update changelog and deprecation test

Author: DuYicong515

CHANGELOG.md

@@ -587,6 +587,9 @@ The format is based on [Keep a Changelog](http://keepachangelog.com/en/1.0.0/).
 - Deprecated passing only the callback state to `Callback.on_load_checkpoint(callback_state)` in favor of passing the callback state to `Callback.load_state_dict` and in 1.8, passing the entire checkpoint dictionary to `Callback.on_load_checkpoint(checkpoint)` ([#11887](https://github.com/PyTorchLightning/pytorch-lightning/pull/11887))
 
 
+- Deprecated `Trainer.tpu_cores` in favor of `Trainer.num_devices` ([#12437](https://github.com/PyTorchLightning/pytorch-lightning/pull/12437))
+
+
 ### Removed
 
 - Removed deprecated parameter `method` in `pytorch_lightning.utilities.model_helpers.is_overridden` ([#10507](https://github.com/PyTorchLightning/pytorch-lightning/pull/10507))
@@ -795,6 +798,9 @@ The format is based on [Keep a Changelog](http://keepachangelog.com/en/1.0.0/).
 - Removed `AcceleratorConnector.devices` property ([#12435](https://github.com/PyTorchLightning/pytorch-lightning/pull/12435))
 
 
+- Removed `AcceleratorConnector.tpu_cores` property ([#12437](https://github.com/PyTorchLightning/pytorch-lightning/pull/12437))
+
+
 ### Fixed
 
 - Fixed an issue where `ModelCheckpoint` could delete older checkpoints when `dirpath` has changed during resumed training ([#12045](https://github.com/PyTorchLightning/pytorch-lightning/pull/12045))

pytorch_lightning/callbacks/xla_stats_monitor.py

@@ -76,7 +76,7 @@ def on_train_start(self, trainer: "pl.Trainer", pl_module: "pl.LightningModule")
         if isinstance(trainer.accelerator, TPUAccelerator):
             raise MisconfigurationException(
                 "You are using XLAStatsMonitor but are not running on TPU."
-                f" The Trainer accelerator type is set to {trainer.accelerator.name().upper()}."
+                f" The accelerator type is set to {trainer.accelerator.name().upper()}."
             )
 
         device = trainer.strategy.root_device

tests/accelerators/test_tpu.py

@@ -103,6 +103,12 @@ def test_accelerator_tpu(accelerator, devices):
     assert isinstance(trainer.accelerator, TPUAccelerator)
     assert isinstance(trainer.strategy, TPUSpawnStrategy)
     assert trainer.num_devices == 8
+    with pytest.deprecated_call(
+        match= "`Trainer.tpu_cores` is deprecated in v1.6 and will be removed in v1.8. "
+        "Please use `Trainer.devices` instead."
+    ):
+        trainer.tpu_cores == 8
+
 
 
 @RunIf(tpu=True)