Allow using pydevd as a regular dependency.
Submitted upstream at: https://github.com/microsoft/debugpy/pull/902

diff --git a/setup.py b/setup.py
index 5fc40070..3a530a29 100644
--- a/setup.py
+++ b/setup.py
@@ -11,6 +11,9 @@ import subprocess
 import sys
 
 
+DEBUGPY_BUNDLING_DISABLED = bool(os.getenv('DEBUGPY_BUNDLING_DISABLED'))
+
+
 sys.path.insert(0, os.path.dirname(os.path.abspath(__file__)))
 import versioneer  # noqa
 
@@ -18,12 +21,15 @@ del sys.path[0]
 
 sys.path.insert(0, os.path.join(os.path.dirname(os.path.abspath(__file__)), "src"))
 import debugpy
-import debugpy._vendored
+
+if not DEBUGPY_BUNDLING_DISABLED:
+    import debugpy._vendored
 
 del sys.path[0]
 
 
-PYDEVD_ROOT = debugpy._vendored.project_root("pydevd")
+PYDEVD_ROOT = (None if DEBUGPY_BUNDLING_DISABLED else
+               debugpy._vendored.project_root("pydevd"))
 DEBUGBY_ROOT = os.path.dirname(os.path.abspath(debugpy.__file__))
 
 
@@ -67,7 +73,7 @@ def iter_vendored_files():
 # relevant setuptools versions.
 class ExtModules(list):
     def __bool__(self):
-        return True
+        return not DEBUGPY_BUNDLING_DISABLED
 
 
 def override_build(cmds):
@@ -133,9 +139,24 @@ with open("DESCRIPTION.md", "r") as fh:
 
 
 if __name__ == "__main__":
-    if not os.getenv("SKIP_CYTHON_BUILD"):
+    if not (os.getenv("SKIP_CYTHON_BUILD") or DEBUGPY_BUNDLING_DISABLED):
         cython_build()
 
+    # Etch bundling status in the source.
+    if debugpy.__bundling_disabled__ != DEBUGPY_BUNDLING_DISABLED:
+
+        with open(os.path.join(DEBUGBY_ROOT, '__init__.py'), 'r') as f:
+            lines = f.readlines()
+        with open(os.path.join(DEBUGBY_ROOT, '__init__.py'), 'w') as f:
+            edited = []
+            for line in lines:
+                if line.startswith('__bundling_disabled__'):
+                    edited.append(
+                        f'__bundling_disabled__ = {DEBUGPY_BUNDLING_DISABLED}\n')
+                else:
+                    edited.append(line)
+            f.writelines(edited)
+
     extras = {}
     platforms = get_buildplatform()
     if platforms is not None:
@@ -145,6 +166,18 @@ if __name__ == "__main__":
     override_build(cmds)
     override_build_py(cmds)
 
+    data = {"debugpy": ["ThirdPartyNotices.txt"]}
+    packages = [
+            "debugpy",
+            "debugpy.adapter",
+            "debugpy.common",
+            "debugpy.launcher",
+            "debugpy.server",
+        ]
+    if not DEBUGPY_BUNDLING_DISABLED:
+        data.update({"debugpy._vendored": list(iter_vendored_files())})
+        packages.append("debugpy._vendored")
+
     setuptools.setup(
         name="debugpy",
         version=versioneer.get_version(),
@@ -173,20 +206,10 @@ if __name__ == "__main__":
             "License :: OSI Approved :: MIT License",
         ],
         package_dir={"": "src"},
-        packages=[
-            "debugpy",
-            "debugpy.adapter",
-            "debugpy.common",
-            "debugpy.launcher",
-            "debugpy.server",
-            "debugpy._vendored",
-        ],
-        package_data={
-            "debugpy": ["ThirdPartyNotices.txt"],
-            "debugpy._vendored": list(iter_vendored_files()),
-        },
+        packages=packages,
+        package_data=data,
         ext_modules=ExtModules(),
-        has_ext_modules=lambda: True,
+        has_ext_modules=lambda: not DEBUGPY_BUNDLING_DISABLED,
         cmdclass=cmds,
         **extras
     )
diff --git a/src/debugpy/__init__.py b/src/debugpy/__init__.py
index baa5a7c5..7b7a29aa 100644
--- a/src/debugpy/__init__.py
+++ b/src/debugpy/__init__.py
@@ -206,6 +206,8 @@ def trace_this_thread(should_trace):
 
 __version__ = _version.get_versions()["version"]
 
+__bundling_disabled__ = False
+
 # Force absolute path on Python 2.
 __file__ = os.path.abspath(__file__)
 
diff --git a/src/debugpy/server/__init__.py b/src/debugpy/server/__init__.py
index e6a1ad66..5f29a87a 100644
--- a/src/debugpy/server/__init__.py
+++ b/src/debugpy/server/__init__.py
@@ -4,6 +4,50 @@
 
 from __future__ import absolute_import, division, print_function, unicode_literals
 
