Adds integration of the Chameleon template language to FastAPI. #pypackage
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Adds integration of the Chameleon template language to FastAPI. #pypackage
 fastapi-chameleon
Adds integration of the Chameleon template language to FastAPI. If you are interested in Jinja instead, see the sister project: [github.com/AGeekInside/fastapi-jinja](https://github.com/AGeekInside/fastapi-jinja).
## Installation
Simply `pip install fastapi_chameleon`.
## Usage
This is easy to use. Just create a folder within your web app to hold the templates such as:
```
├── main.py
├── views.py
│
├── templates
│   ├── home
│   │   └── index.pt
│   └── shared
│       └── layout.pt
```
In the app startup, tell the library about the folder you wish to use:
```python
import os
from pathlib import Path
import fastapi_chameleon
dev_mode = True
BASE_DIR = Path(__file__).resolve().parent
template_folder = str(BASE_DIR / 'templates')
fastapi_chameleon.global_init(template_folder, auto_reload=dev_mode)
```
Then just decorate the FastAPI view methods (works on sync and async methods):
```python
@router.post('/')
@fastapi_chameleon.template('home/index.pt')
async def home_post(request: Request):
    form = await request.form()
    vm = PersonViewModel(**form) 
    return vm.dict() # {'first':'Michael', 'last':'Kennedy', ...}
```
The view method should return a `dict` to be passed as variables/values to the template. 
If a `fastapi.Response` is returned, the template is skipped and the response along with status_code and
other values is directly passed through. This is common for redirects and error responses not meant
for this page template.
## Friendly 404s and errors
A common technique for user-friendly sites is to use a 
[custom HTML page for 404 responses](http://www.instantshift.com/2019/10/16/user-friendly-404-pages/).
This is especially important in FastAPI because FastAPI returns a 404 response + JSON by default.
This library has support for friendly 404 pages using the `fastapi_chameleon.not_found()` function.
Here's an example:
```python
@router.get('/catalog/item/{item_id}')
@fastapi_chameleon.template('catalog/item.pt')
async def item(item_id: int):
    item = service.get_item_by_id(item_id)
    if not item:
        fastapi_chameleon.not_found()
    
    return item.dict()
```
This will render a 404 response with using the template file `templates/errors/404.pt`.
You can specify another template to use for the response, but it's not required.
If you need to return errors other than `Not Found` (status code `404`), you can use a more
generic function: `fastapi_chameleon.generic_error(template_file: str, status_code: int)`.
This function will allow you to return different status codes. It's generic, thus you'll have
to pass a path to your error template file as well as a status code you want the user to get
in response. For example:
```python
@router.get('/catalog/item/{item_id}')
@fastapi_chameleon.template('catalog/item.pt')
async def item(item_id: int):
    item = service.get_item_by_id(item_id)
    if not item:
        fastapi_chameleon.generic_error('errors/unauthorized.pt',
                                        fastapi.status.HTTP_401_UNAUTHORIZED)
    return item.dict()
```