Updated the files.

my-app/node_modules/acorn-import-assertions/README.md

@@ -0,0 +1,15 @@
+# Support for import assertions in acorn
+
+## Usage
+
+This module provides a plugin that can be used to extend the Acorn Parser class:
+
+```js
+const {Parser} = require('acorn');
+const {importAssertions} = require('acorn-import-assertions');
+Parser.extend(importAssertions).parse('...');
+```
+
+## License
+
+This plugin is released under an MIT License.

my-app/node_modules/acorn-import-assertions/lib/index.js

@@ -0,0 +1,235 @@
+"use strict";
+
+Object.defineProperty(exports, "__esModule", {
+  value: true
+});
+exports.importAssertions = importAssertions;
+var _acorn = _interopRequireWildcard(require("acorn"));
+function _getRequireWildcardCache(nodeInterop) { if (typeof WeakMap !== "function") return null; var cacheBabelInterop = new WeakMap(); var cacheNodeInterop = new WeakMap(); return (_getRequireWildcardCache = function (nodeInterop) { return nodeInterop ? cacheNodeInterop : cacheBabelInterop; })(nodeInterop); }
+function _interopRequireWildcard(obj, nodeInterop) { if (!nodeInterop && obj && obj.__esModule) { return obj; } if (obj === null || typeof obj !== "object" && typeof obj !== "function") { return { default: obj }; } var cache = _getRequireWildcardCache(nodeInterop); if (cache && cache.has(obj)) { return cache.get(obj); } var newObj = {}; var hasPropertyDescriptor = Object.defineProperty && Object.getOwnPropertyDescriptor; for (var key in obj) { if (key !== "default" && Object.prototype.hasOwnProperty.call(obj, key)) { var desc = hasPropertyDescriptor ? Object.getOwnPropertyDescriptor(obj, key) : null; if (desc && (desc.get || desc.set)) { Object.defineProperty(newObj, key, desc); } else { newObj[key] = obj[key]; } } } newObj.default = obj; if (cache) { cache.set(obj, newObj); } return newObj; }
+const leftCurlyBrace = "{".charCodeAt(0);
+const space = " ".charCodeAt(0);
+const keyword = "assert";
+const FUNC_STATEMENT = 1,
+  FUNC_HANGING_STATEMENT = 2,
+  FUNC_NULLABLE_ID = 4;
+function importAssertions(Parser) {
+  // Use supplied version acorn version if present, to avoid
+  // reference mismatches due to different acorn versions. This
+  // allows this plugin to be used with Rollup which supplies
+  // its own internal version of acorn and thereby sidesteps
+  // the package manager.
+  const acorn = Parser.acorn || _acorn;
+  const {
+    tokTypes: tt,
+    TokenType
+  } = acorn;
+  return class extends Parser {
+    constructor(...args) {
+      super(...args);
+      this.assertToken = new TokenType(keyword);
+    }
+    _codeAt(i) {
+      return this.input.charCodeAt(i);
+    }
+    _eat(t) {
+      if (this.type !== t) {
+        this.unexpected();
+      }
+      this.next();
+    }
+    readToken(code) {
+      let i = 0;
+      for (; i < keyword.length; i++) {
+        if (this._codeAt(this.pos + i) !== keyword.charCodeAt(i)) {
+          return super.readToken(code);
+        }
+      }
+
+      // ensure that the keyword is at the correct location
+      // ie `assert{...` or `assert {...`
+      for (;; i++) {
+        if (this._codeAt(this.pos + i) === leftCurlyBrace) {
+          // Found '{'
+          break;
+        } else if (this._codeAt(this.pos + i) === space) {
+          // white space is allowed between `assert` and `{`, so continue.
+          continue;
+        } else {
+          return super.readToken(code);
+        }
+      }
+
+      // If we're inside a dynamic import expression we'll parse
+      // the `assert` keyword as a standard object property name
+      // ie `import(""./foo.json", { assert: { type: "json" } })`
+      if (this.type.label === "{") {
+        return super.readToken(code);
+      }
+      this.pos += keyword.length;
+      return this.finishToken(this.assertToken);
+    }
+    parseDynamicImport(node) {
+      this.next(); // skip `(`
+
+      // Parse node.source.
+      node.source = this.parseMaybeAssign();
+      if (this.eat(tt.comma)) {
+        const obj = this.parseObj(false);
+        node.arguments = [obj];
+      }
+      this._eat(tt.parenR);
+      return this.finishNode(node, "ImportExpression");
+    }
+
+    // ported from acorn/src/statement.js pp.parseExport
+    parseExport(node, exports) {
+      this.next();
+      // export * from '...'
