bonzai/design.md

Style and Design

• Use "deciduous tree" emoji 🌳 to mark Bonzai stuff
• Everything through go fmt or equiv, no exceptions
• In Vim set textwidth=72 (not 80 to line numbers fit)
• Use /* */ for package documentation comment, // elsewhere
• Smallest possible names for given scope while still clear
• Favor additional packages (possibly in internal) over long names
• Package globals that will be used a lot can be single capital
• Must be good reason to use more than 4 character pkg name
• Avoid unnecessary comments

Design Considerations

Here is a summary of the thinking behind important design decisions when creating Bonzai.

Promote high-level package library API calls over Cmd bloat

Code belongs in package libraries, not Cmds.

While Bonzai allows for rapid applications development by putting everything initially in Cmd Call first-class function, Cmds are most designed for documentation and completion, not heavy Call implementations (even though many will organically start there from people's personal Bonzai trees).

Eventually, most Call implementations should be moved into their own package libraries, perhaps even in the same Go module. Cmds should never communicate with each other directly (other than calling one another on occasion). While the idea of adding a Channel attribute was intriguing, it quickly became clear that doing so would promote undesirable tight coupling --- even with channels --- between specific commands.

Cmds should be very light

Most Cmds should assign their first-class Call function to one that lightly wraps a similar function signature in a callable, high-level library that works entirely independently from the bonzai package. It's best to promote strong support for sustainable API packages.

Only bash completion and shell.Cmd planned

If it doesn't work with complete -C or equivalent then just run the Bonzai command tree monolith as a temporary shell (shell.Cmd) and use its cross-platform support for tab completion.

Zsh, Powershell, and Fish have no equivalent to complete -C (which allows any executable to provide its own completion). This forces inferior dependencies on overly verbose external "completer" scripts written in only those languages for those specific shells. This dependency completely negates any possibility of providing modular completers and composable commands that carry their own completion logic. This one objective fact alone should give everyone pause before opting to use one of these inferior shells for their command line interactions.

Bonzai commands leverage this best-of-breed completion functionality of bash to provide an unlimited number of completion methods and combinations. The equivalent implementations, perhaps as an export collected from all composed commands providing their shell equivalent of completion scripts, would be preposterously large just for its basic completion tree). Instead, Bonzai uses Go itself to manage that completion --- drawing on a rich collection of completers included in the standard Bonzai module --- and provides documented shortcut aliases when completion is not available (h|help, for example).

Bonzai commands may default to shell.Cmd or help.Cmd

These provide help information and optional interactive assistance including tab completion in runtime environments that do not have complete -C foo foo enabled.

Target users replacing shell scripts in "dot files" collections

By creating a cmd subdirectory of a dot files repo a multi-call Bonzai command named cmd can be easily maintained and added to just as quickly as any shell script. This has the added bonus of allowing others to quickly add one of your little commands with just a simple import (for example, import github.com/rwxrob/dot/cmd and then cmd.Isosec) from their own cmd monoliths. This also enables the fastest possible prototyping of code that would otherwise require significant, problematic mocks. Developers can work out the details of a thing just as fast as with shell scripting --- but with the power of all the Go standard library --- and then factor out their favorites as they grow into their own Bonzai command repos. This approach keeps "Go on the brain" (instead of having to port a bunch of bash later) and promotes the massive benefits of rapid applications development the fullest extent.

Use either foo.Cmd or cmd.Foo convention

People may decide to put all their Bonzai commands into a single cmd package or to put each command into its own package. Both are perfectly acceptable and allow the developer making the import to alias the packages as needed using Go's excellent package import design.

Default capital "Z" import name

People can easily change the default "Z" import name to whatever else if they don't like it (or worse, if has conflicts). But, we actually want naming conflicts even though this seems counter-intuitive. Developers should be putting most of their code into their own pkg libraries and calling into them from their wrapping Bonzai trees and branches that import Z. If someone is importing Z into their package library they are likely doing something they shouldn't. Bonzai should only be imported into the composable branch or standalone command (main). This is a reminder as well to Bonzai developers not to stuff things into the Z package that would never be used outside a Bonzai command, tree or main.go standalone.

