✨ Refactor param extraction using Pydantic Field (#278)

* ✨ Refactor parameter dependency using Pydantic Field

* ⬆️ Upgrade required Pydantic version with latest Shape values

* ✨ Add tutorials and code for using Enum and Optional

* ✅ Add tests for tutorials with new types and extra cases

* ♻️ Format, clean, and add annotations to dependencies.utils

* 📝 Update tutorial for query parameters with list defaults

* ✅ Add tests for query param with list default

docs/tutorial/path-params.md

@@ -35,7 +35,7 @@ If you run this example and open your browser at <a href="http://127.0.0.1:8000/
 
 !!! check
     Notice that the value your function received (and returned) is `3`, as a Python `int`, not a string `"3"`.
-    
+
     So, with that type declaration, **FastAPI** gives you automatic request <abbr title="converting the string that comes from an HTTP request into Python data">"parsing"</abbr>.
 
 ## Data validation
@@ -61,12 +61,11 @@ because the path parameter `item_id` had a value of `"foo"`, which is not an `in
 
 The same error would appear if you provided a `float` instead of an int, as in: <a href="http://127.0.0.1:8000/items/4.2" target="_blank">http://127.0.0.1:8000/items/4.2</a>
 
-
 !!! check
     So, with the same Python type declaration, **FastAPI** gives you data validation.
 
-    Notice that the error also clearly states exactly the point where the validation didn't pass. 
-    
+    Notice that the error also clearly states exactly the point where the validation didn't pass.
+
     This is incredibly helpful while developing and debugging code that interacts with your API.
 
 ## Documentation
@@ -96,8 +95,7 @@ All the data validation is performed under the hood by <a href="https://pydantic
 
 You can use the same type declarations with `str`, `float`, `bool` and many other complex data types.
 
-These are explored in the next chapters of the tutorial.
-
+Several of these are explored in the next chapters of the tutorial.
 
 ## Order matters
 
@@ -115,6 +113,73 @@ Because path operations are evaluated in order, you need to make sure that the p
 
 Otherwise, the path for `/users/{user_id}` would match also for `/users/me`, "thinking" that it's receiving a parameter `user_id` with a value of `"me"`.
 
+## Predefined values
+
+If you have a *path operation* that receives a *path parameter*, but you want the possible valid *path parameter* values to be predefined, you can use a standard Python <abbr title="Enumeration">`Enum`</abbr>.
+
+### Create an `Enum` class
+
+Import `Enum` and create a sub-class that inherits from it.
+
+And create class attributes with fixed values, those fixed values will be the available valid values:
+
+```Python hl_lines="1 6 7 8 9"
+{!./src/path_params/tutorial005.py!}
+```
+
+!!! info
+    <a href="https://docs.python.org/3/library/enum.html" target="_blank">Enumerations (or enums) are available in Python</a> since version 3.4.
+
+!!! tip
+    If you are wondering, "AlexNet", "ResNet", and "LeNet" are just names of Machine Learning <abbr title="Technically, Deep Learning model architectures">models</abbr>.
+
+### Declare a *path parameter*
+
+Then create a *path parameter* with a type annotation using the enum class you created (`ModelName`):
+
+```Python hl_lines="16"
+{!./src/path_params/tutorial005.py!}
+```
+
+### Check the docs
+
+Because the available values for the *path parameter* are specified, the interactive docs can show them nicely:
+
+<img src="/img/tutorial/path-params/image03.png">
+
+### Working with Python *enumerations*
+
+The value of the *path parameter* will be an *enumeration member*.
+
+#### Compare *enumeration members*
+
+You can compare it with the *enumeration member* in your created enum `ModelName`:
+
+```Python hl_lines="17"
+{!./src/path_params/tutorial005.py!}
+```
+
+#### Get the *enumeration value*
+
+You can get the actual value (a `str` in this case) using `model_name.value`, or in general, `your_enum_member.value`:
+
+```Python hl_lines="19"
+{!./src/path_params/tutorial005.py!}
+```
+
+!!! tip
+    You could also access the value `"lenet"` with `ModelName.lenet.value`.
+
+#### Return *enumeration members*
+
+You can return *enum members* from your *path operation*, even nested in a JSON body (e.g. a `dict`).
+
+They will be converted to their corresponding values before returning them to the client:
+
+```Python hl_lines="18 20 21"
+{!./src/path_params/tutorial005.py!}
+```
+
 ## Path parameters containing paths
 
