For Express, emit message if need to upgrade rsconnect-python

shiny/_main.py

@@ -10,7 +10,7 @@
 import sys
 import types
 from pathlib import Path
-from typing import Any, Optional
+from typing import Any, Literal, Optional
 
 import click
 import uvicorn
@@ -288,6 +288,9 @@ def run_app(
             # is "shiny.express.app:_2f_path_2f_to_2f_app_2e_py".
             app = "shiny.express.app:" + escape_to_var_name(str(app_path))
             app_dir = str(app_path.parent)
+
+            # Express apps need min version of rsconnect-python to deploy correctly.
+            _verify_rsconnect_version()
         else:
             app, app_dir = resolve_app(app, app_dir)
 
@@ -626,3 +629,47 @@ class ReloadArgs(TypedDict):
     reload_includes: NotRequired[list[str]]
     reload_excludes: NotRequired[list[str]]
     reload_dirs: NotRequired[list[str]]
+
+
+# Check that the version of rsconnect supports Shiny Express; can be removed in the
+# future once this version of rsconnect is widely used. (Added 2024-03)
+def _verify_rsconnect_version() -> None:
+    PACKAGE_NAME = "rsconnect-python"
+    MIN_VERSION = "1.22.0"
+
+    from importlib.metadata import PackageNotFoundError, version
+
+    def _safe_int(x: str) -> int:
+        try:
+            return int(x)
+        except ValueError:
+            return 0
+
+    def _compare_package_versions(version1: str, version2: str) -> Literal[-1, 0, 1]:
+        parts1 = [_safe_int(x) for x in version1.split(".")]
+        parts2 = [_safe_int(x) for x in version2.split(".")]
+
+        max_length = max(len(parts1), len(parts2))
+        parts1 += [0] * (max_length - len(parts1))
+        parts2 += [0] * (max_length - len(parts2))
+
+        for part1, part2 in zip(parts1, parts2):
+            if part1 > part2:
+                return 1
+            elif part1 < part2:
+                return -1
+
+        return 0
+
+    try:
+        package_version = version(PACKAGE_NAME)
+        print(package_version)
+        if _compare_package_versions(package_version, MIN_VERSION) < 0:
+            print(
+                f"Warning: rsconnect-python {package_version} is installed, but it does not support deploying Shiny Express applications. "
+                f"Please upgrade to at least version {MIN_VERSION}. "
+                "If you are using pip, you can run `pip install --upgrade rsconnect-python`",
+                file=sys.stderr,
+            )
+    except PackageNotFoundError:
+        pass