+      if (this.eat(tt.star)) {
+        if (this.options.ecmaVersion >= 11) {
+          if (this.eatContextual("as")) {
+            node.exported = this.parseIdent(true);
+            this.checkExport(exports, node.exported.name, this.lastTokStart);
+          } else {
+            node.exported = null;
+          }
+        }
+        this.expectContextual("from");
+        if (this.type !== tt.string) {
+          this.unexpected();
+        }
+        node.source = this.parseExprAtom();
+        if (this.type === this.assertToken || this.type === tt._with) {
+          this.next();
+          const assertions = this.parseImportAssertions();
+          if (assertions) {
+            node.assertions = assertions;
+          }
+        }
+        this.semicolon();
+        return this.finishNode(node, "ExportAllDeclaration");
+      }
+      if (this.eat(tt._default)) {
+        // export default ...
+        this.checkExport(exports, "default", this.lastTokStart);
+        var isAsync;
+        if (this.type === tt._function || (isAsync = this.isAsyncFunction())) {
+          var fNode = this.startNode();
+          this.next();
+          if (isAsync) {
+            this.next();
+          }
+          node.declaration = this.parseFunction(fNode, FUNC_STATEMENT | FUNC_NULLABLE_ID, false, isAsync);
+        } else if (this.type === tt._class) {
+          var cNode = this.startNode();
+          node.declaration = this.parseClass(cNode, "nullableID");
+        } else {
+          node.declaration = this.parseMaybeAssign();
+          this.semicolon();
+        }
+        return this.finishNode(node, "ExportDefaultDeclaration");
+      }
+      // export var|const|let|function|class ...
+      if (this.shouldParseExportStatement()) {
+        node.declaration = this.parseStatement(null);
+        if (node.declaration.type === "VariableDeclaration") {
+          this.checkVariableExport(exports, node.declaration.declarations);
+        } else {
+          this.checkExport(exports, node.declaration.id.name, node.declaration.id.start);
+        }
+        node.specifiers = [];
+        node.source = null;
+      } else {
+        // export { x, y as z } [from '...']
+        node.declaration = null;
+        node.specifiers = this.parseExportSpecifiers(exports);
+        if (this.eatContextual("from")) {
+          if (this.type !== tt.string) {
+            this.unexpected();
+          }
+          node.source = this.parseExprAtom();
+          if (this.type === this.assertToken || this.type === tt._with) {
+            this.next();
+            const assertions = this.parseImportAssertions();
+            if (assertions) {
+              node.assertions = assertions;
+            }
+          }
+        } else {
+          for (var i = 0, list = node.specifiers; i < list.length; i += 1) {
+            // check for keywords used as local names
+            var spec = list[i];
+            this.checkUnreserved(spec.local);
+            // check if export is defined
+            this.checkLocalExport(spec.local);
+          }
+          node.source = null;
+        }
+        this.semicolon();
+      }
+      return this.finishNode(node, "ExportNamedDeclaration");
+    }
+    parseImport(node) {
+      this.next();
+      // import '...'
