feat(styleLoader): aggregate stylesheets and dedupe if already loaded

__tests__/server/utils/__snapshots__/renderModuleStyles.spec.js.snap

@@ -1,7 +1,49 @@
 // Jest Snapshot v1, https://goo.gl/fbAQLP
 
-exports[`renderModuleStyles should handle a mix of modules with and without SSR styles 1`] = `"<style class="ssr-css">.test-module-b_class { color: red; }</style><style class="ssr-css">.test-module-d_class { color: red; }</style>"`;
+exports[`renderModuleStyles should deduplicate aggregatedStyles that have the same digest hash 1`] = `
+"
+<style id="shared_hash_deps" data-ssr="true">
+  .test-module-a_deps { color: blue; }
+</style>
+<style id="shared_hash_local" data-ssr="true">
+  .test-module-a_local { color: rebeccapurple; }
+</style>
+<style id="unique-hash_deps" data-ssr="true">
+  .test-module-c_deps { color: blue; }
+</style>
+<style id="unique-hash_local" data-ssr="true">
+  .test-module-c_local { color: rebeccapurple; }
+</style>"
+`;
+
+exports[`renderModuleStyles should handle a mix of modules with and without SSR styles 1`] = `
+"<style class="ssr-css">.test-module-b_class { color: red; }</style><style class="ssr-css">.test-module-d_class { color: red; }</style>
+<style id="test-module-e_deps" data-ssr="true">
+  .test-module-e_deps { color: blue; }
+</style>
+<style id="test-module-e_local" data-ssr="true">
+  .test-module-e_local { color: rebeccapurple; }
+</style>"
+`;
 
 exports[`renderModuleStyles should handle modules with SSR styles 1`] = `"<style class="ssr-css">.test-module_class { color: red; }</style>"`;
 
-exports[`renderModuleStyles should not send empty styles 1`] = `"<style class="ssr-css">.test-module-b_class { color: red; }</style>"`;
+exports[`renderModuleStyles should handle modules with aggregated SSR styles 1`] = `
+"
+<style id="test-module_deps" data-ssr="true">
+  .test-module_deps { color: blue; }
+</style>
+<style id="test-module_local" data-ssr="true">
+  .test-module_local { color: rebeccapurple; }
+</style>"
+`;
+
+exports[`renderModuleStyles should not send empty styles 1`] = `
+"<style class="ssr-css">.test-module-b_class { color: red; }</style>
+<style id="test-module-d_deps" data-ssr="true">
+  .test-module-d_deps { color: blue; }
+</style>
+<style id="test-module-d_local" data-ssr="true">
+  .test-module-d_local { color: rebeccapurple; }
+</style>"
+`;

__tests__/server/utils/renderModuleStyles.spec.js

@@ -17,13 +17,43 @@
 import { Map, Set as iSet, fromJS } from 'immutable';
 import renderModuleStyles from '../../../src/server/utils/renderModuleStyles';
 
+const getModuleWithMisconfiguredAggregatedStyles = (
+  moduleName,
+  includeCSS = true,
+  includeDigest = true
+) => {
+  const moduleWithMisconfiguredAggregatedStyles = () => 0;
+
+  const css = includeCSS && `.${moduleName}_deps { color: blue; }`;
+  const digest = includeDigest && `${moduleName}_hash`;
+
+  moduleWithMisconfiguredAggregatedStyles.ssrStyles = {
+    aggregatedStyles: [{ css, digest }],
+    getFullSheet: () => `.${moduleName}_class { color: red; }`,
+  };
+  return moduleWithMisconfiguredAggregatedStyles;
+};
+
+const getModuleWithAggregatedStyles = (moduleName, digest) => {
+  const moduleWithAggregatedStyles = () => 0;
+  moduleWithAggregatedStyles.ssrStyles = {
+    aggregatedStyles: [
+      { css: `.${moduleName}_deps { color: blue; }`, digest: `${digest || moduleName}_deps` },
+      { css: `.${moduleName}_local { color: rebeccapurple; }`, digest: `${digest || moduleName}_local` },
+    ],
+    getFullSheet: () => `.${moduleName}_class { color: red; }`,
+  };
+  return moduleWithAggregatedStyles;
+};
+
 const getModuleWithStyles = (moduleName) => {
   const moduleWithStyles = () => 0;
   moduleWithStyles.ssrStyles = {
     getFullSheet: () => `.${moduleName}_class { color: red; }`,
   };
   return moduleWithStyles;
 };
+
 const moduleWithoutStyles = () => 0;
 
 describe('renderModuleStyles', () => {
@@ -48,28 +78,61 @@ describe('renderModuleStyles', () => {
     expect(renderModuleStyles(store)).toMatchSnapshot();
   });
 
