Add docstrings for pluginmanager and usercallbackplugin. Enable Sphin…

…x for usercallbackplugin. Add Sphinx HOWTO (#1317)

* tools.daemonize(): Improve doc and replace broken link
* Add documentation for pluginmanager and usercallbackplugin
* Enable Sphinx/autodoc for common/plugin folder. Add Sphinx doc HOWTO

Co-authored-by: aryoda <11374410+aryoda@users.noreply.github.com>

common/doc-dev/1_doc_maintenance_howto.txt

@@ -0,0 +1,154 @@
+This file describes briefly how to
+- build and view the source code "API" documentation of Back In Time "common" (CLI)
+- add new modules to the documentation
+- write docstrings
+- known issues with documentation generation
+
+
+1. Background
+=============
+
+The documentation is generated automatically from the docstrings
+in the python source code files using the tool
+
+  Sphinx (https://www.sphinx-doc.org/en/master/)
+
+together with the Sphinx-Extensions
+
+  - autodoc (to automatically generate rst doc files from the python docstrings)
+    https://www.sphinx-doc.org/en/master/man/sphinx-apidoc.html
+
+  - napoleon (to convert google-style docstrings to reStructuredText "rst" format required for autodoc)
+    https://www.sphinx-doc.org/en/master/usage/extensions/napoleon.html
+
+  - viewcode (to create links to browse the highlighted source code)
+    https://www.sphinx-doc.org/en/master/usage/extensions/napoleon.html
+
+For a brief introduction to Sphinx for Python see:
+https://betterprogramming.pub/auto-documenting-a-python-project-using-sphinx-8878f9ddc6e9
+
+For a reference of rst markups see:
+https://docutils.sourceforge.io/docs/user/rst/quickref.html
+
+For a description of the Google coding style for python see:
+https://google.github.io/styleguide/pyguide.html
+
+
+
+2. Why to use Sphinx to generate the documentation?
+==================================================
+
+Sphinx has eg. the advantage to
+
+- generate the documentation in different formats
+  (eg. html, PDF or Linux man pages).
+
+- report invalid markups contained in the documentation
+
+- inject documentation of attributes and methods from parent classes
+  into sub classes (in case of inheritance)
+
+
+
+3. How to build and view the documentation
+==========================================
+
+Open a terminal in the "doc-dev" folder and call
+
+    make html      # to generate the HTML documentation
+    make htmlOpen  # to open the browser showing the generated HTML pages
+
+
+
+4. How to add new modules to the documentation
+==============================================
+
+There are two scenarios here:
+
+
+
+a) The new module files are in a separate folder (not yet included in the doc generation so far)
+
+- Add the python source code folder to the doc-dev/conf.py file
+  so that autodoc can find the files (navigate "relative" to the "doc-dev" folder)
+
+- Generate the initial rst files for the new modules via "sphinx-apidoc", eg.
+
+      sphinx-apidoc -o ./plugins ../plugins
+
+  to create a sub folder "doc-dev/plugins" with the rst files (one for each source file
+  in "doc-dev/../plugins"
+
+- Add the new modules in the sub folder to the top-most "root" index.rst:
+
+  # under "modules.rst" add this line add a link to new modules
+  plugins/modules.rst
+
+
+
+b) The new module files are in a folder that already contains other modules contained in the doc
+
+   To create the initial version of rst files for new modules eg. in the "common" folder use
+
+       sphinx-apidoc -o . ..
+
+   TODO: How to remove old rst files with non-existing python files (eg. due to renaming or deletion)
+         -> probably the -f ("force") argument could do this. Try it with -d ("dry-run")!
+
+
+
+5. How to write docstrings for Back In Time
+===========================================
+
+"Back In Time" uses the Google style for docstrings:
+
+    https://google.github.io/styleguide/pyguide.html
+
+Please stick to this convention
+
+
+
+5.1 Commonly used rst markups in the docstring
+==============================================
+
+Despite using the Google docstring style rst markups can and should still
+be used to format text and cross-reference code.
+
+- Reference a class (with namespace if not in the same):
+
+      :py:class:`pluginmanager.PluginManager`
+
+  Important: Don't forget to surround the function name with back ticks
+  otherwise Sphinx will not create a cross reference silently!
+
+- Reference a method/function:
+
+      :py:func:`takeSnapshot`
+
+  Important: Don't forget to surround the function name with back ticks
+  otherwise Sphinx will not create a cross reference silently!
+
+- Specify the python type of an method/function argument:
+
+  Add the type name (with namespace if not in the same) in parentheses
+
+    Args:
+        cfg (config.Config): Current configuration
+
+- Indicate python keywords (without cross-referencing them)
+
+      ``True``
+      ``None``
+
+  Surround the keyword with two backticks (it will be shown as code then)
+
+
+
+6. Known issues with documentation generation
+
+- Sphinx' "make html" does not recreate the html file of a sub class if only
+  the parent class docstring was changed.
+
+  Impact: Inherited documentation in the sub class is not up to date
+
+  Work around: Use "make clean" before "make html"

common/doc-dev/conf.py

@@ -22,6 +22,7 @@
 #sys.path.insert(0, os.path.abspath('.'))
 
 sys.path.insert(0, os.path.abspath(os.path.join(os.pardir)))
+sys.path.insert(0, os.path.abspath(os.path.join(os.pardir, "plugins")))
 
 #import config to solve race conditions between config an mount
 import config

common/doc-dev/index.rst

@@ -13,6 +13,8 @@ Contents:
 
     modules.rst
 
+    plugins/modules.rst
+
 Indices and tables
 ==================
 

common/doc-dev/plugins/modules.rst

@@ -0,0 +1,7 @@
+plugins
+=======
+
+.. toctree::
+   :maxdepth: 4
+
+   usercallbackplugin

common/doc-dev/plugins/usercallbackplugin.rst

@@ -0,0 +1,7 @@
+usercallbackplugin module
+=========================
+
+.. automodule:: usercallbackplugin
+    :members:
+    :undoc-members:
+    :show-inheritance: