[docs] add auto docstring and parameter templates documentation for m…

.ai/skills/model-integration/modular-conversion.md

@@ -148,5 +148,6 @@ ComponentSpec(
 - [ ] Create pipeline class with `default_blocks_name`
 - [ ] Assemble blocks in `modular_blocks_<model>.py`
 - [ ] Wire up `__init__.py` with lazy imports
+- [ ] Add `# auto_docstring` above all assembled blocks (SequentialPipelineBlocks, AutoPipelineBlocks, etc.), run `python utils/modular_auto_docstring.py --fix_and_overwrite`, and verify the generated docstrings — all parameters should have proper descriptions with no "TODO" placeholders indicating missing definitions
 - [ ] Run `make style` and `make quality`
 - [ ] Test all workflows for parity with reference

docs/source/en/_toctree.yml

@@ -112,6 +112,8 @@
     title: ModularPipeline
   - local: modular_diffusers/components_manager
     title: ComponentsManager
+  - local: modular_diffusers/auto_docstring
+    title: Auto docstring and parameter templates
   - local: modular_diffusers/custom_blocks
     title: Building Custom Blocks
   - local: modular_diffusers/mellon

docs/source/en/modular_diffusers/auto_docstring.md

@@ -0,0 +1,157 @@
+<!--Copyright 2025 The HuggingFace Team. All rights reserved.
+
+Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with
+the License. You may obtain a copy of the License at
+
+http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on
+an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the
+specific language governing permissions and limitations under the License.
+-->
+
+# Auto docstring and parameter templates
+
+Every [`~modular_pipelines.ModularPipelineBlocks`] has a `doc` property that is automatically generated from its `description`, `inputs`, `intermediate_outputs`, `expected_components`, and `expected_configs`. The auto docstring system keeps docstrings in sync with the block's actual interface. Parameter templates provide standardized descriptions for parameters that appear across many pipelines.
+
+## Auto docstring
+
+Modular pipeline blocks are composable — you can nest them, chain them in sequences, and rearrange them freely. Their docstrings follow the same pattern. When a [`~modular_pipelines.SequentialPipelineBlocks`] aggregates inputs and outputs from its sub-blocks, the documentation should update automatically without manual rewrites.
+
+The `# auto_docstring` marker generates docstrings from the block's properties. Add it above a class definition to mark the class for automatic docstring generation.
+
+```py
+# auto_docstring
+class FluxTextEncoderStep(SequentialPipelineBlocks):
+    ...
+```
+
+Run the following command to generate and insert the docstrings.
+
+```bash
+python utils/modular_auto_docstring.py --fix_and_overwrite
+```
+
+The utility reads the block's `doc` property and inserts it as the class docstring.
+
+```py
+# auto_docstring
+class FluxTextEncoderStep(SequentialPipelineBlocks):
+    """
+    Text input processing step that standardizes text embeddings for the pipeline.
+
+    Inputs:
+        prompt_embeds (`torch.Tensor`) *required*:
+            text embeddings used to guide the image generation.
+        ...
+
+    Outputs:
+        prompt_embeds (`torch.Tensor`):
+            text embeddings used to guide the image generation.
+        ...
+    """
+```
+
+You can also check without overwriting, or target a specific file or directory.
+
+```bash
+# Check that all marked classes have up-to-date docstrings
+python utils/modular_auto_docstring.py
+
+# Check a specific file or directory
+python utils/modular_auto_docstring.py src/diffusers/modular_pipelines/flux/
+```
+
+If any marked class is missing a docstring, the check fails and lists the classes that need updating.
+
+```
+Found the following # auto_docstring markers that need docstrings:
+- src/diffusers/modular_pipelines/flux/encoders.py: FluxTextEncoderStep at line 42
+
+Run `python utils/modular_auto_docstring.py --fix_and_overwrite` to fix them.
+```
+
+## Parameter templates
+
+`InputParam` and `OutputParam` define a block's inputs and outputs. Create them directly or use `.template()` for standardized definitions of common parameters like `prompt`, `num_inference_steps`, or `latents`.
+
+### InputParam
+
+[`~modular_pipelines.InputParam`] describes a single input to a block.
+
+| Field | Type | Description |
+|---|---|---|
+| `name` | `str` | Name of the parameter |
+| `type_hint` | `Any` | Type annotation (e.g., `str`, `torch.Tensor`) |
+| `default` | `Any` | Default value (if not set, parameter has no default) |
+| `required` | `bool` | Whether the parameter is required |
+| `description` | `str` | Human-readable description |
+| `kwargs_type` | `str` | Group name for related parameters (e.g., `"denoiser_input_fields"`) |
+| `metadata` | `dict` | Arbitrary additional information |
+
+#### Creating InputParam directly
+
+```py
+from diffusers.modular_pipelines import InputParam
+
+InputParam(
+    name="guidance_scale",
+    type_hint=float,
+    default=7.5,
+    description="Scale for classifier-free guidance.",
+)
+```
+
+#### Using a template
+
+```py
+InputParam.template("prompt")
+# Equivalent to:
+# InputParam(name="prompt", type_hint=str, required=True,
+#            description="The prompt or prompts to guide image generation.")
+```
+
+Templates set `name`, `type_hint`, `default`, `required`, and `description` automatically. Override any field or add context with the `note` parameter.
+
+```py
+# Override the default value
+InputParam.template("num_inference_steps", default=28)
+
+# Add a note to the description
+InputParam.template("prompt_embeds", note="batch-expanded")
+# description becomes: "text embeddings used to guide the image generation. ... (batch-expanded)"
+```
+
+### OutputParam
+
+[`~modular_pipelines.OutputParam`] describes a single output from a block.
+
+| Field | Type | Description |
+|---|---|---|
+| `name` | `str` | Name of the parameter |
+| `type_hint` | `Any` | Type annotation |
+| `description` | `str` | Human-readable description |
+| `kwargs_type` | `str` | Group name for related parameters |
+| `metadata` | `dict` | Arbitrary additional information |
+
+#### Creating OutputParam directly
+
+```py
+from diffusers.modular_pipelines import OutputParam
+
+OutputParam(name="image_latents", type_hint=torch.Tensor, description="Encoded image latents.")
+```
+
+#### Using a template
+
+```py
+OutputParam.template("latents")
+
+# Add a note to the description
+OutputParam.template("prompt_embeds", note="batch-expanded")
+```
+
+## Available templates
+
+`INPUT_PARAM_TEMPLATES` and `OUTPUT_PARAM_TEMPLATES` are defined in [modular_pipeline_utils.py](https://github.com/huggingface/diffusers/blob/main/src/diffusers/modular_pipelines/modular_pipeline_utils.py). They include common parameters like `prompt`, `image`, `num_inference_steps`, `latents`, `prompt_embeds`, and more. Refer to the source for the full list of available template names.
+