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add eslint rule for platform export
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‎.eslintrc.js‎

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'eslint:recommended',
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'plugin:@typescript-eslint/recommended',
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],
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parser: '@typescript-eslint/parser',
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plugins: ['@typescript-eslint', 'local-rules'],
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globals: {
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Atomics: 'readonly',
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SharedArrayBuffer: 'readonly',
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'rules': {
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'@typescript-eslint/explicit-module-boundary-types': ['error']
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}
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},
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{
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'files': ['*.ts', '!*.spec.ts', '!*.test.ts', '!*.tests.ts', '!*.test-d.ts'],
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'excludedFiles': ['**/__mocks__/**', '**/tests/**'],
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'rules': {
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'local-rules/require-platform-declaration': 'error',
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}
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}
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],
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rules: {

‎ESLINT_TROUBLESHOOTING.md‎

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# ESLint Rule Troubleshooting
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## The Rule is Working!
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The `require-platform-declaration` rule **is** working correctly from the command line:
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```bash
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$ npx eslint lib/core/custom_attribute_condition_evaluator/index.ts
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lib/core/custom_attribute_condition_evaluator/index.ts
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16:1 error File must export __supportedPlatforms to declare which platforms
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it supports. Example: export const __supportedPlatforms = ['__universal__'] as const;
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```
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## VSCode Not Showing Errors?
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If VSCode isn't showing the ESLint errors, try these steps:
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### 1. Restart ESLint Server
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- Open Command Palette: `Cmd+Shift+P` (Mac) or `Ctrl+Shift+P` (Windows/Linux)
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- Type: `ESLint: Restart ESLint Server`
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- Press Enter
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### 2. Check ESLint Extension is Installed
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- Open Extensions panel: `Cmd+Shift+X` (Mac) or `Ctrl+Shift+X` (Windows/Linux)
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- Search for "ESLint" by Microsoft
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- Make sure it's installed and enabled
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### 3. Check ESLint Output
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- Open Output panel: `Cmd+Shift+U` (Mac) or `Ctrl+Shift+U` (Windows/Linux)
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- Select "ESLint" from the dropdown
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- Look for any error messages
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### 4. Reload VSCode Window
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- Open Command Palette: `Cmd+Shift+P` (Mac) or `Ctrl+Shift+P` (Windows/Linux)
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- Type: `Developer: Reload Window`
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- Press Enter
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### 5. Check File is Being Linted
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The rule only applies to:
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- ✅ Files in `lib/` or `src/` directory
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- ✅ TypeScript files (`.ts`)
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- ❌ Test files (`.spec.ts`, `.test.ts`, etc.)
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- ❌ Declaration files (`.d.ts`)
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### 6. Verify ESLint Configuration
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Check that `.eslintrc.js` has the parser set:
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```javascript
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parser: '@typescript-eslint/parser',
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```
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And that the rule is in the overrides:
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```javascript
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overrides: [{
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files: ['*.ts', '!*.spec.ts', '!*.test.ts', '!*.tests.ts', '!*.test-d.ts'],
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rules: {
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'local-rules/require-platform-declaration': 'error',
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}
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}]
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```
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## Manual Verification
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You can always verify the rule works by running:
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```bash
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# Check a specific file
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npx eslint lib/service.ts
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# Check all lib files (shows only errors)
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npx eslint lib/**/*.ts --quiet
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```
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## Adding __supportedPlatforms
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To fix the error, add this export to your file (after imports):
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```typescript
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// Universal file (all platforms)
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export const __supportedPlatforms = ['__universal__'] as const;
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// OR platform-specific file
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export const __supportedPlatforms = ['browser', 'node'] as const;
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```

