DataApiManager: emit fieldLoaded after request completes

The intent of this is to allow for clearing errors after fields
load (e.g. a "field loading" message if the user attempts to continue
past the step when a field hasn't yet finished loading).

* src/dapi/DataApiManager.js (getApiData): Emit fieldLoaded after
  request completes.
* test/dapi/DataApiManagerTest.js: Add test case.

DEV-2299

src/dapi/DataApiManager.js

@@ -126,6 +126,9 @@ module.exports = Class( 'DataApiManager' )
      *
      * The optional request id permits cancelling requests if necessary.
      *
+     * Once a field has finished loading, a `fieldLoaded` event will be
+     * emitted with `name` and `index`.
+     *
      * TODO: refactor argument list; it's just been built upon too much and
      * needs reordering
      *
@@ -197,6 +200,7 @@ module.exports = Class( 'DataApiManager' )
 
                         // clear the pending flag
                         _self._pendingApiCall[ id ] = undefined;
+                        _self.emit( 'fieldLoaded', name, +index );
                     }
                 } );
             }

test/dapi/DataApiManagerTest.js

@@ -0,0 +1,83 @@
+/**
+ * Test of DataApi
+ *
+ *  Copyright (C) 2017 LoVullo Associates, Inc.
+ *
+ *  This file is part of liza.
+ *
+ *  liza is free software: you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License as published by
+ *  the Free Software Foundation, either version 3 of the License, or
+ *  (at your option) any later version.
+ *
+ *  This program is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *  GNU General Public License for more details.
+ *
+ *  You should have received a copy of the GNU General Public License
+ *  along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ * @todo This needs tests for the rest of StagingBucket
+ */
+
+"use strict";
+
+const root   = require( '../../' );
+const expect = require( 'chai' ).expect;
+const Sut    = root.dapi.DataApiManager;
+
+
+describe( 'DataApiManager', () =>
+{
+    it( 'emits fieldLoaded event once request is complete', done =>
+    {
+        const dapi = createStubDapi();
+        const type = 'loaded-test';
+        const name = 'foo';
+
+        // this is intentionally a string to test casting; see below
+        const index = "2";
+
+        const fail = e => { throw( e ) };
+
+        Sut( createStubDapiFactory( { [type]: dapi } ) )
+            .on( 'fieldLoaded', ( given_name, given_index ) =>
+            {
+                expect( given_name ).to.equal( name );
+
+                // should cast index to number
+                expect( given_index ).to.equal( +index );
+
+                done();
+            } )
+            .setApis( { [type]: { type: type } } )
+            .getApiData( type, {}, ()=>{}, name, index, {}, fail );
+    } );
+} );
+
+
+function createStubDapi()
+{
+    return {
+        request( _, callback )
+        {
+            callback();
+        },
+
+        on() {
+            return this;
+        },
+    };
+}
+
+
+function createStubDapiFactory( dapis )
+{
+    return {
+        fromType( type )
+        {
+            return dapis[ type ];
+        },
+    };
+}