2026-02-01T00:00:00Z",
+                "comments": {
+                    "totalCount": 2,
+                    "nodes": comment_nodes,
+                    "pageInfo": {
+                        "hasNextPage": has_next,
+                        "endCursor": "COMMENTS2" if has_next else None,
+                    },
+                },
+            }
+        }
+    }
+
+
+def test_retrieve_discussion_paginates_comments_and_replies(create_args):
+    args = create_args()
+    repository = {"full_name": "owner/repo"}
+
+    reply_1 = {"id": "reply-1", "body": "first reply"}
+    reply_2 = {"id": "reply-2", "body": "second reply"}
+    comment_1 = _comment("comment-1", "first comment", [reply_1], replies_has_next=True)
+    comment_2 = _comment("comment-2", "second comment")
+
+    responses = [
+        _discussion_page([comment_1], has_next=True),
+        {
+            "node": {
+                "replies": {
+                    "totalCount": 2,
+                    "nodes": [reply_2],
+                    "pageInfo": {"hasNextPage": False, "endCursor": None},
+                }
+            }
+        },
+        _discussion_page([comment_2], has_next=False),
+    ]
+
+    with patch(
+        "github_backup.github_backup.retrieve_graphql_data", side_effect=responses
+    ) as mock_retrieve:
+        discussion = github_backup.retrieve_discussion(args, repository, 42)
+
+    assert discussion["number"] == 42
+    assert discussion["comment_count"] == 2
+    assert len(discussion["comment_data"]) == 2
+    assert discussion["comment_data"][0]["body"] == "first comment"
+    assert discussion["comment_data"][0]["reply_count"] == 2
+    assert [r["body"] for r in discussion["comment_data"][0]["reply_data"]] == [
+        "first reply",
+        "second reply",
+    ]
+    assert discussion["comment_data"][1]["body"] == "second comment"
+    assert mock_retrieve.call_count == 3
+    assert [
+        call.kwargs["log_context"] for call in mock_retrieve.call_args_list
+    ] == [
+        "discussion owner/repo#42 details/comments page 1",
+        "discussion owner/repo#42 comment comment-1 replies page 2",
+        "discussion owner/repo#42 details/comments page 2",
+    ]
+
+
+def test_backup_discussions_uses_incremental_checkpoint(create_args, tmp_path):
+    args = create_args(token_classic="fake_token", include_discussions=True, incremental=True)
+    repository = {"full_name": "owner/repo"}
+    discussions_dir = tmp_path / "discussions"
+    discussions_dir.mkdir()
+    (discussions_dir / "last_update").write_text("2026-01-01T00:00:00Z")
+
+    def fake_summaries(passed_args, passed_repository, since=None):
+        assert passed_args is args
+        assert passed_repository == repository
+        assert since == "2026-01-01T00:00:00Z"
+        return (
+            [{"number": 7, "title": "updated", "updatedAt": "2026-02-01T00:00:00Z"}],
+            "2026-02-01T00:00:00Z",
+            True,
+            1,
+        )
+
+    with patch(
+        "github_backup.github_backup.retrieve_discussion_summaries",
+        side_effect=fake_summaries,
+    ), patch(
+        "github_backup.github_backup.retrieve_discussion",
+        return_value={"number": 7, "title": "updated"},
+    ):
+        github_backup.backup_discussions(args, tmp_path, repository)
+
+    with open(discussions_dir / "7.json", encoding="utf-8") as f:
+        assert json.load(f) == {"number": 7, "title": "updated"}
+    assert (discussions_dir / "last_update").read_text() == "2026-02-01T00:00:00Z"
+
+
+def test_backup_discussions_does_not_advance_checkpoint_on_discussion_error(
+    create_args, tmp_path
+):
+    args = create_args(token_classic="fake_token", include_discussions=True, incremental=True)
+    repository = {"full_name": "owner/repo"}
+    discussions_dir = tmp_path / "discussions"
+    discussions_dir.mkdir()
+    (discussions_dir / "last_update").write_text("2026-01-01T00:00:00Z")
+
+    with patch(
+        "github_backup.github_backup.retrieve_discussion_summaries",
+        return_value=(
+            [{"number": 7, "title": "updated", "updatedAt": "2026-02-01T00:00:00Z"}],
+            "2026-02-01T00:00:00Z",
+            True,
+            1,
+        ),
+    ), patch(
+        "github_backup.github_backup.retrieve_discussion",
+        side_effect=Exception("temporary GraphQL error"),
+    ):
+        github_backup.backup_discussions(args, tmp_path, repository)
+
+    assert (discussions_dir / "last_update").read_text() == "2026-01-01T00:00:00Z"
+    assert not os.path.exists(discussions_dir / "7.json")
+
+
+def test_backup_discussions_skips_without_auth(create_args, tmp_path):
+    args = create_args(include_discussions=True)
+    repository = {"full_name": "owner/repo"}
+
+    with patch("github_backup.github_backup.retrieve_discussion_summaries") as mock_retrieve:
+        github_backup.backup_discussions(args, tmp_path, repository)
+
+    assert not mock_retrieve.called
+    assert not os.path.exists(tmp_path / "discussions")