fix: avoid npm reinstall for empty devDependencies (#7566)

* fix: avoid npm reinstall for empty devDependencies

* docs: address review feedback for npm manifest normalization

* ci: install greenlet for the Reflex 0.8.23 smoke test

* fix: add frontend dev packages with -D so npm saves them as devDependencies

npm reads -d as --loglevel info, not --save-dev, so the framework's dev
packages landed in dependencies and devDependencies was never written.
The rendered package.json then differed from the npm-written one on every
reload, which cleared the install cache and reinstalled packages. bun reads
-D as --dev too.

Replace the absent-vs-empty devDependencies normalization with the flag fix.

---------

Co-authored-by: Farhan Ali Raza <62690310+FarhanAliRaza@users.noreply.github.com>
Co-authored-by: Farhan <www.mfarvirus@gmail.com>

Author: harsh21234i

news/7566.bugfix.md

@@ -0,0 +1 @@
+Add development frontend packages with `-D`, so npm saves them under `devDependencies` and source-only hot reloads no longer reinstall frontend packages.

reflex/utils/js_runtimes.py

@@ -804,7 +804,7 @@ def _install_frontend_packages(
                 primary_package_manager,
                 "add",
                 "--legacy-peer-deps",
-                "-d",
+                "-D",
                 *dev_deps_to_add,
             ],
             show_status_message="Installing frontend development dependencies",

tests/units/test_prerequisites.py

@@ -959,7 +959,7 @@ def test_react_compiler_dependencies_toggle(install_packages_env: InstallPackage
     env.install()
     assert len(calls) == 1
     assert "add" in calls[0]
-    assert "-d" in calls[0]
+    assert "-D" in calls[0]
     assert {f"{name}@{version}" for name, version in compiler_deps.items()} <= set(
         calls[0]
     )
@@ -1102,7 +1102,7 @@ def get_frontend_development_dependencies(self):
 
     env.install()
 
-    dev_add_calls = [c for c in calls if "add" in c and "-d" in c]
+    dev_add_calls = [c for c in calls if "add" in c and "-D" in c]
     assert len(dev_add_calls) == 1
     dev_call = dev_add_calls[0]
     assert "fresh-dev" in dev_call
@@ -1145,7 +1145,7 @@ def test_install_frontend_packages_moves_misplaced_unpinned_dep_to_deps(
     assert len(add_calls) == 1
     add_call = add_calls[0]
     assert "some-pkg" in add_call
-    assert "-d" not in add_call
+    assert "-D" not in add_call
 
 
 def test_install_frontend_packages_moves_misplaced_unpinned_dev_dep_to_dev(
@@ -1174,11 +1174,11 @@ def get_frontend_development_dependencies(self):
     assert len(remove_calls) == 1
     assert "some-dev" in remove_calls[0]
 
-    dev_add_calls = [c for c in calls if "add" in c and "-d" in c]
+    dev_add_calls = [c for c in calls if "add" in c and "-D" in c]
     assert len(dev_add_calls) == 1
     assert "some-dev" in dev_add_calls[0]
 
-    deps_add_calls = [c for c in calls if "add" in c and "-d" not in c]
+    deps_add_calls = [c for c in calls if "add" in c and "-D" not in c]
     assert deps_add_calls == []
 
 
@@ -1204,7 +1204,7 @@ def test_install_frontend_packages_moves_misplaced_pinned_framework_dep(
     assert len(add_calls) == 1
     add_call = add_calls[0]
     assert "react@19.2.5" in add_call
-    assert "-d" not in add_call
+    assert "-D" not in add_call
 
 
 def test_install_frontend_packages_conflict_prefers_regular_section(
@@ -1230,7 +1230,7 @@ def get_frontend_development_dependencies(self):
     assert len(add_calls) == 1
     add_call = add_calls[0]
     assert "shared-pkg" in add_call
-    assert "-d" not in add_call
+    assert "-D" not in add_call
 
 
 def test_install_frontend_packages_dev_deps_added_before_regular_deps(
@@ -1254,9 +1254,9 @@ def get_frontend_development_dependencies(self):
 
     add_calls = [c for c in calls if "add" in c]
     assert len(add_calls) == 2
-    assert "-d" in add_calls[0]
+    assert "-D" in add_calls[0]
     assert "some-dev" in add_calls[0]
-    assert "-d" not in add_calls[1]
+    assert "-D" not in add_calls[1]
     assert "some-pkg" in add_calls[1]
 
 
@@ -1289,7 +1289,7 @@ def get_frontend_development_dependencies(self):
     add_calls = [c for c in calls if "add" in c]
     assert len(add_calls) == 1
     assert "shared-pkg" in add_calls[0]
-    assert "-d" not in add_calls[0]
+    assert "-D" not in add_calls[0]
 
 
 def test_install_frontend_packages_does_not_move_correctly_placed_packages(
@@ -1338,11 +1338,11 @@ def test_install_frontend_packages_pins_framework_dependencies(
     add_calls = [c for c in calls if "add" in c]
     pin_deps_call = next(c for c in add_calls if "react@19.2.5" in c)
     assert "isbot@5.1.39" in pin_deps_call
-    assert "-d" not in pin_deps_call
+    assert "-D" not in pin_deps_call
     assert "--only-missing" not in pin_deps_call
 
     pin_dev_deps_call = next(c for c in add_calls if "vite@8.0.9" in c)
-    assert "-d" in pin_dev_deps_call
+    assert "-D" in pin_dev_deps_call
     assert "--only-missing" not in pin_dev_deps_call
 
 
@@ -1367,6 +1367,30 @@ def run_package_manager(args, **kwargs):
     return calls
 
 
+@pytest.mark.parametrize("package_manager", ["bun", "npm"])
+def test_install_frontend_packages_saves_dev_deps_to_dev_section(
+    install_packages_env: InstallPackagesEnv,
+    monkeypatch,
+    package_manager: str,
+):
+    """Dev deps are added with ``-D``, the save-dev flag of both bun and npm.
+
+    npm reads ``-d`` as ``--loglevel info``, not as save-dev.
+
+    Args:
+        install_packages_env: The isolated install environment.
+        monkeypatch: The pytest monkeypatch fixture.
+        package_manager: The primary package manager path.
+    """
+    env = install_packages_env
+    monkeypatch.setattr(constants.PackageJson, "DEV_DEPENDENCIES", {"vite": "1.0.0"})
+    calls = _record_calls_with_pm(env, package_manager)
+
+    env.install()
+
+    assert calls == [[package_manager, "add", "--legacy-peer-deps", "-D", "vite@1.0.0"]]
+
+
 def test_install_frontend_packages_npm_skips_frozen_lockfile(
     install_packages_env: InstallPackagesEnv,
 ):