refactor: extract shared create_prompt_env Jinja2 factory

Deduplicate the identical Environment(FileSystemLoader, StrictUndefined,
keep_trailing_newline=True) setup across JS testgen, Python testgen, and
Python explanations into core/shared/jinja_utils.py.

Also fix tests/testgen/test_testgen_javascript.py which had a stale
copy of build_javascript_prompt and loaded the now-deleted .md files.

django/aiservice/core/languages/js_ts/testgen.py

@@ -12,7 +12,6 @@ from pathlib import Path
 from typing import TYPE_CHECKING
 
 import sentry_sdk
-from jinja2 import Environment, FileSystemLoader, StrictUndefined
 import stamina
 from ninja.errors import HttpError
 from openai import OpenAIError
@@ -26,6 +25,7 @@ from aiservice.validators.javascript_validator import validate_javascript_syntax
 from authapp.auth import AuthenticatedRequest
 from core.log_features.log_event import update_optimization_cost
 from core.log_features.log_features import log_features
+from core.shared.jinja_utils import create_prompt_env
 from core.shared.testgen_models import (
     TestGenerationFailedError,
     TestGenErrorResponseSchema,
@@ -42,7 +42,7 @@ _TEST_FUNC_RE = re.compile(r"(?:test|it)\s*\(\s*['\"]")
 current_dir = Path(__file__).parent
 JS_PROMPTS_DIR = current_dir / "prompts" / "testgen"
 
-_jinja_env = Environment(loader=FileSystemLoader(JS_PROMPTS_DIR), keep_trailing_newline=True, undefined=StrictUndefined)
+_jinja_env = create_prompt_env(JS_PROMPTS_DIR)
 
 # Pattern to extract JavaScript code blocks
 JS_PATTERN = re.compile(r"^```(?:javascript|js|typescript|ts)?\s*\n(.*?)\n```", re.MULTILINE | re.DOTALL)

django/aiservice/core/languages/python/explanations/explanations.py

@@ -5,7 +5,6 @@ import logging
 from pathlib import Path
 
 import sentry_sdk
-from jinja2 import Environment, FileSystemLoader, StrictUndefined
 from ninja import NinjaAPI
 from openai.types.chat import (
     ChatCompletionMessageParam,
@@ -27,17 +26,12 @@ from core.languages.python.explanations.models import (
 )
 from core.log_features.log_event import update_optimization_cost
 from core.log_features.log_features import log_features
+from core.shared.jinja_utils import create_prompt_env
 
 explanations_api = NinjaAPI(urls_namespace="explanations")
 
 _PROMPT_DIR = Path(__file__).parent / "prompts"
-_jinja_env = Environment(  # noqa: S701 — rendering LLM prompts, not HTML
-    loader=FileSystemLoader(_PROMPT_DIR),
-    undefined=StrictUndefined,
-    keep_trailing_newline=True,
-    trim_blocks=True,
-    lstrip_blocks=True,
-)
+_jinja_env = create_prompt_env(_PROMPT_DIR, trim_blocks=True, lstrip_blocks=True)
 
 SYSTEM_PROMPT_TEMPLATE = _jinja_env.get_template("system_prompt.md.j2")
 USER_PROMPT_TEMPLATE = _jinja_env.get_template("user_prompt.md.j2")

django/aiservice/core/languages/python/testgen/generate.py

@@ -10,7 +10,6 @@ from typing import TYPE_CHECKING
 import libcst as cst
 import sentry_sdk
 import stamina
-from jinja2 import Environment, FileSystemLoader, StrictUndefined
 from ninja.errors import HttpError
 from openai import OpenAIError
 
@@ -34,6 +33,7 @@ from core.languages.python.testgen.preprocessing.preprocess_pipeline import gene
 from core.languages.python.testgen.validate import instrument_tests, validate_request_data
 from core.log_features.log_event import update_optimization_cost
 from core.log_features.log_features import log_features
+from core.shared.jinja_utils import create_prompt_env
 from core.shared.testgen_models import (
     TestGenDebugInfo,
     TestGenerationFailedError,
@@ -58,7 +58,7 @@ def select_model_for_test(test_index: int) -> tuple[LLM, str]:
 _current_dir = Path(__file__).parent
 _prompts_dir = _current_dir / "prompts"
 
