flow like the river

BACK_BACK/node_modules/parcel-bundler/lib/visitors/globals.js

@@ -0,0 +1,56 @@
+"use strict";
+
+const Path = require('path');
+
+const types = require('@babel/types');
+
+const VARS = {
+  process: asset => {
+    asset.addDependency('process');
+    return 'var process = require("process");';
+  },
+  global: asset => `var global = arguments[${asset.options.scopeHoist ? 0 : 3}];`,
+  __dirname: asset => `var __dirname = ${JSON.stringify(Path.dirname(asset.name))};`,
+  __filename: asset => `var __filename = ${JSON.stringify(asset.name)};`,
+  Buffer: asset => {
+    asset.addDependency('buffer');
+    return 'var Buffer = require("buffer").Buffer;';
+  },
+  // Prevent AMD defines from working when loading UMD bundles.
+  // Ideally the CommonJS check would come before the AMD check, but many
+  // existing modules do the checks the opposite way leading to modules
+  // not exporting anything to Parcel.
+  define: () => 'var define;'
+};
+module.exports = {
+  Identifier(node, asset, ancestors) {
+    let parent = ancestors[ancestors.length - 2];
+
+    if (VARS.hasOwnProperty(node.name) && !asset.globals.has(node.name) && types.isReferenced(node, parent)) {
+      asset.globals.set(node.name, VARS[node.name](asset));
+    }
+  },
+
+  Declaration(node, asset, ancestors) {
+    // If there is a global declaration of one of the variables, remove our declaration
+    let identifiers = types.getBindingIdentifiers(node);
+
+    for (let id in identifiers) {
+      if (VARS.hasOwnProperty(id) && !inScope(ancestors)) {
+        // Don't delete entirely, so we don't add it again when the declaration is referenced
+        asset.globals.set(id, '');
+      }
+    }
+  }
+
+};
+
+function inScope(ancestors) {
+  for (let i = ancestors.length - 2; i >= 0; i--) {
+    if (types.isScope(ancestors[i]) && !types.isProgram(ancestors[i])) {
+      return true;
+    }
+  }
+
+  return false;
+}