CLDR-17270 st: don't use late cache busting for bundle.js

- instead, let webpack create a bundle name based on the content's hash, which will truly change when and only when the content changes.
- webpack hook to write the file
- read a manifest.json on the server side to serve that

tools/cldr-apps/js/webpack.config.js

@@ -1,6 +1,26 @@
 const path = require("path");
+const fs = require('fs');
 const { VueLoaderPlugin } = require("vue-loader");
-const { DefinePlugin } = require("webpack");
+const { DefinePlugin, Compiler } = require("webpack");
+
+class SurveyToolPlugin {
+  constructor() {
+
+  }
+  /**
+   *
+   * @param {Compiler} compiler
+   */
+  apply(compiler) {
+    compiler.hooks.afterEmit.tap('SurveyToolPlugin', (compilation) => {
+      const { assets } = compilation;
+      const jsfiles = Object.keys(assets).filter(s => /\.js$/.test(s));
+      const manifestFile = path.resolve(compiler.outputPath, 'manifest.json');
+      fs.writeFileSync(manifestFile, JSON.stringify({ jsfiles }), 'utf-8');
+      console.log('# SurveyToolPlugin Wrote: ', manifestFile);
+    });
+  }
+};
 
 module.exports = (env, argv) => {
   const {mode} = argv;
@@ -12,7 +32,7 @@ module.exports = (env, argv) => {
       cacheDirectory: path.resolve(__dirname, '../target/webpack_cache'),
     },
     output: {
-      filename: "bundle.js",
+      filename: "[name].[contenthash].js",
       path: path.resolve(__dirname, "..", "src", "main", "webapp", "dist"),
       library: "cldrBundle",
       libraryTarget: "var",
@@ -43,7 +63,9 @@ module.exports = (env, argv) => {
         // esm bundler flags,
         // see <https://github.com/vuejs/vue-next/tree/master/packages/vue#bundler-build-feature-flags>
         __VUE_PROD_DEVTOOLS__: JSON.stringify(DEV), // TODO: support dev mode
-        __VUE_OPTIONS_API__:   JSON.stringify(true),
-      })],
-    };
+        __VUE_OPTIONS_API__: JSON.stringify(true),
+      }),
+      new SurveyToolPlugin(),
+    ]
+  };
 };

tools/cldr-apps/src/main/java/org/unicode/cldr/web/SurveyTool.java

@@ -1,8 +1,13 @@
 package org.unicode.cldr.web;
 
 import java.io.IOException;
+import java.io.InputStream;
+import java.io.InputStreamReader;
 import java.io.PrintWriter;
+import java.io.Reader;
 import java.io.Writer;
+import java.nio.charset.StandardCharsets;
+import java.util.Set;
 import java.util.logging.Level;
 import java.util.logging.Logger;
 import javax.servlet.ServletConfig;
@@ -14,6 +19,9 @@
 import org.unicode.cldr.util.CLDRURLS;
 import org.unicode.cldr.util.CldrUtility;
 
+import com.google.gson.Gson;
+import com.google.gson.GsonBuilder;
+
 public class SurveyTool extends HttpServlet {
     static final Logger logger = SurveyLog.forClass(SurveyTool.class);
 
@@ -242,6 +250,12 @@ public static void includeMonitoring(Writer out) throws IOException {
         }
     }
 
+    static private final Gson gson = new GsonBuilder().setPrettyPrinting().create();
+
+    private final class STManifest {
+        public String jsfiles[];
+    }
+
     /**
      * Write the script tags for Survey Tool JavaScript files
      *
@@ -253,15 +267,23 @@ public static void includeMonitoring(Writer out) throws IOException {
     public static void includeJavaScript(HttpServletRequest request, Writer out)
             throws IOException, JSONException {
         includeMonitoring(out);
-        // Load the big bundle
-        out.write(
-                "<script src=\"dist/bundle"
-                        + getCacheBustingExtension(request)
-                        + ".js\"></script>\n");
+
+        // use WebPack-built manifest.json to include all chunks.
+        // ideally this would all come from a static .html file built by WebPack.
+        // TODO https://unicode-org.atlassian.net/browse/CLDR-17353
+        try (final InputStream is = request.getServletContext().getResourceAsStream("dist/manifest.json");
+            final Reader r = new InputStreamReader(is, StandardCharsets.UTF_8);) {
+                for(final String f : gson.fromJson(r, STManifest.class).jsfiles) {
+                    out.write("<script src=\"" + request.getContextPath() + "/dist/" + f.toString() + "\"></script>\n");
+                }
+        }
+
         includeJqueryJavaScript(request, out);
         includeCldrJavaScript(request, out);
     }
 
+
+
     private static void includeJqueryJavaScript(HttpServletRequest request, Writer out)
             throws IOException {
         // Per https://en.wikipedia.org/wiki/JQuery#Release_history --