Add 'state' parameter for alternatives (#4557)

* Add 'activate' parameter for alternatives

Allow alternatives to be installed without being set as the current
selection.

* add changelog fragment

* Apply suggestions from code review

Co-authored-by: Felix Fontein <felix@fontein.de>

* rename 'activate' -> 'selected'

* rework 'selected' parameter -> 'state'

* handle unsetting of currently selected alternative

* add integration tests for 'state' parameter

* fix linting issues

* fix for Python 2.7 compatibility

* Remove alternatives file.

Co-authored-by: Felix Fontein <felix@fontein.de>

changelogs/fragments/4557-alternatives-add-state-parameter.yml

@@ -0,0 +1,2 @@
+minor_changes:
+  - alternatives - add ``state`` parameter, which provides control over whether the alternative should be set as the active selection for its alternatives group (https://github.com/ansible-collections/community.general/issues/4543, https://github.com/ansible-collections/community.general/pull/4557).

plugins/modules/system/alternatives.py

@@ -41,6 +41,16 @@
       - The priority of the alternative.
     type: int
     default: 50
+  state:
+    description:
+      - C(present) - install the alternative (if not already installed), but do
+        not set it as the currently selected alternative for the group.
+      - C(selected) - install the alternative (if not already installed), and
+        set it as the currently selected alternative for the group.
+    choices: [ present, selected ]
+    default: selected
+    type: str
+    version_added: 4.8.0
 requirements: [ update-alternatives ]
 '''
 
@@ -61,6 +71,13 @@
     name: java
     path: /usr/lib/jvm/java-7-openjdk-i386/jre/bin/java
     priority: -10
+
+- name: Install Python 3.5 but do not select it
+  community.general.alternatives:
+    name: python
+    path: /usr/bin/python3.5
+    link: /usr/bin/python
+    state: present
 '''
 
 import os
@@ -70,6 +87,15 @@
 from ansible.module_utils.basic import AnsibleModule
 
 
+class AlternativeState:
+    PRESENT = "present"
+    SELECTED = "selected"
+
+    @classmethod
+    def to_list(cls):
+        return [cls.PRESENT, cls.SELECTED]
+
+
 def main():
 
     module = AnsibleModule(
@@ -78,6 +104,11 @@ def main():
             path=dict(type='path', required=True),
             link=dict(type='path'),
             priority=dict(type='int', default=50),
+            state=dict(
+                type='str',
+                choices=AlternativeState.to_list(),
+                default=AlternativeState.SELECTED,
+            ),
         ),
         supports_check_mode=True,
     )
@@ -87,6 +118,7 @@ def main():
     path = params['path']
     link = params['link']
     priority = params['priority']
+    state = params['state']
 
     UPDATE_ALTERNATIVES = module.get_bin_path('update-alternatives', True)
 
@@ -126,9 +158,20 @@ def main():
                         link = line.split()[1]
                         break
 
+    changed = False
     if current_path != path:
+
+        # Check mode: expect a change if this alternative is not already
+        # installed, or if it is to be set as the current selection.
         if module.check_mode:
-            module.exit_json(changed=True, current_path=current_path)
+            module.exit_json(
+                changed=(
+                    path not in all_alternatives or
+                    state == AlternativeState.SELECTED
+                ),
+                current_path=current_path,
+            )
+
         try:
             # install the requested path if necessary
             if path not in all_alternatives:
@@ -141,18 +184,34 @@ def main():
                     [UPDATE_ALTERNATIVES, '--install', link, name, path, str(priority)],
                     check_rc=True
                 )
+                changed = True
 
