salt: Add execution module to retrieve value from map.jinja

In salt we have a function `jinja.load_map` that retrieve a specific
value from a map.jinja (same as what we do in salt SLS) but this
function does not support saltenv
Add a new function to retrieve information from `map.jinja` in MetalK8s
context, so hardcoded map.jinja path and retrieving saltenv from version
stored in the pillar
Sees: saltstack/salt#59300

salt/_modules/metalk8s.py

@@ -10,10 +10,13 @@
 import six
 import socket
 import tempfile
+import textwrap
 import time
 
 from salt.pillar import get_pillar
 from salt.exceptions import CommandExecutionError
+import salt.loader
+import salt.template
 import salt.utils.args
 import salt.utils.files
 from salt.utils.hashutils import get_hash
@@ -557,3 +560,58 @@ def _clean_tmp(sfn):
     if source_filename:
         _clean_tmp(source_filename)
     return ret
+
+
+def get_from_map(value, saltenv=None):
+    """Get a value from map.jinja so that we have an up to date value
+    computed from defaults.yaml and pillar.
+
+    Basically the same as a `jinja.map_load` but with support for saltenv and
+    also hardcoded path to MetalK8s map.jinja.
+
+    Also add logic to retrieve the saltenv using version in the pillar.
+
+    Arguments:
+
+        value (str): Name of the value to retrieve
+
+    CLI Example:
+
+    .. code-block:: bash
+
+        # Retrieve `metalk8s` merge between defaults.yaml and pillar using
+        # current node version as saltenv
+        salt '*' metalk8s.get_from_map metalk8s
+
+        # Retrieve `metalk8s` from a specific saltenv
+        salt '*' metalk8s.get_from_map meltak8s saltenv=my-salt-env
+    """
+    path = "metalk8s/map.jinja"
+    if not saltenv:
+        current_version = __pillar__.get('metalk8s', {}).get('nodes', {}).get(
+            __grains__['id'], {}).get('version')
+        if not current_version:
+            log.warning(
+                'Unable to retrieve current running version, fallback on "base"'
+            )
+            saltenv = 'base'
+        else:
+            saltenv = "metalk8s-{}".format(current_version)
+
+    tmplstr = textwrap.dedent(
+        """\
+        {{% from "{path}" import {value} with context %}}
+        {{{{ {value} | tojson }}}}
+        """.format(
+            path=path, value=value
+        )
+    )
+    return salt.template.compile_template(
+        ":string:",
+        salt.loader.render(__opts__, __salt__),
+        __opts__["renderer"],
+        __opts__["renderer_blacklist"],
+        __opts__["renderer_whitelist"],
+        input_data=tmplstr,
+        saltenv=saltenv
+    )

salt/tests/unit/modules/test_metalk8s.py

@@ -5,6 +5,8 @@
 
 from parameterized import param, parameterized
 from salt.exceptions import CommandExecutionError
+import salt.renderers.jinja
+import salt.renderers.yaml
 import salt.utils.files
 import yaml
 
@@ -41,7 +43,13 @@ class Metalk8sTestCase(TestCase, mixins.LoaderModuleMockMixin):
     loader_module_globals = {
         "__grains__": {
             "id": "my_node_1"
-        }
+        },
+        "__opts__": {
+            "renderer": "jinja|yaml",
+            "renderer_blacklist": [],
+            "renderer_whitelist": []
+        },
+        "__salt__": {}
     }
 
     def test_virtual(self):
@@ -469,3 +477,44 @@ def _get_diff(*_a, **_k):
             self.assertEqual(remove_mock.call_count, 0)
         else:
             self.assertEqual(remove_mock.call_count, 1)
+
+    @parameterized.expand([
+        param(),
+        param(saltenv='my-salt-env', expected_saltenv='my-salt-env'),
+        param(node_version='1.2.3', expected_saltenv='metalk8s-1.2.3'),
+        param(node_version=None, expected_saltenv='base')
+    ])
+    def test_get_from_map(self, saltenv=None, expected_saltenv="base",
+                          node_version=None):
+        """
+        Tests the return of `get_from_map` function
+        """
+        # NOTE: The goal is not to test the `compile_template` function from
+        # salt so just ignore the return of the function but check that we
+        # give the right arguments
+        expected_args = {
+            'input_data': '{% from "metalk8s/map.jinja" import my-key with context %}\n{{ my-key | tojson }}\n',
+            'saltenv': expected_saltenv
+        }
+        pillar_content = {}
+        if node_version:
+            pillar_content = {
+                'metalk8s': {
+                    'nodes': {
+                        'my_node_1': {
+                            'version': node_version
+                        }
+                    }
+                }
+            }
+
+        compile_template_mock = MagicMock()
+        with patch.dict(metalk8s.__pillar__, pillar_content), \
+                patch('salt.loader.render', MagicMock()), \
+                patch("salt.template.compile_template", compile_template_mock):
+            metalk8s.get_from_map('my-key', saltenv=saltenv)
+            compile_template_mock.assert_called_once()
+            self.assertDictContainsSubset(
+                expected_args,
+                compile_template_mock.call_args[1]
+            )