Types for version getter (#1982)

* Update types since .version() returns version.

* Remove extra space

lib/command.js

@@ -1825,17 +1825,16 @@ Expecting one of '${allowedValues.join("', '")}'`);
   }
 
   /**
-   * Set the program version to `str`.
+   * Get or set the program version.
    *
-   * This method auto-registers the "-V, --version" flag
-   * which will print the version number when passed.
+   * This method auto-registers the "-V, --version" option which will print the version number.
    *
-   * You can optionally supply the  flags and description to override the defaults.
+   * 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
+   * @return {this | string | undefined} `this` command for chaining, or version string if no arguments
    */
 
   version(str, flags, description) {
@@ -1844,7 +1843,7 @@ Expecting one of '${allowedValues.join("', '")}'`);
     flags = flags || '-V, --version';
     description = description || 'output the version number';
     const versionOption = this.createOption(flags, description);
-    this._versionOptionName = versionOption.attributeName();
+    this._versionOptionName = versionOption.attributeName(); // [sic] not defined in constructor, partly legacy, partly only needed at root
     this.options.push(versionOption);
     this.on('option:' + versionOption.name(), () => {
       this._outputConfiguration.writeOut(`${str}\n`);

typings/index.d.ts

@@ -294,6 +294,10 @@ export class Command {
    * You can optionally supply the  flags and description to override the defaults.
    */
   version(str: string, flags?: string, description?: string): this;
+  /**
+   * Get the program version.
+   */
+  version(): string | undefined;
 
   /**
    * Define a command, implemented using an action handler.

typings/index.test-d.ts

@@ -36,6 +36,7 @@ expectType<commander.Command | null>(program.parent);
 expectType<commander.Command>(program.version('1.2.3'));
 expectType<commander.Command>(program.version('1.2.3', '-r,--revision'));
 expectType<commander.Command>(program.version('1.2.3', '-r,--revision', 'show revision information'));
+expectType<string | undefined>(program.version());
 
 // command (and CommandOptions)
 expectType<commander.Command>(program.command('action'));