From 91c3d8ecb9a91c0ab197309f1c0bf12d53b1fb5d Mon Sep 17 00:00:00 2001
From: Kaushik B <45285388+kaushikb11@users.noreply.github.com>
Date: Mon, 11 Apr 2022 23:31:17 +0530
Subject: [PATCH] =?UTF-8?q?Raise=20`MisconfigurationException`=20when=20th?=
 =?UTF-8?q?e=20accelerator=20is=20available=20but=E2=80=A6=20(#12708)?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

---
 CHANGELOG.md                                     |  2 +-
 .../trainer/connectors/accelerator_connector.py  | 11 +++++++++++
 tests/accelerators/test_accelerator_connector.py | 16 +++++++---------
 tests/accelerators/test_cpu.py                   |  2 +-
 4 files changed, 20 insertions(+), 11 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 5a31916976..9abc1ccf64 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -120,7 +120,7 @@ The format is based on [Keep a Changelog](http://keepachangelog.com/en/1.0.0/).
 - Don't raise a warning when `nn.Module` is not saved under hparams ([#12669](https://github.com/PyTorchLightning/pytorch-lightning/pull/12669))
 
 
--
+- Raise `MisconfigurationException` when the accelerator is available but the user passes invalid `([]/0/"0")` values to the `devices` flag ([#12708](https://github.com/PyTorchLightning/pytorch-lightning/pull/12708))
 
 
 ## [1.6.0] - 2022-03-29
diff --git a/pytorch_lightning/trainer/connectors/accelerator_connector.py b/pytorch_lightning/trainer/connectors/accelerator_connector.py
index 174051c44c..f4932a2ae8 100644
--- a/pytorch_lightning/trainer/connectors/accelerator_connector.py
+++ b/pytorch_lightning/trainer/connectors/accelerator_connector.py
@@ -412,6 +412,17 @@ class AcceleratorConnector:
         self._num_nodes_flag = int(num_nodes) if num_nodes is not None else 1
         self._devices_flag = devices
 
+        if self._devices_flag in ([], 0, "0"):
+            accelerator_name = (
+                self._accelerator_flag.__class__.__qualname__
+                if isinstance(self._accelerator_flag, Accelerator)
+                else self._accelerator_flag
+            )
+            raise MisconfigurationException(
+                f"`Trainer(devices={self._devices_flag!r})` value is not a valid input"
+                f" using {accelerator_name} accelerator."
+            )
+
         # TODO: Delete this method when num_processes, gpus, ipus and tpu_cores gets removed
         self._map_deprecated_devices_specific_info_to_accelerator_and_device_flag(
             devices, num_processes, gpus, ipus, tpu_cores
diff --git a/tests/accelerators/test_accelerator_connector.py b/tests/accelerators/test_accelerator_connector.py
index 02c946e186..1d64705d1b 100644
--- a/tests/accelerators/test_accelerator_connector.py
+++ b/tests/accelerators/test_accelerator_connector.py
@@ -504,15 +504,6 @@ def test_accelerator_cpu(_):
         trainer = Trainer(accelerator="cpu", gpus=1)
 
 
-@mock.patch("torch.cuda.is_available", return_value=False)
-@pytest.mark.parametrize("devices", ["0", 0, []])
-def test_passing_zero_and_empty_list_to_devices_flag(_, devices):
-    with pytest.raises(
-        MisconfigurationException, match="can not run on your system since the accelerator is not available."
-    ):
-        Trainer(accelerator="gpu", devices=devices)
-
-
 @RunIf(min_gpus=1)
 def test_accelerator_gpu():
     trainer = Trainer(accelerator="gpu", devices=1)
@@ -1014,3 +1005,10 @@ def test_sync_batchnorm_set_in_custom_strategy(tmpdir):
 def test_plugin_only_one_instance_for_one_type(plugins, expected):
     with pytest.raises(MisconfigurationException, match=f"Received multiple values for {expected}"):
         Trainer(plugins=plugins)
+
+
+@pytest.mark.parametrize("accelerator", ("cpu", "gpu", "tpu", "ipu"))
+@pytest.mark.parametrize("devices", ("0", 0, []))
+def test_passing_zero_and_empty_list_to_devices_flag(accelerator, devices):
+    with pytest.raises(MisconfigurationException, match="value is not a valid input using"):
+        Trainer(accelerator=accelerator, devices=devices)
diff --git a/tests/accelerators/test_cpu.py b/tests/accelerators/test_cpu.py
index 8abacd47af..ce9f6d6b21 100644
--- a/tests/accelerators/test_cpu.py
+++ b/tests/accelerators/test_cpu.py
@@ -69,7 +69,7 @@ def test_restore_checkpoint_after_pre_setup(tmpdir, restore_after_pre_setup):
         func(model, ckpt_path=checkpoint_path)
 
 
-@pytest.mark.parametrize("devices", ([3], -1, 0))
+@pytest.mark.parametrize("devices", ([3], -1))
 def test_invalid_devices_with_cpu_accelerator(devices):
     """Test invalid device flag raises MisconfigurationException with CPUAccelerator."""
     with pytest.raises(MisconfigurationException, match="should be an int > 0"):