Allow PromptSession to take Document as default

Text defaults in prompts are nice, but sometimes it is nicer to be able
to specify more than just the text in the default, e.g., cursor
position. Because PromptSession converts the provided default into a
Document anyway, this change makes PromptSession also accept a pre-made
Document as default.

Author: pritambaral

prompt_toolkit/shortcuts/prompt.py

@@ -797,7 +797,7 @@ def prompt(
             tempfile_suffix: Optional[str] = None,
 
             # Following arguments are specific to the current `prompt()` call.
-            default: str = '',
+            default: Union[str, Document] = '',
             accept_default: bool = False,
             pre_run: Optional[Callable[[], None]] = None) -> _T:
         """
@@ -901,7 +901,7 @@ def prompt(
             self.tempfile_suffix = tempfile_suffix
 
         self._add_pre_run_callables(pre_run, accept_default)
-        self.default_buffer.reset(Document(default))
+        self.default_buffer.reset(default if isinstance(default, Document) else Document(default))
         self.app.refresh_interval = self.refresh_interval  # This is not reactive.
 
         return self.app.run()
@@ -950,7 +950,7 @@ async def prompt_async(
             tempfile_suffix: Optional[str] = None,
 
             # Following arguments are specific to the current `prompt()` call.
-            default: str = '',
+            default: Union[str, Document] = '',
             accept_default: bool = False,
             pre_run: Optional[Callable[[], None]] = None) -> _T:
 
@@ -1024,7 +1024,7 @@ async def prompt_async(
             self.tempfile_suffix = tempfile_suffix
 
         self._add_pre_run_callables(pre_run, accept_default)
-        self.default_buffer.reset(Document(default))
+        self.default_buffer.reset(default if isinstance(default, Document) else Document(default))
         self.app.refresh_interval = self.refresh_interval  # This is not reactive.
 
         return await self.app.run_async()