feat: add xml loader for elements from external namespaces (#525)

* feat: add xml loader for elements from external namespaces

* refactor: add comment about special chars

Author: sis0k0

Diff for: templates/webpack.javascript.js

@@ -151,7 +151,7 @@ module.exports = env => {
                     ].filter(loader => !!loader)
                 },
 
-                { test: /\.(html|xml)$/, use: "raw-loader" },
+                { test: /\.(html|xml)$/, use: "nativescript-dev-webpack/xml-namespace-loader"},
 
                 {
                     test: /\.css$/,

Diff for: templates/webpack.typescript.js

@@ -151,7 +151,7 @@ module.exports = env => {
                     ].filter(loader => !!loader)
                 },
 
-                { test: /\.(html|xml)$/, use: "raw-loader" },
+                { test: /\.(html|xml)$/, use: "nativescript-dev-webpack/xml-namespace-loader"},
 
                 {
                     test: /\.css$/,

Diff for: xml-namespace-loader.js

@@ -0,0 +1,34 @@
+module.exports = function(source) {
+    this.value = source;
+
+    const { XmlParser } = require("tns-core-modules/xml");
+
+    let namespaces = [];
+    const parser = new XmlParser((event) => {
+        const namespace = event.namespace;
+        if (
+            namespace &&
+            !namespace.startsWith("http") &&
+            namespaces.indexOf(namespace) === -1
+        ) {
+            namespaces.push(namespace);
+        }
+    }, undefined, true);
+    parser.parse(source);
+
+    const registerModules = namespaces
+        .map(n =>
+            `global.registerModule("${n}", function() { return require("${n}"); })`
+        )
+        .join(";");
+
+    // escape special whitespace characters
+    // see: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/JSON/stringify#Issue_with_plain_JSON.stringify_for_use_as_JavaScript
+    const json = JSON.stringify(source)
+        .replace(/\u2028/g, '\\u2028')
+        .replace(/\u2029/g, '\\u2029');
+
+    const wrapped = `${registerModules}\nmodule.exports = ${json}`;
+
+    this.callback(null, wrapped);
+}