ci: add mypy type checking to CI workflow

- Add mypy step to GitHub Actions workflow
- Fix type errors in commits.py and pull_requests.py
  (add isinstance check when assigning API response to dict variable)

Author: amargiovanni

.github/workflows/tests.yml

@@ -31,6 +31,10 @@ jobs:
         run: |
           ruff check src/github_analyzer/
 
+      - name: Run type checker
+        run: |
+          mypy src/github_analyzer/
+
       - name: Run tests
         run: |
           pytest tests/ -v --tb=short

src/github_analyzer/analyzers/commits.py

@@ -59,7 +59,7 @@ def fetch_and_analyze(
             if sha:
                 detail_endpoint = f"/repos/{repo.full_name}/commits/{sha}"
                 detail = self._client.get(detail_endpoint)
-                if detail:
+                if detail and isinstance(detail, dict):
                     raw = detail
 
             commit = Commit.from_api_response(raw, repo.full_name)

src/github_analyzer/analyzers/pull_requests.py

@@ -77,7 +77,7 @@ def fetch_and_analyze(
                 if number:
                     detail_endpoint = f"/repos/{repo.full_name}/pulls/{number}"
                     detail = self._client.get(detail_endpoint)
-                    if detail:
+                    if detail and isinstance(detail, dict):
                         raw = detail
 
             pr = PullRequest.from_api_response(raw, repo.full_name)