jinja: provide and document jinja-safe key aliases in instance-data (SC-622) (#1123)

Allow #cloud-config and cloud-init query to use underscore-delimited
"jinja-safe" key aliases for any instance-data.json keys
containing jinja operator characters.

This provides a means to use Jinja's dot-notation instead of square brackets
and quoting to reference "unsafe" obtain attribute names.

Support for these aliased keys is available to both #cloud-config user-data and
`cloud-init query`.

For example #cloud-config alias access can look like:
  {{ ds.config.user_network_config }}

  - instead of -

  {{ ds.config["user.network-config"] }}

2 files changed, 19 insertions, 10 deletions

diff --git a/tests/integration_tests/datasources/test_lxd_discovery.py b/tests/integration_tests/datasources/test_lxd_discovery.py
index 93200962..3f05e906 100644
--- a/tests/integration_tests/datasources/test_lxd_discovery.py
+++ b/tests/integration_tests/datasources/test_lxd_discovery.py
@@ -53,7 +53,9 @@ def test_lxd_datasource_discovery(client: IntegrationInstance):
     assert "lxd" == v1["platform"]
     assert "LXD socket API v. 1.0 (/dev/lxd/sock)" == v1["subplatform"]
     ds_cfg = json.loads(client.execute('cloud-init query ds').stdout)
-    assert ["config", "meta_data"] == sorted(list(ds_cfg["1.0"].keys()))
+    assert ["_doc", "_metadata_api_version", "config", "meta-data"] == sorted(
+        list(ds_cfg.keys())
+    )
     if (
         client.settings.PLATFORM == "lxd_vm" and
         ImageSpecification.from_os_image().release in ("xenial", "bionic")
@@ -62,15 +64,18 @@ def test_lxd_datasource_discovery(client: IntegrationInstance):
         # to start the lxd-agent.
         # https://github.com/canonical/pycloudlib/blob/main/pycloudlib/\
         #    lxd/defaults.py#L13-L27
-        lxd_config_keys = ["user.meta_data", "user.vendor_data"]
+        # Underscore-delimited aliases exist for any keys containing hyphens or
+        # dots.
+        lxd_config_keys = ["user.meta-data", "user.vendor-data"]
     else:
-        lxd_config_keys = ["user.meta_data"]
-    assert lxd_config_keys == list(ds_cfg["1.0"]["config"].keys())
+        lxd_config_keys = ["user.meta-data"]
+    assert "1.0" == ds_cfg["_metadata_api_version"]
+    assert lxd_config_keys == list(ds_cfg["config"].keys())
     assert {"public-keys": v1["public_ssh_keys"][0]} == (
-        yaml.safe_load(ds_cfg["1.0"]["config"]["user.meta_data"])
+        yaml.safe_load(ds_cfg["config"]["user.meta-data"])
     )
     assert (
-        "#cloud-config\ninstance-id" in ds_cfg["1.0"]["meta_data"]
+        "#cloud-config\ninstance-id" in ds_cfg["meta-data"]
     )
     # Assert NoCloud seed data is still present in cloud image metadata
     # This will start failing if we redact metadata templates from
diff --git a/tests/integration_tests/modules/test_jinja_templating.py b/tests/integration_tests/modules/test_jinja_templating.py
index 35b8ee2d..fe8eff1a 100644
--- a/tests/integration_tests/modules/test_jinja_templating.py
+++ b/tests/integration_tests/modules/test_jinja_templating.py
@@ -11,6 +11,7 @@ USER_DATA = """\
 runcmd:
   - echo {{v1.local_hostname}} > /var/tmp/runcmd_output
   - echo {{merged_cfg._doc}} >> /var/tmp/runcmd_output
+  - echo {{v1['local-hostname']}} >> /var/tmp/runcmd_output
 """
 
 
@@ -18,13 +19,16 @@ runcmd:
 def test_runcmd_with_variable_substitution(client: IntegrationInstance):
     """Test jinja substitution.
 
-    Ensure we can also substitute variables from instance-data-sensitive
-    LP: #1931392
+    Ensure underscore-delimited aliases exist for hyphenated key and
+    we can also substitute variables from instance-data-sensitive
+    LP: #1931392.
     """
+    hostname = client.execute('hostname').stdout.strip()
     expected = [
-        client.execute('hostname').stdout.strip(),
+        hostname,
         ('Merged cloud-init system config from /etc/cloud/cloud.cfg and '
-            '/etc/cloud/cloud.cfg.d/')
+            '/etc/cloud/cloud.cfg.d/'),
+        hostname
     ]
     output = client.read_from_file('/var/tmp/runcmd_output')
     verify_ordered_items_in_text(expected, output)