✨ Add support for adding multiple examples in request bodies and path…

…, query, cookie, and header params (#1267)

Co-authored-by: Sebastián Ramírez <tiangolo@gmail.com>

docs/en/docs/tutorial/schema-extra-example.md

@@ -1,58 +1,109 @@
-# Schema Extra - Example
+# Declare Request Example Data
 
-You can define extra information to go in JSON Schema.
+You can declare examples of the data your app can receive.
 
-A common use case is to add an `example` that will be shown in the docs.
-
-There are several ways you can declare extra JSON Schema information.
+Here are several ways to do it.
 
 ## Pydantic `schema_extra`
 
-You can declare an example for a Pydantic model using `Config` and `schema_extra`, as described in <a href="https://pydantic-docs.helpmanual.io/usage/schema/#schema-customization" class="external-link" target="_blank">Pydantic's docs: Schema customization</a>:
+You can declare an `example` for a Pydantic model using `Config` and `schema_extra`, as described in <a href="https://pydantic-docs.helpmanual.io/usage/schema/#schema-customization" class="external-link" target="_blank">Pydantic's docs: Schema customization</a>:
 
 ```Python hl_lines="15-23"
 {!../../../docs_src/schema_extra_example/tutorial001.py!}
 ```
 
-That extra info will be added as-is to the output JSON Schema.
+That extra info will be added as-is to the output **JSON Schema** for that model, and it will be used in the API docs.
+
+!!! tip
+    You could use the same technique to extend the JSON Schema and add your own custom extra info.
+
+    For example you could use it to add metadata for a frontend user interface, etc.
 
 ## `Field` additional arguments
 
-In `Field`, `Path`, `Query`, `Body` and others you'll see later, you can also declare extra info for the JSON Schema by passing any other arbitrary arguments to the function, for example, to add an `example`:
+When using `Field()` with Pydantic models, you can also declare extra info for the **JSON Schema** by passing any other arbitrary arguments to the function.
+
+You can use this to add `example` for each field:
 
 ```Python hl_lines="4  10-13"
 {!../../../docs_src/schema_extra_example/tutorial002.py!}
 ```
 
 !!! warning
-    Keep in mind that those extra arguments passed won't add any validation, only annotation, for documentation purposes.
+    Keep in mind that those extra arguments passed won't add any validation, only extra information, for documentation purposes.
+
+## `example` and `examples` in OpenAPI
+
+When using any of:
 
-## `Body` additional arguments
+* `Path()`
+* `Query()`
+* `Header()`
+* `Cookie()`
+* `Body()`
+* `Form()`
+* `File()`
 
-The same way you can pass extra info to `Field`, you can do the same with `Path`, `Query`, `Body`, etc.
+you can also declare a data `example` or a group of `examples` with additional information that will be added to **OpenAPI**.
 
-For example, you can pass an `example` for a body request to `Body`:
+### `Body` with `example`
+
+Here we pass an `example` of the data expected in `Body()`:
 
 ```Python hl_lines="21-26"
 {!../../../docs_src/schema_extra_example/tutorial003.py!}
 ```
 
-## Example in the docs UI
+### Example in the docs UI
 
 With any of the methods above it would look like this in the `/docs`:
 
 <img src="/img/tutorial/body-fields/image01.png">
 
+### `Body` with multiple `examples`
+
+Alternatively to the single `example`, you can pass `examples` using a `dict` with **multiple examples**, each with extra information that will be added to **OpenAPI** too.
+
+The keys of the `dict` identify each example, and each value is another `dict`.
+
+Each specific example `dict` in the `examples` can contain:
+
+* `summary`: Short description for the example.
+* `description`: A long description that can contain Markdown text.
+* `value`: This is the actual example shown, e.g. a `dict`.
+* `externalValue`: alternative to `value`, a URL pointing to the example. Although this might not be supported by as many tools as `value`.
+
+```Python hl_lines="22-48"
+{!../../../docs_src/schema_extra_example/tutorial004.py!}
+```
+
+### Examples in the docs UI
+
+With `examples` added to `Body()` the `/docs` would look like:
+
+<img src="/img/tutorial/body-fields/image02.png">
+
 ## Technical Details
 
-About `example` vs `examples`...
+!!! warning
+    These are very technical details about the standards **JSON Schema** and **OpenAPI**.
+
+    If the ideas above already work for you, that might me enough, and you probably don't need these details, feel free to skip them.
+
+When you add an example inside of a Pydantic model, using `schema_extra` or `Field(example="something")` that example is added to the **JSON Schema** for that Pydantic model.
+
+And that **JSON Schema** of the Pydantic model is included in the **OpenAPI** of your API, and then it's used in the docs UI.
+
+**JSON Schema** doesn't really have a field `example` in the standards. Recent versions of JSON Schema define a field <a href="https://json-schema.org/draft/2019-09/json-schema-validation.html#rfc.section.9.5" class="external-link" target="_blank">`examples`</a>, but OpenAPI 3.0.3 is based on an older version of JSON Schema that didn't have `examples`.
+
+So, OpenAPI 3.0.3 defined its own <a href="https://github.com/OAI/OpenAPI-Specification/blob/master/versions/3.0.3.md#fixed-fields-20" class="external-link" target="_blank">`example`</a> for the modified version of **JSON Schema** it uses, for the same purpose (but it's a single `example`, not `examples`), and that's what is used by the API docs UI (using Swagger UI).
 