+      if (this.type === tt.string) {
+        node.specifiers = [];
+        node.source = this.parseExprAtom();
+      } else {
+        node.specifiers = this.parseImportSpecifiers();
+        this.expectContextual("from");
+        node.source = this.type === tt.string ? this.parseExprAtom() : this.unexpected();
+      }
+      if (this.type === this.assertToken || this.type == tt._with) {
+        this.next();
+        const assertions = this.parseImportAssertions();
+        if (assertions) {
+          node.assertions = assertions;
+        }
+      }
+      this.semicolon();
+      return this.finishNode(node, "ImportDeclaration");
+    }
+    parseImportAssertions() {
+      this._eat(tt.braceL);
+      const attrs = this.parseAssertEntries();
+      this._eat(tt.braceR);
+      return attrs;
+    }
+    parseAssertEntries() {
+      const attrs = [];
+      const attrNames = new Set();
+      do {
+        if (this.type === tt.braceR) {
+          break;
+        }
+        const node = this.startNode();
+
+        // parse AssertionKey : IdentifierName, StringLiteral
+        let assertionKeyNode;
+        if (this.type === tt.string) {
+          assertionKeyNode = this.parseLiteral(this.value);
+        } else {
+          assertionKeyNode = this.parseIdent(true);
+        }
+        this.next();
+        node.key = assertionKeyNode;
+
+        // check if we already have an entry for an attribute
+        // if a duplicate entry is found, throw an error
+        // for now this logic will come into play only when someone declares `type` twice
+        if (attrNames.has(node.key.name)) {
+          this.raise(this.pos, "Duplicated key in assertions");
+        }
+        attrNames.add(node.key.name);
+        if (this.type !== tt.string) {
+          this.raise(this.pos, "Only string is supported as an assertion value");
+        }
+        node.value = this.parseLiteral(this.value);
+        attrs.push(this.finishNode(node, "ImportAttribute"));
+      } while (this.eat(tt.comma));
+      return attrs;
+    }
+  };
+}

my-app/node_modules/acorn-import-assertions/lib/index.mjs

@@ -0,0 +1,242 @@
+import * as _acorn from "acorn";
+
+const leftCurlyBrace = "{".charCodeAt(0);
+const space = " ".charCodeAt(0);
+
+const keyword = "assert";
+const FUNC_STATEMENT = 1, FUNC_HANGING_STATEMENT = 2, FUNC_NULLABLE_ID = 4
+
+export function importAssertions(Parser) {
+  // Use supplied version acorn version if present, to avoid
+  // reference mismatches due to different acorn versions. This
+  // allows this plugin to be used with Rollup which supplies
+  // its own internal version of acorn and thereby sidesteps
+  // the package manager.
+  const acorn = Parser.acorn || _acorn;
+  const { tokTypes: tt, TokenType } = acorn;
+
+  return class extends Parser {
+    constructor(...args) {
+      super(...args);
+      this.assertToken = new TokenType(keyword);
+    }
+
+    _codeAt(i) {
+      return this.input.charCodeAt(i);
+    }
+
+    _eat(t) {
+      if (this.type !== t) {
+        this.unexpected();
+      }
+      this.next();
+    }
+
+    readToken(code) {
+      let i = 0;
+      for (; i < keyword.length; i++) {
+        if (this._codeAt(this.pos + i) !== keyword.charCodeAt(i)) {
+          return super.readToken(code);
+        }
+      }
+
+      // ensure that the keyword is at the correct location
+      // ie `assert{...` or `assert {...`
+      for (;; i++) {
+        if (this._codeAt(this.pos + i) === leftCurlyBrace) {
+          // Found '{'
+          break;
+        } else if (this._codeAt(this.pos + i) === space) {
+          // white space is allowed between `assert` and `{`, so continue.
+          continue;
+        } else {
+          return super.readToken(code);
+        }
+      }
+
+      // If we're inside a dynamic import expression we'll parse
+      // the `assert` keyword as a standard object property name
+      // ie `import(""./foo.json", { assert: { type: "json" } })`
+      if (this.type.label === "{") {
+        return super.readToken(code);
+      }
+
+      this.pos += keyword.length;
+      return this.finishToken(this.assertToken);
+    }
+
+    parseDynamicImport(node) {
+      this.next(); // skip `(`
+
+      // Parse node.source.
+      node.source = this.parseMaybeAssign();
+
+      if (this.eat(tt.comma)) {
+        const obj = this.parseObj(false);
+        node.arguments = [obj];
+      }
+      this._eat(tt.parenR);
+      return this.finishNode(node, "ImportExpression");
+    }
+
+    // ported from acorn/src/statement.js pp.parseExport
+    parseExport(node, exports) {
+      this.next();
+      // export * from '...'
+      if (this.eat(tt.star)) {
+        if (this.options.ecmaVersion >= 11) {
+          if (this.eatContextual("as")) {
+            node.exported = this.parseIdent(true);
+            this.checkExport(exports, node.exported.name, this.lastTokStart);
+          } else {
+            node.exported = null;
+          }
+        }
+        this.expectContextual("from");
+        if (this.type !== tt.string) { this.unexpected(); }
+        node.source = this.parseExprAtom();
+
+        if (this.type === this.assertToken || this.type === tt._with) {
+          this.next();
+          const assertions = this.parseImportAssertions();
+          if (assertions) {
+            node.assertions = assertions;
+          }
+        }
+
+        this.semicolon();
+        return this.finishNode(node, "ExportAllDeclaration")
+      }
+      if (this.eat(tt._default)) { // export default ...
