a

Justfile

@@ -1,6 +1,9 @@
 watch:
 	watchexec -ce py,lark,ag -i gen 'just run'
 
+fmt:
+    pipenv run black .
+
 run:
     mypy *.py
     python agmain.py

aggen.py

@@ -18,6 +18,14 @@ class GenResult:
         self.parse_rules: defaultdict[str, List[str]] = defaultdict(list)
         self.starts: Set[str] = set()
         self.extra = ex
+        self.trans: List[str] = list()
+
+    @property
+    def transdef(self) -> str:
+        s = self.trans
+        if not s:
+            s = ["pass"]
+        return "\n" + "\n".join(map(lambda c: f"    {c}", s))
 
     @property
     def parser_data(self) -> str:

agmain.py

@@ -25,6 +25,8 @@ if __name__ == "__main__":
     with open("gen/arith.py", "w") as f:
         fmt_str = textwrap.dedent(
             """
+            # This documented generated by agtest.
+
             __all__ = ["parse"]
             from typing import Generic, TypeVar, Optional, Callable, Dict, Any
             from lark import Lark, Transformer
@@ -43,15 +45,22 @@ if __name__ == "__main__":
                         self.value = self.func()
                     return self.value
             parser = Lark('''{pd}''', parser='lalr', start={starts}, debug=True)
-            class Trans(Transformer[None]):
-                pass
+            class Trans(Transformer[None]): {transdef}
             {ex}
             def parse(input: str, start: Optional[str] = None) -> Any:
-                return parser.parse(input, start)
+                tree = parser.parse(input, start)
+                trans = Trans()
+                res = trans.transform(tree)
+                return res
         """
         )
         f.write(
-            fmt_str.format(pd=res.parser_data, ex=res.extra, starts=list(res.starts))
+            fmt_str.format(
+                pd=res.parser_data,
+                ex=res.extra,
+                starts=list(res.starts),
+                transdef=res.transdef,
+            )
         )
 
     mod = importlib.import_module("gen.arith")