Fix literal join operands and nested IF translation

- _quote_column_reference now passes numeric literals (e.g. 1, 3.14)
  through unquoted instead of wrapping them as identifiers ("1").
- IF/THEN/ELSE/END translation runs in a loop so nested IF blocks
  (IF x THEN IF y THEN ... END ELSE ... END) are fully converted
  to nested CASE WHEN expressions.

Author: nicosuave

sidemantic/adapters/tableau.py

@@ -459,7 +459,11 @@ def _translate_formula(formula: str | None) -> tuple[str | None, bool]:
     result = _translate_iif(result)
 
     # IF c THEN t ELSE e END -> CASE WHEN c THEN t ELSE e END
-    result = _IF_THEN_RE.sub(_if_to_case, result)
+    # Apply repeatedly for nested IF blocks
+    prev = None
+    while prev != result:
+        prev = result
+        result = _IF_THEN_RE.sub(_if_to_case, result)
 
     # CONTAINS(s, sub) -> s LIKE '%' || sub || '%' (balanced-paren aware)
     result = _translate_contains(result)
@@ -736,10 +740,18 @@ def _quote_sql_identifier(identifier: str) -> str:
     return '"' + identifier.replace('"', '""') + '"'
 
 
+_NUMERIC_LITERAL_RE = re.compile(r"^-?\d+(\.\d+)?$")
+
+
 def _quote_identifier_if_needed(identifier: str) -> str:
-    """Quote a raw Tableau field name when it is not a simple SQL identifier."""
+    """Quote a raw Tableau field name when it is not a simple SQL identifier.
+
+    Passes through numeric literals and already-quoted identifiers unchanged.
+    """
     if identifier.startswith('"') and identifier.endswith('"'):
         return identifier
+    if _NUMERIC_LITERAL_RE.match(identifier):
+        return identifier
     if _SIMPLE_SQL_IDENTIFIER_RE.match(identifier):
         return identifier
     if "." in identifier:
@@ -748,9 +760,15 @@ def _quote_identifier_if_needed(identifier: str) -> str:
 
 
 def _quote_column_reference(column_name: str) -> str:
-    """Quote a possibly-qualified column reference."""
-    parts = _strip_brackets(column_name).split(".")
-    return ".".join(_quote_sql_identifier(part) for part in parts if part)
+    """Quote a possibly-qualified column reference.
+
+    Passes through numeric literals unchanged.
+    """
+    stripped = _strip_brackets(column_name)
+    if _NUMERIC_LITERAL_RE.match(stripped):
+        return stripped
+    parts = stripped.split(".")
+    return ".".join(_quote_identifier_if_needed(part) for part in parts if part)
 
 
 def _quote_table_reference(table_name: str) -> str:

tests/adapters/tableau/test_formula.py

@@ -388,3 +388,11 @@ def test_contains_nested_args():
     assert "LIKE" in sql
     assert "COALESCE" in sql
     assert "'x'" in sql
+
+
+def test_nested_if_blocks():
+    """Nested IF/THEN/ELSE/END blocks are fully translated."""
+    sql, ok = _translate_formula("IF [x]=1 THEN IF [y]=2 THEN 'a' ELSE 'b' END ELSE 'c' END")
+    assert ok
+    assert "IF" not in sql.upper().replace("CASE WHEN", "")
+    assert sql.upper().count("CASE WHEN") == 2