Add support for helm template (#368)

* Add support for helm template
This commit adds basic support for helm template. The functionality
allows one to either render a chart's templates to a specific directory,
or capture the rendered templates as a string of concatenated yaml
documents.
* Add changelog fragment
* Address PR feedback
* Set changed to true

changelogs/fragments/368-helm_template.yaml

@@ -0,0 +1,2 @@
+minor_changes:
+  - helm_template - add helm_template module to support template functionality (https://github.com/ansible-collections/community.kubernetes/issues/367).

molecule/default/roles/helm/tasks/tests_chart.yml

@@ -1,4 +1,15 @@
 ---
+- name: Chart tests
+  block:
+    - name: Create temp directory
+      tempfile:
+        state: directory
+      register: tmpdir
+
+    - name: Set temp directory fact
+      set_fact:
+        temp_dir: "{{ tmpdir.path }}"
+
     - name: Check helm_info empty
       helm_info:
         binary_path: "{{ helm_binary }}"
@@ -311,6 +322,39 @@
         that:
           - not (install is changed)
 
+    - name: Render templates
+      helm_template:
+        binary_path: "{{ helm_binary }}"
+        chart_ref: "{{ chart_source }}"
+        chart_version: "{{ chart_source_version | default(omit) }}"
+        output_dir: "{{ temp_dir }}"
+        values_files:
+          - "{{ role_path }}/files/values.yaml"
+      register: result
+
+    - assert:
+        that:
+          - result is changed
+          - result is not failed
+          - result.rc == 0
+          - result.command is match("{{ helm_binary }} template {{ chart_source }}")
+
+    - name: Check templates created
+      stat:
+        path: "{{ temp_dir }}/{{ chart_test }}/templates"
+      register: result
+
+    - assert:
+        that:
+          result.stat.exists
+
+  always:
+    - name: Clean up temp dir
+      file:
+        state: absent
+        path: "{{ temp_dir }}"
+      ignore_errors: true
+
     - name: Remove helm namespace
       k8s:
         api_version: v1

