Var substitution (#51)

* moves var expand line to command.py

* adds test

src/sql/command.py

@@ -11,6 +11,10 @@ class SQLCommand:
     """
 
     def __init__(self, magic, user_ns, line, cell) -> None:
+        # Parse variables (words wrapped in {}) for %%sql magic
+        # (for %sql this is done automatically)
+        cell = magic.shell.var_expand(cell)
+
         self.args = parse.magic_args(magic.execute, line)
 
         if (

src/sql/magic.py

@@ -232,10 +232,6 @@ def execute(self, line="", cell="", local_ns={}):
         user_ns = self.shell.user_ns.copy()
         user_ns.update(local_ns)
 
-        # Parse variables (words wrapped in {}) for %%sql magic
-        # (for %sql this is done automatically)
-        cell = self.shell.var_expand(cell)
-
         command = SQLCommand(self, user_ns, line, cell)
         # args.line: contains the line after the magic with all options removed
         args = command.args

src/tests/test_command.py

@@ -165,3 +165,16 @@ def test_parse_sql_when_passing_engine(ip, sql_magic, tmp_empty, line):
     assert cmd.connection is engine
     assert cmd.sql == sql_expected
     assert cmd.sql_original == sql_expected
+
+
+def test_variable_substitution_cell_magic(ip, sql_magic):
+    ip.user_global_ns["username"] = "some-user"
+
+    cmd = SQLCommand(
+        sql_magic,
+        ip.user_ns,
+        line="",
+        cell="GRANT CONNECT ON DATABASE postgres TO $username;",
+    )
+
+    assert cmd.parsed["sql"] == "\nGRANT CONNECT ON DATABASE postgres TO some-user;"