Fix mypy errors (#2753)

Apparently I wasn't paying attention in my last PR :)

ci/requirements-py36.yml

@@ -32,4 +32,4 @@ dependencies:
   - lxml
   - pip:
     - cfgrib>=0.9.2
-    - mypy==0.650
+    - mypy==0.660

xarray/core/alignment.py

@@ -3,7 +3,7 @@
 import warnings
 from collections import OrderedDict, defaultdict
 from contextlib import suppress
-from typing import Any, Mapping, Optional
+from typing import Any, Mapping, Optional, Tuple
 
 import numpy as np
 import pandas as pd
@@ -317,7 +317,7 @@ def reindex_variables(
 
     # build up indexers for assignment along each dimension
     int_indexers = {}
-    targets = OrderedDict()
+    targets = OrderedDict()  # type: OrderedDict[Any, pd.Index]
     masked_dims = set()
     unchanged_dims = set()
 
@@ -357,7 +357,7 @@ def reindex_variables(
                     'the new index %r' % (dim, existing_size, new_size))
 
     # create variables for the new dataset
-    reindexed = OrderedDict()
+    reindexed = OrderedDict()  # type: OrderedDict[Any, Variable]
 
     for dim, indexer in indexers.items():
         if isinstance(indexer, DataArray) and indexer.dims != (dim,):

xarray/core/computation.py

@@ -224,7 +224,7 @@ def apply_dataarray_ufunc(func, *args, **kwargs):
 
 
 def ordered_set_union(all_keys: List[Iterable]) -> Iterable:
-    result_dict = OrderedDict()
+    result_dict = OrderedDict()  # type: OrderedDict[Any, None]
     for keys in all_keys:
         for key in keys:
             result_dict[key] = None
@@ -284,11 +284,10 @@ def _as_variables_or_variable(arg):
 
 
 def _unpack_dict_tuples(
-        result_vars,  # type: Mapping[Any, Tuple[Variable]]
-        num_outputs,  # type: int
-):
-    # type: (...) -> Tuple[Dict[Any, Variable], ...]
-    out = tuple(OrderedDict() for _ in range(num_outputs))
+    result_vars: Mapping[Any, Tuple[Variable]],
+    num_outputs: int,
+) -> 'Tuple[OrderedDict[Any, Variable], ...]':
+    out = tuple(OrderedDict() for _ in range(num_outputs))  # type: ignore
     for name, values in result_vars.items():
         for value, results_dict in zip(values, out):
             results_dict[name] = value
@@ -444,7 +443,7 @@ def unified_dim_sizes(
     exclude_dims: AbstractSet = frozenset(),
 ) -> 'OrderedDict[Any, int]':
 
-    dim_sizes = OrderedDict()
+    dim_sizes = OrderedDict()  # type: OrderedDict[Any, int]
 
     for var in variables:
         if len(set(var.dims)) < len(var.dims):

xarray/core/dataset.py

@@ -192,11 +192,11 @@ def merge_indexes(
 
 
 def split_indexes(
-        dims_or_levels,  # type: Union[Any, List[Any]]
-        variables,  # type: Dict[Any, Variable]
-        coord_names,  # type: Set
-        level_coords,  # type: Dict[Any, Any]
-        drop=False,  # type: bool
+    dims_or_levels,  # type: Union[Any, List[Any]]
+    variables,  # type: OrderedDict[Any, Variable]
+    coord_names,  # type: Set
+    level_coords,  # type: Dict[Any, Any]
+    drop=False,  # type: bool
 ):
     # type: (...) -> Tuple[OrderedDict[Any, Variable], Set]
     """Extract (multi-)indexes (levels) as variables.
@@ -216,7 +216,7 @@ def split_indexes(
             dims.append(k)
 
     vars_to_replace = {}
-    vars_to_create = OrderedDict()
+    vars_to_create = OrderedDict()  # type: OrderedDict[Any, Variable]
     vars_to_remove = []
 
     for d in dims:
@@ -696,11 +696,14 @@ def _from_vars_and_coord_names(cls, variables, coord_names, attrs=None):
         dims = dict(calculate_dimensions(variables))
         return cls._construct_direct(variables, coord_names, dims, attrs)
 
