Refactor code that adds UNLINK step

This provides a pivot point that allows us to add ENSURE_WRITE at all
points when an unlink is happening.

conda/plan.py

@@ -184,6 +184,12 @@ def nothing_to_do(actions):
     return True
 
 
+def add_unlink(actions, dist):
+    if inst.UNLINK not in actions:
+        actions[inst.UNLINK] = []
+    actions[inst.UNLINK].append(dist)
+
+
 def plan_from_actions(actions):
     if 'op_order' in actions and actions['op_order']:
         op_order = actions['op_order']
@@ -296,7 +302,7 @@ def force_linked_actions(dists, index, prefix):
         actions[inst.RM_EXTRACTED].append(dist)
         actions[inst.EXTRACT].append(dist)
         if isfile(join(prefix, 'conda-meta', dist + '.json')):
-            actions[inst.UNLINK].append(dist)
+            add_unlink(actions, dist)
         actions[inst.LINK].append(dist)
     return actions
 
@@ -426,7 +432,7 @@ def install_actions(prefix, index, specs, force=False, only_names=None,
     for dist in sorted(linked):
         name = install.name_dist(dist)
         if name in must_have and dist != must_have[name]:
-            actions[inst.UNLINK].append(dist)
+            add_unlink(actions, dist)
 
     return actions
 
@@ -454,7 +460,7 @@ def remove_actions(prefix, specs, index=None, pinned=True):
                     "Cannot remove %s because it is pinned. Use --no-pin "
                     "to override." % dist)
 
-            actions[inst.UNLINK].append(dist)
+            add_unlink(actions, dist)
             if r and fn in index and r.track_features(fn):
                 features_actions = remove_features_actions(
                     prefix, index, r.track_features(fn))
@@ -482,9 +488,9 @@ def remove_features_actions(prefix, index, features):
         if fn not in index:
             continue
         if r.track_features(fn).intersection(features):
-            actions[inst.UNLINK].append(dist)
+            add_unlink(actions, dist)
         if r.features(fn).intersection(features):
-            actions[inst.UNLINK].append(dist)
+            add_unlink(actions, dist)
             subst = r.find_substitute(_linked, features, fn)
             if subst:
                 to_link.append(subst[:-8])
@@ -508,7 +514,7 @@ def revert_actions(prefix, revision=-1):
 
     actions = ensure_linked_actions(state, prefix)
     for dist in curr - state:
-        actions[inst.UNLINK].append(dist)
+        add_unlink(actions, dist)
 
     return actions
 

tests/test_plan.py

@@ -1,9 +1,12 @@
 import sys
 import json
+import random
 import unittest
 from os.path import dirname, join
 from collections import defaultdict
 
+import pytest
+
 from conda.config import default_python, pkgs_dirs
 import conda.config
 from conda.install import LINK_HARD
@@ -12,13 +15,17 @@
 from conda.plan import display_actions
 from conda.resolve import Resolve
 
+# FIXME This should be a relative import
 from tests.helpers import captured
 from conda.exceptions import CondaException
 
+from .helpers import mock
+
 with open(join(dirname(__file__), 'index.json')) as fi:
     index = json.load(fi)
     r = Resolve(index)
 
+
 def solve(specs):
     return [fn[:-8] for fn in r.solve(specs)]
 
@@ -34,6 +41,35 @@ def test_split_linkarg(self):
             self.assertEqual(inst.split_linkarg(arg), res)
 
 
+@pytest.mark.parametrize("args", [
+    (),
+    ("one", ),
+    ("one", "two", "three", ),
+])
+def test_add_unlink_takes_two_arguments(args):
+    with pytest.raises(TypeError):
+        plan.add_unlink(*args)
+
+
+class add_unlink_TestCase(unittest.TestCase):
+    def test_simply_adds_unlink_on_non_windows(self):
+        actions = {}
+        dist = {"foo": "bar%s" % random.randint(100, 200)}
+        with mock.patch.object(plan, "sys") as sys:
+            sys.platform = "not win32"
+            plan.add_unlink(actions, dist)
+        self.assertIn(inst.UNLINK, actions)
+        self.assertEqual(actions[inst.UNLINK], [dist, ])
+
+    def test_adds_to_existing_actions(self):
+        actions = {inst.UNLINK: [{"foo": "bar"}]}
+        dist = {"foo": "bar%s" % random.randint(100, 200)}
+        with mock.patch.object(plan, "sys") as sys:
+            sys.platform = "not win32"
+            plan.add_unlink(actions, dist)
+        self.assertEqual(2, len(actions[inst.UNLINK]))
+
+
 class TestAddDeaultsToSpec(unittest.TestCase):
     # tests for plan.add_defaults_to_specs(r, linked, specs)