added rich cast to protocol

CHANGELOG.md

@@ -5,7 +5,7 @@ All notable changes to this project will be documented in this file.
 The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
-## [10.13.1] - 2021-11-09
+## [10.14.0] - Unreleased
 
 ### Fixed
 
@@ -17,6 +17,11 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 ### Added
 
 - Added file protocol to URL highlighter https://github.com/willmcgugan/rich/issues/1681
+- Added rich.protocol.rich_cast
+
+### Changed
+
+- Allowed `__rich__` to work recursively
 
 ## [10.13.0] - 2021-11-07
 

rich/console.py

@@ -25,6 +25,7 @@ from typing import (
     Mapping,
     NamedTuple,
     Optional,
+    Set,
     TextIO,
     Tuple,
     Type,
@@ -53,6 +54,7 @@ from .markup import render as render_markup
 from .measure import Measurement, measure_renderables
 from .pager import Pager, SystemPager
 from .pretty import Pretty, is_expandable
+from .protocol import rich_cast
 from .region import Region
 from .scope import render_scope
 from .screen import Screen
@@ -1220,8 +1222,8 @@ class Console:
             # No space to render anything. This prevents potential recursion errors.
             return
         render_iterable: RenderResult
-        if hasattr(renderable, "__rich__") and not isclass(renderable):
-            renderable = renderable.__rich__()  # type: ignore
+
+        renderable = rich_cast(renderable)
         if hasattr(renderable, "__rich_console__") and not isclass(renderable):
             render_iterable = renderable.__rich_console__(self, _options)  # type: ignore
         elif isinstance(renderable, str):
@@ -1439,15 +1441,7 @@ class Console:
                 del text[:]
 
         for renderable in objects:
-            # I promise this is sane
-            # This detects an object which claims to have all attributes, such as MagicMock.mock_calls
-            if hasattr(
-                renderable, "jwevpw_eors4dfo6mwo345ermk7kdnfnwerwer"
-            ):  # pragma: no cover
-                renderable = repr(renderable)
-            rich_cast = getattr(renderable, "__rich__", None)
-            if rich_cast:
-                renderable = rich_cast()
+            renderable = rich_cast(renderable)
             if isinstance(renderable, str):
                 append_text(
                     self.render_str(

rich/measure.py

@@ -2,7 +2,7 @@ from operator import itemgetter
 from typing import Callable, Iterable, NamedTuple, Optional, TYPE_CHECKING
 
 from . import errors
-from .protocol import is_renderable
+from .protocol import is_renderable, rich_cast
 
 if TYPE_CHECKING:
     from .console import Console, ConsoleOptions, RenderableType
@@ -97,8 +97,7 @@ class Measurement(NamedTuple):
             return Measurement(0, 0)
         if isinstance(renderable, str):
             renderable = console.render_str(renderable, markup=options.markup)
-        if hasattr(renderable, "__rich__"):
-            renderable = renderable.__rich__()  # type: ignore
+        renderable = rich_cast(renderable)
         if is_renderable(renderable):
             get_console_width: Optional[
                 Callable[["Console", "ConsoleOptions"], "Measurement"]

rich/protocol.py

@@ -1,4 +1,10 @@
-from typing import Any
+from typing import Any, Callable, cast, Set, TYPE_CHECKING
+from inspect import isclass
+
+if TYPE_CHECKING:
+    from rich.console import RenderableType
+
+_GIBBERISH = """aihwerij235234ljsdnp34ksodfipwoe234234jlskjdf"""
 
 
 def is_renderable(check_object: Any) -> bool:
@@ -8,3 +14,29 @@ def is_renderable(check_object: Any) -> bool:
         or hasattr(check_object, "__rich__")
         or hasattr(check_object, "__rich_console__")
     )
+
+
+def rich_cast(renderable: object) -> "RenderableType":
+    """Cast an object to a renderable by calling __rich__ if present.
+
+    Args:
+        renderable (object): A potentially renderable object
+
+    Returns:
+        object: The result of recursively calling __rich__.
+    """
+    from rich.console import RenderableType
+
+    rich_visited_set: Set[type] = set()  # Prevent potential infinite loop
+    while hasattr(renderable, "__rich__") and not isclass(renderable):
+        # Detect object which claim to have all the attributes
+        if hasattr(renderable, _GIBBERISH):
+            return repr(renderable)
+        cast_method = getattr(renderable, "__rich__")
+        renderable = cast_method()
+        renderable_type = type(renderable)
+        if renderable_type in rich_visited_set:
+            break
+        rich_visited_set.add(renderable_type)
+
+    return cast(RenderableType, renderable)

tests/test_protocol.py

@@ -33,3 +33,37 @@ def test_abc():
     assert not isinstance(foo, str)
     assert not isinstance("foo", RichRenderable)
     assert not isinstance([], RichRenderable)
+
+
+def test_cast_deep():
+    class B:
+        def __rich__(self) -> Foo:
+            return Foo()
+
+    class A:
+        def __rich__(self) -> B:
+            return B()
+
+    console = Console(file=io.StringIO())
+    console.print(A())
+    assert console.file.getvalue() == "Foo\n"
+
+
+def test_cast_recursive():
+    class B:
+        def __rich__(self) -> "A":
+            return A()
+
+        def __repr__(self) -> str:
+            return "<B>"
+
+    class A:
+        def __rich__(self) -> B:
+            return B()
+
+        def __repr__(self) -> str:
+            return "<A>"
+
+    console = Console(file=io.StringIO())
+    console.print(A())
+    assert console.file.getvalue() == "<B>\n"