fix: resolve error when webpack output.futureEmitAssets is enabled (#314

)

Webpack 4.29.0 introduced this option, which when enabled, breaks this
plugin. The fix is to read the file contents from disk after emit
instead of depending on the sources being available in the compilation.

closes #61

src/RollbarSourceMapPlugin.js

@@ -1,3 +1,5 @@
+import { promises as fs } from 'fs';
+import { join } from 'path';
 import fetch from 'node-fetch';
 import FormData from 'form-data';
 import isString from 'lodash.isstring';
@@ -49,6 +51,19 @@ class RollbarSourceMapPlugin {
     compiler.hooks.afterEmit.tapPromise(PLUGIN_NAME, this.afterEmit.bind(this));
   }
 
+  // eslint-disable-next-line class-methods-use-this
+  getAssetPath(compilation, name) {
+    return join(
+      compilation.getPath(compilation.compiler.outputPath),
+      name.split('?')[0]
+    );
+  }
+
+  getSource(compilation, name) {
+    const path = this.getAssetPath(compilation, name);
+    return fs.readFile(path, { encoding: 'utf-8' });
+  }
+
   getAssets(compilation) {
     const { includeChunks, encodeFilename } = this;
     const { chunks } = compilation.getStats().toJson();
@@ -86,12 +101,19 @@ class RollbarSourceMapPlugin {
 
   async uploadSourceMap(compilation, { sourceFile, sourceMap }) {
     const errMessage = `failed to upload ${sourceMap} to Rollbar`;
-    const form = new FormData();
+    let sourceMapSource;
 
+    try {
+      sourceMapSource = await this.getSource(compilation, sourceMap);
+    } catch (err) {
+      throw new VError(err, errMessage);
+    }
+
+    const form = new FormData();
     form.append('access_token', this.accessToken);
     form.append('version', this.version);
     form.append('minified_url', this.getPublicPath(sourceFile));
-    form.append('source_map', compilation.assets[sourceMap].source(), {
+    form.append('source_map', sourceMapSource, {
       filename: sourceMap,
       contentType: 'application/json'
     });

test/RollbarSourceMapPlugin.test.js

@@ -1,3 +1,4 @@
+import { promises as fs } from 'fs';
 import nock from 'nock';
 import RollbarSourceMapPlugin from '../src/RollbarSourceMapPlugin';
 import { PLUGIN_NAME, ROLLBAR_ENDPOINT } from '../src/constants';
@@ -409,23 +410,33 @@ describe('RollbarSourceMapPlugin', () => {
   });
 
   describe('uploadSourceMap', () => {
+    const outputPath = '/some/fake/path/';
     let info;
     let compilation;
     let chunk;
+    let spyReadFile;
 
     beforeEach(() => {
       compilation = {
         assets: {
           'vendor.5190.js.map': { source: () => '{"version":3,"sources":[]' },
           'app.81c1.js.map': { source: () => '{"version":3,"sources":[]' }
         },
-        errors: []
+        compiler: {
+          outputPath
+        },
+        errors: [],
+        getPath: () => outputPath
       };
 
       chunk = {
         sourceFile: 'vendor.5190.js',
         sourceMap: 'vendor.5190.js.map'
       };
+
+      spyReadFile = jest
+        .spyOn(fs, 'readFile')
+        .mockImplementation(() => Promise.resolve('data'));
     });
 
     it('logs to console if upload is success', async () => {
@@ -476,6 +487,14 @@ describe('RollbarSourceMapPlugin', () => {
       );
     });
 
+    it('returns error message if unable to read sourceMap file', async () => {
+      const err = new Error('ENOENT: no such file or directory');
+      spyReadFile.mockImplementationOnce(() => Promise.reject(err));
+      await expect(plugin.uploadSourceMap(compilation, chunk)).rejects.toThrow(
+        `failed to upload vendor.5190.js.map to Rollbar: ${err.message}`
+      );
+    });
+
     it('returns response status text if response body does not have message', async () => {
       const scope = nock('https://api.rollbar.com:443') // eslint-disable-line no-unused-vars
         .post('/api/1/sourcemap')