Fix all of our tests to be ESM compatible.

[samouri]

summary
As discovered by @jridgewell and esbuild, our tests are all using import/export and yet some of them still do things that are technically illegal. They modify the namespaced import. For the full list see #33443 (comment).

Once all incorrect usages of esm are fixed, we can turn off module transpilation from our pre-esbuild babel transformation for out tests.

cc @jridgewell / @rsimha.

PS: @jridgewell: can you share the rule that let you discover the list of breakages?

[jridgewell]

// build-system/eslint-rules/no-ambiguous-namespace-import.js

/**
 * Copyright 2018 The AMP HTML Authors. All Rights Reserved.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS-IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
'use strict';

module.exports = function (context) {
  const namespaces = new Set();
  return {
    Program(node) {
      const imports = node.body.filter((n) => n.type === 'ImportDeclaration');
      imports.forEach((node) => {
        const specifiers = node.specifiers.filter(
          (n) => n.type === 'ImportNamespaceSpecifier'
        );
        specifiers.forEach((s) => namespaces.add(s.local.name));
      });
    },

    'Program:exit': function () {
      namespaces.clear();
    },

    Identifier(node) {
      switch (node.parent.type) {
        case 'ImportNamespaceSpecifier':
          return;
        case 'MemberExpression':
          if (node.parent.object === node) {
            return;
          }
      }
      if (!namespaces.has(node.name)) {
        return;
      }
      context.report({
        node,
        message: `Ambiguous use of a namespace import. All uses must be \`${node.name}.foo\` property accesses`,
      });
    },
  };
};

This is a little too overzealous, but would prevent every bad use.

[jridgewell]

There's also a slightly less zealous https://github.com/benmosher/eslint-plugin-import/blob/HEAD/docs/rules/namespace.md, but that doesn't catch sandbox.stub(ns, 'export') indirections.

[samouri]

cc @alanorozco who was interested in using sinon to stub the Services namespace object.

[stale]

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