Allow rejection of attempted load via returning falsy loadPath (#88)

* Allow rejection of attempted load via returning falsy loadPath

* callback with empty object {} if resolvedLoadPath is falsy

README.md

@@ -70,6 +70,7 @@ for plain browser:
   // function(lngs, namespaces) { return customPath; }
   // the returned path will interpolate lng, ns if provided like giving a static path
   // the function might return a promise
+  // returning falsy will abort the download
   //
   // If allowMultiLoading is false, lngs and namespaces will have only one element each,
   // If allowMultiLoading is true, lngs and namespaces can have multiple elements

lib/index.js

@@ -59,6 +59,7 @@ class Backend {
     loadPath = makePromise(loadPath)
 
     loadPath.then(resolvedLoadPath => {
+      if (!resolvedLoadPath) return callback(null, {})
       const url = this.services.interpolator.interpolate(resolvedLoadPath, { lng: languages.join('+'), ns: namespaces.join('+') })
       this.loadUrl(url, callback, loadUrlLanguages, loadUrlNamespaces)
     })

test/http.spec.js

@@ -165,6 +165,40 @@ describe(`http backend using ${hasXMLHttpRequest ? 'XMLHttpRequest' : 'fetch'}`,
     })
   })
 
+  describe('with loadPath function returning falsy', () => {
+    let backend
+    let calledLanguages = []
+    let calledNamespaces = []
+    const loadPathSpy = (languages, namespaces) => {
+      calledLanguages = calledLanguages.concat(languages)
+      calledNamespaces = calledNamespaces.concat(namespaces)
+      return ''
+    }
+
+    before(() => {
+      backend = new Http(
+        {
+          interpolator: i18next.services.interpolator
+        },
+        {
+          loadPath: loadPathSpy
+        }
+      )
+    })
+
+    describe('#read', () => {
+      it('should not load data', (done) => {
+        backend.read('en', 'test', (err, data) => {
+          expect(err).not.to.be.ok()
+          expect(calledLanguages).to.eql(['en'])
+          expect(calledNamespaces).to.eql(['test'])
+          expect(data).to.eql({})
+          done()
+        })
+      })
+    })
+  })
+
   describe('with addPath function', () => {
     let backend
     const calledLanguages = []