feat: warn when a newer version is available

docs/CHANGELOG.md

@@ -7,6 +7,10 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## Unreleased
 
+- `rsconnect deploy` commands now check PyPI once a day for a newer release of
+  rsconnect-python and print an upgrade hint to stderr when one is available.
+  The result is cached so most invocations make no network request. Set
+  `RSCONNECT_DISABLE_VERSION_CHECK=1` to turn the check off entirely.
 - The "no package-lock.json" error when deploying Node.js content now states
   that Connect installs Node.js dependencies with npm, helping publishers who
   build with yarn or pnpm understand why a `package-lock.json` is required.

docs/deploying.md

@@ -432,6 +432,21 @@ is uploaded and deployed. If the deployment fails, the new environment variables
 will still take effect.
 
 
+### Update notifications
+
+When you run a `rsconnect deploy` command, rsconnect-python checks PyPI for a
+newer release and prints an upgrade hint to stderr if one is available. The
+result is cached for 24 hours, so most deployments make no extra network
+request, and the check never blocks or fails a deployment.
+
+To disable the check entirely, set the `RSCONNECT_DISABLE_VERSION_CHECK`
+environment variable to `1` (or `true`/`yes`):
+
+```bash
+export RSCONNECT_DISABLE_VERSION_CHECK=1
+```
+
+
 ### Updating a Deployment
 
 If you deploy a file again to the same server, `rsconnect` will update the previous

pyproject.toml

@@ -14,6 +14,7 @@ dependencies = [
     "semver>=2.0.0,<4.0.0",
     "pyjwt>=2.4.0",
     "click>=8.0.0",
+    "packaging>=20.0",
     "toml>=0.10; python_version < '3.11'",
 ]
 

rsconnect/main.py

@@ -39,6 +39,7 @@
 from rsconnect.certificates import read_certificate_file
 
 from . import VERSION, api, validation
+from .version_check import BackgroundVersionCheck
 from .actions import (
     cli_feedback,
     create_quarto_deployment_bundle,
@@ -1325,8 +1326,19 @@ def quickstart(app_type: str, name: str, python_version: Optional[str]):
 
 
 @cli.group(no_args_is_help=True, help="Deploy content to Posit Connect, Posit Cloud, or shinyapps.io.")
-def deploy():
-    pass
+@click.pass_context
+def deploy(ctx: click.Context):
+    checker = BackgroundVersionCheck()
+    checker.start()
+
+    def _print_version_warning() -> None:
+        message = checker.get_warning_message()
+        if message:
+            click.secho(message, fg="yellow", err=True)
+
+    # Registered on the context (not as a result callback) so the hint prints on
+    # every exit path, including failed deploys that raise or call sys.exit().
+    ctx.call_on_close(_print_version_warning)
 
 
 def _warn_on_ignored_manifest(directory: str):

