fix(cli): stack pfs elements --dry-run reads the replica, never the writer (refs #684)

src/cli/pfs.py

@@ -66,6 +66,16 @@ def _classifier() -> Any:
     return closed_vocab_classifier(cfg, HostPool.from_config(cfg))
 
 
+def _run_elements(
+    con: Any, store: Any, targets: list[str], classify: Any, *, write: bool
+) -> None:
+    for c in targets:
+        x = extract_code(store, con, c, classify=classify)
+        if write:
+            write_elements(con, c, x.rows, x.reviews)
+        typer.echo(f"{c}: {len(x.rows)} elements, {len(x.reviews)} for review")
+
+
 def _codes_for(con: Any, codes: list[str], family: str, all_payable: bool) -> list[str]:
     out: list[str] = [c.upper() for c in codes]
     if family:
@@ -106,15 +116,21 @@ def elements(
     """Extract typed elements for codes into pfs.code_element (+ review queue)."""
     store = _store()
     classify = None if no_llm else _classifier()
-    with _batch() as con:
-        ensure_tables(con)
-        targets = _codes_for(con, code, family, all_payable)
-        for c in targets:
-            x = extract_code(store, con, c, classify=classify)
-            if not dry_run:
-                write_elements(con, c, x.rows, x.reviews)
-            typer.echo(f"{c}: {len(x.rows)} elements, {len(x.reviews)} for review")
-    if not dry_run:
+    if dry_run:
+        # A preview never contends for the DuckDB single-writer lock a
+        # notebook may be holding (#508-#514) — read the replica, don't
+        # open a batch writer.
+        con = _read()
+        try:
+            targets = _codes_for(con, code, family, all_payable)
+            _run_elements(con, store, targets, classify, write=False)
+        finally:
+            con.close()
+    else:
+        with _batch() as con:
+            ensure_tables(con)
+            targets = _codes_for(con, code, family, all_payable)
+            _run_elements(con, store, targets, classify, write=True)
         _publish()
 
 
@@ -155,7 +171,7 @@ def families(write: bool = typer.Option(False, "--write")) -> None:
                 "UNION SELECT DISTINCT hcpcs FROM pfs.rvu WHERE year = (SELECT max(year) FROM pfs.rvu) AND status_code IN ('A','R','T')"
             ).fetchall()
         ]
-        elements = {c: read_elements(con, c) for c in codes}
+        elements_by_code = {c: read_elements(con, c) for c in codes}
         events = {c: read_events(con, c) for c in codes}
         descriptions = {
             r[0]: r[1]
@@ -163,7 +179,7 @@ def families(write: bool = typer.Option(False, "--write")) -> None:
                 "SELECT hcpcs, arg_max(description, year) FROM pfs.rvu WHERE mod IS NULL OR mod = '' GROUP BY hcpcs"
             ).fetchall()
         }
-        rows = derive_families(elements, events, descriptions)
+        rows = derive_families(elements_by_code, events, descriptions)
         by_key: dict[str, list[str]] = {}
         for r in rows:
             by_key.setdefault(r.key, []).append(f"{r.code}({r.role})")

tests/cli/test_pfs_cli.py

@@ -121,10 +121,27 @@ class TestElements:
             "extract_code",
             lambda s, c, code, *, classify=None: Extraction(code, (), ()),
         )
+
+        def fail_batch():
+            raise AssertionError("--dry-run must not open a RW duckdb_batch connection")
+
+        monkeypatch.setattr(pfs_cli, "_batch", fail_batch)
+
+        read_calls = []
+        orig_read = pfs_cli._read
+
+        def spy_read():
+            read_calls.append(True)
+            return orig_read()
+
+        monkeypatch.setattr(pfs_cli, "_read", spy_read)
+
         res = runner.invoke(
             app, ["pfs", "elements", "--code", "G0556", "--no-llm", "--dry-run"]
         )
-        assert res.exit_code == 0 and con.published == []
+        assert res.exit_code == 0, res.output
+        assert con.published == []
+        assert read_calls == [True]
 
     def test_all_payable_selects_art_status_in_newest_year(self, con, monkeypatch):
         seen = []