fix(azure-devops): fall back to full review when commit dates are unreliable

- _get_commit_range now returns None (not []) when the previous review
  has no timestamp, no PR commits exist, or every commit author date is
  None, and disables incremental so PRReviewer's existing
  `commits_range is None` fallback path runs a full review instead of
  silently exiting via the threshold check.
- _get_incremental_commits short-circuits when _get_commit_range
  returns None, avoiding TypeError on the iteration that follows.
- Wraps the over-120-char incremental-skip conditional in
  PRReviewer.run for ruff compliance.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

Author: agonzales-ipcoop

pr_agent/git_providers/azuredevops_provider.py

@@ -215,6 +215,8 @@ def _get_incremental_commits(self):
             return
 
         self.incremental.commits_range = self._get_commit_range()
+        if self.incremental.commits_range is None:
+            return
         candidate_paths = []
         had_errors = False
         for commit in self.incremental.commits_range:
@@ -258,18 +260,32 @@ def _get_incremental_commits(self):
     def _get_commit_range(self):
         last_review_time = _to_naive_utc(getattr(self.previous_review, "created_at", None))
         if last_review_time is None or not self.pr_commits:
-            return []
+            get_logger().info(
+                "Cannot compute incremental commit range "
+                "(missing previous review timestamp or PR commits); falling back to full review."
+            )
+            self.incremental.is_incremental = False
+            return None
         first_new_commit_index = None
+        saw_reliable_date = False
         for index in range(len(self.pr_commits) - 1, -1, -1):
             cdate = self.pr_commits[index].commit.author.date
             if cdate is None:
                 continue
+            saw_reliable_date = True
             if cdate > last_review_time:
                 self.incremental.first_new_commit = self.pr_commits[index]
                 first_new_commit_index = index
             else:
                 self.incremental.last_seen_commit = self.pr_commits[index]
                 break
+        if not saw_reliable_date:
+            get_logger().info(
+                "All PR commit author dates are missing; cannot compute incremental range. "
+                "Falling back to full review."
+            )
+            self.incremental.is_incremental = False
+            return None
         return self.pr_commits[first_new_commit_index:] if first_new_commit_index is not None else []
 
     def get_previous_review(self, *, full: bool, incremental: bool):

pr_agent/tools/pr_reviewer.py

@@ -142,7 +142,11 @@ async def run(self) -> None:
             # ticket extraction if exists
             await extract_and_cache_pr_tickets(self.git_provider, self.vars)
 
-            if self.incremental.is_incremental and hasattr(self.git_provider, "unreviewed_files_map") and not self.git_provider.unreviewed_files_map:
+            if (
+                self.incremental.is_incremental
+                and hasattr(self.git_provider, "unreviewed_files_map")
+                and not self.git_provider.unreviewed_files_map
+            ):
                 get_logger().info(f"Incremental review is enabled for {self.pr_url} but there are no new files")
                 previous_review_url = ""
                 if hasattr(self.git_provider, "previous_review") and self.git_provider.previous_review is not None: