Extensible package documentation

[ktraunmueller]

In the first iteration of code completion, there will be two categories of commands:

• Built-in commands (i.e., commands provided by LaTeX2e). These will have detailed manual documentation taken from the unofficial LaTeX2e manual showing in the code completions window.
• All other commands (i.e., commands provided by currently installed packages). These will have different levels of documentation information showing in the code completions window:
  • Commands declared with one of \newcommand, \renewcommand, \providecommand, or \DeclareRobustCommand will have basic documentation about the number of arguments, and the default value of an optional argument.
  • Commands declared in any way (which isn't uncommon, see e.g., the \url command of url.sty) will not have any information about the number or structure of arguments.

To provide better code completion documentation for non built-in commands, an extensible package documentation mechanism would be nice. In the simplest case, a set of json files that can be discovered by a documentation scanner.

As an example, here's the documentation of a built-in LaTeX2e command (\section) (this is Swift code, not json):

// \section[toc-title]{title}
CommandDescriptor(filename: "latex.ltx",
                  cmd: "\\section",
                  shortHelp: "Start a section. Can be used in the standard document classes article, book, and report.",
                  helpUrl: "https://latex2e.org/_005csection.html",
                  allowedIn: .documentBody,
                  numberOfArguments: 2,
                  arguments: [
                    CommandArgumentDescriptor(name: "short title",
                                              optionality: .optional,
                                              shortHelp: "The optional shorter title will appear as the section title in the table of contents and in running headers."),
                    CommandArgumentDescriptor(name: "title",
                                              optionality: .required,
                                              shortHelp: "The section title.")