feat: allow configuration of prefix for boolean negation (#94)

Author: yitzchak

README.md

@@ -250,6 +250,25 @@ node example.js -x 1 2 -x 3 4
 { _: [], x: [[1, 2], [3, 4]] }
 ```
 
+### negation prefix
+
+* default: `no-`
+* key: `negation-prefix`
+
+The prefix to use for negated boolean variables.
+
+```sh
+node example.js --no-foo
+{ _: [], foo: false }
+```
+
+_if set to `quux`:_
+
+```sh
+node example.js --quuxfoo
+{ _: [], foo: false }
+```
+
 ### populate --
 
 * default: `false`.

index.js

@@ -16,6 +16,7 @@ function parse (args, opts) {
     'dot-notation': true,
     'parse-numbers': true,
     'boolean-negation': true,
+    'negation-prefix': 'no-',
     'duplicate-arguments-array': true,
     'flatten-duplicate-arrays': true,
     'populate--': false
@@ -45,6 +46,7 @@ function parse (args, opts) {
     coercions: {}
   }
   var negative = /^-[0-9]+(\.[0-9]+)?/
+  var negatedBoolean = new RegExp('^--' + configuration['negation-prefix'] + '(.+)')
 
   ;[].concat(opts.array).filter(Boolean).forEach(function (key) {
     flags.arrays[key] = true
@@ -141,8 +143,8 @@ function parse (args, opts) {
       } else {
         setArg(m[1], m[2])
       }
-    } else if (arg.match(/^--no-.+/) && configuration['boolean-negation']) {
-      key = arg.match(/^--no-(.+)/)[1]
+    } else if (arg.match(negatedBoolean) && configuration['boolean-negation']) {
+      key = arg.match(negatedBoolean)[1]
       setArg(key, false)
 
     // -- seperated by space.

test/yargs-parser.js

@@ -1968,6 +1968,16 @@ describe('yargs-parser', function () {
         parsed['no-dice'].should.equal(true)
         expect(parsed.dice).to.equal(undefined)
       })
+
+      it('negates boolean arguments with correct prefix', function () {
+        var parsed = parser(['--foodice'], {
+          configuration: {
+            'negation-prefix': 'foo'
+          }
+        })
+
+        expect(parsed['dice']).to.equal(false)
+      })
     })
 
     describe('duplicate arguments array', function () {