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      1 """Fixer for import statements.
      2 If spam is being imported from the local directory, this import:
      3     from spam import eggs
      4 Becomes:
      5     from .spam import eggs
      6 
      7 And this import:
      8     import spam
      9 Becomes:
     10     from . import spam
     11 """
     12 
     13 # Local imports
     14 from .. import fixer_base
     15 from os.path import dirname, join, exists, sep
     16 from ..fixer_util import FromImport, syms, token
     17 
     18 
     19 def traverse_imports(names):
     20     """
     21     Walks over all the names imported in a dotted_as_names node.
     22     """
     23     pending = [names]
     24     while pending:
     25         node = pending.pop()
     26         if node.type == token.NAME:
     27             yield node.value
     28         elif node.type == syms.dotted_name:
     29             yield "".join([ch.value for ch in node.children])
     30         elif node.type == syms.dotted_as_name:
     31             pending.append(node.children[0])
     32         elif node.type == syms.dotted_as_names:
     33             pending.extend(node.children[::-2])
     34         else:
     35             raise AssertionError("unkown node type")
     36 
     37 
     38 class FixImport(fixer_base.BaseFix):
     39     BM_compatible = True
     40 
     41     PATTERN = """
     42     import_from< 'from' imp=any 'import' ['('] any [')'] >
     43     |
     44     import_name< 'import' imp=any >
     45     """
     46 
     47     def start_tree(self, tree, name):
     48         super(FixImport, self).start_tree(tree, name)
     49         self.skip = "absolute_import" in tree.future_features
     50 
     51     def transform(self, node, results):
     52         if self.skip:
     53             return
     54         imp = results['imp']
     55 
     56         if node.type == syms.import_from:
     57             # Some imps are top-level (eg: 'import ham')
     58             # some are first level (eg: 'import ham.eggs')
     59             # some are third level (eg: 'import ham.eggs as spam')
     60             # Hence, the loop
     61             while not hasattr(imp, 'value'):
     62                 imp = imp.children[0]
     63             if self.probably_a_local_import(imp.value):
     64                 imp.value = u"." + imp.value
     65                 imp.changed()
     66         else:
     67             have_local = False
     68             have_absolute = False
     69             for mod_name in traverse_imports(imp):
     70                 if self.probably_a_local_import(mod_name):
     71                     have_local = True
     72                 else:
     73                     have_absolute = True
     74             if have_absolute:
     75                 if have_local:
     76                     # We won't handle both sibling and absolute imports in the
     77                     # same statement at the moment.
     78                     self.warning(node, "absolute and local imports together")
     79                 return
     80 
     81             new = FromImport(u".", [imp])
     82             new.prefix = node.prefix
     83             return new
     84 
     85     def probably_a_local_import(self, imp_name):
     86         if imp_name.startswith(u"."):
     87             # Relative imports are certainly not local imports.
     88             return False
     89         imp_name = imp_name.split(u".", 1)[0]
     90         base_path = dirname(self.filename)
     91         base_path = join(base_path, imp_name)
     92         # If there is no __init__.py next to the file its not in a package
     93         # so can't be a relative import.
     94         if not exists(join(dirname(base_path), "__init__.py")):
     95             return False
     96         for ext in [".py", sep, ".pyc", ".so", ".sl", ".pyd"]:
     97             if exists(base_path + ext):
     98                 return True
     99         return False
    100