recon + sqlglot validator + drill_down package; guard ReAct dimension picks against candidate list

tests/test_recon_validate.py

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+"""Regression: recon SQL validator catches LLM-generated schema mismatches.
+
+Bug captured: drill_down generated `SELECT district_id FROM loan` —
+syntactically valid, parses, but `loan` doesn't have a `district_id` column.
+We want to catch this BEFORE Postgres does, with a clear message naming
+where the column actually lives.
+"""
+
+import pytest
+
+from api.recon.types import Column, Metric, Recon, Relationship, Table
+from api.recon.validate import ReconValidationError, validate_sql
+
+
+def _recon() -> Recon:
+    return Recon(
+        schema="financial",
+        tables={
+            "loan": Table("loan", None, [
+                Column("loan_id", "BIGINT", False),
+                Column("account_id", "BIGINT", True),
+                Column("amount", "BIGINT", True),
+                Column("status", "TEXT", True),
+            ]),
+            "account": Table("account", None, [
+                Column("account_id", "BIGINT", False),
+                Column("district_id", "BIGINT", True),
+            ]),
+            "district": Table("district", None, [
+                Column("district_id", "BIGINT", False),
+                Column("A2", "TEXT", True),
+                Column("A13", "BIGINT", True),
+            ]),
+        },
+        metrics={},
+        column_to_tables={
+            "loan_id": ["loan"],
+            "account_id": ["account", "loan"],
+            "amount": ["loan"],
+            "status": ["loan"],
+            "district_id": ["account", "district"],
+            "A2": ["district"],
+            "A13": ["district"],
+        },
+        relationships=[
+            Relationship("account", "district_id", "district", "district_id"),
+            Relationship("loan", "account_id", "account", "account_id"),
+        ],
+    )
+
+
+def test_valid_sql_passes():
+    sql = "SELECT account_id, amount FROM loan WHERE status = 'B'"
+    validate_sql(sql, _recon())
+
+
+def test_valid_join_passes():
+    sql = """
+      SELECT d.A2, AVG(l.amount)
+      FROM loan l
+      JOIN account a ON l.account_id = a.account_id
+      JOIN district d ON a.district_id = d.district_id
+      GROUP BY d.A2
+    """
+    validate_sql(sql, _recon())
+
+
+def test_unknown_column_on_table_raises():
+    # The exact bug we hit in production: district_id picked from loan
+    # without joining through account.
+    sql = """
+      WITH x AS (SELECT district_id, AVG(amount) FROM loan GROUP BY district_id)
+      SELECT * FROM x
+    """
+    with pytest.raises(ReconValidationError) as exc:
+        validate_sql(sql, _recon())
+    msg = str(exc.value)
+    assert "district_id" in msg
+    # The hint should name where district_id actually lives.
+    assert "account" in msg and "district" in msg
+
+
+def test_misspelled_column_raises():
+    sql = "SELECT amnt FROM loan"
+    with pytest.raises(ReconValidationError) as exc:
+        validate_sql(sql, _recon())
+    assert "amnt" in str(exc.value)
+
+
+def test_qualified_column_on_wrong_table_raises():
+    # district.amount doesn't exist (amount is on loan).
+    sql = "SELECT d.amount FROM district d"
+    with pytest.raises(ReconValidationError):
+        validate_sql(sql, _recon())