chore: use private fields (#8506)

.eslintrc.js

@@ -1,3 +1,12 @@
+// TODO: Enable this at some point.
+// const RESTRICTED_UNDERSCORED_IDENTIFIERS = [
+//   'PropertyDefinition > Identifier[name=/^_[a-z].*$/]',
+// ].map((selector) => ({
+//   selector,
+//   message:
+//     'Use private fields (fields prefixed with #) and an appropriate getter/setter.',
+// }));
+
 module.exports = {
   root: true,
   env: {
@@ -15,14 +24,6 @@ module.exports = {
     // Error if files are not formatted with Prettier correctly.
     'prettier/prettier': 2,
     // syntax preferences
-    quotes: [
-      2,
-      'single',
-      {
-        avoidEscape: true,
-        allowTemplateLiterals: true,
-      },
-    ],
     'spaced-comment': [
       2,
       'always',
@@ -116,6 +117,12 @@ module.exports = {
       },
     ],
     'import/extensions': ['error', 'ignorePackages'],
+
+    'no-restricted-syntax': [
+      'error',
+      // Don't allow underscored declarations on camelCased variables/properties.
+      // ...RESTRICTED_UNDERSCORED_IDENTIFIERS,
+    ],
   },
   overrides: [
     {
@@ -144,8 +151,6 @@ module.exports = {
         // We don't require explicit return types on basic functions or
         // dummy functions in tests, for example
         '@typescript-eslint/explicit-function-return-type': 0,
-        // We know it's bad and use it very sparingly but it's needed :(
-        '@typescript-eslint/ban-ts-ignore': 0,
         // We allow non-null assertions if the value was asserted using `assert` API.
         '@typescript-eslint/no-non-null-assertion': 0,
         /**
@@ -176,6 +181,18 @@ module.exports = {
         ],
         // By default this is a warning but we want it to error.
         '@typescript-eslint/explicit-module-boundary-types': 2,
+
+        'no-restricted-syntax': [
+          'error',
+          {
+            // Never use `require` in TypeScript since they are transpiled out.
+            selector: "CallExpression[callee.name='require']",
+            message: '`require` statements are not allowed. Use `import`.',
+          },
+
+          // Don't allow underscored declarations on camelCased variables/properties.
+          // ...RESTRICTED_UNDERSCORED_IDENTIFIERS,
+        ],
       },
     },
   ],