Merge pull request #1622 from jjhelmus/check_build_sprint

Display user friendly error message when importing broken skimage / uncompiled from source tree

setup.py

@@ -24,6 +24,19 @@ import sys
 import setuptools
 from distutils.command.build_py import build_py
 
+if sys.version_info[0] < 3:
+    import __builtin__ as builtins
+else:
+    import builtins
+
+# This is a bit (!) hackish: we are setting a global variable so that the main
+# skimage __init__ can detect if it is being loaded by the setup routine, to
+# avoid attempting to load components that aren't built yet:
+# the numpy distutils extensions that are used by scikit-image to recursively
+# build the compiled extensions in sub-packages is based on the Python import
+# machinery.
+builtins.__SKIMAGE_SETUP__ = True
+
 
 with open('skimage/__init__.py') as fid:
     for line in fid:

skimage/__init__.py

@@ -60,7 +60,7 @@ import os.path as osp
 import imp
 import functools
 import warnings
-from .util.dtype import *
+import sys
 
 pkg_dir = osp.abspath(osp.dirname(__file__))
 data_dir = osp.join(pkg_dir, 'data')
@@ -109,4 +109,51 @@ doctest.__doc__ = doctest.__doc__
 doctest_verbose = functools.partial(test, doctest=True, verbose=True)
 doctest_verbose.__doc__ = doctest.__doc__
 
-del warnings, functools, osp, imp
+
+# Logic for checking for improper install and importing while in the source
+# tree when package has not been installed inplace.
+# Code adapted from scikit-learn's __check_build module.
+_INPLACE_MSG = """
+It appears that you are importing a local scikit-image source tree. For
+this, you need to have an inplace install. Maybe you are in the source
+directory and you need to try from another location."""
+
+_STANDARD_MSG = """
+Your install of scikit-image appears to be broken.
+Try re-installing the package following the instructions at:
+http://scikit-image.org/docs/stable/install.html """
+
+
+def _raise_build_error(e):
+    # Raise a comprehensible error
+    local_dir = osp.split(__file__)[0]
+    msg = _STANDARD_MSG
+    if local_dir == "skimage":
+        # Picking up the local install: this will work only if the
+        # install is an 'inplace build'
+        msg = _INPLACE_MSG
+    raise ImportError("""%s
+It seems that scikit-image has not been built correctly.
+%s""" % (e, msg))
+
+try:
+    # This variable is injected in the __builtins__ by the build
+    # process. It used to enable importing subpackages of skimage when
+    # the binaries are not built
+    __SKIMAGE_SETUP__
+except NameError:
+    __SKIMAGE_SETUP__ = False
+
+if __SKIMAGE_SETUP__:
+    sys.stderr.write('Partial import of skimage during the build process.\n')
+    # We are not importing the rest of the scikit during the build
+    # process, as it may not be compiled yet
+else:
+    try:
+        from ._shared import geometry
+        del geometry
+    except ImportError as e:
+        _raise_build_error(e)
+    from .util.dtype import *
+
+del warnings, functools, osp, imp, sys