Add linting to frontend (#4341)

# Description of Changes
There's no current linter running over our TypeScript code, which means
we've got a bunch of dead code and other code smells around with nothing
notifying us. This PR adds ESLint with the typescript-eslint plugin and
enables the recommended settings as a starting point for us.

I've disabled all of the failing rules for the scope of this PR, just to
get linting running without causing a massive diff. I'll follow up with
future PRs that enable the failing rules one by one.

Also updates our version of TypeScript, which introduces a new type
error in the code (which I've had to fix)

.editorconfig

@@ -24,7 +24,7 @@ indent_size = 2
 insert_final_newline = false
 trim_trailing_whitespace = false
 
-[{*.js,*.jsx,*.ts,*.tsx}]
+[{*.js,*.jsx,*.mjs,*.ts,*.tsx}]
 indent_size = 2
 
 [*.css]

.github/workflows/build.yml

@@ -147,6 +147,8 @@ jobs:
           cache-dependency-path: frontend/package-lock.json
       - name: Install frontend dependencies
         run: cd frontend && npm ci
+      - name: Lint frontend
+        run: cd frontend && npm run lint
       - name: Build frontend
         run: cd frontend && npm run build
       - name: Run frontend tests

.vscode/extensions.json

@@ -19,5 +19,6 @@
     "yzhang.markdown-all-in-one", // Markdown All-in-One extension for enhanced Markdown editing
     "stylelint.vscode-stylelint", // Stylelint extension for CSS and SCSS linting
     "redhat.vscode-yaml", // YAML extension for Visual Studio Code
+    "dbaeumer.vscode-eslint", // ESLint extension for TypeScript linting
   ]
 }

frontend/eslint.config.mjs

@@ -0,0 +1,32 @@
+// @ts-check
+
+import eslint from '@eslint/js';
+import { defineConfig } from 'eslint/config';
+import tseslint from 'typescript-eslint';
+
+export default defineConfig(
+  eslint.configs.recommended,
+  tseslint.configs.recommended,
+  {
+    ignores: [
+      "dist", // Contains 3rd party code
+      "public", // Contains 3rd party code
+    ],
+  },
+  {
+    rules: {
+      "no-empty": "off", // Temporarily disabled until codebase conformant
+      "no-empty-pattern": "off", // Temporarily disabled until codebase conformant
+      "no-undef": "off", // Temporarily disabled until codebase conformant
+      "no-useless-escape": "off", // Temporarily disabled until codebase conformant
+      "no-case-declarations": "off", // Temporarily disabled until codebase conformant
+      "prefer-const": "off", // Temporarily disabled until codebase conformant
+      "@typescript-eslint/ban-ts-comment": "off", // Temporarily disabled until codebase conformant
+      "@typescript-eslint/no-empty-object-type": "off", // Temporarily disabled until codebase conformant
+      "@typescript-eslint/no-explicit-any": "off", // Temporarily disabled until codebase conformant
+      "@typescript-eslint/no-require-imports": "off", // Temporarily disabled until codebase conformant
+      "@typescript-eslint/no-unused-expressions": "off", // Temporarily disabled until codebase conformant
+      "@typescript-eslint/no-unused-vars": "off", // Temporarily disabled until codebase conformant
+    },
+  }
+);

frontend/package.json

@@ -40,6 +40,7 @@
     "predev": "npm run generate-icons",
     "dev": "npx tsc --noEmit && vite",
     "prebuild": "npm run generate-icons",
+    "lint": "npx eslint",
     "build": "npx tsc --noEmit && vite build",
     "preview": "vite preview",
     "typecheck": "tsc --noEmit",
@@ -72,6 +73,7 @@
     ]
   },
   "devDependencies": {
+    "@eslint/js": "^9.34.0",
     "@iconify-json/material-symbols": "^1.2.33",
     "@iconify/utils": "^3.0.1",
     "@playwright/test": "^1.40.0",
@@ -80,6 +82,7 @@
     "@types/react-dom": "^19.1.5",
     "@vitejs/plugin-react": "^4.5.0",
     "@vitest/coverage-v8": "^1.0.0",
+    "eslint": "^9.34.0",
     "jsdom": "^23.0.0",
     "license-checker": "^25.0.1",
     "madge": "^8.0.0",
@@ -87,7 +90,8 @@
     "postcss-cli": "^11.0.1",
     "postcss-preset-mantine": "^1.17.0",
     "postcss-simple-vars": "^7.0.1",
-    "typescript": "^5.8.3",
+    "typescript": "^5.9.2",
+    "typescript-eslint": "^8.42.0",
     "vite": "^6.3.5",
     "vitest": "^1.0.0"
   }

frontend/src/services/pdfExportService.ts

@@ -130,7 +130,7 @@ export class PDFExportService {
     newDoc.setModificationDate(new Date());
 
     const pdfBytes = await newDoc.save();
-    return new Blob([pdfBytes], { type: 'application/pdf' });
+    return new Blob([pdfBytes as BlobPart], { type: 'application/pdf' });
   }
 
   /**
@@ -176,7 +176,7 @@ export class PDFExportService {
     newDoc.setModificationDate(new Date());
 
     const pdfBytes = await newDoc.save();
-    return new Blob([pdfBytes], { type: 'application/pdf' });
+    return new Blob([pdfBytes as BlobPart], { type: 'application/pdf' });
   }