gh-124412: Add helpers for converting annotations to source format (#124551)

Lib/annotationlib.py

@@ -15,6 +15,8 @@ __all__ = [
     "call_evaluate_function",
     "get_annotate_function",
     "get_annotations",
+    "annotations_to_source",
+    "value_to_source",
 ]
 
 
@@ -693,7 +695,7 @@ def get_annotations(
                 return ann
             # But if we didn't get it, we use __annotations__ instead.
             ann = _get_dunder_annotations(obj)
-            return ann
+            return annotations_to_source(ann)
         case _:
             raise ValueError(f"Unsupported format {format!r}")
 
@@ -762,6 +764,33 @@ def get_annotations(
     return return_value
 
 
+def value_to_source(value):
+    """Convert a Python value to a format suitable for use with the SOURCE format.
+
+    This is inteded as a helper for tools that support the SOURCE format but do
+    not have access to the code that originally produced the annotations. It uses
+    repr() for most objects.
+
+    """
+    if isinstance(value, type):
+        if value.__module__ == "builtins":
+            return value.__qualname__
+        return f"{value.__module__}.{value.__qualname__}"
+    if value is ...:
+        return "..."
+    if isinstance(value, (types.FunctionType, types.BuiltinFunctionType)):
+        return value.__name__
+    return repr(value)
+
+
+def annotations_to_source(annotations):
+    """Convert an annotation dict containing values to approximately the SOURCE format."""
+    return {
+        n: t if isinstance(t, str) else value_to_source(t)
+        for n, t in annotations.items()
+    }
+
+
 def _get_and_call_annotate(obj, format):
     annotate = get_annotate_function(obj)
     if annotate is not None: