Merge pull request #20015 from basepi/grainsprecedencedocs19611

Fix grains precedence issues

doc/topics/targeting/grains.rst

@@ -205,15 +205,15 @@ defining custom grains, there is an order of precedence which should be kept in
 mind when defining them. The order of evaluation is as follows:
 
 1. Core grains.
-2. Custom grains in ``/etc/salt/grains``.
-3. Custom grains in ``/etc/salt/minion``.
-4. Custom grain modules in ``_grains`` directory, synced to minions.
+2. Custom grain modules in ``_grains`` directory, synced to minions.
+3. Custom grains in ``/etc/salt/grains``.
+4. Custom grains in ``/etc/salt/minion``.
 
 Each successive evaluation overrides the previous ones, so any grains defined
-in ``/etc/salt/grains`` that have the same name as a core grain will override
-that core grain. Similarly, ``/etc/salt/minion`` overrides both core grains and
-grains set in ``/etc/salt/grains``, and custom grain modules will override
-*any* grains of the same name.
+by custom grains modules synced to minions that have the same name as a core
+grain will override that core grain. Similarly, grains from
+``/etc/salt/grains`` override both core grains and custom grain modules, and
+grains in ``/etc/salt/minion`` will override *any* grains of the same name.
 
 
 Examples of Grains

salt/loader.py

@@ -18,6 +18,7 @@ from collections import MutableMapping
 from salt.exceptions import LoaderError
 from salt.template import check_render_pipe_str
 from salt.utils.decorators import Depends
+from salt.utils.odict import OrderedDict
 
 # Solve the Chicken and egg problem where grains need to run before any
 # of the modules are loaded and are generally available for any usage.
@@ -714,7 +715,7 @@ class Loader(object):
         '''
         Return a dict of functions found in the defined module_dirs
         '''
-        funcs = {}
+        funcs = OrderedDict()
         self.load_modules()
         for mod in self.modules:
             # If this is a proxy minion then MOST modules cannot work.  Therefore, require that
@@ -824,7 +825,7 @@ class Loader(object):
         self.modules = []
 
         log.trace('loading {0} in {1}'.format(self.tag, self.module_dirs))
-        names = {}
+        names = OrderedDict()
         disable = set(self.opts.get('disable_{0}s'.format(self.tag), []))
 
         cython_enabled = False
@@ -1238,15 +1239,6 @@ class Loader(object):
         grains_data = {}
         funcs = self.gen_functions()
         for key, fun in funcs.items():
-            if not key.startswith('core.'):
-                continue
-            ret = fun()
-            if not isinstance(ret, dict):
-                continue
-            grains_data.update(ret)
-        for key, fun in funcs.items():
-            if key.startswith('core.'):
-                continue
             try:
                 ret = fun()
             except Exception:
@@ -1260,7 +1252,10 @@ class Loader(object):
                 continue
             if not isinstance(ret, dict):
                 continue
-            grains_data.update(ret)
+            # The OrderedDict of funcs has core grains at the end. So earlier
+            # grains are the ones which should override
+            ret.update(grains_data)
+            grains_data = ret
         # Write cache if enabled
         if self.opts.get('grains_cache', False):
             cumask = os.umask(077)