plugins/modules/helm_template.py

@@ -0,0 +1,220 @@
+#!/usr/bin/python
+# -*- coding: utf-8 -*-
+
+# Copyright: (c) 2021, Ansible Project
+# GNU General Public License v3.0+ (see COPYING or https://www.gnu.org/licenses/gpl-3.0.txt)
+
+from __future__ import absolute_import, division, print_function
+
+__metaclass__ = type
+
+
+DOCUMENTATION = r'''
+
+module: helm_template
+
+short_description: Render chart templates
+
+author:
+  - Mike Graves (@gravesm)
+
+description:
+  - Render chart templates to an output directory or as text of concatenated yaml documents.
+
+options:
+  binary_path:
+    description:
+      - The path of a helm binary to use.
+    required: false
+    type: path
+  chart_ref:
+    description:
+      - Chart reference with repo prefix, for example, C(nginx-stable/nginx-ingress).
+      - Path to a packaged chart.
+      - Path to an unpacked chart directory.
+      - Absolute URL.
+    required: true
+    type: path
+  chart_repo_url:
+    description:
+      - Chart repository URL where the requested chart is located.
+    required: false
+    type: str
+  chart_version:
+    description:
+      - Chart version to use. If this is not specified, the latest version is installed.
+    required: false
+    type: str
+  include_crds:
+    description:
+      - Include custom resource descriptions in rendered templates.
+    required: false
+    type: bool
+    default: false
+  output_dir:
+    description:
+      - Output directory where templates will be written.
+      - If the directory already exists, it will be overwritten.
+    required: false
+    type: path
+  release_values:
+    description:
+        - Values to pass to chart.
+    required: false
+    default: {}
+    aliases: [ values ]
+    type: dict
+  values_files:
+    description:
+        - Value files to pass to chart.
+        - Paths will be read from the target host's filesystem, not the host running ansible.
+        - I(values_files) option is evaluated before I(values) option if both are used.
+        - Paths are evaluated in the order the paths are specified.
+    required: false
+    default: []
+    type: list
+    elements: str
+  update_repo_cache:
+    description:
+      - Run C(helm repo update) before the operation. Can be run as part of the template generation or as a separate step.
+    default: false
+    type: bool
+'''
+
+EXAMPLES = r'''
+- name: Render templates to specified directory
+  community.kubernetes.helm_template:
+    chart_ref: stable/prometheus
+    output_dir: mycharts
+
+- name: Render templates
+  community.kubernetes.helm_template:
+    chart_ref: stable/prometheus
+  register: result
+
+- name: Write templates to file
+  copy:
+    dest: myfile.yaml
+    content: "{{ result.stdout }}"
+'''
+
+RETURN = r'''
+stdout:
+  type: str
+  description: Full C(helm) command stdout. If no I(output_dir) has been provided this will contain the rendered templates as concatenated yaml documents.
+  returned: always
+  sample: ''
+stderr:
+  type: str
+  description: Full C(helm) command stderr, in case you want to display it or examine the event log.
+  returned: always
+  sample: ''
+command:
+  type: str
+  description: Full C(helm) command run by this module, in case you want to re-run the command outside the module or debug a problem.
+  returned: always
+  sample: helm template --output-dir mychart nginx-stable/nginx-ingress
+'''
+
+import tempfile
+import traceback
+
+try:
+    import yaml
+    IMP_YAML = True
+except ImportError:
+    IMP_YAML_ERR = traceback.format_exc()
+    IMP_YAML = False
+
+from ansible.module_utils.basic import AnsibleModule, missing_required_lib
+from ansible_collections.community.kubernetes.plugins.module_utils.helm import run_helm
+
+
+def template(cmd, chart_ref, chart_repo_url=None, chart_version=None, output_dir=None,
+             release_values=None, values_files=None, include_crds=False):
+    cmd += " template " + chart_ref
+
+    if chart_repo_url:
+        cmd += " --repo=" + chart_repo_url
+
+    if chart_version:
+        cmd += " --version=" + chart_version
+
+    if output_dir:
+        cmd += " --output-dir=" + output_dir
+
+    if release_values:
+        fd, path = tempfile.mkstemp(suffix='.yml')
+        with open(path, 'w') as yaml_file:
+            yaml.dump(release_values, yaml_file, default_flow_style=False)
+        cmd += " -f=" + path
+
+    if values_files:
+        for values_file in values_files:
+            cmd += " -f=" + values_file
+
+    if include_crds:
+        cmd += " --include-crds"
+
+    return cmd
+
+
+def main():
+    module = AnsibleModule(
+        argument_spec=dict(
+            binary_path=dict(type='path'),
+            chart_ref=dict(type='path', required=True),
+            chart_repo_url=dict(type='str'),
+            chart_version=dict(type='str'),
+            include_crds=dict(type='bool', default=False),
+            output_dir=dict(type='path'),
+            release_values=dict(type='dict', default={}, aliases=['values']),
+            values_files=dict(type='list', default=[], elements='str'),
+            update_repo_cache=dict(type='bool', default=False)
+        ),
+        supports_check_mode=True
+    )
+
+    check_mode = module.check_mode
+    bin_path = module.params.get('binary_path')
+    chart_ref = module.params.get('chart_ref')
+    chart_repo_url = module.params.get('chart_repo_url')
+    chart_version = module.params.get('chart_version')
+    include_crds = module.params.get('include_crds')
+    output_dir = module.params.get('output_dir')
+    release_values = module.params.get('release_values')
+    values_files = module.params.get('values_files')
+    update_repo_cache = module.params.get('update_repo_cache')
+
+    if not IMP_YAML:
+        module.fail_json(msg=missing_required_lib("yaml"), exception=IMP_YAML_ERR)
+
+    helm_cmd = bin_path or module.get_bin_path('helm', required=True)
+
+    if update_repo_cache:
+        update_cmd = helm_cmd + " repo update"
+        run_helm(module, update_cmd)
+
+    tmpl_cmd = template(helm_cmd, chart_ref, chart_repo_url=chart_repo_url,
+                        chart_version=chart_version, output_dir=output_dir,
+                        release_values=release_values, values_files=values_files,
+                        include_crds=include_crds)
+
+    if not check_mode:
+        rc, out, err = run_helm(module, tmpl_cmd)
+    else:
+        out = err = ""
+        rc = 0
+
+    module.exit_json(
+        failed=False,
+        changed=True,
+        command=tmpl_cmd,
+        stdout=out,
+        stderr=err,
+        rc=rc
+    )
+
+
+if __name__ == '__main__':
+    main()