Change the list of extensions to a dict

The stage-output role accepts a list of extensions to be replaced as txt
so that they can be seen directly from within a web browser.
Using a list means that children jobs cannot add to the parent setting,
only overwrite. Adding support for dicts while preserving, at least for
now, support for lists - to avoid breaking existing implementations.

This reverts change 844b3333aa.

Change-Id: I5052c873f0a5da7ecaa38627e8900af86bbec2f9
Needed-By: https://review.openstack.org/539686
Needed-By: https://review.openstack.org/539708
Needed-By: https://review.openstack.org/539854

roles/stage-output/README.rst

@@ -31,7 +31,7 @@ intended to be used before output fetching in a base job's post-playbook.
 .. zuul:rolevar:: extensions_to_txt
    :default: null
 
-   A list of file extensions to be replaced with .txt when staging.
+   A dict of file extensions to be replaced with .txt when staging.
    This can be useful to ensure that text files with an extension not
    registered in the web server may be viewed via browser when uploaded
    to a file server.
@@ -43,8 +43,9 @@ intended to be used before output fetching in a base job's post-playbook.
    Example:
 
      extensions_to_txt:
-     - conf
-     - log
+       conf: True
+       log: True
+       txt: False
 
      zuul.conf --(staged as)--> zuul_conf.txt
 

roles/stage-output/tasks/main.yaml

@@ -4,12 +4,38 @@
   with_dict: "{{ zuul_copy_output }}"
   register: sources
 
-- name: Build the replace regex
-  set_fact:
-    extensions_regex: "{{ extensions_to_txt | join('|') | default('__do_not_replace__') }}"
+- name: Output a warning when input is not a dict and not empty
+  debug:
+    msg: "WARNING: extensions_to_txt is a list, values defined by parents will be overwritten"
+  when:
+    - extensions_to_txt is not mapping
+    - extensions_to_txt
 
-- debug:
-    var: extensions_regex
+- name: Build the extensions list when input is not a dict (including empty)
+  set_fact:
+    extension_list: >
+      {% set extensions = ['__does_not_match__'] -%}
+      {% if extensions_to_txt -%}
+        {% set extensions = extensions_to_txt -%}
+      {% endif -%}
+      {{- extensions -}}
+  when: extensions_to_txt is not mapping
+
+- name: Build the extensions list when input is a dict
+  set_fact:
+    extension_list: >
+      {% set extensions = [] -%}
+      {% for extension, extension_bool in extensions_to_txt.items() -%}
+        {% if extension_bool -%}
+          {% set _ = extensions.append(extension) -%}
+        {% endif -%}
+      {% endfor -%}
+      {{- extensions -}}
+  when: extensions_to_txt is mapping
+
+- name: Build the extensions regular expression
+  set_fact:
+    extensions_regex: "{{ extension_list | join('|') }}"
 
 # TODO(andreaf) We might want to enforce that item.value is a valid value
 # in docs, artifacts, logs. Null case already handled.