Allow dynamically updating version number and version option flags and description

lib/command.js

@@ -77,6 +77,9 @@ class Command extends EventEmitter {
     this._helpCommandnameAndArgs = 'help [command]';
     this._helpCommandDescription = 'display help for command';
     this._helpConfiguration = {};
+
+    this._version = undefined;
+    this._versionOption = undefined;
   }
 
   /**
@@ -1559,10 +1562,11 @@ Expecting one of '${allowedValues.join("', '")}'`);
       // Preserve original behaviour so backwards compatible when still using properties
       const result = {};
       const len = this.options.length;
+      const versionOptionName = this._versionOption?.attributeName();
 
       for (let i = 0; i < len; i++) {
         const key = this.options[i].attributeName();
-        result[key] = key === this._versionOptionName ? this._version : this[key];
+        result[key] = key === versionOptionName ? this._version : this[key];
       }
       return result;
     }
@@ -1807,24 +1811,31 @@ Expecting one of '${allowedValues.join("', '")}'`);
    *
    * You can optionally supply the  flags and description to override the defaults.
    *
-   * @param {string} str
+   * @param {string} [str]
    * @param {string} [flags]
    * @param {string} [description]
    * @return {this | string} `this` command for chaining, or version string if no arguments
    */
 
   version(str, flags, description) {
-    if (str === undefined) return this._version;
-    this._version = str;
-    flags = flags || '-V, --version';
-    description = description || 'output the version number';
-    const versionOption = this.createOption(flags, description);
-    this._versionOptionName = versionOption.attributeName();
-    this.options.push(versionOption);
-    this.on('option:' + versionOption.name(), () => {
-      this._outputConfiguration.writeOut(`${str}\n`);
-      this._exit(0, 'commander.version', str);
-    });
+    if (str === undefined && flags === undefined && description === undefined) {
+      return this._version;
+    }
+    if (str !== undefined) {
+      this._version = str;
+    }
+    if (!this._versionOption) {
+      flags = flags || '-V, --version';
+      description = description || 'output the version number';
+      this._versionOption = this.createOption(flags, description);
+      this.options.push(this._versionOption);
+      this.on('option:' + this._versionOption.name(), () => {
+        this._outputConfiguration.writeOut(`${this._version}\n`);
+        this._exit(0, 'commander.version', this._version);
+      });
+    } else {
+      this._versionOption.setFlagsAndDescription(flags, description);
+    }
     return this;
   }
 

lib/option.js

@@ -11,21 +11,8 @@ class Option {
    */
 
   constructor(flags, description) {
-    this.flags = flags;
-    this.description = description || '';
-
-    this.required = flags.includes('<'); // A value must be supplied when the option is specified.
-    this.optional = flags.includes('['); // A value is optional when the option is specified.
-    // variadic test ignores <value,...> et al which might be used to describe custom splitting of single argument
-    this.variadic = /\w\.\.\.[>\]]$/.test(flags); // The option can take multiple values.
+    this.setFlagsAndDescription(flags, description);
     this.mandatory = false; // The option must have a value after parsing, which usually means it must be specified on command line.
-    const optionFlags = splitOptionFlags(flags);
-    this.short = optionFlags.shortFlag;
-    this.long = optionFlags.longFlag;
-    this.negate = false;
-    if (this.long) {
-      this.negate = this.long.startsWith('--no-');
-    }
     this.defaultValue = undefined;
     this.defaultValueDescription = undefined;
     this.presetArg = undefined;
@@ -37,6 +24,51 @@ class Option {
     this.implied = undefined;
   }
 
+  /**
+   * Set the option flags and description, if provided.
+   * Leave unchanged otherwise.
+   *
+   * @param {string} [flags]
+   * @param {string} [description]
+   */
+
+  setFlagsAndDescription(flags, description) {
+    this.setFlags(flags);
+    this.setDescription(description);
+  }
+
+  /**
+   * Set the option flags, if provided.
+   * Leave unchanged otherwise.
+   *
+   * @param {string} [flags]
+   */
+
+  setFlags(flags) {
+    if (flags !== undefined) {
+      this.flags = flags;
+      this.required = flags.includes('<'); // A value must be supplied when the option is specified.
+      this.optional = flags.includes('['); // A value is optional when the option is specified.
+      // variadic test ignores <value,...> et al which might be used to describe custom splitting of single argument
+      this.variadic = /\w\.\.\.[>\]]$/.test(flags); // The option can take multiple values.
+      const optionFlags = splitOptionFlags(flags);
+      this.short = optionFlags.shortFlag;
+      this.long = optionFlags.longFlag;
+      this.negate = this.long ? this.long.startsWith('--no-') : false;
+    }
+  }
+
+  /**
+   * Set the option description, if provided.
+   * Leave unchanged otherwise.
+   *
+   * @param {string} [description]
+   */
+
+  setDescription(description) {
+    this.description = description || this.description || '';
+  }
+
   /**
    * Set the default value, and optionally supply the description to be displayed in the help.
    *

typings/index.d.ts

@@ -293,7 +293,7 @@ export class Command {
    *
    * You can optionally supply the  flags and description to override the defaults.
    */
-  version(str: string, flags?: string, description?: string): this;
+  version(str?: string, flags?: string, description?: string): this;
 
   /**
    * Define a command, implemented using an action handler.