+        this.checkExport(exports, "default", this.lastTokStart);
+        var isAsync;
+        if (this.type === tt._function || (isAsync = this.isAsyncFunction())) {
+          var fNode = this.startNode();
+          this.next();
+          if (isAsync) { this.next(); }
+          node.declaration = this.parseFunction(fNode, FUNC_STATEMENT | FUNC_NULLABLE_ID, false, isAsync);
+        } else if (this.type === tt._class) {
+          var cNode = this.startNode();
+          node.declaration = this.parseClass(cNode, "nullableID");
+        } else {
+          node.declaration = this.parseMaybeAssign();
+          this.semicolon();
+        }
+        return this.finishNode(node, "ExportDefaultDeclaration")
+      }
+      // export var|const|let|function|class ...
+      if (this.shouldParseExportStatement()) {
+        node.declaration = this.parseStatement(null);
+        if (node.declaration.type === "VariableDeclaration")
+          { this.checkVariableExport(exports, node.declaration.declarations); }
+        else
+          { this.checkExport(exports, node.declaration.id.name, node.declaration.id.start); }
+        node.specifiers = [];
+        node.source = null;
+      } else { // export { x, y as z } [from '...']
+        node.declaration = null;
+        node.specifiers = this.parseExportSpecifiers(exports);
+        if (this.eatContextual("from")) {
+          if (this.type !== tt.string) { this.unexpected(); }
+          node.source = this.parseExprAtom();
+
+          if (this.type === this.assertToken || this.type === tt._with) {
+            this.next();
+            const assertions = this.parseImportAssertions();
+            if (assertions) {
+              node.assertions = assertions;
+            }
+          }
+        } else {
+          for (var i = 0, list = node.specifiers; i < list.length; i += 1) {
+            // check for keywords used as local names
+            var spec = list[i];
+
+            this.checkUnreserved(spec.local);
+            // check if export is defined
+            this.checkLocalExport(spec.local);
+          }
+
+          node.source = null;
+        }
+        this.semicolon();
+      }
+      return this.finishNode(node, "ExportNamedDeclaration")
+    }
+
+    parseImport(node) {
+      this.next();
+      // import '...'
+      if (this.type === tt.string) {
+        node.specifiers = [];
+        node.source = this.parseExprAtom();
+      } else {
+        node.specifiers = this.parseImportSpecifiers();
+        this.expectContextual("from");
+        node.source =
+          this.type === tt.string ? this.parseExprAtom() : this.unexpected();
+      }
+
+      if (this.type === this.assertToken || this.type == tt._with) {
+        this.next();
+        const assertions = this.parseImportAssertions();
+        if (assertions) {
+          node.assertions = assertions;
+        }
+      }
+      this.semicolon();
+      return this.finishNode(node, "ImportDeclaration");
+    }
+
+    parseImportAssertions() {
+      this._eat(tt.braceL);
+      const attrs = this.parseAssertEntries();
+      this._eat(tt.braceR);
+      return attrs;
+    }
+
+    parseAssertEntries() {
+      const attrs = [];
+      const attrNames = new Set();
+
+      do {
+        if (this.type === tt.braceR) {
+          break;
+        }
+
+        const node = this.startNode();
+
+        // parse AssertionKey : IdentifierName, StringLiteral
+        let assertionKeyNode;
+        if (this.type === tt.string) {
+          assertionKeyNode = this.parseLiteral(this.value);
+        } else {
+          assertionKeyNode = this.parseIdent(true);
+        }
+        this.next();
+        node.key = assertionKeyNode;
+
+        // check if we already have an entry for an attribute
+        // if a duplicate entry is found, throw an error
+        // for now this logic will come into play only when someone declares `type` twice
+        if (attrNames.has(node.key.name)) {
+          this.raise(this.pos, "Duplicated key in assertions");
+        }
+        attrNames.add(node.key.name);
+
+        if (this.type !== tt.string) {
+          this.raise(
+            this.pos,
+            "Only string is supported as an assertion value"
+          );
+        }
+
+        node.value = this.parseLiteral(this.value);
+
+        attrs.push(this.finishNode(node, "ImportAttribute"));
+      } while (this.eat(tt.comma));
+
+      return attrs;
+    }
+  };
+}

my-app/node_modules/acorn-import-assertions/package.json

@@ -0,0 +1,49 @@
+{
+  "name": "acorn-import-assertions",
+  "version": "1.9.0",
+  "description": "Support for import assertions in acorn",
