Call fn by api_name when using Blocks.load (#2593)

* Updated implementation + test

* Add changelog

* Fix unit test

CHANGELOG.md

@@ -1,7 +1,20 @@
 # Upcoming Release 
 
 ## New Features:
-No changes to highlight.
+
+### Calling functions by api_name in loaded apps
+
+When you load an upstream app with `gr.Blocks.load`, you can now specify which fn
+to call with the `api_name` parameter.
+
+```python
+import gradio as gr
+english_translator = gr.Blocks.load(name="spaces/gradio/english-translator")
+german = english_translator("My name is Freddy", api_name='translate-to-german')
+```
+
+The `api_name` parameter will take precendence over the `fn_index` parameter.
+
 
 ## Bug Fixes:
 * Fixed bug where None could not be used for File,Model3D, and Audio examples by [@freddyaboulton](https://github.com/freddyaboulton) in [PR 2588](https://github.com/gradio-app/gradio/pull/2588)
@@ -17,7 +30,7 @@ No changes to highlight.
 No changes to highlight.
 
 ## Full Changelog:
-No changes to highlight.
+* Add `api_name` to `Blocks.__call__` by  [@freddyaboulton](https://github.com/freddyaboulton) in [PR 2593](https://github.com/gradio-app/gradio/pull/2593) 
 
 ## Contributors Shoutout:
 No changes to highlight.

demo/english_translator/run.py

@@ -17,7 +17,7 @@ with gr.Blocks() as demo:
         with gr.Column():
             german = gr.Textbox(label="German Text")
 
-    translate_btn.click(translate, inputs=english, outputs=german)
+    translate_btn.click(translate, inputs=english, outputs=german, api_name="translate-to-german")
     examples = gr.Examples(examples=["I went to the supermarket yesterday.", "Helen is a good swimmer."],
                            inputs=[english])
 

demo/generate_english_german/run.py

@@ -2,7 +2,7 @@ import gradio as gr
 
 from transformers import pipeline
 
-english_translator = gr.Blocks.load(name="spaces/freddyaboulton/english-translator")
+english_translator = gr.Blocks.load(name="spaces/gradio/english-translator")
 english_generator = pipeline("text-generation", model="distilgpt2")
 
 

gradio/blocks.py

@@ -45,7 +45,7 @@ from gradio.documentation import (
     document_component_api,
     set_documentation_group,
 )
-from gradio.exceptions import DuplicateBlockError
+from gradio.exceptions import DuplicateBlockError, InvalidApiName
 from gradio.utils import (
     check_function_inputs_match,
     component_or_layout_class,
@@ -734,7 +734,7 @@ class Blocks(BlockContext):
 
         return True
 
-    def __call__(self, *inputs, fn_index: int = 0):
+    def __call__(self, *inputs, fn_index: int = 0, api_name: str = None):
         """
         Allows Blocks objects to be called as functions. Supply the parameters to the
         function as positional arguments. To choose which function to call, use the
@@ -743,7 +743,19 @@ class Blocks(BlockContext):
         Parameters:
         *inputs: the parameters to pass to the function
         fn_index: the index of the function to call (defaults to 0, which for Interfaces, is the default prediction function)
+        api_name: The api_name of the dependency to call. Will take precedence over fn_index.
         """
+        if api_name is not None:
+            fn_index = next(
+                (
+                    i
+                    for i, d in enumerate(self.dependencies)
+                    if d.get("api_name") == api_name
+                ),
+                None,
+            )
+            if fn_index is None:
+                raise InvalidApiName(f"Cannot find a function with api_name {api_name}")
         if not (self.is_callable(fn_index)):
             raise ValueError(
                 "This function is not callable because it is either stateful or is a generator. Please use the .launch() method instead to create an interactive user interface."

gradio/exceptions.py

@@ -10,6 +10,10 @@ class TooManyRequestsError(Exception):
     pass
 
 
+class InvalidApiName(ValueError):
+    pass
+
+
 class Error(Exception):
     def __init__(self, message: str):
         self.message = message

guides/5)other_tutorials/using_blocks_like_functions.md

@@ -25,7 +25,7 @@ $code_english_translator
 I already went ahead and hosted it in Hugging Face spaces at [freddyaboulton/english-to-german](https://huggingface.co/spaces/freddyaboulton/english-to-german).
 You can see the demo below as well:
 
-<gradio-app space="freddyaboulton/english-to-german"> </gradio-app>
+<gradio-app space="gradio/english-to-german"> </gradio-app>
 
 Now, let's say you have an app that generates english text, but you wanted to additionally generate german text.
 
@@ -48,13 +48,29 @@ Note that the variable `english_translator` is my english to german app, but its
 
 $code_generate_english_german
 
-<gradio-app space="freddyaboulton/generate-english-german"> </gradio-app>
+<gradio-app space="gradio/generate-english-german"> </gradio-app>
 
 ## How to control which function in the app to use
 
-If the app you are loading defines more than one function, you can specify which function to use with the `fn_index` parameter.
-Imagine my app also defined an english to spanish translation function. In order to use it in our text generation app,
-we would use the following code:
+If the app you are loading defines more than one function, you can specify which function to use
+with the `fn_index` and `api_name` parameters.
+
+In the code for our english to german demo, you'll see the following line:
+
+```python
+translate_btn.click(translate, inputs=english, outputs=german, api_name="translate-to-german")
+```
+
+The `api_name` gives this function a unique name in our app. You can use this name to tell gradio which
+function in the upstream space you want to use:
+
+```python
+english_generator(text, api_name="translate-to-german")[0]["generated_text"]
+```
+
+You can also use the `fn_index` parameter.
+Imagine my app also defined an english to spanish translation function.
+In order to use it in our text generation app, we would use the following code:
 
 ```python
 english_generator(text, fn_index=1)[0]["generated_text"]

test/test_external.py

@@ -11,6 +11,7 @@ import pytest
 import gradio
 import gradio as gr
 from gradio import utils
+from gradio.exceptions import InvalidApiName
 from gradio.external import (
     TooManyRequestsError,
     cols_to_rows,
@@ -417,5 +418,22 @@ def test_respect_queue_when_load_from_config():
             assert interface("bob") == "foo"
 
 
+def test_raise_value_error_when_api_name_invalid():
+    with pytest.raises(InvalidApiName):
+        demo = gr.Blocks.load(name="spaces/gradio/hello_world")
+        demo("freddy", api_name="route does not exist")
+
+
+def test_use_api_name_in_call_method():
+    # Interface
+    demo = gr.Blocks.load(name="spaces/gradio/hello_world")
+    assert demo("freddy", api_name="predict") == "Hello freddy!"
+
+    # Blocks demo with multiple functions
+    app = gr.Blocks.load(name="spaces/gradio/multiple-api-name-test")
+    assert app(15, api_name="minus_one") == 14
+    assert app(4, api_name="double") == 8
+
+
 if __name__ == "__main__":
     unittest.main()