Promote lower "z" personal Bonzai trees

Just as "dotfiles" has become a convention, use of the simple "z" GitHub repo should be promoted as a common, "ez" way to find people's personal monoliths. Obviously, people can use what they want. This is also consistent with the capital "Z" import name of the bonzai package.

Use simple regular expressions for usage

Bonzai takes a fundamentally different approach to the command line and usage documentation. Any command line is a minimal domain specific language. As such, usage notation simple is not enough. Regular expressions allow the quick understanding of what is allowed and should become mandatory learning in a world of minimal domain specific grammars. Only the most basic regular expressions are required to produce rich usage strings for any Bonzai command. However, those wanting traditional usage notation can easily override the DefaultUsageFunc with their own.

Prioritize output to VT100-compatible terminals

Every modern terminal supports VT100 compatibility. If it doesn't, people should just not use it. This means emphasis and formatting are dependent on the rwxrob/term package for the main output. Bonzai tree developers will likely want terminal output helpers more than anything (yes even web rendering).

Secondary output to local web browser

Bonzai will eventually provide the option to enable use of the local web browser instead of terminal output for help and other documentation output. This will allow graphic application executables to simple be double-clicked from graphic desktops. Bonzai will ship with an embedded web template for such applications, but will also allow users to granularly customize their own modifications to the default theme. Bonzai branch creators are encouraged to provide downloadable themes in this regard. In this way, Bonzai will provide the web shell to encapsulate other web applications.

Prefer local web apps over other GUI platforms

While it is obviously possible to create any graphic application with Bonzai, the creation of localized web applications should be the preferred convention of the Bonzai GUI applications community. This simplifies application development and takes aim at bloated alternatives that embed full GUI web clients (such as Electron) while still providing a rich terminal interface for those who prefer it. Every Bonzai binary is its own local web server which Go's rich standard library to draw on.

[]Section instead of map[string]string for Other

This allows composition notation and ensures the author has control of how the Other sections appear.

Move help.Cmd into its own package

Although it breaks backward compatibility for many applications updating between v0.1 and v0.2 the decision to put help.Cmd into it's own Bonzai branch git repo was the right one. It is now on equal footing with every other potential Bonzai branch and can keep its Version in sync with Git version (as all Bonzai branches should). It is highly likely that GUI/web/hybrid help commands will be preferred by some and including one over another --- when not used --- ends up just being unnecessary bloat. This also serves to clarify that the legal information is related to that specific help.Cmd Bonzai branch and not Bonzai itself. It's conceivable that another help.Cmd creator may wish another legal agreement.

Leave hidden default command params

When the default command is invoked any of it's params will be automatically passed as if the command specified them. But they are not included in the tab completion. This is because there will inevitably be conflicts between default command params and other potential completions at that level for other commands. Rather than disable this, or add tab completion, it was decided to keep them as a useful shortcut side-effect without calling direct attention to them. When and if dependencies on them become an issue it can be addressed then.

Not exporting Dynamic FuncMap builtins

Since those builtins will land in mark subpackage eventually, don't want to build any dependencies on them now that will break. The builtins themselves can obviously be used immediately and has a much smaller chance of changing in the future.

Reserve -- for BonzaiShell pipe assignment

The only operator of the BonzaiShell (that is not a Bonzai leaf command allowing maximum extensibility) is the "into" (--) operator. It is observed by Seek (called from Run) and is processed in a consistent way. All it does is follow the precedent set by text/template of buffering standard output of the command immediately before it and adding it as the last argument to the following command. That's it. Not only is this consistent will well established practices, it's drop dead simple to remember and implement. Ultimately, this will result in BonzaiShell scripts that look something like this (where lines with any space are line continuations, unless they are --, which joins them as a pipe):

  produce output with lines
  --
  each line
  foo the line
  --
  prefix someprefix

The fact that -- is observed by most shells as the "end of arguments" mark makes it somewhat intuitive for regular shell users who know that if they have anything that contains such a thing that it would have to be quoted. Therefore, no Bonzai command must ever require a double-dash argument because it will be handled before the command ever sees it signifying this pipe relationship to the next command.

