Introduce Callback template

mapbox · Jun 28, 2017 · 2fa14be · 2fa14be
1 parent b828503
commit 2fa14be
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Showing 4 changed files with 23 additions and 7 deletions.
diff --git a/flow-interfaces/callback.js b/flow-interfaces/callback.js
@@ -0,0 +1,17 @@
+
+// Flow can't perfectly type Node-style callbacks yet; it does not have a way to
+// express that if the first parameter is null, the second is not, so for the time
+// being, both parameters must be optional. Use the following convention when defining
+// a callback:
+//
+//    asyncFunction((error, result) => {
+//        if (error) {
+//            // handle error
+//        } else if (result) {
+//            // handle success
+//        }
+//    });
+//
+// See https://github.com/facebook/flow/issues/2123 for more.
+
+declare type Callback<T> = (error: ?Error, result: ?T) => void;
diff --git a/src/source/geojson_worker_source.js b/src/source/geojson_worker_source.js
@@ -29,8 +29,7 @@ export type LoadGeoJSONParameters = {
     geojsonVtOptions?: Object
 };
 
-export type LoadGeoJSONCallback = (error: ?Error, result: ?GeoJSON) => void;
-export type LoadGeoJSON = (params: LoadGeoJSONParameters, callback: LoadGeoJSONCallback) => void;
+export type LoadGeoJSON = (params: LoadGeoJSONParameters, callback: Callback<GeoJSON>) => void;
 
 export interface GeoJSONIndex {
 }
@@ -102,7 +101,7 @@ class GeoJSONWorkerSource extends VectorTileWorkerSource {
      * @param params.source The id of the source.
      * @param callback
      */
-    loadData(params: LoadGeoJSONParameters, callback: (error: ?Error) => void) {
+    loadData(params: LoadGeoJSONParameters, callback: Callback<void>) {
         this.loadGeoJSON(params, (err, data) => {
             if (err || !data) {
                 return callback(err);
@@ -157,7 +156,7 @@ class GeoJSONWorkerSource extends VectorTileWorkerSource {
      * @param [params.url] A URL to the remote GeoJSON data.
      * @param [params.data] Literal GeoJSON data. Must be provided if `params.url` is not.
      */
-    loadGeoJSON(params: LoadGeoJSONParameters, callback: LoadGeoJSONCallback) {
+    loadGeoJSON(params: LoadGeoJSONParameters, callback: Callback<GeoJSON>) {
         // Because of same origin issues, urls must either include an explicit
         // origin or absolute path.
         // ie: /foo/bar.json or http://example.com/bar.json

diff --git a/src/source/vector_tile_worker_source.js b/src/source/vector_tile_worker_source.js
@@ -25,7 +25,7 @@ import type {StyleLayerIndex} from '../style/style_layer_index';
  * @param vectorTile
  * @private
  */
-export type LoadVectorDataCallback = (error: ?Error, result: ?AugmentedVectorTile) => void;
+export type LoadVectorDataCallback = Callback<?AugmentedVectorTile>;
 
 export type AbortVectorData = () => void;
 export type LoadVectorData = (params: WorkerTileParameters, callback: LoadVectorDataCallback) => ?AbortVectorData;

diff --git a/src/source/worker.js b/src/source/worker.js
@@ -108,7 +108,7 @@ class Worker {
      * function taking `(name, workerSourceObject)`.
      *  @private
      */
-    loadWorkerSource(map: string, params: {url: string}, callback: Function) {
+    loadWorkerSource(map: string, params: {url: string}, callback: Callback<void>) {
         try {
             this.self.importScripts(params.url);
             callback();
@@ -117,7 +117,7 @@ class Worker {
         }
     }
 
-    loadRTLTextPlugin(map: string, pluginURL: string, callback: Function) {
+    loadRTLTextPlugin(map: string, pluginURL: string, callback: Callback<void>) {
         try {
             if (!globalRTLTextPlugin.applyArabicShaping && !globalRTLTextPlugin.processBidirectionalText) {
                 this.self.importScripts(pluginURL);