Dynamic help text from command options

src/commands/ls.ts

@@ -4,9 +4,9 @@ import { BooleanOption } from "../option"
 import { Options } from "../options"
 
 class LsOptions extends Options {
-  commaSeparated = new BooleanOption("m")
-  long = new BooleanOption("l")
-  reverse = new BooleanOption("r")
+  commaSeparated = new BooleanOption("m", "", "List files across the page, separated by commas.")
+  long = new BooleanOption("l", "", "List files in long format.")
+  reverse = new BooleanOption("r", "", "Reverse the order of the sort.")
 }
 
 export class LsCommand extends Command<LsOptions> {

src/option.ts

@@ -1,5 +1,9 @@
 export abstract class Option {
-  constructor(readonly shortName: string) {}
+  constructor(
+    readonly shortName: string,
+    readonly longName: string,
+    readonly description: string,
+  ) {}
 
   get isSet(): boolean {
     return this._isSet
@@ -13,7 +17,7 @@ export abstract class Option {
 }
 
 export class BooleanOption extends Option {
-  constructor(shortName: string) {
-    super(shortName)
+  constructor(shortName: string, longName: string, description: string) {
+    super(shortName, longName, description)
   }
 }

src/options.ts

@@ -1,9 +1,20 @@
 import { Option } from "./option"
 
 export abstract class Options {
-  private static _findByShortName<T extends Options>(options: T, shortName: string): Option {
+  static fromArgs<T extends Options>(args: string[], optionsType: (new () => T)): T {
+    const options = new optionsType
+    for (const arg of args) {
+      if (arg[0] == "-") {
+        const shortName = arg[1]
+        options._findByShortName(shortName).set()
+      }
+    }
+    return options
+  }
+
+  private _findByShortName<T extends Options>(shortName: string): Option {
     let v: Option
-    for (v of Object.values(options)) {
+    for (v of Object.values(this)) {
       if (v.shortName == shortName) {
         return v
       }
@@ -12,15 +23,12 @@ export abstract class Options {
     throw new Error(`No such shortName option "${shortName}"`)
   }
 
-  static fromArgs<T extends Options>(args: string[], optionsType: (new () => T)): T {
-    const options = new optionsType
-    for (const arg of args) {
-      if (arg[0] == "-") {
-        const shortName = arg[1]
-        this._findByShortName(options, shortName).set()
-      }
-    }
-
-    return options
+  _help(): string[] {
+    // Dynamically create help text from options.
+    // Could have short form for usage, and longer form for man page.
+    const sorted = [...Object.values(this)].sort(
+      (a, b) => (a.shortName ?? a.longName) > (b.shortName ?? b.longName) ? 1 : -1
+    )
+    return sorted.map((option) => `-${option.shortName}  ${option.description}`)
   }
 }