Add onTransformStart method

Author: eduardoboucas

lib/sourcebit.js

@@ -183,6 +183,21 @@ class Sourcebit {
             objects: []
         };
         const contextSnapshot = cloneDeep(this.context);
+
+        this.pluginBlocks.forEach((pluginBlock, index) => {
+            const plugin = this.pluginModules[index];
+            const pluginName = this.getNameOfPluginAtIndex(index);
+
+            if (typeof plugin.onTransformStart === 'function') {
+                plugin.onTransformStart({
+                    debug: this.getDebugMethodForPlugin(pluginName),
+                    getPluginContext: () => contextSnapshot[pluginName] || {},
+                    log: this.logFromPlugin.bind(this),
+                    options: this.parsePluginOptions(plugin, pluginBlock.options)
+                });
+            }
+        });
+
         const onTransformEndCallbacks = [];
         const queue = this.pluginBlocks.reduce((queue, pluginBlock, index) => {
             // If the plugin hasn't been bootstrapped, we don't want to run its

lib/sourcebit.test.js

@@ -896,12 +896,14 @@ describe('`transform()`', () => {
         expect(callbackData).not.toBeDefined();
     });
 
-    test('calls the `onTransformEndFn` callback of each plugin, if defined, when `transform` has finished running', async () => {
+    test('calls the `onTransformStart` and `onTransformEnd` callbacks of each plugin, if defined, when `transform` has finished running', async () => {
+        const onTransformStartFn = jest.fn();
         const onTransformEndFn = jest.fn();
         const plugins = [
             {
                 module: {
                     name: 'sourcebit-test1',
+                    onTransformStart: onTransformStartFn,
                     onTransformEnd: onTransformEndFn,
                     transform: async ({ data }) => {
                         return {
@@ -942,6 +944,7 @@ describe('`transform()`', () => {
             {
                 module: {
                     name: 'sourcebit-test4',
+                    onTransformStart: onTransformStartFn,
                     onTransformEnd: onTransformEndFn
                 }
             }
@@ -956,8 +959,16 @@ describe('`transform()`', () => {
 
         const data = await sourcebit.transform();
 
+        expect(onTransformStartFn).toHaveBeenCalledTimes(2);
         expect(onTransformEndFn).toHaveBeenCalledTimes(4);
 
+        onTransformStartFn.mock.calls.forEach(call => {
+            expect(call[0].debug).toBeInstanceOf(Function);
+            expect(call[0].getPluginContext).toBeInstanceOf(Function);
+            expect(call[0].log).toBeInstanceOf(Function);
+            expect(call[0].options).toEqual({});
+        });
+
         onTransformEndFn.mock.calls.forEach(call => {
             expect(call[0].debug).toBeInstanceOf(Function);
             expect(call[0].getPluginContext).toBeInstanceOf(Function);