-JSON Schema defines a field <a href="https://json-schema.org/draft/2019-09/json-schema-validation.html#rfc.section.9.5" class="external-link" target="_blank">`examples`</a> in the most recent versions, but OpenAPI is based on an older version of JSON Schema that didn't have `examples`.
+So, although `example` is not part of JSON Schema, it is part of OpenAPI's custom version of JSON Schema, and that's what will be used by the docs UI.
 
-So, OpenAPI defined its own <a href="https://github.com/OAI/OpenAPI-Specification/blob/master/versions/3.0.3.md#fixed-fields-20" class="external-link" target="_blank">`example`</a> for the same purpose (as `example`, not `examples`), and that's what is used by the docs UI (using Swagger UI).
+But when you use `example` or `examples` with any of the other utilities (`Query()`, `Body()`, etc.) those examples are not added to the JSON Schema that describes that data (not even to OpenAPI's own version of JSON Schema), they are added directly to the *path operation* declaration in OpenAPI (outside the parts of OpenAPI that use JSON Schema).
 
-So, although `example` is not part of JSON Schema, it is part of OpenAPI, and that's what will be used by the docs UI.
+For `Path()`, `Query()`, `Header()`, and `Cookie()`, the `example` or `examples` are added to the <a href="https://github.com/OAI/OpenAPI-Specification/blob/main/versions/3.0.3.md#parameter-object" class="external-link" target="_blank">OpenAPI definition, to the `Parameter Object` (in the specification)</a>.
 
-## Other info
+And for `Body()`, `File()`, and `Form()`, the `example` or `examples` are equivalently added to the <a href="https://github.com/OAI/OpenAPI-Specification/blob/main/versions/3.0.3.md#mediaTypeObject" class="external-link" target="_blank">OpenAPI definition, to the `Request Body Object`, in the field `content`, on the `Media Type Object` (in the specification)</a>.
 
-The same way, you could add your own custom extra info that would be added to the JSON Schema for each model, for example to customize a frontend user interface, etc.
+On the other hand, there's a newer version of OpenAPI: **3.1.0**, recently released. It is based on the latest JSON Schema and most of the modifications from OpenAPI's custom version of JSON Schema are removed, in exchange of the features from the recent versions of JSON Schema, so all these small differences are reduced. Nevertheless, Swagger UI currently doesn't support OpenAPI 3.1.0, so, for now, it's better to continue using the ideas above.

docs_src/schema_extra_example/tutorial004.py

@@ -0,0 +1,52 @@
+from typing import Optional
+
+from fastapi import Body, FastAPI
+from pydantic import BaseModel
+
+app = FastAPI()
+
+
+class Item(BaseModel):
+    name: str
+    description: Optional[str] = None
+    price: float
+    tax: Optional[float] = None
+
+
+@app.put("/items/{item_id}")
+async def update_item(
+    *,
+    item_id: int,
+    item: Item = Body(
+        ...,
+        examples={
+            "normal": {
+                "summary": "A normal example",
+                "description": "A **normal** item works correctly.",
+                "value": {
+                    "name": "Foo",
+                    "description": "A very nice Item",
+                    "price": 35.4,
+                    "tax": 3.2,
+                },
+            },
+            "converted": {
+                "summary": "An example with converted data",
+                "description": "FastAPI can convert price `strings` to actual `numbers` automatically",
+                "value": {
+                    "name": "Bar",
+                    "price": "35.4",
+                },
+            },
+            "invalid": {
+                "summary": "Invalid data is rejected with an error",
+                "value": {
+                    "name": "Baz",
+                    "price": "thirty five point four",
+                },
+            },
+        },
+    ),
+):
+    results = {"item_id": item_id, "item": item}
+    return results

fastapi/openapi/utils.py

@@ -21,7 +21,7 @@
     get_model_definitions,
 )
 from pydantic import BaseModel
-from pydantic.fields import ModelField
+from pydantic.fields import ModelField, Undefined
 from pydantic.schema import (
     field_schema,
     get_flat_models_from_fields,
@@ -101,6 +101,10 @@ def get_openapi_operation_parameters(
         }
         if field_info.description:
             parameter["description"] = field_info.description
+        if field_info.examples:
+            parameter["examples"] = jsonable_encoder(field_info.examples)
+        elif field_info.example != Undefined:
+            parameter["example"] = jsonable_encoder(field_info.example)
         if field_info.deprecated:
             parameter["deprecated"] = field_info.deprecated
         parameters.append(parameter)
@@ -124,7 +128,12 @@ def get_openapi_operation_request_body(
     request_body_oai: Dict[str, Any] = {}
     if required:
         request_body_oai["required"] = required
-    request_body_oai["content"] = {request_media_type: {"schema": body_schema}}
+    request_media_content: Dict[str, Any] = {"schema": body_schema}
+    if field_info.examples:
+        request_media_content["examples"] = jsonable_encoder(field_info.examples)
+    elif field_info.example != Undefined:
+        request_media_content["example"] = jsonable_encoder(field_info.example)
+    request_body_oai["content"] = {request_media_type: request_media_content}
     return request_body_oai
 