+  it('should handle modules with aggregated SSR styles', () => {
+    const state = fromJS({ holocron: { loaded: iSet(['test-module']) } });
+    const modules = new Map({ 'test-module': getModuleWithAggregatedStyles('test-module') });
+    const store = { getState: () => state, modules };
+    expect(renderModuleStyles(store)).toMatchSnapshot();
+  });
+
+  it('should handle modules with misconfigured aggregated SSR styles', () => {
+    const state = fromJS({ holocron: { loaded: iSet(['no-css', 'no-digest']) } });
+    const modules = new Map({
+      'no-css': getModuleWithMisconfiguredAggregatedStyles('no-css', false, true),
+      'no-digest': getModuleWithMisconfiguredAggregatedStyles('no-digest', true, false),
+    });
+    const store = { getState: () => state, modules };
+    expect(renderModuleStyles(store)).toBe('');
+  });
+
   it('should handle a mix of modules with and without SSR styles', () => {
     const state = fromJS({
       holocron: {
-        loaded: iSet(['test-module-a', 'test-module-b', 'test-module-c', 'test-module-d']),
+        loaded: iSet(['test-module-a', 'test-module-b', 'test-module-c', 'test-module-d', 'test-module-e']),
       },
     });
     const modules = new Map({
       'test-module-a': moduleWithoutStyles,
       'test-module-b': getModuleWithStyles('test-module-b'),
       'test-module-c': moduleWithoutStyles,
       'test-module-d': getModuleWithStyles('test-module-d'),
+      'test-module-e': getModuleWithAggregatedStyles('test-module-e'),
     });
     const store = { getState: () => state, modules };
     expect(renderModuleStyles(store)).toMatchSnapshot();
   });
 
-  it('should not send empty styles', () => {
+  it('should deduplicate aggregatedStyles that have the same digest hash', () => {
     const state = fromJS({
       holocron: {
         loaded: iSet(['test-module-a', 'test-module-b', 'test-module-c']),
       },
     });
+    const modules = new Map({
+      'test-module-a': getModuleWithAggregatedStyles('test-module-a', 'shared_hash'),
+      'test-module-b': getModuleWithAggregatedStyles('test-module-b', 'shared_hash'),
+      'test-module-c': getModuleWithAggregatedStyles('test-module-c', 'unique-hash'),
+    });
+    const store = { getState: () => state, modules };
+    expect(renderModuleStyles(store)).toMatchSnapshot();
+  });
+
+  it('should not send empty styles', () => {
+    const state = fromJS({
+      holocron: {
+        loaded: iSet(['test-module-a', 'test-module-b', 'test-module-c', 'test-module-d']),
+      },
+    });
     const moduleWithEmptyStyles = () => 0;
     moduleWithEmptyStyles.ssrStyles = {
       getFullSheet: () => undefined,
@@ -78,6 +141,7 @@ describe('renderModuleStyles', () => {
       'test-module-a': moduleWithoutStyles,
       'test-module-b': getModuleWithStyles('test-module-b'),
       'test-module-c': moduleWithEmptyStyles,
+      'test-module-d': getModuleWithAggregatedStyles('test-module-d'),
     });
     const store = { getState: () => state, modules };
     expect(renderModuleStyles(store)).toMatchSnapshot();

src/server/utils/renderModuleStyles.js

@@ -16,12 +16,58 @@
 
 import { getModule } from 'holocron';
 
+/**
+ * Generates a style tag with unique ID attribute per CSS file loaded.
+ * @returns {string}
+ */
+const generateStyleTag = ({ css, digest }) => `
+<style id="${digest}" data-ssr="true">
+  ${css}
+</style>`;
+
+const generateServerStyleTag = (css) => `<style class="ssr-css">${css}</style>`;
+
+const filterOutDuplicateDigests = (sheet, existingDigests) => sheet
+  .filter(({ css, digest }) => css && digest && !existingDigests.has(digest))
+  .map((styles) => {
+    existingDigests.add(styles.digest);
+    return styles;
+  });
+
 export default function renderModuleStyles(store) {
-  return store.getState().getIn(['holocron', 'loaded'], [])
+  const existingDigests = new Set();
+  const modulesWithSSRStyles = store.getState().getIn(['holocron', 'loaded'], [])
     .map((moduleName) => getModule(moduleName, store.modules))
-    .filter((module) => !!module.ssrStyles)
-    .map((module) => module.ssrStyles.getFullSheet())
+    .filter((module) => !!module.ssrStyles);
+
+  const collatedStyles = modulesWithSSRStyles
+    .reduce((acc, module) => {
+      // Backwards compatibility for older bundles.
+      if (!module.ssrStyles.aggregatedStyles) {
+        const ssrStylesFullSheet = module.ssrStyles.getFullSheet();
+        if (ssrStylesFullSheet) {
+          acc.legacy.push({ css: ssrStylesFullSheet });
+        }
+        return acc;
+      }
+
+      const { aggregatedStyles } = module.ssrStyles;
+      return {
+        ...acc,
+        aggregated: [
+          ...acc.aggregated,
+          ...filterOutDuplicateDigests(aggregatedStyles, existingDigests),
+        ],
+      };
+    }, { aggregated: [], legacy: [] });
+
+  return [...collatedStyles.legacy, ...collatedStyles.aggregated]
     .filter(Boolean)
-    .map((ssrStylesFullSheet) => `<style class="ssr-css">${ssrStylesFullSheet}</style>`)
-    .join('');
+    .reduce((acc, { css, digest }) => {
+      if (!digest) {
+        return acc + generateServerStyleTag(css);
+      }
+
+      return acc + generateStyleTag({ css, digest });
+    }, '');
 }