fix: replace asyncio subprocess proxy with thread-based Popen proxy

asyncio subprocess PIPE unreliable for long-lived stdio bridging. Use Popen + threads instead. Also fix smoke_test.sh stdin handling.

Dockerfile

@@ -27,7 +27,7 @@ RUN pip install --upgrade pip build \
 # ── Stage 3: final runtime ────────────────────────────────────────────────────
 # Use Microsoft's official .NET runtime image — avoids the SHA1-signed APT key
 # issue on newer Debian hosts (trixie+ rejects packages.microsoft.com GPG since 2026-02-01).
-FROM mcr.microsoft.com/dotnet/runtime:8.0
+FROM mcr.microsoft.com/dotnet/runtime:10.0
 
 # Install Python 3 + pip (the dotnet base image is Debian bookworm)
 RUN apt-get update \

ilsp/bicep_lsp/proxy.py

@@ -1,19 +1,23 @@
 """
-Asyncio TCP proxy that wraps Bicep.LangServer.dll.
+Thread-based TCP proxy that wraps Bicep.LangServer.dll.
 
 Architecture:
   Editor (TCP:2088) ──► BicepProxy ──► Bicep.LangServer subprocess (stdio)
 
-The proxy intercepts textDocument/completion responses and injects
+Uses subprocess.Popen + threads instead of asyncio subprocess — far more
-LRU Bicep module completions with higher sort priority (sortText "0_lru_...").
+reliable for stdin/stdout bridging of long-lived processes.
+
+Intercepts textDocument/completion responses and injects LRU Bicep module
+completions with higher sort priority (sortText "0_lru_...").
 All other LSP messages are forwarded unchanged.
 """
 
-import asyncio
 import json
 import logging
 import os
+import socket
 import subprocess
+import threading
 from typing import Any
 
 from .modules import BicepModuleCatalog
@@ -24,141 +28,159 @@ BICEP_LS_PATH = os.getenv(
     "BICEP_LS_PATH",
     "/opt/bicep-langserver/Bicep.LangServer.dll",
 )
-LISTEN_PORT = int(os.getenv("BICEP_LSP_PORT", "2088"))
 
 
-class _ContentLengthFramer:
+def _read_message(fileobj) -> bytes:
-    """Reads/writes LSP Content-Length framed messages."""
+    """Read one LSP Content-Length framed message from a file-like object."""
+    header = b""
+    while not header.endswith(b"\r\n\r\n"):
+        ch = fileobj.read(1)
+        if not ch:
+            raise EOFError("Stream closed")
+        header += ch
 
-    def __init__(self, reader: asyncio.StreamReader):
+    content_length = 0
-        self._reader = reader
+    for line in header.split(b"\r\n"):
+        if line.lower().startswith(b"content-length:"):
+            content_length = int(line.split(b":")[1].strip())
 
-    async def read_message(self) -> bytes:
+    return fileobj.read(content_length)
-        headers = b""
-        while not headers.endswith(b"\r\n\r\n"):
-            chunk = await self._reader.read(1)
-            if not chunk:
-                raise EOFError("Connection closed")
-            headers += chunk
-
-        content_length = 0
-        for line in headers.split(b"\r\n"):
-            if line.lower().startswith(b"content-length:"):
-                content_length = int(line.split(b":")[1].strip())
-
-        body = await self._reader.readexactly(content_length)
-        return body
-
-    @staticmethod
-    def frame(body: bytes) -> bytes:
-        return f"Content-Length: {len(body)}\r\n\r\n".encode() + body
 
 
-class BicepProxy:
+def _frame(body: bytes) -> bytes:
-    """Per-connection proxy between one editor client and one Bicep LS process."""
+    return f"Content-Length: {len(body)}\r\n\r\n".encode() + body
 
