fix(recon): resolve Classroom 50 roster columns in discover_repos

lectern/recon_discover.py

@@ -12,10 +12,25 @@ def discover_repos(roster_csv: Path, *, repo_prefix: str) -> list[RepoRef]:
     refs: list[RepoRef] = []
     with Path(roster_csv).open(newline="") as f:
         for row in csv.DictReader(f):
-            gid = (row.get("github_username") or row.get("github_id") or "").strip()
+            # Identifier precedence. `username` must outrank `github_id` because
+            # a Classroom 50 roster.csv uses BOTH columns with different meanings
+            # than a legacy GitHub Classroom roster does: `username` is the login
+            # and `github_id` is the immutable NUMERIC id. Legacy rosters put the
+            # login in `github_id` (see examples/.../.cohort-spec.json), so that
+            # stays in the chain as the last resort and old behavior is unchanged
+            # whenever `username` is absent. Reading `github_id` first would build
+            # repo names like `<prefix>-1548364` instead of `<prefix>-agiacalone`.
+            gid = (row.get("github_username") or row.get("username")
+                   or row.get("github_id") or "").strip()
             if not gid:
                 continue
             name = (row.get("student_name") or row.get("canonical_name")
                     or row.get("name") or "").strip()
+            if not name:
+                # Classroom 50 splits the name across two columns.
+                name = " ".join(p for p in (
+                    (row.get("first_name") or "").strip(),
+                    (row.get("last_name") or "").strip(),
+                ) if p)
             refs.append(RepoRef(github_id=gid, student=name, repo=f"{repo_prefix}{gid}"))
     return refs

tests/test_recon_discover.py

@@ -20,3 +20,61 @@ def test_discover_uses_canonical_name(tmp_path):
     refs = discover_repos(csv_path, repo_prefix="pre-")
     assert refs[0].student == "Barbara Gordon"
     assert refs[0].repo == "pre-lucfox"
+
+
+# --- Classroom 50 roster shape -------------------------------------------
+# A C50 roster.csv carries BOTH `username` (the login) and `github_id` (the
+# immutable NUMERIC id), and splits the name across first_name/last_name.
+# A legacy GitHub Classroom roster put the LOGIN in `github_id`, so the two
+# formats collide on that column name and precedence is what separates them.
+
+C50_HEADER = "username,first_name,last_name,email,section,github_id,role\n"
+
+
+def test_discover_c50_roster_prefers_username_over_numeric_github_id(tmp_path):
+    """Reading github_id first would name the repo `<prefix>-1548364`."""
+    csv_path = tmp_path / "roster.csv"
+    csv_path.write_text(C50_HEADER +
+                        "agiacalone,Anthony,Giacalone,,section-1,1548364,student\n")
+    refs = discover_repos(csv_path, repo_prefix="c50-tst0-lab-01-")
+    assert len(refs) == 1
+    assert refs[0].github_id == "agiacalone"
+    assert refs[0].repo == "c50-tst0-lab-01-agiacalone"
+
+
+def test_discover_c50_roster_composes_name_from_first_last(tmp_path):
+    csv_path = tmp_path / "roster.csv"
+    csv_path.write_text(C50_HEADER +
+                        "bruce-wayne,Bruce,Wayne,,section-1,,student\n")
+    refs = discover_repos(csv_path, repo_prefix="pre-")
+    assert refs[0].student == "Bruce Wayne"
+
+
+def test_discover_c50_roster_keeps_rows_with_unresolved_github_id(tmp_path):
+    """A blank numeric github_id must not drop the student from the population."""
+    csv_path = tmp_path / "roster.csv"
+    csv_path.write_text(C50_HEADER +
+                        "bruce-wayne,Bruce,Wayne,,section-1,,student\n"
+                        "dick-grayson,Dick,Grayson,,section-1,,student\n")
+    refs = discover_repos(csv_path, repo_prefix="pre-")
+    assert [r.repo for r in refs] == ["pre-bruce-wayne", "pre-dick-grayson"]
+
+
+def test_discover_legacy_github_id_login_still_wins_when_no_username(tmp_path):
+    """Back-compat: legacy rosters store the LOGIN in github_id and have no
+    `username` column, so behavior there must be unchanged."""
+    csv_path = tmp_path / "roster.csv"
+    csv_path.write_text("github_id,name\nbruce-wayne,Bruce Wayne\n")
+    refs = discover_repos(csv_path, repo_prefix="cecs-378-su26-01-lab-03-")
+    assert refs[0].github_id == "bruce-wayne"
+    assert refs[0].repo == "cecs-378-su26-01-lab-03-bruce-wayne"
+    assert refs[0].student == "Bruce Wayne"
+
+
+def test_discover_explicit_github_username_outranks_c50_username(tmp_path):
+    """`github_username` stays top of the chain as the explicit override."""
+    csv_path = tmp_path / "roster.csv"
+    csv_path.write_text("username,github_username,first_name,last_name\n"
+                        "campus-sso-id,reallogin,Barbara,Gordon\n")
+    refs = discover_repos(csv_path, repo_prefix="pre-")
+    assert refs[0].repo == "pre-reallogin"