+  "main": "lib/index.js",
+  "module": "src/index.js",
+  "exports": {
+    ".": {
+      "import": "./lib/index.mjs",
+      "require": "./lib/index.js"
+    },
+    "./package.json": "./package.json",
+    "./": "./"
+  },
+  "scripts": {
+    "build": "babel ./src --out-dir ./lib && node post-build.js",
+    "prepublishOnly": "npm run build",
+    "test": "mocha ./test/index.js",
+    "test:test262": "node run_test262.js",
+    "watch": "babel ./src --out-dir ./lib --watch"
+  },
+  "author": "Sven Sauleau <sven@sauleau.com>",
+  "license": "MIT",
+  "devDependencies": {
+    "@babel/cli": "^7.14.8",
+    "@babel/core": "^7.15.0",
+    "@babel/preset-env": "^7.15.0",
+    "@babel/register": "^7.15.3",
+    "acorn": "^8.4.1",
+    "chai": "^4.3.4",
+    "mocha": "^9.1.0",
+    "test262": "tc39/test262#47ab262658cd97ae35c9a537808cac18fa4ab567",
+    "test262-parser-runner": "^0.5.0"
+  },
+  "peerDependencies": {
+    "acorn": "^8"
+  },
+  "repository": {
+    "type": "git",
+    "url": "https://github.com/xtuc/acorn-import-assertions"
+  },
+  "browserslist": [
+    "maintained node versions"
+  ],
+  "files": [
+    "lib",
+    "src"
+  ]
+}

my-app/node_modules/acorn-import-assertions/src/index.js

@@ -0,0 +1,242 @@
+import * as _acorn from "acorn";
+
+const leftCurlyBrace = "{".charCodeAt(0);
+const space = " ".charCodeAt(0);
+
+const keyword = "assert";
+const FUNC_STATEMENT = 1, FUNC_HANGING_STATEMENT = 2, FUNC_NULLABLE_ID = 4
+
+export function importAssertions(Parser) {
+  // Use supplied version acorn version if present, to avoid
+  // reference mismatches due to different acorn versions. This
+  // allows this plugin to be used with Rollup which supplies
+  // its own internal version of acorn and thereby sidesteps
+  // the package manager.
+  const acorn = Parser.acorn || _acorn;
+  const { tokTypes: tt, TokenType } = acorn;
+
+  return class extends Parser {
+    constructor(...args) {
+      super(...args);
+      this.assertToken = new TokenType(keyword);
+    }
+
+    _codeAt(i) {
+      return this.input.charCodeAt(i);
+    }
+
+    _eat(t) {
+      if (this.type !== t) {
+        this.unexpected();
+      }
+      this.next();
+    }
+
+    readToken(code) {
+      let i = 0;
+      for (; i < keyword.length; i++) {
+        if (this._codeAt(this.pos + i) !== keyword.charCodeAt(i)) {
+          return super.readToken(code);
+        }
+      }
+
+      // ensure that the keyword is at the correct location
+      // ie `assert{...` or `assert {...`
+      for (;; i++) {
+        if (this._codeAt(this.pos + i) === leftCurlyBrace) {
+          // Found '{'
+          break;
+        } else if (this._codeAt(this.pos + i) === space) {
+          // white space is allowed between `assert` and `{`, so continue.
+          continue;
+        } else {
+          return super.readToken(code);
+        }
+      }
+
+      // If we're inside a dynamic import expression we'll parse
+      // the `assert` keyword as a standard object property name
+      // ie `import(""./foo.json", { assert: { type: "json" } })`
+      if (this.type.label === "{") {
+        return super.readToken(code);
+      }
+
+      this.pos += keyword.length;
+      return this.finishToken(this.assertToken);
+    }
+
+    parseDynamicImport(node) {
+      this.next(); // skip `(`
+
+      // Parse node.source.
+      node.source = this.parseMaybeAssign();
+
+      if (this.eat(tt.comma)) {
+        const obj = this.parseObj(false);
+        node.arguments = [obj];
+      }
+      this._eat(tt.parenR);
+      return this.finishNode(node, "ImportExpression");
+    }
+
+    // ported from acorn/src/statement.js pp.parseExport
+    parseExport(node, exports) {
+      this.next();
+      // export * from '...'
+      if (this.eat(tt.star)) {
+        if (this.options.ecmaVersion >= 11) {
+          if (this.eatContextual("as")) {
+            node.exported = this.parseIdent(true);
+            this.checkExport(exports, node.exported.name, this.lastTokStart);
+          } else {
+            node.exported = null;
+          }
+        }
+        this.expectContextual("from");
+        if (this.type !== tt.string) { this.unexpected(); }
+        node.source = this.parseExprAtom();
+
+        if (this.type === this.assertToken || this.type === tt._with) {
+          this.next();
+          const assertions = this.parseImportAssertions();
+          if (assertions) {
+            node.assertions = assertions;
+          }
+        }
+
+        this.semicolon();
+        return this.finishNode(node, "ExportAllDeclaration")
+      }
+      if (this.eat(tt._default)) { // export default ...
