Allow user to specify custom typeshed directory

Author: ddfisher

docs/source/command_line.rst

@@ -17,13 +17,13 @@ flag (or its long form ``--help``)::
               [--strict-optional]
               [--strict-optional-whitelist [GLOB [GLOB ...]]] [--pdb]
               [--show-traceback] [--stats] [--inferstats]
-              [--custom-typing MODULE] [--scripts-are-modules]
-              [--config-file CONFIG_FILE] [--show-column-numbers]
-              [--html-report DIR] [--linecount-report DIR]
-              [--linecoverage-report DIR] [--memory-xml-report DIR]
-              [--old-html-report DIR] [--txt-report DIR] [--xml-report DIR]
-              [--xslt-html-report DIR] [--xslt-txt-report DIR]
-              [-m MODULE] [-c PROGRAM_TEXT] [-p PACKAGE]
+              [--custom-typing MODULE] [--custom-typeshed-dir DIR]
+              [--scripts-are-modules] [--config-file CONFIG_FILE]
+              [--show-column-numbers] [--html-report DIR]
+              [--linecount-report DIR] [--linecoverage-report DIR]
+              [--memory-xml-report DIR] [--old-html-report DIR]
+              [--txt-report DIR] [--xml-report DIR] [--xslt-html-report DIR]
+              [--xslt-txt-report DIR] [-m MODULE] [-c PROGRAM_TEXT] [-p PACKAGE]
               [files [files ...]]
 
   (etc., too long to show everything here)
@@ -326,6 +326,12 @@ Here are some more useful flags:
   package, the behavior enabled by this flag is often more
   convenient.)
 
+- ``--custom-typeshed-dir DIR`` specifies the directory where mypy looks for
+  typeshed stubs, instead of the typeshed that ships with mypy.  This is
+  primarily intended to make it easier to test typeshed changes before
+  submitting them upstream, but also allows you to use a forked version of
+  typeshed.
+
 .. _config-file-flag:
 
 - ``--config-file CONFIG_FILE`` causes configuration settings to be

mypy/build.py

@@ -127,12 +127,20 @@ def build(sources: List[BuildSource],
         directories; if omitted, use '.' as the data directory
     """
 
-    data_dir = default_data_dir(bin_dir)
+    if options.custom_typeshed_dir:
+        custom_data_dir, custom_typeshed_name = os.path.split(
+            options.custom_typeshed_dir.rstrip(os.sep))
+        data_dir = custom_data_dir
+    else:
+        custom_typeshed_name = None
+        data_dir = default_data_dir(bin_dir)
 
     find_module_clear_caches()
 
     # Determine the default module search path.
-    lib_path = default_lib_path(data_dir, options.python_version)
+    lib_path = default_lib_path(data_dir,
+                                options.python_version,
+                                custom_typeshed_name=custom_typeshed_name)
 
     if options.use_builtins_fixtures:
         # Use stub builtins (to speed up test cases and to make them easier to
@@ -249,10 +257,13 @@ def mypy_path() -> List[str]:
     return path_env.split(os.pathsep)
 
 
-def default_lib_path(data_dir: str, pyversion: Tuple[int, int]) -> List[str]:
+def default_lib_path(data_dir: str,
+                     pyversion: Tuple[int, int],
+                     custom_typeshed_name: str = None) -> List[str]:
     """Return default standard library search paths."""
     # IDEA: Make this more portable.
     path = []  # type: List[str]
+    typeshed_name = custom_typeshed_name or 'typeshed'
 
     auto = os.path.join(data_dir, 'stubs-auto')
     if os.path.isdir(auto):
@@ -266,7 +277,7 @@ def default_lib_path(data_dir: str, pyversion: Tuple[int, int]) -> List[str]:
     # (Note that 3.1 and 3.0 aren't really supported, but we don't care.)
     for v in versions + [str(pyversion[0]), '2and3']:
         for lib_type in ['stdlib', 'third_party']:
-            stubdir = os.path.join(data_dir, 'typeshed', lib_type, v)
+            stubdir = os.path.join(data_dir, typeshed_name, lib_type, v)
             if os.path.isdir(stubdir):
                 path.append(stubdir)
 

mypy/main.py

@@ -188,6 +188,8 @@ def process_options(args: List[str],
                         help="dump type inference stats")
     parser.add_argument('--custom-typing', metavar='MODULE', dest='custom_typing_module',
                         help="use a custom typing module")
+    parser.add_argument('--custom-typeshed-dir', metavar='DIR',
+                        help="use the custom typeshed in DIR")
     parser.add_argument('--scripts-are-modules', action='store_true',
                         help="Script x becomes module x instead of __main__")
     parser.add_argument('--config-file',

mypy/options.py

@@ -34,7 +34,8 @@ def __init__(self) -> None:
         self.build_type = BuildType.STANDARD
         self.python_version = defaults.PYTHON3_VERSION
         self.platform = sys.platform
-        self.custom_typing_module = None  # type: str
+        self.custom_typing_module = None  # type: Optional[str]
+        self.custom_typeshed_dir = None  # type: Optional[str]
         self.report_dirs = {}  # type: Dict[str, str]
         self.silent_imports = False
         self.almost_silent = False