core: Add encoding config to json for load_prompt()

libs/core/langchain_core/prompts/loading.py

@@ -51,9 +51,13 @@ def _load_template(var_name: str, config: dict) -> dict:
             )
         # Pop the template path from the config.
         template_path = Path(config.pop(f"{var_name}_path"))
+        if f"{var_name}_encoding" in config:
+            encoding = config.pop(f"{var_name}_encoding")
+        else:
+            encoding = None
         # Load the template.
         if template_path.suffix == ".txt":
-            with open(template_path) as f:
+            with open(template_path, encoding=encoding) as f:
                 template = f.read()
         else:
             raise ValueError

libs/core/tests/unit_tests/examples/simple_prompt_with_template_file_cp932.json

@@ -0,0 +1,6 @@
+{
+    "_type": "prompt",
+    "input_variables": ["adjective", "content"],
+    "template_path": "simple_template_cp932.txt",
+    "template_encoding": "cp932"
+}

libs/core/tests/unit_tests/examples/simple_prompt_with_template_file_utf8.json

@@ -0,0 +1,6 @@
+{
+    "_type": "prompt",
+    "input_variables": ["adjective", "content"],
+    "template_path": "simple_template_utf8.txt",
+    "template_encoding": "utf-8"
+}

libs/core/tests/unit_tests/examples/simple_template_cp932.txt

@@ -0,0 +1 @@
+Tell me a {adjective} joke about {content}. SJIS���{��e�X�g

libs/core/tests/unit_tests/examples/simple_template_utf8.txt

@@ -0,0 +1 @@
+Tell me a {adjective} joke about {content}. AÁĂȀ🐌😁

libs/core/tests/unit_tests/prompts/test_loading.py

@@ -99,6 +99,28 @@ def test_loading_with_template_as_file() -> None:
         assert prompt == expected_prompt
 
 
+def test_loading_from_json_utf8() -> None:
+    """Test loading when the template is a file."""
+    with change_directory(EXAMPLE_DIR):
+        prompt = load_prompt("simple_prompt_with_template_file_utf8.json")
+        expected_prompt = PromptTemplate(
+            input_variables=["adjective", "content"],
+            template="Tell me a {adjective} joke about {content}. AÁĂȀ🐌😁",
+        )
+        assert prompt == expected_prompt
+
+
+def test_loading_from_json_cp932() -> None:
+    """Test loading when the template is a file."""
+    with change_directory(EXAMPLE_DIR):
+        prompt = load_prompt("simple_prompt_with_template_file_cp932.json")
+        expected_prompt = PromptTemplate(
+            input_variables=["adjective", "content"],
+            template="Tell me a {adjective} joke about {content}. SJIS日本語テスト",
+        )
+        assert prompt == expected_prompt
+
+
 def test_loading_few_shot_prompt_from_yaml() -> None:
     """Test loading few shot prompt from yaml."""
     with change_directory(EXAMPLE_DIR):