Improve lf.function_gen().

1. Improve the default behavior: num_retries=1 and no unittest.
2. Improve the meaning of unittest field. User should set to 'auto' to explicitely enable auto unittest. By default, the None value means no unittest.

PiperOrigin-RevId: 703607882

langfun/core/structured/function_generation.py

@@ -16,7 +16,7 @@
 import functools
 import inspect
 import re
-from typing import Any, Callable, Optional, Tuple
+from typing import Any, Callable, Literal, Optional, Tuple
 
 from langfun.core import language_model
 from langfun.core import template
@@ -25,7 +25,7 @@
 import pyglove as pg
 
 
-def unittest_gen(signature, lm, num_retries=10):
+def unittest_gen(signature, lm, num_retries=1):
   """Generates unit tests for a python function signature."""
 
   class UnitTest(pg.Object):
@@ -78,10 +78,13 @@ def _function_gen(
     func: Callable[..., Any],
     signature: str,
     lm: language_model.LanguageModel,
-    num_retries: int = 10,
+    num_retries: int = 1,
     unittest: Optional[
-        Callable[[Callable[..., Any]], None] | list[Tuple[Any, Any]]
+        Callable[[Callable[..., Any]], None]
+        | list[Tuple[Any, Any]]
+        | Literal["auto"]
     ] = None,
+    unittest_num_retries: int = 1,
 ):
   """Generates a python function with LLM and verify its quality with unit testing."""
 
@@ -131,9 +134,11 @@ def calculate_area_circle(radius: float) -> float:
     """
 
   unittest_examples = None
-  if unittest is None:
-    unittest_examples = unittest_gen(signature, lm=lm)
-  elif not callable(unittest):
+  if unittest == "auto":
+    unittest_examples = unittest_gen(
+        signature, lm=lm, num_retries=unittest_num_retries
+    )
+  elif isinstance(unittest, list):
     unittest_examples = unittest
 
   for _ in range(num_retries):
@@ -145,11 +150,16 @@ def calculate_area_circle(radius: float) -> float:
 
       # Check whether the sigantures are the same.
       if inspect.signature(f) != inspect.signature(func):
+        pg.logging.warning(
+            "Signature mismatch. Expected: %s, Actual: %s",
+            inspect.signature(func),
+            inspect.signature(f),
+        )
         continue
 
       if callable(unittest):
         unittest(f)
-      else:
+      elif unittest_examples:
         unittest_with_test_cases(f, unittest_examples)
 
       return f, source_code
@@ -172,10 +182,13 @@ def _process_signature(signature):
 def function_gen(
     lm: language_model.LanguageModel,
     cache_filename: str | None = None,
-    num_retries: int = 10,
+    num_retries: int = 1,
     unittest: Optional[
-        Callable[[Callable[..., Any]], None] | list[Tuple[Any, Any]]
+        Callable[[Callable[..., Any]], None]
+        | list[Tuple[Any, Any]]
+        | Literal["auto"]
     ] = None,
+    unittest_num_retries: int = 1,
 ):
   """A decorator for automating function generation using a language model.
 
@@ -192,9 +205,12 @@ def function_gen(
         make to generate a suitable function implementation.
       unittest: This optional parameter enables the definition of custom unit
         tests. You can either provide a list of test cases as tuples of inputs
-        and outputs, or a function that throws an error if a test fails. If left
-        as None (the default setting), the LLM will automatically create the
-        unit test cases.
+        and outputs, or a function that throws an error if a test fails, or let
+        LLM automatically create the unit test cases. If a generated function is
+        and returned, it should pass all the unittests.
+      unittest_num_retries: If unittest is set to "auto", this parameter
+        specifies the number of times the LLM's attempts to generate unit test
+        cases.
 
   Returns:
       The implemented function object.
@@ -226,7 +242,12 @@ def lm_generated_func(*args, **kwargs):
           return func.__function__(*args, **kwargs)
 
       func.__function__, func.__source_code__ = _function_gen(
-          func, signature, lm, num_retries=num_retries, unittest=unittest
+          func,
+          signature,
+          lm,
+          num_retries=num_retries,
+          unittest=unittest,
+          unittest_num_retries=unittest_num_retries,
       )
       if func.__function__ is None:
         raise ValueError(f"Function generation failed. Signature:\n{signature}")

langfun/core/structured/function_generation_test.py

@@ -63,6 +63,42 @@ def linear_search(items, target):
 
     lm = fake.StaticSequence([unittest_lm_response, function_gen_lm_response])
 
+    @function_generation.function_gen(lm=lm, unittest='auto')
+    def linear_search(items, target):  # pylint: disable=unused-argument
+      """Performs a linear search on a list to find a target value.
+
+      Args:
+          items (list): The list to search within.
+          target: The value to search for.
+
+      Returns:
+          int: The index of the target value if found, otherwise -1.
+      """
+
+    self.assertEqual(linear_search(['a', 'b', 'c'], 'c'), 2)
+    self.assertEqual(linear_search.source(), function_gen_lm_response)
+
+  def test_generate_function_without_unittest(self):
+    function_gen_lm_response = inspect.cleandoc("""
+        def linear_search(items, target):
+            \"\"\"
+            Performs a linear search on a list to find a target value.
+
+            Args:
+                items (list): The list to search within.
+                target: The value to search for.
+
+            Returns:
+                int: The index of the target value if found, otherwise -1.
+            \"\"\"
+            for i, item in enumerate(items):
+                if item == target:
+                    return i
+            return -1
+        """)
+
+    lm = fake.StaticSequence([function_gen_lm_response])
+
     @function_generation.function_gen(lm=lm)
     def linear_search(items, target):  # pylint: disable=unused-argument
       """Performs a linear search on a list to find a target value.
@@ -258,7 +294,9 @@ def _unittest_fn(func):
     cache_file = os.path.join(cache_file_dir, 'cache_file.json')
 
     @function_generation.function_gen(
-        lm=lm, unittest=_unittest_fn, cache_filename=cache_file
+        lm=lm,
+        unittest=_unittest_fn,
+        cache_filename=cache_file,
     )
     def linear_search(items, target):  # pylint: disable=unused-argument
       """Performs a linear search on a list to find a target value.
@@ -310,7 +348,9 @@ def _unittest_fn(func):
 
     custom_unittest = _unittest_fn
 
-    @function_generation.function_gen(lm=lm, unittest=custom_unittest)
+    @function_generation.function_gen(
+        lm=lm, unittest=custom_unittest, num_retries=2
+    )
     def linear_search(items, target):  # pylint: disable=unused-argument
       """Performs a linear search on a list to find a target value.