Add server config, move plugin file

server/plugins/unpkgRewrite.js

@@ -0,0 +1,48 @@
+const URL = require("whatwg-url");
+const warning = require("warning");
+
+const config = require("../config");
+
+const bareIdentifierFormat = /^((?:@[^\/]+\/)?[^\/]+)(\/.*)?$/;
+
+function unpkgRewrite(dependencies = {}) {
+  return {
+    inherits: require("babel-plugin-syntax-export-extensions"),
+
+    visitor: {
+      "ImportDeclaration|ExportNamedDeclaration|ExportAllDeclaration"(path) {
+        if (!path.node.source) return; // probably a variable declaration
+
+        if (
+          URL.parseURL(path.node.source.value) != null ||
+          path.node.source.value.substr(0, 2) === "//"
+        )
+          return; // valid URL or URL w/o protocol, leave it alone
+
+        if ([".", "/"].indexOf(path.node.source.value.charAt(0)) >= 0) {
+          // local path
+          path.node.source.value = `${path.node.source.value}?module`;
+        } else {
+          // "bare" identifier
+          const match = bareIdentifierFormat.exec(path.node.source.value);
+          const packageName = match[1];
+          const file = match[2] || "";
+
+          warning(
+            dependencies[packageName],
+            'Missing version info for package "%s" in dependencies; falling back to "latest"',
+            packageName
+          );
+
+          const version = dependencies[packageName] || "latest";
+
+          path.node.source.value = `${
+            config.origin
+          }/${packageName}@${version}${file}?module`;
+        }
+      }
+    }
+  };
+}
+
+module.exports = unpkgRewrite;