feat(gatsby): Preserve user-provided source map settings

packages/gatsby/gatsby-node.js

@@ -7,8 +7,24 @@ const SENTRY_USER_CONFIG = ['./sentry.config.js', './sentry.config.ts'];
 exports.onCreateWebpackConfig = ({ getConfig, actions }, options) => {
   const enableClientWebpackPlugin = options.enableClientWebpackPlugin !== false;
   if (process.env.NODE_ENV === 'production' && enableClientWebpackPlugin) {
-    const deleteSourcemapsAfterUpload = options.deleteSourcemapsAfterUpload === true;
+    const prevSourceMapSetting = getConfig() && 'devtool' in getConfig() ? getConfig().devtool : undefined;
+    const shouldAutomaticallyEnableSourceMaps =
+      prevSourceMapSetting !== 'source-map' && prevSourceMapSetting !== 'hidden-source-map';
+
+    if (shouldAutomaticallyEnableSourceMaps) {
+      // eslint-disable-next-line no-console
+      console.log(
+        '[Sentry] Automatically enabling source map generation by setting `devtool: "hidden-source-map"`. Those source maps will be deleted after they were uploaded to Sentry',
+      );
+    }
+
+    // Delete source maps per default or when this is explicitly set to `true` (`deleteSourceMapsAfterUpload: true` can override the default behavior)
+    const deleteSourcemapsAfterUpload =
+      options.deleteSourcemapsAfterUpload ||
+      (options.deleteSourcemapsAfterUpload !== false && shouldAutomaticallyEnableSourceMaps);
+
     actions.setWebpackConfig({
+      devtool: shouldAutomaticallyEnableSourceMaps ? 'hidden-source-map' : prevSourceMapSetting,
       plugins: [
         sentryWebpackPlugin({
           sourcemaps: {

packages/gatsby/test/gatsby-node.test.ts

@@ -28,43 +28,134 @@ describe('onCreateWebpackConfig', () => {
       setWebpackConfig: jest.fn(),
     };
 
-    const getConfig = jest.fn();
+    const getConfig = jest.fn().mockReturnValue({ devtool: 'source-map' });
 
     onCreateWebpackConfig({ actions, getConfig }, {});
 
     expect(actions.setWebpackConfig).toHaveBeenCalledTimes(1);
-    expect(actions.setWebpackConfig).toHaveBeenLastCalledWith({ plugins: expect.any(Array) });
+    expect(actions.setWebpackConfig).toHaveBeenLastCalledWith({ devtool: 'source-map', plugins: expect.any(Array) });
   });
 
   it('does not set a webpack config if enableClientWebpackPlugin is false', () => {
     const actions = {
       setWebpackConfig: jest.fn(),
     };
 
-    const getConfig = jest.fn();
+    const getConfig = jest.fn().mockReturnValue({ devtool: 'source-map' });
 
     onCreateWebpackConfig({ actions, getConfig }, { enableClientWebpackPlugin: false });
 
     expect(actions.setWebpackConfig).toHaveBeenCalledTimes(0);
   });
 
-  it('sets sourceMapFilesToDeleteAfterUpload when provided in options', () => {
+  describe('delete source maps after upload', () => {
+    beforeEach(() => {
+      jest.clearAllMocks();
+    });
+
     const actions = {
       setWebpackConfig: jest.fn(),
     };
 
     const getConfig = jest.fn();
 
-    onCreateWebpackConfig({ actions, getConfig }, { deleteSourcemapsAfterUpload: true });
+    it('sets sourceMapFilesToDeleteAfterUpload when provided in options', () => {
+      const actions = {
+        setWebpackConfig: jest.fn(),
+      };
 
-    expect(actions.setWebpackConfig).toHaveBeenCalledTimes(1);
+      const getConfig = jest.fn().mockReturnValue({ devtool: 'source-map' });
 
-    expect(sentryWebpackPlugin).toHaveBeenCalledWith(
-      expect.objectContaining({
-        sourcemaps: expect.objectContaining({
-          filesToDeleteAfterUpload: ['./public/**/*.map'],
+      onCreateWebpackConfig({ actions, getConfig }, { deleteSourcemapsAfterUpload: true });
+
+      expect(actions.setWebpackConfig).toHaveBeenCalledTimes(1);
+
+      expect(sentryWebpackPlugin).toHaveBeenCalledWith(
+        expect.objectContaining({
+          sourcemaps: expect.objectContaining({
+            filesToDeleteAfterUpload: ['./public/**/*.map'],
+          }),
+        }),
+      );
+    });
+
+    test.each([
+      {
+        name: 'without provided options: sets hidden source maps and deletes source maps',
+        initialConfig: undefined,
+        options: {},
+        expected: {
+          devtool: 'hidden-source-map',
+          deleteSourceMaps: true,
+        },
+      },
+      {
+        name: "preserves enabled source-map and doesn't delete",
+        initialConfig: { devtool: 'source-map' },
+        options: {},
+        expected: {
+          devtool: 'source-map',
+          deleteSourceMaps: false,
+        },
+      },
+      {
+        name: "preserves enabled hidden-source-map and doesn't delete",
+        initialConfig: { devtool: 'hidden-source-map' },
+        options: {},
+        expected: {
+          devtool: 'hidden-source-map',
+          deleteSourceMaps: false,
+        },
+      },
+      {
+        name: 'deletes source maps, when user explicitly sets it',
+        initialConfig: { devtool: 'eval' },
+        options: {},
+        expected: {
+          devtool: 'hidden-source-map',
+          deleteSourceMaps: true,
+        },
+      },
+      {
+        name: 'explicit deleteSourcemapsAfterUpload true',
+        initialConfig: { devtool: 'source-map' },
+        options: { deleteSourcemapsAfterUpload: true },
+        expected: {
+          devtool: 'source-map',
+          deleteSourceMaps: true,
+        },
+      },
+      {
+        name: 'explicit deleteSourcemapsAfterUpload false',
+        initialConfig: { devtool: 'hidden-source-map' },
+        options: { deleteSourcemapsAfterUpload: false },
+        expected: {
+          devtool: 'hidden-source-map',
+          deleteSourceMaps: false,
+        },
+      },
+    ])('$name', ({ initialConfig, options, expected }) => {
+      getConfig.mockReturnValue(initialConfig);
+
+      onCreateWebpackConfig({ actions: actions, getConfig: getConfig }, options);
+
+      expect(actions.setWebpackConfig).toHaveBeenCalledTimes(1);
+
+      expect(actions.setWebpackConfig).toHaveBeenCalledWith(
+        expect.objectContaining({
+          devtool: expected.devtool,
+          plugins: expect.arrayContaining([expect.any(Object)]),
+        }),
+      );
+
+      expect(sentryWebpackPlugin).toHaveBeenCalledWith(
+        expect.objectContaining({
+          sourcemaps: expect.objectContaining({
+            assets: ['./public/**'],
+            filesToDeleteAfterUpload: expected.deleteSourceMaps ? ['./public/**/*.map'] : undefined,
+          }),
         }),
-      }),
-    );
+      );
+    });
   });
 });