Support MYPY_VERSION for overriding version

mypy/version.py

@@ -5,12 +5,22 @@
 # - Release versions have the form "0.NNN".
 # - Dev versions have the form "0.NNN+dev" (PLUS sign to conform to PEP 440).
 # - For 1.0 we'll switch back to 1.2.3 form.
-__version__ = '0.950+dev'
-base_version = __version__
+base_version = '0.950+dev'
+# Overridden by setup.py
+__version__ = base_version
 
-mypy_dir = os.path.abspath(os.path.dirname(os.path.dirname(__file__)))
-if __version__.endswith('+dev') and git.is_git_repo(mypy_dir) and git.have_git():
-    __version__ += '.' + git.git_revision(mypy_dir).decode('utf-8')
-    if git.is_dirty(mypy_dir):
-        __version__ += '.dirty'
-del mypy_dir
+
+def setup_compute_version() -> str:
+    # We allow an environment variable to override version, but we should probably
+    # enforce that it is consistent with the existing version minus additional information.
+    if "MYPY_VERSION" in os.environ:
+        assert os.environ["MYPY_VERSION"].startswith(base_version)
+        return os.environ["MYPY_VERSION"]
+
+    mypy_dir = os.path.abspath(os.path.dirname(os.path.dirname(__file__)))
+    if base_version.endswith('+dev') and git.is_git_repo(mypy_dir) and git.have_git():
+        version = base_version + '.' + git.git_revision(mypy_dir).decode('utf-8')
+        if git.is_dirty(mypy_dir):
+            return version + ".dirty"
+        return version
+    return base_version

setup.py

@@ -17,7 +17,7 @@
 # alternative forms of installing, as suggested by README.md).
 from setuptools import setup, find_packages
 from setuptools.command.build_py import build_py
-from mypy.version import __version__ as version
+from mypy.version import setup_compute_version
 
 description = 'Optional static typing for Python'
 long_description = '''
@@ -32,6 +32,8 @@
 types.
 '''.lstrip()
 
+version = setup_compute_version()
+
 
 def find_package_data(base, globs, root='mypy'):
     """Find all interesting data files, for setup(package_data=)