-_jinja_env = Environment(loader=FileSystemLoader(_prompts_dir), keep_trailing_newline=True, undefined=StrictUndefined)  # noqa: S701 - rendering LLM prompts, not HTML
+_jinja_env = create_prompt_env(_prompts_dir)
 
 
 def build_prompt(

django/aiservice/core/shared/jinja_utils.py

@@ -0,0 +1,18 @@
+from pathlib import Path
+
+from jinja2 import Environment, FileSystemLoader, StrictUndefined
+
+
+def create_prompt_env(
+    prompt_dir: Path,
+    *,
+    trim_blocks: bool = False,
+    lstrip_blocks: bool = False,
+) -> Environment:
+    return Environment(  # noqa: S701 — rendering LLM prompts, not HTML
+        loader=FileSystemLoader(prompt_dir),
+        keep_trailing_newline=True,
+        undefined=StrictUndefined,
+        trim_blocks=trim_blocks,
+        lstrip_blocks=lstrip_blocks,
+    )

django/aiservice/tests/testgen/test_testgen_javascript.py

@@ -1,23 +1,13 @@
 """Tests for JavaScript test generation module.
 
-Tests the prompt building and validation functions without importing
-the full testgen module (to avoid LLM dependencies in tests).
+Tests the prompt building and validation functions.
 """
 
 import re
-from pathlib import Path
 
 import pytest
 
-# Load prompts directly to avoid importing testgen_javascript.py
-JS_PROMPTS_DIR = Path(__file__).parent.parent.parent / "core" / "languages" / "js_ts" / "prompts" / "testgen"
-
-JS_EXECUTE_SYSTEM_PROMPT = (JS_PROMPTS_DIR / "execute_system_prompt.md").read_text()
-JS_EXECUTE_USER_PROMPT = (JS_PROMPTS_DIR / "execute_user_prompt.md").read_text()
-JS_EXECUTE_ASYNC_SYSTEM_PROMPT = (JS_PROMPTS_DIR / "execute_async_system_prompt.md").read_text()
-JS_EXECUTE_ASYNC_USER_PROMPT = (JS_PROMPTS_DIR / "execute_async_user_prompt.md").read_text()
-
-JS_PATTERN = re.compile(r"^```(?:javascript|js|typescript|ts)?\s*\n(.*?)\n```", re.MULTILINE | re.DOTALL)
+from core.languages.js_ts.testgen import build_javascript_prompt, parse_and_validate_js_output
 
 
 def _has_test_functions(code: str) -> bool:
@@ -26,55 +16,6 @@ def _has_test_functions(code: str) -> bool:
     return bool(re.search(test_pattern, code))
 
 
-def build_javascript_prompt(
-    function_name: str, function_code: str, module_path: str, test_framework: str, is_async: bool
-) -> tuple[list[dict[str, str]], str]:
-    """Build the prompt messages for JavaScript test generation."""
-    if is_async:
-        system_prompt = JS_EXECUTE_ASYNC_SYSTEM_PROMPT
-        user_prompt = JS_EXECUTE_ASYNC_USER_PROMPT
-        posthog_event_suffix = "async-"
-    else:
-        system_prompt = JS_EXECUTE_SYSTEM_PROMPT
-        user_prompt = JS_EXECUTE_USER_PROMPT
-        posthog_event_suffix = ""
-
-    import_statement = f"import {{ {function_name} }} from '{module_path}';"
-
-    system_message = {"role": "system", "content": system_prompt.format(function_name=function_name)}
-
-    user_message = {
-        "role": "user",
-        "content": user_prompt.format(
-            test_framework=test_framework,
-            function_name=function_name,
-            function_code=function_code,
-            import_statement=import_statement,
-            package_comment="",
-        ),
-    }
-
-    messages = [system_message, user_message]
-    return messages, posthog_event_suffix
-
-
-def parse_and_validate_js_output(response_content: str) -> str:
-    """Parse and validate the LLM response for JavaScript code."""
-    if "```" not in response_content:
-        raise ValueError("LLM response did not contain a code block.")
-
-    pattern_res = JS_PATTERN.search(response_content)
-    if not pattern_res:
-        raise ValueError("No JavaScript code block found in the LLM response.")
-
-    code = pattern_res.group(1).strip()
-
-    if not _has_test_functions(code):
-        raise ValueError("Generated code does not contain any test functions.")
-
-    return code
-
-
 class TestHasTestFunctions:
     """Tests for detecting Jest test functions in code."""