✨ Auto-generate OpenAPI servers from root_path (#1596)

* root_path included in servers object instead of path prefix

* ♻️ Refactor implementation of auto-including root_path in OpenAPI servers

* 📝 Update docs and examples for Behind a Proxy, including servers

* 📝 Update Extending OpenAPI as openapi_prefix is no longer needed

* ✅ Add extra tests for root_path in servers and root_path_in_servers=False

* 🍱 Update security docs images with relative token URL

* 📝 Update security docs with relative token URL

* 📝 Update example sources with relative token URLs

* ✅ Update tests with relative tokens

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

Author: rkbeatss

docs/en/docs/advanced/behind-a-proxy.md

@@ -42,16 +42,19 @@ proxy --> server
 !!! tip
     The IP `0.0.0.0` is commonly used to mean that the program listens on all the IPs available in that machine/server.
 
-The docs UI would also need that the JSON payload with the OpenAPI schema has the path defined as `/api/v1/app` (behind the proxy) instead of `/app`. For example, something like:
+The docs UI would also need the OpenAPI schema to declare that this API `server` is located at `/api/v1` (behind the proxy). For example:
 
-```JSON hl_lines="5"
+```JSON hl_lines="4 5 6 7 8"
 {
     "openapi": "3.0.2",
     // More stuff here
+    "servers": [
+        {
+            "url": "/api/v1"
+        }
+    ],
     "paths": {
-        "/api/v1/app": {
             // More stuff here
-        }
     }
 }
 ```
@@ -264,15 +267,77 @@ You can check it at <a href="http://127.0.0.1:8000/docs" class="external-link" t
 
 <img src="/img/tutorial/behind-a-proxy/image01.png">
 
-But if we access the docs UI at the "official" URL using the proxy, at `/api/v1/docs`, it works correctly! 🎉
+But if we access the docs UI at the "official" URL using the proxy with port `9999`, at `/api/v1/docs`, it works correctly! 🎉
+
+You can check it at <a href="http://127.0.0.1:9999/api/v1/docs" class="external-link" target="_blank">http://127.0.0.1:9999/api/v1/docs</a>:
+
+<img src="/img/tutorial/behind-a-proxy/image02.png">
 
 Right as we wanted it. ✔️
 
-This is because FastAPI uses this `root_path` internally to tell the docs UI to use the URL for OpenAPI with the path prefix provided by `root_path`.
+This is because FastAPI uses this `root_path` to create the default `server` in OpenAPI with the URL provided by `root_path`.
 
-You can check it at <a href="http://127.0.0.1:9999/api/v1/docs" class="external-link" target="_blank">http://127.0.0.1:9999/api/v1/docs</a>:
+## Additional servers
 
-<img src="/img/tutorial/behind-a-proxy/image02.png">
+!!! warning
+    This is a more advanced use case. Feel free to skip it.
+
+By default, **FastAPI** will create a `server` in the OpenAPI schema with the URL for the `root_path`.
+
+But you can also provide other alternative `servers`, for example if you want *the same* docs UI to interact with a staging and production environments.
+
+If you pass a custom list of `servers` and there's a `root_path` (because your API lives behind a proxy), **FastAPI** will insert a "server" with this `root_path` at the beginning of the list.
+
+For example:
+
+```Python hl_lines="4 5 6 7"
+{!../../../docs_src/behind_a_proxy/tutorial003.py!}
+```
+
+Will generate an OpenAPI schema like:
+
+```JSON hl_lines="5 6 7"
+{
+    "openapi": "3.0.2",
+    // More stuff here
+    "servers": [
+        {
+            "url": "/api/v1"
+        },
+        {
+            "url": "https://stag.example.com",
+            "description": "Staging environment"
+        },
+        {
+            "url": "https://prod.example.com",
+            "description": "Production environment"
+        }
+    ],
+    "paths": {
+            // More stuff here
+    }
+}
+```
+
+!!! tip
+    Notice the auto-generated server with a `url` value of `/api/v1`, taken from the `root_path`.
+
+In the docs UI at <a href="http://127.0.0.1:9999/api/v1/docs" class="external-link" target="_blank">http://127.0.0.1:9999/api/v1/docs</a> it would look like:
+
+<img src="/img/tutorial/behind-a-proxy/image03.png">
+
+!!! tip
+    The docs UI will interact with the server that you select.
+
+### Disable automatic server from `root_path`
+
+If you don't want **FastAPI** to include an automatic server using the `root_path`, you can use the parameter `root_path_in_servers=False`:
+
+```Python hl_lines="9"
+{!../../../docs_src/behind_a_proxy/tutorial004.py!}
+```
+
+and then it won't include it in the OpenAPI schema.
 
 ## Mounting a sub-application
 

docs/en/docs/advanced/extending-openapi.md

@@ -32,7 +32,6 @@ And that function `get_openapi()` receives as parameters:
 * `openapi_version`: The version of the OpenAPI specification used. By default, the latest: `3.0.2`.
 * `description`: The description of your API.
 * `routes`: A list of routes, these are each of the registered *path operations*. They are taken from `app.routes`.
-* `openapi_prefix`: The URL prefix to be used in your OpenAPI.
 
 ## Overriding the defaults
 
@@ -52,22 +51,15 @@ First, write all your **FastAPI** application as normally:
 
 Then, use the same utility function to generate the OpenAPI schema, inside a `custom_openapi()` function:
 
-```Python hl_lines="2  15 16 17 18 19 20 21"
+```Python hl_lines="2  15 16 17 18 19 20"
 {!../../../docs_src/extending_openapi/tutorial001.py!}
 ```
 
-!!! tip
-    The `openapi_prefix` will contain any prefix needed for the generated OpenAPI *path operations*.
-
-    FastAPI will automatically use the `root_path` to pass it in the `openapi_prefix`.
-
-    But the important thing is that your function should receive that parameter `openapi_prefix` and pass it along.
-
 ### Modify the OpenAPI schema
 
 Now you can add the ReDoc extension, adding a custom `x-logo` to the `info` "object" in the OpenAPI schema:
 
-```Python hl_lines="22 23 24"
+```Python hl_lines="21 22 23"
 {!../../../docs_src/extending_openapi/tutorial001.py!}
 ```
 
@@ -79,15 +71,15 @@ That way, your application won't have to generate the schema every time a user o
 
 It will be generated only once, and then the same cached schema will be used for the next requests.
 
-```Python hl_lines="13 14  25 26"
+```Python hl_lines="13 14  24 25"
 {!../../../docs_src/extending_openapi/tutorial001.py!}
 ```
 
 ### Override the method
 
 Now you can replace the `.openapi()` method with your new function.
 
-```Python hl_lines="29"
+```Python hl_lines="28"
 {!../../../docs_src/extending_openapi/tutorial001.py!}
 ```