WIP: Custom eslint rule to catch unsafe Record<string, T>

.eslintrc.js

@@ -19,11 +19,19 @@ module.exports = {
     ecmaVersion: 2018,
     sourceType: 'module',
   },
-  plugins: ['react', '@typescript-eslint', 'typescript-sort-keys', 'sort-destructure-keys', 'sort-keys-fix'],
+  plugins: [
+    'react',
+    '@typescript-eslint',
+    'typescript-sort-keys',
+    'sort-destructure-keys',
+    'sort-keys-fix',
+    'no-direct-record-string',
+  ],
   rules: {
     '@typescript-eslint/explicit-module-boundary-types': 0, // Verbose
     '@typescript-eslint/no-empty-function': 0, // unnecessary
     '@typescript-eslint/no-unused-vars': 1, // hint not error
+    'no-direct-record-string/no-direct-record-string': 'error', // type safety
     'react/jsx-sort-props': [2, { callbacksLast: true, shorthandFirst: true }], // style
     'react/no-unknown-property': [2, { ignore: ['jsx', 'global'] }], // inserted by next's styled-jsx
     'react/react-in-jsx-scope': 0, // Handled by Next.js

package.json

@@ -105,6 +105,7 @@
     "eslint": "^8",
     "eslint-config-prettier": "^6.10.1",
     "eslint-plugin-cypress": "^2.12.1",
+    "eslint-plugin-no-direct-record-string": "file:src/_shared/custom-lint-plugins/no-direct-record-string",
     "eslint-plugin-react": "^7.20.1",
     "eslint-plugin-sort-destructure-keys": "1.5.0",
     "eslint-plugin-sort-keys-fix": "^1.1.1",

src/_shared/custom-lint-plugins/no-direct-record-string/index.js

@@ -0,0 +1,5 @@
+module.exports = {
+  rules: {
+    'no-direct-record-string': require('./no-direct-record-string'),
+  },
+}

src/_shared/custom-lint-plugins/no-direct-record-string/no-direct-record-string.js

@@ -0,0 +1,30 @@
+module.exports = {
+  create(context) {
+    return {
+      TSTypeReference(node) {
+        if (
+          node.typeName.name === 'Record' &&
+          node.typeParameters.params.length === 2 &&
+          node.typeParameters.params[0].type === 'TSStringKeyword'
+        ) {
+          // Check if the parent node is a TSTypeReference or TSTypeOperator
+          // This handles cases like Partial<Record<string, T>>
+          let parent = node.parent
+          while (parent) {
+            if (parent.type === 'TSTypeReference' || parent.type === 'TSTypeOperator') {
+              // If the parent type is TSTypeReference or TSTypeOperator, it means
+              // Record<string, T> is nested inside another type, so skip reporting
+              return
+            }
+            parent = parent.parent
+          }
+
+          context.report({
+            message: 'Direct use of Record<string, T> is unsafe. Use Partial<Record<string, T>> or explicit indices.',
+            node,
+          })
+        }
+      },
+    }
+  },
+}

src/_shared/custom-lint-plugins/no-direct-record-string/package.json

@@ -0,0 +1,15 @@
+{
+  "name": "eslint-plugin-no-direct-record-string",
+  "version": "1.0.0",
+  "description": "Custom eslint rule to warn against type Record<string, T>, which is unsafe. Use Partial<Record<string, T>",
+  "keywords": [
+    "eslint",
+    "eslintplugin",
+    "eslint-plugin",
+    "typescript",
+    "typesafety"
+  ],
+  "license": "ISC",
+  "author": "dsernst",
+  "main": "index.js"
+}

src/status/tally-votes.ts

@@ -4,12 +4,17 @@ import { Item } from 'src/vote/storeElectionInfo'
 import { mapValues } from '../utils'
 import { tally_IRV_Items } from './tallying/rcv-irv'
 
-export function tallyVotes(ballot_items_by_id: Record<string, Item>, votes: Record<string, string>[]) {
+type SafeRecord<V> = Partial<Record<string, V>>
+
+export function tallyVotes(
+  ballot_items_by_id: Partial<Record<string, Item>>,
+  votes: Partial<Record<string, string>>[],
+) {
   const multi_vote_regex = /_(\d+)$/
 
   // Sum up votes
-  const tallies: Record<string, Record<string, number>> = {}
-  const IRV_columns_seen: Record<string, boolean> = {}
+  const tallies: SafeRecord<SafeRecord<number>> = {}
+  const IRV_columns_seen: SafeRecord<boolean> = {}
   votes.forEach((vote) => {
     Object.keys(vote).forEach((key) => {
       // Skip 'tracking' key
@@ -41,7 +46,7 @@ export function tallyVotes(ballot_items_by_id: Record<string, Item>, votes: Reco
   })
 
   // Calc total votes cast per item, to speed up calc'ing %s
-  const totalsCastPerItems: Record<string, number> = {}
+  const totalsCastPerItems: SafeRecord<number> = {}
   Object.keys(tallies).forEach((item) => {
     totalsCastPerItems[item] = 0
     Object.keys(tallies[item]).forEach((choice) => (totalsCastPerItems[item] += tallies[item][choice]))
@@ -50,11 +55,11 @@ export function tallyVotes(ballot_items_by_id: Record<string, Item>, votes: Reco
   // Sort each item's totals from highest to lowest, with ties sorted alphabetically
   const ordered = mapValues(tallies, (item_totals, item_id) =>
     orderBy(
-      orderBy(Object.keys(item_totals as Record<string, number>)),
+      orderBy(Object.keys(item_totals as SafeRecord<number>)),
       (selection) => tallies[item_id][selection],
       'desc',
     ),
-  ) as Record<string, string[]>
+  ) as SafeRecord<string[]>
 
   // Go back and IRV tally any of those that we skipped
   const irv = tally_IRV_Items(IRV_columns_seen, ballot_items_by_id, votes)