gh-108851: Fix tomllib recursion tests (#108853)

* Add get_recursion_available() and get_recursion_depth() functions
  to the test.support module.
* Change infinite_recursion() default max_depth from 75 to 100.
* Fix test_tomllib recursion tests for WASI buildbots: reduce the
  recursion limit and compute the maximum nested array/dict depending
  on the current available recursion limit.
* test.pythoninfo logs sys.getrecursionlimit().
* Enhance test_sys tests on sys.getrecursionlimit()
  and sys.setrecursionlimit().

1 files changed, 40 insertions, 3 deletions

diff --git a/Lib/test/support/__init__.py b/Lib/test/support/__init__.py
index 7bac116..d39f529 100644
--- a/Lib/test/support/__init__.py
+++ b/Lib/test/support/__init__.py
@@ -2241,6 +2241,39 @@ def check_disallow_instantiation(testcase, tp, *args, **kwds):
     msg = f"cannot create '{re.escape(qualname)}' instances"
     testcase.assertRaisesRegex(TypeError, msg, tp, *args, **kwds)
 
+def get_recursion_depth():
+    """Get the recursion depth of the caller function.
+
+    In the __main__ module, at the module level, it should be 1.
+    """
+    try:
+        import _testinternalcapi
+        depth = _testinternalcapi.get_recursion_depth()
+    except (ImportError, RecursionError) as exc:
+        # sys._getframe() + frame.f_back implementation.
+        try:
+            depth = 0
+            frame = sys._getframe()
+            while frame is not None:
+                depth += 1
+                frame = frame.f_back
+        finally:
+            # Break any reference cycles.
+            frame = None
+
+    # Ignore get_recursion_depth() frame.
+    return max(depth - 1, 1)
+
+def get_recursion_available():
+    """Get the number of available frames before RecursionError.
+
+    It depends on the current recursion depth of the caller function and
+    sys.getrecursionlimit().
+    """
+    limit = sys.getrecursionlimit()
+    depth = get_recursion_depth()
+    return limit - depth
+
 @contextlib.contextmanager
 def set_recursion_limit(limit):
     """Temporarily change the recursion limit."""
@@ -2251,14 +2284,18 @@ def set_recursion_limit(limit):
     finally:
         sys.setrecursionlimit(original_limit)
 
-def infinite_recursion(max_depth=75):
+def infinite_recursion(max_depth=100):
     """Set a lower limit for tests that interact with infinite recursions
     (e.g test_ast.ASTHelpers_Test.test_recursion_direct) since on some
     debug windows builds, due to not enough functions being inlined the
     stack size might not handle the default recursion limit (1000). See
     bpo-11105 for details."""
-    return set_recursion_limit(max_depth)
-
+    if max_depth < 3:
+        raise ValueError("max_depth must be at least 3, got {max_depth}")
+    depth = get_recursion_depth()
+    depth = max(depth - 1, 1)  # Ignore infinite_recursion() frame.
+    limit = depth + max_depth
+    return set_recursion_limit(limit)
 
 def ignore_deprecations_from(module: str, *, like: str) -> object:
     token = object()