Avoid exceptions in environment diagnostics

src/debugpy/common/log.py

@@ -5,6 +5,7 @@
 import atexit
 import contextlib
 import functools
+from importlib import metadata as importlib_metadata
 import inspect
 import io
 import os
@@ -16,7 +17,6 @@
 import debugpy
 from debugpy.common import json, timestamp, util
 
-
 LEVELS = ("debug", "info", "warning", "error")
 """Logging levels, lowest to highest importance.
 """
@@ -284,6 +284,7 @@ def get_environment_description(header):
     import site  # noqa
 
     result = [header, "\n\n"]
+    missing = object()
 
     def report(s, *args, **kwargs):
         result.append(s.format(*args, **kwargs))
@@ -308,6 +309,10 @@ def report_paths(get_paths, label=None):
             )
             return
 
+        if paths is missing:
+            report("{0}<missing>\n", prefix)
+            return
+
         if not isinstance(paths, (list, tuple)):
             paths = [paths]
 
@@ -325,7 +330,7 @@ def report_paths(get_paths, label=None):
     report_paths("sys.executable")
     report_paths("sys.prefix")
     report_paths("sys.base_prefix")
-    report_paths("sys.real_prefix")
+    report_paths(lambda: getattr(sys, "real_prefix", missing), "sys.real_prefix")
     report_paths("site.getsitepackages()")
     report_paths("site.getusersitepackages()")
 
@@ -345,25 +350,12 @@ def report_paths(get_paths, label=None):
     report_paths("debugpy.__file__")
     report("\n")
 
-    importlib_metadata = None
+    report("Installed packages:\n")
     try:
-        import importlib_metadata
-    except ImportError:  # pragma: no cover
-        try:
-            from importlib import metadata as importlib_metadata
-        except ImportError:
-            pass
-    if importlib_metadata is None:  # pragma: no cover
-        report("Cannot enumerate installed packages - missing importlib_metadata.")
-    else:
-        report("Installed packages:\n")
-        try:
-            for pkg in importlib_metadata.distributions():
-                report("    {0}=={1}\n", pkg.name, pkg.version)
-        except Exception:  # pragma: no cover
-            swallow_exception(
-                "Error while enumerating installed packages.", level="info"
-            )
+        for pkg in importlib_metadata.distributions():
+            report("    {0}=={1}\n", pkg.name, pkg.version)
+    except Exception:  # pragma: no cover
+        swallow_exception("Error while enumerating installed packages.", level="info")
 
     return "".join(result).rstrip("\n")
 

tests/debugpy/test_log.py

@@ -3,12 +3,49 @@
 # for license information.
 
 import contextlib
+import os
+import sys
+
 import pytest
 
+import debugpy
+from debugpy.common import log
 from tests import debug
 from tests.debug import runners, targets
 
 
+def test_environment_description_does_not_raise_internal_exceptions(monkeypatch):
+    from importlib import metadata as importlib_metadata
+
+    monkeypatch.delattr(sys, "real_prefix", raising=False)
+    monkeypatch.setattr(importlib_metadata, "distributions", lambda: ())
+
+    debugpy_root = os.path.dirname(debugpy.__file__)
+    real_prefix_exceptions = []
+
+    def trace(frame, event, arg):
+        # Only record AttributeErrors that mention ``real_prefix``. ``exception``
+        # events fire for every exception raised in a debugpy frame, including
+        # ones that unrelated environment probes intentionally raise and catch
+        # (e.g. ``site.getsitepackages()``), so an unfiltered assertion would be
+        # environment-dependent. Narrow it to the behavior this test targets.
+        if event == "exception" and frame.f_code.co_filename.startswith(debugpy_root):
+            exc = arg[1]
+            if isinstance(exc, AttributeError) and "real_prefix" in str(exc):
+                real_prefix_exceptions.append(exc)
+        return trace
+
+    previous_trace = sys.gettrace()
+    sys.settrace(trace)
+    try:
+        description = log.get_environment_description("Environment:")
+    finally:
+        sys.settrace(previous_trace)
+
+    assert "sys.real_prefix: <missing>" in description
+    assert real_prefix_exceptions == []
+
+
 @contextlib.contextmanager
 def check_logs(tmpdir, run):
     # For attach_pid, there's ptvsd.server process that performs the injection,