[Haik]: ckpt, abstracted utils into their own folder

backend/apps/app_builder/utils/execute_backend_code.py

@@ -0,0 +1,71 @@
+import asyncio
+import json
+import sys
+from typing import Dict, Any
+from pydantic import BaseModel
+from typeguard import typechecked
+
+TIMEOUT_SECONDS = 30
+
+class BackendExecResult(BaseModel):
+    result: Dict[str, Any]
+    stdout: str
+    stderr: str
+
+@typechecked
+async def execute_backend_code(code: str) -> BackendExecResult:
+    """Execute user-provided Python code in a subprocess.
+
+    The code must assign its result to a global ``result`` dict.
+    User print() calls are captured separately from the result via
+    an in-process StringIO redirect.
+    """
+
+    preamble: str = (
+        "import json, sys, io\n"
+        "_orig_stdout = sys.stdout\n"
+        "_capture = io.StringIO()\n"
+        "sys.stdout = _capture\n"
+        "result = {}\n"
+    )
+    postamble: str = (
+        "\nsys.stdout = _orig_stdout\n"
+        'json.dump({"__stdout__": _capture.getvalue(), "__result__": result}, sys.stdout)\n'
+    )
+    wrapper: str = preamble + code + postamble
+
+    proc: asyncio.subprocess.Process = await asyncio.create_subprocess_exec(
+        sys.executable, "-c", wrapper,
+        stdout=asyncio.subprocess.PIPE,
+        stderr=asyncio.subprocess.PIPE,
+    )
+
+    try:
+        stdout: bytes
+        stderr: bytes
+        stdout, stderr = await asyncio.wait_for(
+            proc.communicate(),
+            timeout=TIMEOUT_SECONDS,
+        )
+    except asyncio.TimeoutError:
+        proc.kill()
+        await proc.wait()
+        raise RuntimeError(f"Backend code execution timed out after {TIMEOUT_SECONDS}s")
+
+    stderr_text: str = stderr.decode(errors="replace").strip()
+
+    if proc.returncode != 0:
+        raise RuntimeError(f"Backend code error (exit {proc.returncode}): {stderr_text}")
+
+    try:
+        parsed: Dict[str, Any] = json.loads(stdout.decode())
+        return BackendExecResult(
+            result=parsed.get("__result__", {}),
+            stdout=parsed.get("__stdout__", ""),
+            stderr=stderr_text,
+        )
+    except json.JSONDecodeError:
+        raw: str = stdout.decode(errors="replace").strip()
+        raise RuntimeError(
+            f"Backend code did not produce valid JSON. Raw output: {raw[:500]}"
+        )