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>

plugins/modules/system/alternatives.py

@@ -41,6 +41,16 @@ options:
       - 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 @@ EXAMPLES = r'''
     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 @@ import subprocess
 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
-            module.run_command(
-                [UPDATE_ALTERNATIVES, '--set', name, path],
-                check_rc=True
-            )
+            # 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
 
-            module.exit_json(changed=True)
         except subprocess.CalledProcessError as cpe:
             module.fail_json(msg=str(dir(cpe)))
-    else:
-        module.exit_json(changed=False)
+    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, '--auto', name],
+                check_rc=True,
+            )
+        except subprocess.CalledProcessError as cpe:
+            module.fail_json(msg=str(dir(cpe)))
+
+    module.exit_json(changed=changed)
 
 
 if __name__ == '__main__':