 

fastapi/param_functions.py

@@ -1,6 +1,7 @@
-from typing import Any, Callable, Optional, Sequence
+from typing import Any, Callable, Dict, Optional, Sequence
 
 from fastapi import params
+from pydantic.fields import Undefined
 
 
 def Path(  # noqa: N802
@@ -16,6 +17,8 @@ def Path(  # noqa: N802
     min_length: Optional[int] = None,
     max_length: Optional[int] = None,
     regex: Optional[str] = None,
+    example: Any = Undefined,
+    examples: Optional[Dict[str, Any]] = None,
     deprecated: Optional[bool] = None,
     **extra: Any,
 ) -> Any:
@@ -31,6 +34,8 @@ def Path(  # noqa: N802
         min_length=min_length,
         max_length=max_length,
         regex=regex,
+        example=example,
+        examples=examples,
         deprecated=deprecated,
         **extra,
     )
@@ -49,6 +54,8 @@ def Query(  # noqa: N802
     min_length: Optional[int] = None,
     max_length: Optional[int] = None,
     regex: Optional[str] = None,
+    example: Any = Undefined,
+    examples: Optional[Dict[str, Any]] = None,
     deprecated: Optional[bool] = None,
     **extra: Any,
 ) -> Any:
@@ -64,6 +71,8 @@ def Query(  # noqa: N802
         min_length=min_length,
         max_length=max_length,
         regex=regex,
+        example=example,
+        examples=examples,
         deprecated=deprecated,
         **extra,
     )
@@ -83,6 +92,8 @@ def Header(  # noqa: N802
     min_length: Optional[int] = None,
     max_length: Optional[int] = None,
     regex: Optional[str] = None,
+    example: Any = Undefined,
+    examples: Optional[Dict[str, Any]] = None,
     deprecated: Optional[bool] = None,
     **extra: Any,
 ) -> Any:
@@ -99,6 +110,8 @@ def Header(  # noqa: N802
         min_length=min_length,
         max_length=max_length,
         regex=regex,
+        example=example,
+        examples=examples,
         deprecated=deprecated,
         **extra,
     )
@@ -117,6 +130,8 @@ def Cookie(  # noqa: N802
     min_length: Optional[int] = None,
     max_length: Optional[int] = None,
     regex: Optional[str] = None,
+    example: Any = Undefined,
+    examples: Optional[Dict[str, Any]] = None,
     deprecated: Optional[bool] = None,
     **extra: Any,
 ) -> Any:
@@ -132,6 +147,8 @@ def Cookie(  # noqa: N802
         min_length=min_length,
         max_length=max_length,
         regex=regex,
+        example=example,
+        examples=examples,
         deprecated=deprecated,
         **extra,
     )
@@ -152,6 +169,8 @@ def Body(  # noqa: N802
     min_length: Optional[int] = None,
     max_length: Optional[int] = None,
     regex: Optional[str] = None,
+    example: Any = Undefined,
+    examples: Optional[Dict[str, Any]] = None,
     **extra: Any,
 ) -> Any:
     return params.Body(
@@ -168,6 +187,8 @@ def Body(  # noqa: N802
         min_length=min_length,
         max_length=max_length,
         regex=regex,
+        example=example,
+        examples=examples,
         **extra,
     )
 
@@ -186,6 +207,8 @@ def Form(  # noqa: N802
     min_length: Optional[int] = None,
     max_length: Optional[int] = None,
     regex: Optional[str] = None,
+    example: Any = Undefined,
+    examples: Optional[Dict[str, Any]] = None,
     **extra: Any,
 ) -> Any:
     return params.Form(
@@ -201,6 +224,8 @@ def Form(  # noqa: N802
         min_length=min_length,
         max_length=max_length,
         regex=regex,
+        example=example,
+        examples=examples,
         **extra,
     )
 
@@ -219,6 +244,8 @@ def File(  # noqa: N802
     min_length: Optional[int] = None,
     max_length: Optional[int] = None,
     regex: Optional[str] = None,
+    example: Any = Undefined,
+    examples: Optional[Dict[str, Any]] = None,
     **extra: Any,
 ) -> Any:
     return params.File(
@@ -234,6 +261,8 @@ def File(  # noqa: N802
         min_length=min_length,
         max_length=max_length,
         regex=regex,
+        example=example,
+        examples=examples,
         **extra,
     )