Add ensure-bazelisk role

This adds a role which installs bazelisk if it is not already
present.  It also adds a test job which exercises the role; the
job will be run on any changes to the new role.

Change-Id: I69b28b58338b46ec3fea696f9d97be4271ed6ae4

doc/source/general-roles.rst

@@ -14,6 +14,7 @@ General Purpose Roles
 .. zuul:autorole:: dstat-graph
 .. zuul:autorole:: emit-job-header
 .. zuul:autorole:: enable-netconsole
+.. zuul:autorole:: ensure-bazelisk
 .. zuul:autorole:: ensure-dstat-graph
 .. zuul:autorole:: ensure-markdownlint
 .. zuul:autorole:: fetch-markdownlint

roles/ensure-bazelisk/README.rst

@@ -0,0 +1,34 @@
+Ensure that bazelisk is present.
+
+If bazelisk is already installed, this role does nothing.  Otherwise,
+it downloads bazelisk from GitHub and installs it in the user's
+home directory by default.
+
+**Role Variables**
+
+.. zuul:rolevar:: bazelisk_version
+   :default: v1.3.0
+
+   Version of bazelisk to install.
+
+.. zuul:rolevar:: bazelisk_arch
+   :default: linux-amd64
+
+   Architecture to install.
+
+.. zuul:rolevar:: bazelisk_url
+   :default: https://github.com/bazelbuild/bazelisk/releases/download/{{ bazelisk_version }}/bazelisk-{{ bazelisk_arch }}
+
+   The URL from which to download bazelisk.
+
+.. zuul:rolevar:: bazelisk_executable
+   :default: bazelisk
+
+   The bazelisk executable.  If this already exists, the
+   role will not perform any further actions.
+
+.. zuul:rolevar:: bazelisk_target
+   :default: "{{ ansible_user_dir }}/.local/bin/bazelisk"
+
+   Where to install bazelisk.  If the role downloads bazelisk, it will
+   set :zuul:rolevar:`ensure-bazelisk.bazelisk_executable` to this value as well.

roles/ensure-bazelisk/defaults/main.yaml

@@ -0,0 +1,6 @@
+bazelisk_version: v1.3.0
+bazelisk_arch: linux-amd64
+bazelisk_url: "https://github.com/bazelbuild/bazelisk/releases/download/{{ bazelisk_version }}/bazelisk-{{ bazelisk_arch }}"
+bazelisk_executable: bazelisk
+# If we have to download it, store it here:
+bazelisk_target: "{{ ansible_user_dir }}/.local/bin/bazelisk"

roles/ensure-bazelisk/tasks/main.yaml

@@ -0,0 +1,25 @@
+- name: Check if bazelisk is installed
+  command: bash -c "type -p {{ bazelisk_executable }}"
+  failed_when: false
+  register: bazelisk_installed
+
+- name: Ensure target directory exists
+  file:
+    state: directory
+    path: "{{ bazelisk_target | dirname }}"
+  when: bazelisk_installed.rc != 0
+
+- name: Download bazelisk
+  get_url:
+    url: "{{ bazelisk_url }}"
+    dest: "{{ bazelisk_target }}"
+    mode: '0755'
+  when: bazelisk_installed.rc != 0
+  register: bazelisk_downloaded
+
+# This will apply to further plays and playbooks
+- name: Set bazelisk_executable fact
+  set_fact:
+    bazelisk_executable: "{{ bazelisk_target }}"
+    cacheable: true
+  when: bazelisk_downloaded is changed

zuul-tests.d/general-roles-jobs.yaml

@@ -233,6 +233,15 @@
     vars:
       role_name: clear-firewall
 
+- job:
+    name: zuul-jobs-test-ensure-bazelisk
+    description: Test the ensure-bazelisk role
+    files:
+      - roles/ensure-bazelisk/.*
+    run: test-playbooks/simple-role-test.yaml
+    vars:
+      role_name: ensure-bazelisk
+
 - job:
     name: zuul-jobs-test-netconsole
     description: Test the netconsole setup role
@@ -482,6 +491,7 @@
         - zuul-jobs-test-base-roles-ubuntu-xenial
         - zuul-jobs-test-bindep
         - zuul-jobs-test-clear-firewall
+        - zuul-jobs-test-ensure-bazelisk
         - zuul-jobs-test-netconsole
         - zuul-jobs-test-dstat-graph
         - zuul-jobs-test-multinode-roles-centos-7
@@ -510,6 +520,7 @@
         - zuul-jobs-test-base-roles-ubuntu-xenial
         - zuul-jobs-test-bindep
         - zuul-jobs-test-clear-firewall
+        - zuul-jobs-test-ensure-bazelisk
         - zuul-jobs-test-netconsole
         - zuul-jobs-test-dstat-graph
         - zuul-jobs-test-multinode-roles-centos-7