Allow boolean flag with .demand()

README.md

@@ -372,7 +372,7 @@ Set `argv[key]` to `value` if no option was specified on `process.argv`.
 
 Optionally `.default()` can take an object that maps keys to default values.
 
-.demand(key, [msg])
+.demand(key, [boolean | msg])
 ------------
 
 If `key` is a string, show the usage information and exit if `key` wasn't
@@ -383,9 +383,12 @@ up in `argv._`.
 
 If `key` is an Array, demand each element.
 
-If `msg` is supplied, it will be printed when the argument is missing,
+If a `msg` string is given, it will be printed when the argument is missing,
 instead of the standard error message. This is especially helpful for the non-option arguments in `argv._`.
 
+If a `boolean` value is given, it controls whether the option is demanded;
+this is useful when using `.options()` to specify command line parameters.
+
 .requiresArg(key)
 -----------------
 

index.js

@@ -122,7 +122,12 @@ function Argv (processArgs, cwd) {
             });
         }
         else {
-            demanded[keys] = { msg: msg };
+            if (typeof msg === 'string') {
+                demanded[keys] = { msg: msg };
+            }
+            else if (msg === true || typeof msg === 'undefined') {
+                demanded[keys] = { msg: null };
+            }
         }
 
         return self;

test/usage.js

@@ -532,6 +532,32 @@ describe('usage', function () {
         ]);
     });
 
+    it('should allow demand option with boolean flag', function () {
+        var r = checkUsage(function () {
+            return yargs('-y 10 -z 20'.split(' '))
+                .usage('Usage: $0 -x NUM [-y NUM]')
+                .options({
+                    'x': { description: 'an option',      demand: true  },
+                    'y': { description: 'another option', demand: false }
+                })
+                .argv;
+        });
+        r.result.should.have.property('y', 10);
+        r.result.should.have.property('z', 20);
+        r.result.should.have.property('_').with.length(0);
+        r.errors.join('\n').split(/\n/).should.deep.equal([
+            'Usage: ./usage -x NUM [-y NUM]',
+            '',
+            'Options:',
+            '  -x  an option       [required]',
+            '  -y  another option',
+            '',
+            'Missing required arguments: x'
+        ]);
+        r.logs.should.have.length(0);
+        r.exit.should.be.ok;
+    });
+
     it('should succeed when rebase', function () {
         yargs.rebase('/home/chevex', '/home/chevex/foo/bar/baz').should.equal('./foo/bar/baz');
         yargs.rebase('/home/chevex/foo/bar/baz', '/home/chevex').should.equal('../../..');