-    def _replace(
+    # TODO(shoyer): renable type checking on this signature when pytype has a
+    # good way to handle defaulting arguments to a sentinel value:
+    # https://github.com/python/mypy/issues/1803
+    def _replace(  # type: ignore
         self: T,
         variables: 'OrderedDict[Any, Variable]' = None,
         coord_names: set = None,
-        dims: 'OrderedDict[Any, int]' = None,
+        dims: Dict[Any, int] = None,
         attrs: 'Optional[OrderedDict]' = __default,
         indexes: 'Optional[OrderedDict[Any, pd.Index]]' = __default,
         encoding: Optional[dict] = __default,
@@ -745,7 +748,7 @@ def _replace(
                 variables, coord_names, dims, attrs, indexes, encoding)
         return obj
 
-    def _replace_with_new_dims(
+    def _replace_with_new_dims(  # type: ignore
         self: T,
         variables: 'OrderedDict[Any, Variable]' = None,
         coord_names: set = None,
@@ -758,7 +761,7 @@ def _replace_with_new_dims(
         return self._replace(
             variables, coord_names, dims, attrs, indexes, inplace=inplace)
 
-    def _replace_vars_and_dims(
+    def _replace_vars_and_dims(  # type: ignore
         self: T,
         variables: 'OrderedDict[Any, Variable]' = None,
         coord_names: set = None,
@@ -931,7 +934,7 @@ def _copy_listed(self: T, names) -> T:
         """Create a new Dataset with the listed variables from this dataset and
         the all relevant coordinates. Skips all validation.
         """
-        variables = OrderedDict()
+        variables = OrderedDict()  # type: OrderedDict[Any, Variable]
         coord_names = set()
 
         for name in names:
@@ -976,7 +979,7 @@ def _construct_dataarray(self, name) -> 'DataArray':
 
         needed_dims = set(variable.dims)
 
-        coords = OrderedDict()
+        coords = OrderedDict()  # type: OrderedDict[Any, Variable]
         for k in self.coords:
             if set(self.variables[k].dims) <= needed_dims:
                 coords[k] = self.variables[k]
@@ -1823,12 +1826,12 @@ def relevant_keys(mapping):
         else:
             # dim is a string
             dim_name = dim
-            dim_coord = None
+            dim_coord = None  # type: ignore
 
         reordered = self.transpose(
             *(list(indexer_dims) + list(non_indexed_dims)))
 
-        variables = OrderedDict()
+        variables = OrderedDict()  # type: ignore
 
         for name, var in reordered.variables.items():
             if name in indexers_dict or any(

xarray/core/merge.py

@@ -22,13 +22,14 @@
                         'no_conflicts': 4})
 
 
-def broadcast_dimension_size(variables):
-    # type: (List[Variable],) -> Variable
+def broadcast_dimension_size(
+    variables: List[Variable],
+) -> 'OrderedDict[Any, int]':
     """Extract dimension sizes from a dictionary of variables.
 
     Raises ValueError if any dimensions have different sizes.
     """
-    dims = OrderedDict()
+    dims = OrderedDict()  # type: OrderedDict[Any, int]
     for var in variables:
         for dim, size in zip(var.dims, var.shape):
             if dim in dims and size != dims[dim]:
@@ -149,7 +150,7 @@ def merge_variables(
 
     # n.b. it's important to fill up merged in the original order in which
     # variables appear
-    merged = OrderedDict()
+    merged = OrderedDict()  # type: OrderedDict[Any, Variable]
 
     for name, var_list in lookup.items():
         if name in priority_vars:
@@ -177,7 +178,7 @@ def merge_variables(
 
 def expand_variable_dicts(
     list_of_variable_dicts: 'List[Union[Dataset, OrderedDict]]',
-) -> 'List[OrderedDict[Any, Variable]]':
+) -> 'List[Mapping[Any, Variable]]':
     """Given a list of dicts with xarray object values, expand the values.
 
     Parameters