enable import `lightning.app` if it is installed (#20059)

.github/workflows/README.md

@@ -14,7 +14,6 @@ Brief description of all our automation tools used for boosting development perf
 | .azure-pipelines/gpu-tests-fabric.yml  | Run only GPU-specific tests, standalone\*, and examples.                                  | GPU         |
 | .azure-pipelines/gpu-tests-pytorch.yml | Run only GPU-specific tests, standalone\*, and examples.                                  | GPU         |
 | .azure-pipelines/gpu-benchmarks.yml    | Run speed/memory benchmarks for parity with vanila PyTorch.                               | GPU         |
-| .github/workflows/ci-flagship-apps.yml | Run end-2-end tests with full applications, including deployment to the production cloud. | CPU         |
 | .github/workflows/ci-tests-pytorch.yml | Run all tests except for accelerator-specific, standalone and slow tests.                 | CPU         |
 | .github/workflows/tpu-tests.yml        | Run only TPU-specific tests. Requires that the PR title contains '\[TPU\]'                | TPU         |
 

.github/workflows/ci-pkg-extend.yml

@@ -0,0 +1,53 @@
+name: Package extras
+
+# see: https://help.github.com/en/actions/reference/events-that-trigger-workflows
+on:
+  push:
+    branches: [master, "release/*"]
+  pull_request:
+    branches: [master, "release/*"]
+    types: [opened, reopened, ready_for_review, synchronize] # added `ready_for_review` since draft is skipped
+    paths:
+      - ".github/workflows/ci-pkg-extend.yml"
+      - "requirements/ci.txt"
+      - "requirements/app/*"
+      - "requirements/data/*"
+      - "src/lightning/app/*"
+      - "src/lightning/data/*"
+      - "!*.md"
+      - "!**/*.md"
+
+concurrency:
+  group: ${{ github.workflow }}-${{ github.ref }}-${{ github.head_ref }}
+  cancel-in-progress: ${{ github.event_name == 'pull_request' }}
+
+defaults:
+  run:
+    shell: bash
+
+jobs:
+
+  import-pkg:
+    runs-on: ${{ matrix.os }}
+    strategy:
+      fail-fast: true
+      matrix:
+        os: ["ubuntu-22.04", "macOS-12", "windows-2022"]
+        pkg-name: ["app", "data"]
+        python-version: ["3.8", "3.11"]
+    env:
+      TORCH_URL: "https://download.pytorch.org/whl/cpu/torch_stable.html"
+    steps:
+      - uses: actions/checkout@v4
+      - uses: actions/setup-python@v5
+        with:
+          python-version: ${{ matrix.python-version }}
+
+      - name: Install package
+        run: pip install lightning[${{ matrix.pkg-name }}] -f $TORCH_URL
+        timeout-minutes: 10
+
+      - name: Try importing
+        run: from lightning.${{ matrix.pkg-name }} import *
+        shell: python
+

.github/workflows/ci-pkg-install.yml

@@ -88,7 +88,7 @@ jobs:
         if: ${{ matrix.pkg-name == 'lightning' || matrix.pkg-name == 'notset' }}
         working-directory: src/lit
         run: |
-          items=("data")
+          items=("app" "data")
           for item in "${items[@]}"; do
             echo "Removing $item"
             rm -rf $item

examples/fabric/tensor_parallel/train.py

@@ -1,13 +1,14 @@
 import lightning as L
 import torch
 import torch.nn.functional as F
-from data import RandomTokenDataset
 from lightning.fabric.strategies import ModelParallelStrategy
 from model import ModelArgs, Transformer
 from parallelism import parallelize
 from torch.distributed.tensor.parallel import loss_parallel
 from torch.utils.data import DataLoader
 
+from data import RandomTokenDataset
+
 
 def train():
     strategy = ModelParallelStrategy(

examples/pytorch/tensor_parallel/train.py

@@ -1,13 +1,14 @@
 import lightning as L
 import torch
 import torch.nn.functional as F
-from data import RandomTokenDataset
 from lightning.pytorch.strategies import ModelParallelStrategy
 from model import ModelArgs, Transformer
 from parallelism import parallelize
 from torch.distributed.tensor.parallel import loss_parallel
 from torch.utils.data import DataLoader
 
+from data import RandomTokenDataset
+
 
 class Llama3(L.LightningModule):
     def __init__(self):

requirements/app/app.txt

@@ -0,0 +1,3 @@
+# NOTE: this is here only to expose `pip install lightning[app]`. we don't install or test it in this project's CI
+
+lightning_app >= 2.3.3, <2.3.4

src/lightning/app/__init__.py

@@ -0,0 +1,26 @@
+import sys
+
+from lightning_utilities.core.imports import RequirementCache, module_available
+
+__all__ = []
+
+if not RequirementCache("lightning_app"):
+    raise ModuleNotFoundError("Please, run `pip install lightning-app`")  # E111
+
+else:
+    import lightning_app
+
+    # Enable resolution at least for lower data namespace
+    sys.modules["lightning.app"] = lightning_app
+
+    from lightning_app.core.app import LightningApp  # noqa: E402
+    from lightning_app.core.flow import LightningFlow  # noqa: E402
+    from lightning_app.core.work import LightningWork  # noqa: E402
+    from lightning_app.plugin.plugin import LightningPlugin  # noqa: E402
+    from lightning_app.utilities.packaging.build_config import BuildConfig  # noqa: E402
+    from lightning_app.utilities.packaging.cloud_compute import CloudCompute  # noqa: E402
+
+    if module_available("lightning_app.components.demo"):
+        from lightning.app.components import demo  # noqa: F401
+
+    __all__ = ["LightningApp", "LightningFlow", "LightningWork", "LightningPlugin", "BuildConfig", "CloudCompute"]