rsconnect/version_check.py

@@ -0,0 +1,140 @@
+"""Background version update check against PyPI.
+
+Checked only on deploy commands. The latest known version from PyPI is cached on
+disk and refreshed at most once per :data:`_CACHE_TTL_SECONDS`, so the common case
+adds no network traffic and no latency.
+"""
+
+from __future__ import annotations
+
+import json
+import os
+import threading
+import time
+from http.client import HTTPSConnection
+from os.path import join
+from typing import Optional, Tuple
+
+from packaging.version import Version
+
+from . import VERSION
+from .metadata import config_dirname, makedirs
+
+RSCONNECT_DISABLE_VERSION_CHECK = "RSCONNECT_DISABLE_VERSION_CHECK"
+_PYPI_HOST = "pypi.org"
+_PYPI_PATH = "/pypi/rsconnect-python/json"
+_PYPI_TIMEOUT_SECONDS = 2
+_CACHE_TTL_SECONDS = 24 * 60 * 60  # Re-check PyPI at most once a day.
+_CACHE_FILENAME = "version_check.json"
+
+
+def _is_check_disabled() -> bool:
+    value = os.environ.get(RSCONNECT_DISABLE_VERSION_CHECK, "").strip().lower()
+    return value in ("1", "true", "yes")
+
+
+def _is_dev_version(version_str: str) -> bool:
+    try:
+        return Version(version_str).is_devrelease
+    except Exception:
+        return True
+
+
+def _cache_path() -> str:
+    return join(config_dirname(), _CACHE_FILENAME)
+
+
+def _read_cache() -> Tuple[bool, Optional[str]]:
+    """Return ``(is_fresh, latest)``.
+
+    ``latest`` is the last known PyPI version recorded in the cache (or None when
+    the cache is missing/unreadable or the last fetch failed). It is returned
+    regardless of freshness so even a stale value can drive the upgrade hint while
+    a refresh runs in the background. ``is_fresh`` is True only when the entry is
+    within the TTL, signalling that no background refresh is needed.
+    """
+    try:
+        with open(_cache_path()) as f:
+            data = json.load(f)
+        latest = data.get("latest")
+        latest = latest if isinstance(latest, str) else None
+        is_fresh = time.time() - float(data["checked_at"]) <= _CACHE_TTL_SECONDS
+        return (is_fresh, latest)
+    except Exception:
+        return (False, None)
+
+
+def _write_cache(latest: Optional[str]) -> None:
+    """Persist the latest known version (or None) with the current timestamp.
+
+    A None value is still cached so repeated failures don't re-hit PyPI on every
+    deploy until the TTL expires.
+    """
+    try:
+        path = _cache_path()
+        makedirs(path)
+        with open(path, "w") as f:
+            json.dump({"checked_at": time.time(), "latest": latest}, f)
+    except Exception:
+        pass
+
+
+def _fetch_latest_version() -> Optional[str]:
+    conn = None
+    try:
+        conn = HTTPSConnection(_PYPI_HOST, timeout=_PYPI_TIMEOUT_SECONDS)
+        conn.request("GET", _PYPI_PATH, headers={"Accept": "application/json"})
+        response = conn.getresponse()
+        if response.status != 200:
+            return None
+        data = json.loads(response.read())
+        return data.get("info", {}).get("version")
+    except Exception:
+        return None
+    finally:
+        if conn is not None:
+            conn.close()
+
+
+def _update_message(latest: Optional[str]) -> Optional[str]:
+    """Return an upgrade warning if ``latest`` is newer than the running version."""
+    try:
+        if latest is not None and Version(latest) > Version(VERSION):
+            return (
+                f"A new version of rsconnect-python is available: {latest} "
+                f"(you have {VERSION}).\n"
+                f"Upgrade with: pip install --upgrade rsconnect-python"
+            )
+    except Exception:
+        pass
+    return None
+
+
+class BackgroundVersionCheck:
+    """Resolves the latest available version, using a cache and a background fetch."""
+
+    def __init__(self) -> None:
+        self._thread: Optional[threading.Thread] = None
+        self._latest: Optional[str] = None
+
+    def start(self) -> None:
+        if _is_check_disabled() or _is_dev_version(VERSION):
+            return
+        is_fresh, latest = _read_cache()
+        # Drive the hint from the cached value, synchronously. Even a stale value
+        # is good enough to suggest an upgrade and reading it adds no latency, so
+        # the warning prints reliably on every exit path -- including commands
+        # that fail fast before any network fetch could have completed.
+        self._latest = latest
+        if not is_fresh:
+            # Refresh the cache in the background for the next invocation. This
+            # run never waits on or reads the result, so its output (and timing)
+            # are unaffected by the fetch.
+            self._thread = threading.Thread(target=self._run, daemon=True)
+            self._thread.start()
+
+    def _run(self) -> None:
+        _write_cache(_fetch_latest_version())
+
+    def get_warning_message(self) -> Optional[str]:
+        return _update_message(self._latest)