flags_usage

Adds “–help” to Deno’s std/flags module, for printing out command line usage/option information.

Example

main.ts:

import { processFlags } from "https://deno.land/x/flags_usage/mod.ts";

const options = {
    preamble: "Usage: my-tool <options>",        // New: Optional preamble for describing non-flag/positional arguments
    description: { output: "Output directory" }, // New: Description of flag
    argument: { output: "dir" },                 // New: "<dir>" in the output below
    string: [ "output" ],
    default: { output: "out" },
};

// `processFlags` parses normally, except it will print usage and exit on `--help`
const { output } = processFlags(Deno.args, options);

Output:

$ deno run main.ts --help
Usage: my-tool <options>

Options:
  --output <dir>  Output directory (default: "out")
  -h, -?, --help  Display usage information

Note that parseFlags, logUsage, etc. (see API) can be used if automatically exiting on --help is not desirable.

API

Options

All options arguments follow std/flags’s interface, with the following new, optional properties:

• preamble: An optional string to print out before flag information on --help
• description: An object mapping flags to descriptions that will be displayed on --help
• argument: An object mapping flags to names for their arguments to be displayed on --help (e.g. mapping out to path will display --out <path> ... instead of the generic --out <str> for string arguments)

processFlags(Deno.args, options)

Parse options as usual, but add --help and automatically print usage and exit if --help/-h/-? are specified.

parseFlags(Deno.args, options)

Parse options as usual, with --help/-h/-? added as a Boolean flag (note: with this function, the caller must decide what to do if the help flag is set to true–use processFlags to automatically print usage and exit).

formatUsage(options)

Format usage information as a string.

logUsage(options)

Format usage information and print to the console.