fix: boolean values and null values are not allowed

Cause: The user could specify a value like `value: on` or `value: yes` thinking that these would
be converted to the string `"on"` or `"yes"`. But instead, YAML treats these
as [YAML bool type](https://yaml.org/type/bool.html) and writes them as the string `"True"`.

Consequence: The user who is unaware of YAML boolean handling is not able to set
values to `"on"`, `"off"`, or the like.

Fix: The role will reject any value of boolean or `null` type.

Result: Users must quote such YAML boolean type values as strings in order to write
them to the bootloader configuration.

Signed-off-by: Rich Megginson <rmeggins@redhat.com>

Author: richm

README.md

@@ -77,6 +77,12 @@ Each entry should specify a kernel using one or more keys.
 
     * `name` - The name of the setting. Omit `name` when using `replaced`.
     * `value` - The value for the setting. You must omit `value` if the setting has no value, e.g. `quiet`.
+      **NOTE** - a value must not be [YAML bool type](https://yaml.org/type/bool.html).
+      One situation where this might be a problem is using `value: on` or other
+      YAML `bool` typed value.  You must quote these values, or otherwise pass
+      them as a value of `str` type e.g.  `value: "on"`.  The same applies to `null` values.
+      If you specify a value, it must not be `null` - values such as `value:` or `value: ~`
+      or `value: null` are not allowed and will raise an error.
     * `state` - `present` (default) or `absent`. The value `absent` means to remove a setting with the given `name` - the name must be provided.
     * `previous` - Optional - the only supported value is `replaced` - use this to specify that the previous settings should be replaced with the given settings.
     * `copy_default` - Optional - when creating a kernel, you can specify `copy_default: true` to copy the default arguments to the created kernel.

tasks/main.yml

@@ -10,6 +10,24 @@
       Let us know if you need the role to support it.
   when: ansible_architecture == 's390x'
 
+# null is allowed as a value for state: absent - but it is not needed
+# and should not be used
+- name: Check bootloader settings for boolean and null values
+  fail:
+    msg: Boolean and null values are not allowed for bootloader settings
+  when:
+    - (__values | selectattr("value", "sameas", true) | list | length > 0) or
+      (__values | selectattr("value", "sameas", false) | list | length > 0) or
+      (__values_with_null_and_state_present | length > 0) or
+      (__values_with_null_and_no_state | length > 0)
+  vars:
+    __values: "{{ bootloader_settings | selectattr('options', 'defined') |
+      map(attribute='options') | flatten | selectattr('value', 'defined') | list }}"
+    __values_with_null_and_state_present: "{{ __values | selectattr('state', 'defined') |
+      selectattr('state', 'match', 'present$') | selectattr('value', 'sameas', none) | list }}"
+    __values_with_null_and_no_state: "{{ __values | rejectattr('state', 'defined') |
+      selectattr('value', 'sameas', none) | list }}"
+
 - name: Ensure required packages are installed
   package:
     name: "{{ __bootloader_packages }}"