-    def __init__(self, reader: asyncio.StreamReader, writer: asyncio.StreamWriter):
-        self._client_reader = reader
-        self._client_writer = writer
-        self._proc: subprocess.Popen | None = None
-        self._ls_reader: asyncio.StreamReader | None = None
-        self._ls_writer: asyncio.StreamWriter | None = None
-
-    async def run(self) -> None:
-        peer = self._client_writer.get_extra_info("peername")
-        logger.info("New Bicep client: %s", peer)
-
-        self._proc = await asyncio.create_subprocess_exec(
-            "dotnet", BICEP_LS_PATH, "--stdio",
-            stdin=asyncio.subprocess.PIPE,
-            stdout=asyncio.subprocess.PIPE,
-            stderr=asyncio.subprocess.PIPE,
-        )
-
-        self._ls_reader = self._proc.stdout
-        self._ls_writer = self._proc.stdin
-
-        try:
-            await asyncio.gather(
-                self._client_to_ls(),
-                self._ls_to_client(),
-            )
-        except (EOFError, ConnectionResetError, asyncio.CancelledError):
-            pass
-        finally:
-            self._cleanup()
-
-    async def _client_to_ls(self) -> None:
-        framer = _ContentLengthFramer(self._client_reader)
-        while True:
-            body = await framer.read_message()
-            framed = _ContentLengthFramer.frame(body)
-            self._ls_writer.write(framed)
-            await self._ls_writer.drain()
-
-    async def _ls_to_client(self) -> None:
-        framer = _ContentLengthFramer(self._ls_reader)
-        while True:
-            body = await framer.read_message()
-
-            try:
-                msg = json.loads(body)
-                body = self._maybe_inject_completions(msg)
-            except json.JSONDecodeError:
-                pass
-
-            framed = _ContentLengthFramer.frame(
-                body if isinstance(body, bytes) else json.dumps(body).encode()
-            )
-            self._client_writer.write(framed)
-            await self._client_writer.drain()
-
-    def _maybe_inject_completions(self, msg: dict[str, Any]) -> dict[str, Any] | bytes:
-        """Inject LRU modules into completion responses."""
-        result = msg.get("result")
-        if result is None:
-            return json.dumps(msg).encode()
-
-        # Completion result is either a list or {isIncomplete, items}
-        items: list | None = None
-        if isinstance(result, list):
-            items = result
-        elif isinstance(result, dict) and "items" in result:
-            items = result["items"]
-
-        if items is None:
-            return json.dumps(msg).encode()
-
-        lru_items = BicepModuleCatalog.as_completion_items()
-        if lru_items:
-            # Downgrade standard items so LRU sorts first
-            for item in items:
-                st = item.get("sortText", item.get("label", ""))
-                item["sortText"] = f"1_az_{st}"
-
-            if isinstance(result, list):
-                msg["result"] = lru_items + items
-            else:
-                result["items"] = lru_items + items
-                result["isIncomplete"] = True
 
+def _inject_completions(msg: dict[str, Any]) -> bytes:
+    """Inject LRU modules into completion responses."""
+    result = msg.get("result")
+    if result is None:
         return json.dumps(msg).encode()
 
-    def _cleanup(self) -> None:
+    items: list | None = None
-        if self._proc and self._proc.returncode is None:
+    if isinstance(result, list):
-            self._proc.terminate()
+        items = result
-        self._client_writer.close()
+    elif isinstance(result, dict) and "items" in result:
+        items = result["items"]
+
+    if items is None:
+        return json.dumps(msg).encode()
+
+    lru_items = BicepModuleCatalog.as_completion_items()
+    if lru_items:
+        for item in items:
+            st = item.get("sortText", item.get("label", ""))
+            item["sortText"] = f"1_az_{st}"
+        if isinstance(result, list):
+            msg["result"] = lru_items + items
+        else:
+            result["items"] = lru_items + items
+            result["isIncomplete"] = True
+
+    return json.dumps(msg).encode()
 
 
-async def serve_bicep(port: int = LISTEN_PORT) -> None:
+def _client_to_ls(
-    """Start the Bicep LSP TCP proxy server."""
+    conn_file,
-    await BicepModuleCatalog.start_background_refresh()
+    proc_stdin,
+) -> None:
+    try:
+        while True:
+            body = _read_message(conn_file)
+            logger.debug("Client→LS: %d bytes", len(body))
+            framed = _frame(body)
+            proc_stdin.write(framed)
+            proc_stdin.flush()
+            logger.debug("Client→LS: flushed")
+    except EOFError:
+        logger.debug("Client write side closed — signalling EOF to LS")
+    except Exception as exc:
+        logger.debug("Client→LS error: %s", exc)
+    finally:
+        # Half-close: tell the LS that no more input is coming.
+        # The LS may still send responses, so we don't kill it here.
+        try:
+            proc_stdin.close()
+        except Exception:
+            pass
 
-    async def _handle(reader: asyncio.StreamReader, writer: asyncio.StreamWriter) -> None:
-        proxy = BicepProxy(reader, writer)
-        await proxy.run()
 
-    server = await asyncio.start_server(_handle, "0.0.0.0", port)
+def _ls_to_client(
+    proc_stdout,
+    conn: socket.socket,
+) -> None:
+    try:
+        while True:
+            body = _read_message(proc_stdout)
+            logger.debug("LS→Client: %d bytes", len(body))
+            try:
+                out = _inject_completions(json.loads(body))
+            except json.JSONDecodeError:
+                out = body
+            conn.sendall(_frame(out))
+    except EOFError:
+        logger.debug("Bicep LS stdout closed")
+    except Exception as exc:
+        logger.debug("LS→Client error: %s", exc)
+
+
+def _handle_client(conn: socket.socket, addr: tuple) -> None:
+    logger.info("New Bicep client: %s", addr)
+    proc = subprocess.Popen(
+        ["dotnet", BICEP_LS_PATH, "--stdio"],
+        stdin=subprocess.PIPE,
+        stdout=subprocess.PIPE,
+        stderr=subprocess.DEVNULL,
+    )
+    logger.info("Bicep LS subprocess started (pid=%d)", proc.pid)
+
+    # Unbuffered read from the socket — critical for correct LSP framing
+    conn_file = conn.makefile("rb", buffering=0)
+
+    # t1: client → LS  (finishes when client closes write side)
+    t1 = threading.Thread(
+        target=_client_to_ls,
+        args=(conn_file, proc.stdin),
+        daemon=True,
+    )
+    # t2: LS → client  (finishes when LS closes stdout)
+    t2 = threading.Thread(
+        target=_ls_to_client,
+        args=(proc.stdout, conn),
+        daemon=True,
+    )
+    t1.start()
+    t2.start()
+    # Session ends when LS is done (not when client closes write side)
+    t2.join()
+
+    try:
+        proc.wait(timeout=3)
+    except Exception:
+        proc.terminate()
+    try:
+        conn.close()
+    except Exception:
+        pass
+
+    logger.info("Bicep client %s disconnected", addr)
+
+
+def serve_bicep(port: int) -> None:
+    """Blocking TCP server — run in a daemon thread alongside asyncio."""
+    server = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
+    server.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
+    server.bind(("0.0.0.0", port))
+    server.listen(10)
     logger.info("Bicep LSP proxy listening on TCP :%d", port)
-    async with server:
+
-        await server.serve_forever()
+    while True:
+        try:
+            conn, addr = server.accept()
+            threading.Thread(
+                target=_handle_client,
+                args=(conn, addr),
+                daemon=True,
+            ).start()
+        except Exception as exc:
+            logger.error("Accept error: %s", exc)

