fix prompt saving (#4987)

will add unit tests

docs/modules/prompts/prompt_templates/examples/prompt_serialization.ipynb

@@ -559,7 +559,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 18,
+   "execution_count": 1,
    "id": "0b6dd7b8",
    "metadata": {},
    "outputs": [
@@ -631,6 +631,84 @@
     "prompt = load_prompt(\"few_shot_prompt_example_prompt.json\")\n",
     "print(prompt.format(adjective=\"funny\"))"
    ]
+  },
+  {
+   "cell_type": "markdown",
+   "id": "c6e3f9fe",
+   "metadata": {},
+   "source": [
+    "## PromptTempalte with OutputParser\n",
+    "This shows an example of loading a prompt along with an OutputParser from a file."
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 13,
+   "id": "500dab26",
+   "metadata": {},
+   "outputs": [
+    {
+     "name": "stdout",
+     "output_type": "stream",
+     "text": [
+      "{\r\n",
+      "    \"input_variables\": [\r\n",
+      "        \"question\",\r\n",
+      "        \"student_answer\"\r\n",
+      "    ],\r\n",
+      "    \"output_parser\": {\r\n",
+      "        \"regex\": \"(.*?)\\\\nScore: (.*)\",\r\n",
+      "        \"output_keys\": [\r\n",
+      "            \"answer\",\r\n",
+      "            \"score\"\r\n",
+      "        ],\r\n",
+      "        \"default_output_key\": null,\r\n",
+      "        \"_type\": \"regex_parser\"\r\n",
+      "    },\r\n",
+      "    \"partial_variables\": {},\r\n",
+      "    \"template\": \"Given the following question and student answer, provide a correct answer and score the student answer.\\nQuestion: {question}\\nStudent Answer: {student_answer}\\nCorrect Answer:\",\r\n",
+      "    \"template_format\": \"f-string\",\r\n",
+      "    \"validate_template\": true,\r\n",
+      "    \"_type\": \"prompt\"\r\n",
+      "}"
+     ]
+    }
+   ],
+   "source": [
+    "! cat prompt_with_output_parser.json"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 20,
+   "id": "d267a736",
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "prompt = load_prompt(\"prompt_with_output_parser.json\")"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 21,
+   "id": "cb770399",
+   "metadata": {},
+   "outputs": [
+    {
+     "data": {
+      "text/plain": [
+       "{'answer': 'George Washington was born in 1732 and died in 1799.',\n",
+       " 'score': '1/2'}"
+      ]
+     },
+     "execution_count": 21,
+     "metadata": {},
+     "output_type": "execute_result"
+    }
+   ],
+   "source": [
+    "prompt.output_parser.parse(\"George Washington was born in 1732 and died in 1799.\\nScore: 1/2\")"
+   ]
   }
  ],
  "metadata": {
@@ -649,7 +727,7 @@
    "name": "python",
    "nbconvert_exporter": "python",
    "pygments_lexer": "ipython3",
-   "version": "3.9.1"
+   "version": "3.11.3"
   },
   "vscode": {
    "interpreter": {

docs/modules/prompts/prompt_templates/examples/prompt_with_output_parser.json

@@ -0,0 +1,20 @@
+{
+    "input_variables": [
+        "question",
+        "student_answer"
+    ],
+    "output_parser": {
+        "regex": "(.*?)\nScore: (.*)",
+        "output_keys": [
+            "answer",
+            "score"
+        ],
+        "default_output_key": null,
+        "_type": "regex_parser"
+    },
+    "partial_variables": {},
+    "template": "Given the following question and student answer, provide a correct answer and score the student answer.\nQuestion: {question}\nStudent Answer: {student_answer}\nCorrect Answer:",
+    "template_format": "f-string",
+    "validate_template": true,
+    "_type": "prompt"
+}

langchain/prompts/loading.py

@@ -74,15 +74,14 @@ def _load_examples(config: dict) -> dict:
 
 def _load_output_parser(config: dict) -> dict:
     """Load output parser."""
-    if "output_parsers" in config:
-        if config["output_parsers"] is not None:
-            _config = config["output_parsers"]
-            output_parser_type = _config["_type"]
-            if output_parser_type == "regex_parser":
-                output_parser = RegexParser(**_config)
-            else:
-                raise ValueError(f"Unsupported output parser {output_parser_type}")
-            config["output_parsers"] = output_parser
+    if "output_parser" in config and config["output_parser"]:
+        _config = config.pop("output_parser")
+        output_parser_type = _config.pop("_type")
+        if output_parser_type == "regex_parser":
+            output_parser = RegexParser(**_config)
+        else:
+            raise ValueError(f"Unsupported output parser {output_parser_type}")
+        config["output_parser"] = output_parser
     return config
 
 

tests/unit_tests/prompts/test_loading.py

@@ -5,6 +5,7 @@ from contextlib import contextmanager
 from pathlib import Path
 from typing import Iterator
 
+from langchain.output_parsers import RegexParser
 from langchain.prompts.few_shot import FewShotPromptTemplate
 from langchain.prompts.loading import load_prompt
 from langchain.prompts.prompt import PromptTemplate
@@ -160,3 +161,24 @@ def test_loading_few_shot_prompt_example_prompt() -> None:
             suffix="Input: {adjective}\nOutput:",
         )
         assert prompt == expected_prompt
+
+
+def test_loading_with_output_parser() -> None:
+    with change_directory():
+        prompt = load_prompt("prompt_with_output_parser.json")
+        expected_template = """\
+Given the following question and student answer, \
+provide a correct answer and score the student answer.
+Question: {question}
+Student Answer: {student_answer}
+Correct Answer:\
+"""
+        expected_prompt = PromptTemplate(
+            input_variables=["question", "student_answer"],
+            output_parser=RegexParser(
+                regex="(.*?)\nScore: (.*)",
+                output_keys=["answer", "score"],
+            ),
+            template=expected_template,
+        )
+        assert prompt == expected_prompt