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* Create CLI UX Guidelines * More tweaking * Address review comments * More tweaks * Add recommendation for generating and installing completion files * Update documentation to include base class information * Use ExitCodes base class
144 lines
7.0 KiB
ReStructuredText
144 lines
7.0 KiB
ReStructuredText
.. highlight:: kotlin
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.. raw:: html
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<script type="text/javascript" src="_static/jquery.js"></script>
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<script type="text/javascript" src="_static/codesets.js"></script>
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CLI UX Guide
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============
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Command line options
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--------------------
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Command line utilities should use picocli (http://picocli.info) to provide a unified interface and follow the conventions in the picocli documentation, some of the more important of which are repeated below.
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Option names
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~~~~~~~~~~~~
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* Options should be specified on the command line using a double dash, e.g. ``--parameter``.
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* Options that consist of multiple words should be separated via hyphens e.g. ``--my-multiple-word-parameter-name``.
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Short names
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~~~~~~~~~~~
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* Where possible a POSIX style short option should be provided for ease of use (see http://pubs.opengroup.org/onlinepubs/9699919799/basedefs/V1_chap12.html#tag_12_02).
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* These should be prefixed with a single hyphen.
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* For example ``-V`` for ``--verbose``, ``-d`` for ``--dev-mode``.
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* Consider adding short options for commands that would be ran regularly as part of troubleshooting/operational processes.
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* Short options should not be used for commands that would be used just once, for example initialising/registration type tasks.
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* The picocli interface allows combinations of options without parameters, for example, ```-v`` and ```-d`` can be combined as ``-vd``.
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Positional parameters
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~~~~~~~~~~~~~~~~~~~~~
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* Parameters specified without an option should ideally all be part of a list.
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* For example, in ``java -jar test.jar file1 file2 file3``, the parameters file1, file2 and file3 should be a list of files that are all acted on together (e.g. a list of CorDapps).
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* Avoid using positional parameters to mean different things, which involves someone remembering in which order things need to be specified.
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* For example, avoid ``java -jar test.jar configfile1 cordapp1 cordapp2`` where parameter 1 is the config file and any subsequent parameters are the CorDapps.
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* Use ``java -jar test.jar cordapp1 cordapp2 --config-file configfile1`` instead.
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Standard options
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~~~~~~~~~~~~~~~~
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* A ``--help`` option should be provided which details all possible options with a brief description and any short name equivalents. A ``-h`` short option should also be provided.
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* A ``--version`` option that should output the version number of the software. A ``-V`` short option should also be provided.
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* A ``--logging-level`` option should be provided which specifies the logging level to be used in any logging files. Acceptable values should be ``DEBUG``, ``TRACE``, ``INFO``, ``WARN`` and ``ERROR``.
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* ``--verbose`` and ``--log-to-console`` options should be provided (both equivalent) which specifies that logging output should be displayed in the console.
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A ``-v`` short option should also be provided.
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* A ``--install-shell-extensions`` option should be provided that creates and installs a bash completion file.
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Defaults
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~~~~~~~~
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* Flags should have sensible defaults.
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* Boolean flags should always default to false. Specifying the flag without a parameter should set it to true. For example ``--use-something` should be equal to ``--use-something=true`` and no option should be equal to ``--my-flag=false``.
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* Do a bit of work to figure out reasonable defaults. Nobody likes having to set a dozen flags before the tool will cooperate.
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Adding a new option
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~~~~~~~~~~~~~~~~~~~
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* Boolean options should start with is, has or with. For example, ``--is-cheesy``, ``--with-cheese``, ``--has-cheese-on``.
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* Any new options must be documented in the docsite and via the ``--help`` screen.
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* Never use acronyms in option names and try and make them as descriptive as possible.
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Parameter stability
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~~~~~~~~~~~~~~~~~~~
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* Avoid removing parameters. If, for some reason, a parameter needs to be renamed, add a new parameter with the new name and deprecate the old parameter, or alternatively keep both versions of the parameter.
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The ``CordaCliWrapper`` base class
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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The ``CordaCliWrapper`` base class from the ``cliutils`` module should be used as a base where practicable, this will provide a set of default options out of the box.
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In order to use it, create a class containing your command line options using the syntax provided at (see the `picocli<https://picocli.info/>`_ website for more information)
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.. container:: codeset
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.. sourcecode:: kotlin
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import net.corda.cliutils.ExitCodes
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import net.corda.cliutils.CordaCliWrapper
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class UsefulUtilityExitCodes: ExitCodes {
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companion object {
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val APPLICATION_SPECIFIC_ERROR_CODE: Int = 100
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}
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}
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class UsefulUtility : CordaCliWrapper(
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"useful-utility", // the alias to be used for this utility in bash. When --install-shell-extensions is run
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// you will be able to invoke this command by running <useful-utility --opts> from the command line
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"A command line utility that is super useful!" // A description of this utility to be displayed when --help is run
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) {
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@Option(names = ["--extra-usefulness", "-e"], // A list of the different ways this option can be referenced
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description = ["Use this option to add extra usefulness"] // Help description to be displayed for this option
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)
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private var extraUsefulness: Boolean = false // This default option will be shown in the help output
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override fun runProgram(): Int { // override this function to run the actual program
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try {
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// do some stuff
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} catch (KnownException: ex) {
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return UsefulUtilityExitCodes.APPLICATION_SPECIFIC_ERROR_CODE // return a special exit code for known exceptions
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}
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return UsefulUtilityExitCodes.SUCCESS // this is the exit code to be returned to the system inherited from the ExitCodes base class
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}
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}
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Then in your ``main()`` method:
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.. container:: codeset
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.. sourcecode:: kotlin
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import net.corda.cliutils.start
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fun main(args: Array<String>) {
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UsefulUtility().start(args)
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}
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Application behavior
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--------------------
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* Set exit codes using exitProcess.
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* Zero means success.
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* Other numbers mean errors.
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* Setting a unique error code (starting from 1) for each thing that can conceivably break makes your tool shell-scripting friendly.
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* Make sure all exit codes are documented with recommended remedies where applicable.
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* Your ``--help`` text or other docs should ideally include examples. Writing examples is also a good way to find out if your program requires a dozen flags to do anything.
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* Don’t print logging output to the console unless the user requested it via a ``-–verbose`` flag (conventionally shortened to ``-v``). Logs should be either suppressed or saved to a text file during normal usage, except for errors, which are always OK to print.
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* Don't print stack traces to the console. Stack traces can be added to logging files, but the user should see as meaningful error description as possible. |