-            # select the requested path
+            # set the current selection to this path (if requested)
+            if state == AlternativeState.SELECTED:
+                module.run_command(
+                    [UPDATE_ALTERNATIVES, '--set', name, path],
+                    check_rc=True
+                )
+                changed = True
+
+        except subprocess.CalledProcessError as cpe:
+            module.fail_json(msg=str(dir(cpe)))
+    elif current_path == path and state == AlternativeState.PRESENT:
+        # Case where alternative is currently selected, but state is set
+        # to 'present'. In this case, we set to auto mode.
+        if module.check_mode:
+            module.exit_json(changed=True, current_path=current_path)
+
+        changed = True
+        try:
             module.run_command(
-                [UPDATE_ALTERNATIVES, '--set', name, path],
-                check_rc=True
+                [UPDATE_ALTERNATIVES, '--auto', name],
+                check_rc=True,
             )
-
-            module.exit_json(changed=True)
         except subprocess.CalledProcessError as cpe:
             module.fail_json(msg=str(dir(cpe)))
-    else:
-        module.exit_json(changed=False)
+
+    module.exit_json(changed=changed)
 
 
 if __name__ == '__main__':

tests/integration/targets/alternatives/tasks/main.yml

@@ -49,6 +49,12 @@
   # Test that path is checked: alternatives must fail when path is nonexistent
   - import_tasks: path_is_checked.yml
 
+  # Test operation of the 'state' parameter
+  - block:
+    - include_tasks: remove_links.yml
+    - include_tasks: tests_state.yml
+
+  # Cleanup
   always:
     - include_tasks: remove_links.yml
 
@@ -62,6 +68,7 @@
         path: '/usr/bin/dummy{{ item }}'
         state: absent
       with_sequence: start=1 end=4
+
   # *Disable tests on Fedora 24*
   # Shippable Fedora 24 image provides chkconfig-1.7-2.fc24.x86_64 but not the
   # latest available version (chkconfig-1.8-1.fc24.x86_64). update-alternatives

tests/integration/targets/alternatives/tasks/remove_links.yml

@@ -3,5 +3,6 @@
     path: '{{ item }}'
     state: absent
   with_items:
+    - "{{ alternatives_dir }}/dummy"
     - /etc/alternatives/dummy
     - /usr/bin/dummy

tests/integration/targets/alternatives/tasks/tests_state.yml

@@ -0,0 +1,71 @@
+# Add a few dummy alternatives with state = present and make sure that the
+# group is in 'auto' mode and the highest priority alternative is selected.
+- name: Add some dummy alternatives with state = present
+  alternatives:
+    name: dummy
+    path: "/usr/bin/dummy{{ item.n }}"
+    link: /usr/bin/dummy
+    priority: "{{ item.priority }}"
+    state: present
+  loop:
+    - { n: 1, priority: 50 }
+    - { n: 2, priority: 70 }
+    - { n: 3, priority: 25 }
+
+- name: Ensure that the link group is in auto mode
+  shell: 'head -n1 {{ alternatives_dir }}/dummy | grep "^auto$"'
+
+# Execute current selected 'dummy' and ensure it's the alternative we expect
+- name: Execute the current dummy command
+  shell: dummy
+  register: cmd
+
+- name: Ensure that the expected command was executed
+  assert:
+    that:
+      - cmd.stdout == "dummy2"
+
+# Add another alternative with state = 'selected' and make sure that
+# this change results in the group being set to manual mode, and the
+# new alternative being the selected one.
+- name: Add another dummy alternative with state = selected
+  alternatives:
+    name: dummy
+    path: /usr/bin/dummy4
+    link: /usr/bin/dummy
+    priority: 10
+    state: selected
+
+- name: Ensure that the link group is in manual mode
+  shell: 'head -n1 {{ alternatives_dir }}/dummy | grep "^manual$"'
+
+- name: Execute the current dummy command
+  shell: dummy
+  register: cmd
+
+- name: Ensure that the expected command was executed
+  assert:
+    that:
+      - cmd.stdout == "dummy4"
+
+# Set the currently selected alternative to state = 'present' (was previously
+# selected), and ensure that this results in the group being set to 'auto'
+# mode, and the highest priority alternative is selected.
+- name: Set current selected dummy to state = present
+  alternatives:
+    name: dummy
+    path: /usr/bin/dummy4
+    link: /usr/bin/dummy
+    state: present
+
+- name: Ensure that the link group is in auto mode
+  shell: 'head -n1 {{ alternatives_dir }}/dummy | grep "^auto$"'
+
+- name: Execute the current dummy command
+  shell: dummy
+  register: cmd
+
+- name: Ensure that the expected command was executed
+  assert:
+    that:
+      - cmd.stdout == "dummy2"