Unlike most host shells (which will create their own conflicts with most Bonzai commands) this is the only reserved keyword. When BonzaiShell is complete, users will be able to start a REPL with z shell, or, if the Bonzai tree developer decides to make shell the default argument (which will probably become the recommended convention) then users will be able to write BonzaiShell scripts or even use #!/usr/bin/env z on Unix systems (despite that probably being discouraged over just writing a simple Bonzai leaf command that does the same and compiling it into your tree).

In fact, BonzaiShell scripts could provide for great prototyping before writing all that code in Go. Hell, we could even create a BonzaiShell to Bonzai Cmd code generator with very little effort at that point.

Custom errors as package globals

When it became clear that there are a number of canned error conditions that we want to allow Cmd developers to use quickly and easily, and that not all of them directly relate to a particular Cmd (x) is was decided to move all errors into a central errors.go file as package global custom error structures that implement error interface (Error() string) and have concrete, public fields so that composition notation can be used (instead of forcing an unnecessary function call). The benefits of custom errors that can be interrogated with the errors functions are obvious and this also consolidates most English language usage for later when we add full language-by-locale support.

Note that this was a breaking change (added in v0.10.0) with high-impact because so many have hard-coded x.UsageError (which is why the full v1.0 is not expected until December 25th 2022, some months after things should feel settled and finished).

Move package global Aliases/Shortcuts into Cmd

In Cmd they can be documented. They also tend to be long and eat up too much of the command line when using them with completion. Better to just have them in the help docs to lookup when the full path is wanted.

Allow dashes, but discourage

Being able to put a command anywhere in the commands tree path of arguments will never be allowed since it is fundamentally against the entire raison d'etre of Bonzai. We want people to memorize specific paths and create the occasional alias and shortcut, not just through whatever onto the command line hoping it will work. This is why getopt things are so problematic, they all deal with the "end of options and switch" and the "beginning of arguments" differently. Not Bonzai, where the arguments are always consistent as well as the command paths. Because of this, dashes should never be used by any Bonzai command or alias. In fact, the only time a dash will exist is when passing on arguments to the underlying command shell. For example, when delegating to gh which requires it (although every effort should be made to remake the entire UI for such things to be Bonzai friendly).

However, the no-getopt approach is so foreign to those training in decades of this insanity that we need to support dashed aliases (and other options) that will be intuitive to these people for a very long time. Of particular note are things like -h, --help, -help, and /? all of which are indelibly marked into most of our muscle memory. will be intuitive to such people. The addition of support for aliases that begin with dashes --- but that do not appear in the help documentation --- is specifically to address this issue. Like all aliases, the bash shell will dynamically change the -h into help when the user taps tab prompting them with the correct word, but, also like all aliases, if they execute the command with -h it will just work.

Allowing dashed aliases does carry the risk that some will permanently use them in their scripts. But not allowing them in most help documentation should be enough to discourage it. Theoretically, it is entirely possible to create a Bonzai command that does parse its arguments and parameters using getopt notation. Having this freedom is a part of FOSS and for those who insist is supported. It is simply strongly discouraged by the Bonzai project itself which will make specific design decisions based on the assumptions that dashes are never used in command names. One such design decision is to use -- as the pipe operator in eventual bonsh.Shell command.

No shebang (#!) line ever in bonsh scripts

We don't want to create an ecosystem of Bonzai shell scripts that are associated with a specific operating system. All bonsh scripts must be passed to an interpreter, which is any Bonzai composite command tree that imports bon.Shell, which includes z bon [shell], the default for the bon command, which many will create a shortcut for z sh (pronounced zee S H or bonzai shell, what's zsh?).