ilsp/server.py

@@ -11,6 +11,7 @@ import asyncio
 import logging
 import os
 import signal
+import threading
 
 from aiohttp import web
 
@@ -58,13 +59,23 @@ async def main_async() -> None:
         level=logging.INFO,
         format="%(asctime)s [%(levelname)s] %(name)s: %(message)s",
     )
+    logging.getLogger("ilsp.bicep_lsp.proxy").setLevel(logging.DEBUG)
 
     # Pre-warm caches
     logger.info("Pre-warming catalogs…")
+    from .bicep_lsp.modules import BicepModuleCatalog
     await asyncio.gather(
         PypiCatalog.start_background_refresh(),
+        BicepModuleCatalog.start_background_refresh(),
     )
 
+    # Start Bicep LSP proxy in a daemon thread (blocking socket server)
+    threading.Thread(
+        target=serve_bicep,
+        args=(BICEP_LSP_PORT,),
+        daemon=True,
+    ).start()
+
     # Build health app
     health_app = await _health_app()
     runner = web.AppRunner(health_app)
@@ -73,11 +84,8 @@ async def main_async() -> None:
     await site.start()
     logger.info("Health endpoint on http://0.0.0.0:%d/health", HEALTH_PORT)
 
-    # Run all services
+    # Run remaining asyncio services
-    await asyncio.gather(
+    await _serve_python_lsp(PYTHON_LSP_PORT)
-        _serve_python_lsp(PYTHON_LSP_PORT),
-        serve_bicep(BICEP_LSP_PORT),
-    )
 
 
 def main() -> None:

pyproject.toml

@@ -1,6 +1,6 @@
 [build-system]
 requires = ["setuptools>=68", "wheel"]
-build-backend = "setuptools.backends.legacy:build"
+build-backend = "setuptools.build_meta"
 
 [project]
 name = "ilsp"

scripts/smoke_test.sh

@@ -13,8 +13,8 @@ HEALTH_PORT="${HEALTH_PORT:-2089}"
 PASS=0
 FAIL=0
 
-ok()   { echo "  ✓ $*"; ((PASS++)); }
+ok()   { echo "  ✓ $*"; PASS=$((PASS+1)); }
-fail() { echo "  ✗ $*"; ((FAIL++)); }
+fail() { echo "  ✗ $*"; FAIL=$((FAIL+1)); }
 
 # ── Helper: send LSP initialize and read response ─────────────────────────────
 
@@ -28,8 +28,14 @@ send_lsp_init() {
 lsp_check() {
     local name="$1"
     local port="$2"
+    local timeout="${3:-3}"
     local response
-    response=$(send_lsp_init "$port" | nc -w 3 "$HOST" "$port" 2>/dev/null || true)
+    # Keep stdin open during LSP server startup: the server must NOT see EOF
+    # on stdin before it has finished responding (especially slow .NET JIT).
+    # We send the init message and then sleep for the full timeout so that nc
+    # keeps the TCP write-side open while reading the server's response.
+    response=$({ send_lsp_init "$port"; sleep "$timeout"; } \
+        | nc -w "$timeout" "$HOST" "$port" 2>/dev/null || true)
     if echo "$response" | grep -q '"result"'; then
         ok "$name LSP responded to initialize (port $port)"
     else
@@ -65,11 +71,11 @@ else
     echo "  ⚠ nc not found — skipping TCP tests"
 fi
 
-# 3. Bicep LSP
+# 3. Bicep LSP (longer timeout — .NET startup takes a few seconds)
 echo ""
 echo "Bicep LSP (TCP :$BICEP_PORT)"
 if command -v nc &>/dev/null; then
-    lsp_check "Bicep" "$BICEP_PORT"
+    lsp_check "Bicep" "$BICEP_PORT" 12
 fi
 
 # ── Summary ───────────────────────────────────────────────────────────────────