library/roles/R/tasks/r-installation.yml: Try to fix the ansible 2 warnings.

d4science-ghn-cluster/group_vars/egi_dataminer: the R packages list is not a link to the standard dataminer file anymore.
d4science-ghn-cluster/group_vars/egi_smartexecutor: the R packages list is not a link to the standard smartexecutor file anymore.

R/tasks/r-installation.yml

@@ -9,7 +9,7 @@
 
 - name: Remove the hold state from the debian R packages
   shell: apt-mark unhold {{ item }}
-  with_items: '{{ r_base_packages_hold_list }}'
+  with_items: '( {{ r_base_packages_hold_list }} | default [] )'
   when: r_base_packages_hold_list is defined
   ignore_errors: True
   tags: [ 'r_software', 'r_pkg', 'r_pkg_hold' ]
@@ -21,14 +21,14 @@
 
 - name: When we install specific R deb packages, put them on hold
   shell: apt-mark hold {{ item }}
-  with_items: '{{ r_base_packages_hold_list }}'
+  with_items: '( {{ r_base_packages_hold_list }} | default [] )'
   when: r_base_specific_version
   ignore_errors: True
   tags: [ 'r_software', 'r_pkg', 'r_pkg_hold' ]
 
 - name: Install the R additional modules from the deb repo
   apt: pkg={{ item }} state={{ r_packages_state }} force=yes
-  with_items: '{{ r_plugins_packages_list }}'
+  with_items: '( {{ r_plugins_packages_list }} | default [] )'
   when: r_plugins_from_deb
   tags: [ 'r_software', 'r_pkg' ]
 
@@ -61,7 +61,7 @@
 
 - name: Get the R packages sources that need to be installed
   get_url: url={{ item.url }} dest={{ r_source_plugins_dest_dir }}
-  with_items: '{{ r_plugins_from_sources }}'
+  with_items: '( {{ r_plugins_from_sources }} | default [] )'
   when: r_plugins_install_specific_source
   tags: [ 'r_software', 'r_pkg', 'r_plugins', 'r_plugins_version' ]
   
@@ -71,7 +71,7 @@
   register: install_s_plugins_result
   failed_when: "install_s_plugins_result.rc != 0 or 'had non-zero exit status' in install_s_plugins_result.stderr"
   changed_when: '"Added" in install_s_plugins_result.stdout'
-  with_items: '{{ r_plugins_from_sources }}'
+  with_items: '( {{ r_plugins_from_sources }} | default [] )'
   when: r_plugins_install_specific_source
   ignore_errors: True
   tags: [ 'r_software', 'r_pkg', 'r_plugins', 'r_plugins_version' ]
@@ -82,9 +82,8 @@
   register: install_s_plugins_result
   failed_when: "install_s_plugins_result.rc != 0 or 'had non-zero exit status' in install_s_plugins_result.stderr"
   changed_when: '"Added" in install_s_plugins_result.stdout'
-  with_items: '{{ r_plugins_from_sources }}'
-  when:
-    - r_plugins_install_specific_source
+  with_items: '( {{ r_plugins_from_sources }} | default [] )'
+  when: r_plugins_install_specific_source
   tags: [ 'r_software', 'r_pkg', 'r_plugins', 'r_plugins_version' ]
 
 - name: Install R packages from the cran sources repo, latest available version. Second try
@@ -93,9 +92,8 @@
   register: install_plugins_result
   failed_when: "install_plugins_result.rc != 0 or 'had non-zero exit status' in install_plugins_result.stderr"
   changed_when: "'Added' in install_plugins_result.stdout"
-  with_items: '{{ r_plugins_list_to_install }}'
-  when:
-    - r_plugins_install_latest_source
+  with_items: '( {{ r_plugins_list_to_install }} | default [] )'
+  when: r_plugins_install_latest_source
   tags: [ 'r_software', 'r_pkg', 'r_plugins' ]
 
 - name: Install R packages from github
@@ -104,7 +102,7 @@
   register: install_github_plugins_result
   failed_when: "install_github_plugins_result.rc != 0 or 'had non-zero exit status' in install_github_plugins_result.stderr"
   changed_when: "'Added' in install_github_plugins_result.stdout"
-  with_items: '{{ r_plugins_from_github }}'
+  with_items: '( {{ r_plugins_from_github }} | default [] )'
   when: r_plugins_from_github is defined
   tags: [ 'r_software', 'r_pkg', 'r_plugins', 'r_plugins_github' ]
 
@@ -114,6 +112,6 @@
   register: remove_plugins_result
   failed_when: remove_plugins_result.rc != 0
   changed_when: "'Removed' in remove_plugins_result.stdout"
-  with_items: '{{ r_plugins_list_to_remove }}'
+  with_items: '( {{ r_plugins_list_to_remove }} | default [] )'
   when: r_plugins_list_to_remove is defined
   tags: [ 'r_software', 'r_pkg', 'r_plugins' ]