Restrict concat rewrite to VARCHAR, hide untranslatable fields

- _convert_string_concat no longer matches + CAST(...) generically;
  only AS VARCHAR) + triggers the rewrite, preserving INT/FLOAT
  arithmetic.
- Untranslatable formulas (LOD, table calcs) now set public=False
  and sql='NULL' to prevent raw Tableau syntax from being emitted
  in generated SQL queries.

Author: nicosuave

sidemantic/adapters/tableau.py

@@ -418,7 +418,8 @@ def _convert_string_concat(text: str) -> str:
     """Convert Tableau's + string concatenation to SQL ||.
 
     Replaces + with || when at least one adjacent operand is a string-producing
-    expression: a string literal ('...') or a CAST(... AS VARCHAR).
+    expression: a string literal ('...') or a CAST(... AS VARCHAR) result.
+    Only matches VARCHAR casts (not INTEGER/DOUBLE) to avoid breaking arithmetic.
     """
     result = text
     prev = None
@@ -427,9 +428,8 @@ def _convert_string_concat(text: str) -> str:
         # 'string' + ... or ... + 'string'
         result = re.sub(r"('\s*)\+(\s*)", r"\1||\2", result)
         result = re.sub(r"(\s*)\+(\s*')", r"\1||\2", result)
-        # CAST(... AS VARCHAR) + ... or ... + CAST(... AS VARCHAR)
+        # CAST(... AS VARCHAR) + ... (only VARCHAR, not INTEGER/DOUBLE)
         result = re.sub(r"(AS\s+VARCHAR\)\s*)\+(\s*)", r"\1||\2", result, flags=re.IGNORECASE)
-        result = re.sub(r"(\s*)\+(\s*CAST\()", r"\1||\2", result, flags=re.IGNORECASE)
     return result
 
 
@@ -994,6 +994,12 @@ def _parse_column(
             if not is_translatable:
                 metadata = {"tableau_formula": formula}
 
+        # Untranslatable formulas (LOD, table calcs) produce non-queryable fields
+        # with NULL sql to prevent raw Tableau syntax in generated SQL
+        if not is_translatable:
+            hidden = True
+            sql_expr = "NULL"
+
         if role == "measure":
             return self._build_metric(
                 col_name, aggregation, sql_expr, caption, hidden, is_translatable, formula, metadata
@@ -1056,10 +1062,13 @@ def _build_metric(
 
         if agg_lower in _PASSTHROUGH_AGGS or not is_translatable:
             # Passthrough or untranslatable: make derived metric
+            # Use NULL placeholder for untranslatable formulas to prevent
+            # raw Tableau syntax from being emitted in SQL queries
+            safe_sql = "NULL" if not is_translatable else (sql or name)
             return Metric(
                 name=name,
                 type="derived",
-                sql=sql or name,
+                sql=safe_sql,
                 label=caption,
                 public=not hidden,
                 metadata=metadata,

tests/adapters/tableau/test_formula.py

@@ -284,6 +284,14 @@ def test_arithmetic_plus_preserved():
     assert "||" not in sql
 
 
+def test_numeric_cast_plus_preserved():
+    """INT() + FLOAT() keeps arithmetic +, not ||."""
+    sql, ok = _translate_formula("[x] + INT([y])")
+    assert ok
+    assert "+" in sql
+    assert "||" not in sql
+
+
 def test_dateadd():
     """DATEADD('unit', n, date) -> date_add(date, INTERVAL (n) unit)."""
     sql, ok = _translate_formula("DATEADD('hour', 3, [created_at])")

tests/adapters/tableau/test_parsing.py

@@ -188,7 +188,7 @@ def test_aggregation_mapping_all_aggs(adapter):
 
 
 def test_lod_expression_preserved(adapter):
-    """LOD expressions are not translated; raw formula stored in metadata."""
+    """LOD expressions are not translated; raw formula stored in metadata, hidden from queries."""
     graph = adapter.parse(FIXTURES / "kitchen_sink.tds")
     model = graph.models["kitchen_sink"]
 
@@ -198,6 +198,9 @@ def test_lod_expression_preserved(adapter):
     assert lod.metadata is not None
     assert "tableau_formula" in lod.metadata
     assert "{FIXED" in lod.metadata["tableau_formula"]
+    # Untranslatable formulas should be hidden and use safe SQL
+    assert lod.public is False
+    assert lod.sql == "NULL"
 
 
 # =============================================================================