feat: support multi-main entry in pages config (#3595)

Author: haoqunjiang

packages/@vue/cli-service/__tests__/multiPage.spec.js

@@ -15,7 +15,7 @@ async function makeProjectMultiPage (project) {
         index: { entry: 'src/main.js' },
         foo: { entry: 'src/foo.js' },
         bar: { entry: 'src/bar.js' },
-        foobar: { entry: 'src/foobar.js' }
+        foobar: { entry: ['src/foobar.js'] }
       },
       chainWebpack: config => {
         const splitOptions = config.optimization.get('splitChunks')

packages/@vue/cli-service/lib/config/app.js

@@ -199,7 +199,8 @@ module.exports = (api, options) => {
         }
 
         // inject entry
-        webpackConfig.entry(name).add(api.resolve(entry))
+        const entries = Array.isArray(entry) ? entry : [entry]
+        webpackConfig.entry(name).merge(entries.map(e => api.resolve(e)))
 
         // resolve page index template
         const hasDedicatedTemplate = fs.existsSync(api.resolve(template))

packages/@vue/cli-service/lib/options.js

@@ -15,9 +15,14 @@ const schema = createSchema(joi => joi.object({
   pages: joi.object().pattern(
     /\w+/,
     joi.alternatives().try([
-      joi.string(),
+      joi.string().required(),
+      joi.array().items(joi.string().required()),
+
       joi.object().keys({
-        entry: joi.string().required()
+        entry: joi.alternatives().try([
+          joi.string().required(),
+          joi.array().items(joi.string().required())
+        ]).required()
       }).unknown(true)
     ])
   ),