 Let's say you have a *path operation* with a path `/files/{file_path}`.

docs/tutorial/query-params-str-validations.md

@@ -12,7 +12,6 @@ The query parameter `q` is of type `str`, and by default is `None`, so it is opt
 
 We are going to enforce that even though `q` is optional, whenever it is provided, it **doesn't exceed a length of 50 characters**.
 
-
 ### Import `Query`
 
 To achieve that, first import `Query` from `fastapi`:
@@ -29,7 +28,7 @@ And now use it as the default value of your parameter, setting the parameter `ma
 {!./src/query_params_str_validations/tutorial002.py!}
 ```
 
-As we have to replace the default value `None` with `Query(None)`, the first parameter to `Query` serves the same purpose of defining that default value. 
+As we have to replace the default value `None` with `Query(None)`, the first parameter to `Query` serves the same purpose of defining that default value.
 
 So:
 
@@ -41,7 +40,7 @@ q: str = Query(None)
 
 ```Python
 q: str = None
-``` 
+```
 
 But it declares it explicitly as being a query parameter.
 
@@ -53,7 +52,6 @@ q: str = Query(None, max_length=50)
 
 This will validate the data, show a clear error when the data is not valid, and document the parameter in the OpenAPI schema path operation.
 
-
 ## Add more validations
 
 You can also add a parameter `min_length`:
@@ -119,7 +117,7 @@ So, when you need to declare a value as required while using `Query`, you can us
 {!./src/query_params_str_validations/tutorial006.py!}
 ```
 
-!!! info 
+!!! info
     If you hadn't seen that `...` before: it is a a special single value, it is <a href="https://docs.python.org/3/library/constants.html#Ellipsis" target="_blank">part of Python and is called "Ellipsis"</a>.
 
 This will let **FastAPI** know that this parameter is required.
@@ -156,11 +154,35 @@ So, the response to that URL would be:
 !!! tip
     To declare a query parameter with a type of `list`, like in the example above, you need to explicitly use `Query`, otherwise it would be interpreted as a request body.
 
-
 The interactive API docs will update accordingly, to allow multiple values:
 
 <img src="/img/tutorial/query-params-str-validations/image02.png">
 
+### Query parameter list / multiple values with defaults
+
+And you can also define a default `list` of values if none are provided:
+
+```Python hl_lines="9"
+{!./src/query_params_str_validations/tutorial012.py!}
+```
+
+If you go to:
+
+```
+http://localhost:8000/items/
+```
+
+the default of `q` will be: `["foo", "bar"]` and your response will be:
+
+```JSON
+{
+  "q": [
+    "foo",
+    "bar"
+  ]
+}
+```
+
 ## Declare more metadata
 
 You can add more information about the parameter.

docs/tutorial/query-params.md

@@ -186,3 +186,39 @@ In this case, there are 3 query parameters:
 * `needy`, a required `str`.
 * `skip`, an `int` with a default value of `0`.
 * `limit`, an optional `int`.
+
+!!! tip
+    You could also use `Enum`s <a href="https://fastapi.tiangolo.com/tutorial/path-params/#predefined-values" target="_blank">the same way as with *path parameters*</a>.
+
+## Optional type declarations
+
+!!! warning
+    This might be an advanced use case.
+
+    You might want to skip it.
+
+If you are using `mypy` it could complain with type declarations like:
+
+```Python
+limit: int = None
+```
+
+With an error like:
+
+```
+Incompatible types in assignment (expression has type "None", variable has type "int")
+```
+
+In those cases you can use `Optional` to tell `mypy` that the value could be `None`, like:
+
+```Python
+from typing import Optional
+
+limit: Optional[int] = None
+```
+
+In a *path operation* that could look like:
+
+```Python hl_lines="9"
+{!./src/query_params/tutorial007.py!}
+```