+from importlib import import_module
+import os
+
 # "force_pydevd" must be imported first to ensure (via side effects)
 # that the debugpy-vendored copy of pydevd gets used.
-import debugpy._vendored.force_pydevd  # noqa
+import debugpy
+if debugpy.__bundling_disabled__:
+    # Do what force_pydevd.py does, but using the system-provided
+    # pydevd.
+
+    # XXX: This is copied here so that the whole '_vendored' directory
+    # can be deleted when DEBUGPY_BUNDLING_DISABLED is set.
+
+    # If debugpy logging is enabled, enable it for pydevd as well
+    if "DEBUGPY_LOG_DIR" in os.environ:
+        os.environ[str("PYDEVD_DEBUG")] = str("True")
+        os.environ[str("PYDEVD_DEBUG_FILE")] = \
+            os.environ["DEBUGPY_LOG_DIR"] + str("/debugpy.pydevd.log")
+
+    # Work around https://github.com/microsoft/debugpy/issues/346.
+    # Disable pydevd frame-eval optimizations only if unset, to allow opt-in.
+    if "PYDEVD_USE_FRAME_EVAL" not in os.environ:
+        os.environ[str("PYDEVD_USE_FRAME_EVAL")] = str("NO")
+
+    # Constants must be set before importing any other pydevd module
+    # due to heavy use of "from" in them.
+    pydevd_constants = import_module('_pydevd_bundle.pydevd_constants')
+    # The default pydevd value is 1000.
+    pydevd_constants.MAXIMUM_VARIABLE_REPRESENTATION_SIZE = 2 ** 32
+
+    # When pydevd is imported it sets the breakpoint behavior, but it needs to be
+    # overridden because by default pydevd will connect to the remote debugger using
+    # its own custom protocol rather than DAP.
+    import pydevd   # noqa
+    import debugpy  # noqa
+
+    def debugpy_breakpointhook():
+        debugpy.breakpoint()
+
+    pydevd.install_breakpointhook(debugpy_breakpointhook)
+
+    # Ensure that pydevd uses JSON protocol
+    from _pydevd_bundle import pydevd_constants
+    from _pydevd_bundle import pydevd_defaults
+    pydevd_defaults.PydevdCustomization.DEFAULT_PROTOCOL = pydevd_constants.HTTP_JSON_PROTOCOL
+else:
+    import debugpy._vendored.force_pydevd  # noqa
diff --git a/src/debugpy/server/attach_pid_injected.py b/src/debugpy/server/attach_pid_injected.py
index e6345996..87cfdd53 100644
--- a/src/debugpy/server/attach_pid_injected.py
+++ b/src/debugpy/server/attach_pid_injected.py
@@ -8,6 +8,7 @@ from __future__ import absolute_import, division, print_function, unicode_litera
 
 import os
 
+import debugpy
 
 __file__ = os.path.abspath(__file__)
 _debugpy_dir = os.path.dirname(os.path.dirname(os.path.dirname(__file__)))
@@ -30,25 +31,29 @@ def attach(setup):
                 def on_critical(msg):
                     print(msg, file=sys.stderr)
 
-                pydevd_attach_to_process_path = os.path.join(
-                    _debugpy_dir,
-                    "debugpy",
-                    "_vendored",
-                    "pydevd",
-                    "pydevd_attach_to_process",
-                )
-                assert os.path.exists(pydevd_attach_to_process_path)
-                sys.path.insert(0, pydevd_attach_to_process_path)
-
-                # NOTE: that it's not a part of the pydevd PYTHONPATH
-                import attach_script
+                if debugpy.__bundling_disabled__:
+                    from pydevd_attach_to_process import attach_script
+                else:
+                    pydevd_attach_to_process_path = os.path.join(
+                        _debugpy_dir,
+                        "debugpy",
+                        "_vendored",
+                        "pydevd",
+                        "pydevd_attach_to_process",
+                    )
+                    assert os.path.exists(pydevd_attach_to_process_path)
+                    sys.path.insert(0, pydevd_attach_to_process_path)
+
+                    # NOTE: that it's not a part of the pydevd PYTHONPATH
+                    import attach_script
 
                 attach_script.fix_main_thread_id(
                     on_warn=on_warn, on_exception=on_exception, on_critical=on_critical
                 )
 
-                # NOTE: At this point it should be safe to remove this.
-                sys.path.remove(pydevd_attach_to_process_path)
+                if not debugpy.__bundling_disabled__:
+                    # NOTE: At this point it should be safe to remove this.
+                    sys.path.remove(pydevd_attach_to_process_path)
             except:
                 import traceback
 
diff --git a/tests/tests/test_vendoring.py b/tests/tests/test_vendoring.py
index dd6c4269..28c03702 100644
--- a/tests/tests/test_vendoring.py
+++ b/tests/tests/test_vendoring.py
@@ -1,3 +1,8 @@
+import pytest
+
+import debugpy
+
+@pytest.mark.skipif(debugpy.__bundling_disabled__, reason='Bundling disabled')
 def test_vendoring(pyfile):
     @pyfile
     def import_debugpy():
-- 
2.34.0