[cli] detect composite block classes in custom_blocks

.ai/skills/custom-blocks/SKILL.md

@@ -57,7 +57,8 @@ diffusers-cli custom_blocks [--block_module_name <file.py>] [--block_class_name
 ### What it does
 
 1. **AST scan**: parses `<file>` without executing it, walks top-level `ClassDef` nodes, and collects every
-   class whose `bases` include `ModularPipelineBlocks`.
+   class whose `bases` include `ModularPipelineBlocks` or one of its composite subclasses
+   (`SequentialPipelineBlocks`, `AutoPipelineBlocks`, `ConditionalPipelineBlocks`, `LoopSequentialPipelineBlocks`).
 2. **Pick a class**: uses `--block_class_name` if given, else the first found. Errors with the list of available
    classes if your name doesn't match.
 3. **Load and save**: imports the file via `importlib.util.spec_from_file_location` (this does execute the
@@ -137,9 +138,9 @@ diffusers-cli run --model my-user/my-denoise-block --trust-remote-code \
 - **`block_class_name could not be retrieved. Available classes from <file>: [ClassA, ClassB]`** — your
   `--block_class_name` doesn't match any `ModularPipelineBlocks` subclass found. Pick from the list shown.
 - **No classes found**: silent — the command will try to use the first entry in an empty list and raise
-  `IndexError`. If you hit that, double-check your class actually inherits from `ModularPipelineBlocks`
-  (the AST scan looks for that literal base-class name; aliased imports like `from diffusers import ...
-  as MPB` won't be picked up).
+  `IndexError`. If you hit that, double-check your class actually inherits from `ModularPipelineBlocks` or one
+  of the composite classes listed above (the AST scan looks for those literal class names; aliased imports like
+  `from diffusers import ... as MPB` won't be picked up).
 - **Block requires constructor args**: the command calls `<ClassName>()` with no args. If your block needs
   `__init__` parameters, refactor to take them from `state`/`components` at `__call__` time instead, or
   hardcode defaults in `__init__`.

docs/source/en/using-diffusers/cli.md

@@ -290,8 +290,9 @@ hf sandbox kill <id>
 ## `custom_blocks`
 
 Package a local `ModularPipelineBlocks` subclass for upload to the Hub. Reads a Python file, AST-scans it for
-subclasses of `ModularPipelineBlocks`, instantiates the chosen one, and calls `save_pretrained` in the current
-working directory.
+classes deriving from `ModularPipelineBlocks` or one of its composite subclasses (`SequentialPipelineBlocks`,
+`AutoPipelineBlocks`, `ConditionalPipelineBlocks`, `LoopSequentialPipelineBlocks`), instantiates the chosen one, and
+calls `save_pretrained` in the current working directory.
 
 ```bash
 # Package the first block found in ./block.py

src/diffusers/commands/custom_blocks.py

@@ -28,7 +28,14 @@
 from . import BaseDiffusersCLICommand
 
 
-EXPECTED_PARENT_CLASSES = ["ModularPipelineBlocks"]
+# the block base class and its composite subclasses; a class deriving from any of them is a packageable block
+EXPECTED_PARENT_CLASSES = [
+    "ModularPipelineBlocks",
+    "SequentialPipelineBlocks",
+    "AutoPipelineBlocks",
+    "ConditionalPipelineBlocks",
+    "LoopSequentialPipelineBlocks",
+]
 
 
 def conversion_command_factory(args: Namespace):
@@ -128,7 +135,10 @@ def _get_class_names(self, file_path):
             if not isinstance(node, ast.ClassDef):
                 continue
 
-            base_names = [bname for b in node.bases if (bname := self._get_base_name(b)) is not None]
+            # compare on the class name only, so `diffusers.modular_pipelines.SequentialPipelineBlocks` matches too
+            base_names = [
+                bname.rsplit(".", 1)[-1] for b in node.bases if (bname := self._get_base_name(b)) is not None
+            ]
 
             for allowed in EXPECTED_PARENT_CLASSES:
                 if allowed in base_names:

tests/others/test_cli_commands.py

@@ -432,9 +432,16 @@ def test_class_discovery(self, tmp_path):
             "class OtherBase:\n    pass\n"
             "class NotABlock(OtherBase):\n    pass\n"
             "class MyBlock(ModularPipelineBlocks):\n    pass\n"
+            # composite blocks are packageable too, and the base may be referenced through its module
+            "class MyBlocks(SequentialPipelineBlocks):\n    pass\n"
+            "class MyAutoBlocks(diffusers.modular_pipelines.AutoPipelineBlocks):\n    pass\n"
         )
         cmd = CustomBlocksCommand()
-        assert cmd._get_class_names(block_py) == [("MyBlock", "ModularPipelineBlocks")]
+        assert cmd._get_class_names(block_py) == [
+            ("MyBlock", "ModularPipelineBlocks"),
+            ("MyBlocks", "SequentialPipelineBlocks"),
+            ("MyAutoBlocks", "AutoPipelineBlocks"),
+        ]
 
         broken = tmp_path / "broken.py"
         broken.write_text("class Broken(:\n    pass\n")
@@ -457,6 +464,25 @@ def test_packaging_writes_pipeline_index(self, tmp_path, monkeypatch):
         assert (tmp_path / "modular_config.json").exists()
         assert (tmp_path / "modular_model_index.json").exists()
 
+    def test_packaging_composite_block(self, tmp_path, monkeypatch):
+        # a `SequentialPipelineBlocks` subclass is the usual thing to publish; it must be selectable by name
+        block_py = tmp_path / "block.py"
+        block_py.write_text(
+            "from diffusers.modular_pipelines import ModularPipelineBlocks, SequentialPipelineBlocks\n"
+            "\n"
+            "class MyStep(ModularPipelineBlocks):\n"
+            "    model_name = 'test'\n"
+            "\n"
+            "class MyBlocks(SequentialPipelineBlocks):\n"
+            "    model_name = 'test'\n"
+            "    block_classes = [MyStep]\n"
+            "    block_names = ['step']\n"
+        )
+        monkeypatch.chdir(tmp_path)
+        CustomBlocksCommand(str(block_py), "MyBlocks").run()
+        config = json.loads((tmp_path / "modular_config.json").read_text())
+        assert config["auto_map"] == {"ModularPipelineBlocks": "block.MyBlocks"}
+
 
 class TestCli:
     def test_toplevel_help_lists_all_commands(self):