Mark --cert option on run as is_eager

CHANGES.rst

@@ -7,6 +7,8 @@ Unreleased
 
 -   Fix type annotation for ``json.loads``, it accepts str or bytes.
     :issue:`4519`
+-   The ``--cert`` and ``--key`` options on ``flask run`` can be given
+    in either order. :issue:`4459`
 
 
 Version 2.1.1

src/flask/cli.py

@@ -763,7 +763,10 @@ def convert(self, value, param, ctx):
 @click.option("--host", "-h", default="127.0.0.1", help="The interface to bind to.")
 @click.option("--port", "-p", default=5000, help="The port to bind to.")
 @click.option(
-    "--cert", type=CertParamType(), help="Specify a certificate file to use HTTPS."
+    "--cert",
+    type=CertParamType(),
+    help="Specify a certificate file to use HTTPS.",
+    is_eager=True,
 )
 @click.option(
     "--key",

tests/test_cli.py

@@ -553,9 +553,14 @@ def test_run_cert_path():
     with pytest.raises(click.BadParameter):
         run_command.make_context("run", ["--key", __file__])
 
+    # cert specified first
     ctx = run_command.make_context("run", ["--cert", __file__, "--key", __file__])
     assert ctx.params["cert"] == (__file__, __file__)
 
+    # key specified first
+    ctx = run_command.make_context("run", ["--key", __file__, "--cert", __file__])
+    assert ctx.params["cert"] == (__file__, __file__)
+
 
 def test_run_cert_adhoc(monkeypatch):
     monkeypatch.setitem(sys.modules, "cryptography", None)