Fixed a name clash in the 'from_environment_diff' function (#12116)

* Added a unit test reproducing the failure in 12085

* Fixed name clash in the 'from_environment_diff' function

The bug reported in #12085 stemmed from a name clash among variables,
introduced during the refactor in #10753 and not caught by unit tests
and reviews.

lib/spack/spack/test/environment_modifications.py

@@ -399,6 +399,7 @@ def test_sanitize_regex(env, blacklist, whitelist, expected, deleted):
     assert all(x not in after for x in deleted)
 
 
+@pytest.mark.regression('12085')
 @pytest.mark.parametrize('before,after,search_list', [
     # Set environment variables
     ({}, {'FOO': 'foo'}, [environment.SetEnv('FOO', 'foo')]),
@@ -420,7 +421,12 @@ def test_sanitize_regex(env, blacklist, whitelist, expected, deleted):
     ({'FOO_PATH': '/a/path:/b/path'}, {'FOO_PATH': '/c/path:/a/path'}, [
         environment.RemovePath('FOO_PATH', '/b/path'),
         environment.PrependPath('FOO_PATH', '/c/path')
-    ])
+    ]),
+    # Modify two variables in the same environment
+    ({'FOO': 'foo', 'BAR': 'bar'}, {'FOO': 'baz', 'BAR': 'baz'}, [
+        environment.SetEnv('FOO', 'baz'),
+        environment.SetEnv('BAR', 'baz'),
+    ]),
 ])
 def test_from_environment_diff(before, after, search_list):
 

lib/spack/spack/util/environment.py

@@ -607,12 +607,12 @@ def return_separator_if_any(*args):
             env.unset(x)
 
         for x in modified_variables:
-            before = before[x]
+            value_before = before[x]
-            after = after[x]
+            value_after = after[x]
-            sep = return_separator_if_any(before, after)
+            sep = return_separator_if_any(value_before, value_after)
             if sep:
-                before_list = before.split(sep)
+                before_list = value_before.split(sep)
-                after_list = after.split(sep)
+                after_list = value_after.split(sep)
 
                 # Filter out empty strings
                 before_list = list(filter(None, before_list))
@@ -623,8 +623,8 @@ def return_separator_if_any(*args):
                     before_list = list(dedupe(before_list))
                     after_list = list(dedupe(after_list))
                     # The reassembled cleaned entries
-                    before = sep.join(before_list)
+                    value_before = sep.join(before_list)
-                    after = sep.join(after_list)
+                    value_after = sep.join(after_list)
 
                 # Paths that have been removed
                 remove_list = [
@@ -638,12 +638,12 @@ def return_separator_if_any(*args):
                     end = after_list.index(remaining_list[-1])
                     search = sep.join(after_list[start:end + 1])
                 except IndexError:
-                    env.prepend_path(x, after)
+                    env.prepend_path(x, value_after)
                     continue
 
-                if search not in before:
+                if search not in value_before:
                     # We just need to set the variable to the new value
-                    env.prepend_path(x, after)
+                    env.prepend_path(x, value_after)
                 else:
                     try:
                         prepend_list = after_list[:start]
@@ -663,7 +663,7 @@ def return_separator_if_any(*args):
                         env.prepend_path(x, item)
             else:
                 # We just need to set the variable to the new value
-                env.set(x, after)
+                env.set(x, value_after)
 
         return env