Correct WSGI adapter handling of root path.

Fixes #442

asgiref/wsgi.py

@@ -54,10 +54,14 @@ def build_environ(self, scope, body):
         """
         Builds a scope and request body into a WSGI environ object.
         """
+        script_name = scope.get("root_path", "").encode("utf8").decode("latin1")
+        path_info = scope["path"].encode("utf8").decode("latin1")
+        if path_info.startswith(script_name):
+            path_info = path_info[len(script_name) :]
         environ = {
             "REQUEST_METHOD": scope["method"],
-            "SCRIPT_NAME": scope.get("root_path", "").encode("utf8").decode("latin1"),
-            "PATH_INFO": scope["path"].encode("utf8").decode("latin1"),
+            "SCRIPT_NAME": script_name,
+            "PATH_INFO": path_info,
             "QUERY_STRING": scope["query_string"].decode("ascii"),
             "SERVER_PROTOCOL": "HTTP/%s" % scope["http_version"],
             "wsgi.version": (1, 0),

setup.cfg

@@ -47,7 +47,7 @@ asyncio_mode = strict
 
 [flake8]
 exclude = venv/*,tox/*,specs/*
-ignore = E123,E128,E266,E402,W503,E731,W601
+ignore = E123,E128,E266,E402,W503,E731,W601,E203
 max-line-length = 119
 
 [isort]

tests/test_wsgi.py

@@ -3,14 +3,15 @@
 import pytest
 
 from asgiref.testing import ApplicationCommunicator
-from asgiref.wsgi import WsgiToAsgi
+from asgiref.wsgi import WsgiToAsgi, WsgiToAsgiInstance
 
 
 @pytest.mark.asyncio
 async def test_basic_wsgi():
     """
     Makes sure the WSGI wrapper has basic functionality.
     """
+
     # Define WSGI app
     def wsgi_application(environ, start_response):
         assert environ["HTTP_TEST_HEADER"] == "test value 1,test value 2"
@@ -55,11 +56,32 @@ def wsgi_application(environ, start_response):
     assert (await instance.receive_output(1)) == {"type": "http.response.body"}
 
 
+def test_script_name():
+    scope = {
+        "type": "http",
+        "http_version": "1.0",
+        "method": "GET",
+        "root_path": "/base",
+        "path": "/base/foo/",
+        "query_string": b"bar=baz",
+        "headers": [
+            [b"test-header", b"test value 1"],
+            [b"test-header", b"test value 2"],
+        ],
+    }
+    adapter = WsgiToAsgiInstance(None)
+    adapter.scope = scope
+    environ = adapter.build_environ(scope, None)
+    assert environ["SCRIPT_NAME"] == "/base"
+    assert environ["PATH_INFO"] == "/foo/"
+
+
 @pytest.mark.asyncio
 async def test_wsgi_path_encoding():
     """
     Makes sure the WSGI wrapper has basic functionality.
     """
+
     # Define WSGI app
     def wsgi_application(environ, start_response):
         assert environ["SCRIPT_NAME"] == "/中国".encode().decode("latin-1")