+        this.checkExport(exports, "default", this.lastTokStart);
+        var isAsync;
+        if (this.type === tt._function || (isAsync = this.isAsyncFunction())) {
+          var fNode = this.startNode();
+          this.next();
+          if (isAsync) { this.next(); }
+          node.declaration = this.parseFunction(fNode, FUNC_STATEMENT | FUNC_NULLABLE_ID, false, isAsync);
+        } else if (this.type === tt._class) {
+          var cNode = this.startNode();
+          node.declaration = this.parseClass(cNode, "nullableID");
+        } else {
+          node.declaration = this.parseMaybeAssign();
+          this.semicolon();
+        }
+        return this.finishNode(node, "ExportDefaultDeclaration")
+      }
+      // export var|const|let|function|class ...
+      if (this.shouldParseExportStatement()) {
+        node.declaration = this.parseStatement(null);
+        if (node.declaration.type === "VariableDeclaration")
+          { this.checkVariableExport(exports, node.declaration.declarations); }
+        else
+          { this.checkExport(exports, node.declaration.id.name, node.declaration.id.start); }
+        node.specifiers = [];
+        node.source = null;
+      } else { // export { x, y as z } [from '...']
+        node.declaration = null;
+        node.specifiers = this.parseExportSpecifiers(exports);
+        if (this.eatContextual("from")) {
+          if (this.type !== tt.string) { this.unexpected(); }
+          node.source = this.parseExprAtom();
+
+          if (this.type === this.assertToken || this.type === tt._with) {
+            this.next();
+            const assertions = this.parseImportAssertions();
+            if (assertions) {
+              node.assertions = assertions;
+            }
+          }
+        } else {
+          for (var i = 0, list = node.specifiers; i < list.length; i += 1) {
+            // check for keywords used as local names
+            var spec = list[i];
+
+            this.checkUnreserved(spec.local);
+            // check if export is defined
+            this.checkLocalExport(spec.local);
+          }
+
+          node.source = null;
+        }
+        this.semicolon();
+      }
+      return this.finishNode(node, "ExportNamedDeclaration")
+    }
+
+    parseImport(node) {
+      this.next();
+      // import '...'
+      if (this.type === tt.string) {
+        node.specifiers = [];
+        node.source = this.parseExprAtom();
+      } else {
+        node.specifiers = this.parseImportSpecifiers();
+        this.expectContextual("from");
+        node.source =
+          this.type === tt.string ? this.parseExprAtom() : this.unexpected();
+      }
+
+      if (this.type === this.assertToken || this.type == tt._with) {
+        this.next();
+        const assertions = this.parseImportAssertions();
+        if (assertions) {
+          node.assertions = assertions;
+        }
+      }
+      this.semicolon();
+      return this.finishNode(node, "ImportDeclaration");
+    }
+
+    parseImportAssertions() {
+      this._eat(tt.braceL);
+      const attrs = this.parseAssertEntries();
+      this._eat(tt.braceR);
+      return attrs;
+    }
+
+    parseAssertEntries() {
+      const attrs = [];
+      const attrNames = new Set();
+
+      do {
+        if (this.type === tt.braceR) {
+          break;
+        }
+
+        const node = this.startNode();
+
+        // parse AssertionKey : IdentifierName, StringLiteral
+        let assertionKeyNode;
+        if (this.type === tt.string) {
+          assertionKeyNode = this.parseLiteral(this.value);
+        } else {
+          assertionKeyNode = this.parseIdent(true);
+        }
+        this.next();
+        node.key = assertionKeyNode;
+
+        // check if we already have an entry for an attribute
+        // if a duplicate entry is found, throw an error
+        // for now this logic will come into play only when someone declares `type` twice
+        if (attrNames.has(node.key.name)) {
+          this.raise(this.pos, "Duplicated key in assertions");
+        }
+        attrNames.add(node.key.name);
+
+        if (this.type !== tt.string) {
+          this.raise(
+            this.pos,
+            "Only string is supported as an assertion value"
+          );
+        }
+
+        node.value = this.parseLiteral(this.value);
+
+        attrs.push(this.finishNode(node, "ImportAttribute"));
+      } while (this.eat(tt.comma));
+
+      return attrs;
+    }
+  };
+}