‎eslint-local-rules/README.md‎

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# Local ESLint Rules
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This directory contains custom ESLint rules specific to this project.
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## Rules
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### `require-platform-declaration`
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**Purpose:** Ensures all source files (except tests) export `__supportedPlatforms` to declare which platforms they support.
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**Why:** This enforces platform isolation at the linting level, catching missing declarations before build time.
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**Enforcement:**
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- ✅ Enabled for all `.ts` files in `lib/` directory
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- ❌ Disabled for test files (`.spec.ts`, `.test.ts`, etc.)
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- ❌ Disabled for `__mocks__` and `tests` directories
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**Valid Examples:**
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```typescript
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// Universal file (all platforms)
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export const __supportedPlatforms = ['__universal__'] as const;
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// Platform-specific file
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export const __supportedPlatforms = ['browser', 'node'] as const;
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// With type annotation
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export const __supportedPlatforms: Platform[] = ['react_native'] as const;
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```
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**Invalid:**
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```typescript
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// Missing __supportedPlatforms export
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// ESLint Error: File must export __supportedPlatforms to declare which platforms it supports
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```
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## Configuration
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The rules are loaded via `eslint-plugin-local-rules` and configured in `.eslintrc.js`:
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```javascript
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{
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plugins: ['local-rules'],
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overrides: [{
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files: ['*.ts', '!*.spec.ts', '!*.test.ts'],
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rules: {
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'local-rules/require-platform-declaration': 'error'
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}
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}]
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}
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```
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## Adding New Rules
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1. Create a new rule file in this directory (e.g., `my-rule.js`)
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2. Export the rule following ESLint's rule format
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3. Add it to `index.js`:
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```javascript
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module.exports = {
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'require-platform-declaration': require('./require-platform-declaration'),
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'my-rule': require('./my-rule'), // Add here
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};
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```
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4. Enable it in `.eslintrc.js`
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## Testing Rules
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Run ESLint on specific files to test:
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```bash
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# Test on a specific file
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npx eslint lib/service.ts
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# Test on all lib files
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npx eslint lib/**/*.ts --quiet
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```

‎eslint-local-rules/index.js‎

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/**
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* Local ESLint Rules
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*
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* Custom ESLint rules for the project.
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* Loaded by eslint-plugin-local-rules.
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*/
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module.exports = {
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'require-platform-declaration': require('./require-platform-declaration'),
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};

‎eslint-local-rules/require-platform-declaration.js‎

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/**
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* ESLint Rule: require-platform-declaration
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*
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* Ensures that all non-test source files export __supportedPlatforms
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*
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* Valid:
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* export const __supportedPlatforms = ['browser'] as const;
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* export const __supportedPlatforms = ['__universal__'] as const;
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* export const __supportedPlatforms: Platform[] = ['browser', 'node'];
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*
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* Invalid:
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* // Missing __supportedPlatforms export
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*/
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module.exports = {
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meta: {
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type: 'problem',
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docs: {
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description: 'Require __supportedPlatforms export in all source files',
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category: 'Best Practices',
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recommended: true,
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},
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messages: {
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missingPlatformDeclaration: 'File must export __supportedPlatforms to declare which platforms it supports. Example: export const __supportedPlatforms = [\'__universal__\'] as const;',
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invalidPlatformDeclaration: '__supportedPlatforms must be exported as a const array. Example: export const __supportedPlatforms = [\'browser\', \'node\'] as const;',
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},
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schema: [],
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},
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create(context) {
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const filename = context.getFilename();
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// Skip test files
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if (filename.endsWith('.spec.ts') ||
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filename.endsWith('.test.ts') ||
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filename.endsWith('.tests.ts') ||
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filename.endsWith('.test.js') ||
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filename.endsWith('.spec.js') ||
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filename.endsWith('.tests.js') ||
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filename.endsWith('.test-d.ts') ||
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filename.endsWith('.d.ts') ||
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filename.includes('/__mocks__/') ||
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filename.includes('/tests/')) {
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return {};
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}
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// Skip non-source files
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if (!filename.includes('/lib/') && !filename.includes('/src/')) {
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return {};
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}
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let hasPlatformExport = false;
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let isValidExport = false;
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return {
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ExportNamedDeclaration(node) {
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// Check for: export const __supportedPlatforms = [...]
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if (node.declaration &&
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node.declaration.type === 'VariableDeclaration') {
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for (const declarator of node.declaration.declarations) {
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if (declarator.id.type === 'Identifier' &&
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declarator.id.name === '__supportedPlatforms') {
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hasPlatformExport = true;
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// Validate it's a const
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if (node.declaration.kind !== 'const') {
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context.report({
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node: declarator,
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messageId: 'invalidPlatformDeclaration',
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});
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return;
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}
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// Validate it's an array
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let init = declarator.init;
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// Handle TSAsExpression: [...] as const
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if (init && init.type === 'TSAsExpression') {
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init = init.expression;
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}
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// Handle TSTypeAssertion: <const>[...]
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if (init && init.type === 'TSTypeAssertion') {
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init = init.expression;
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}
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if (init && init.type === 'ArrayExpression') {
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isValidExport = true;
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} else {
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context.report({
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node: declarator,
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messageId: 'invalidPlatformDeclaration',
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});
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}
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}
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}
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}
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},
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'Program:exit'(node) {
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// At the end of the file, check if __supportedPlatforms was exported
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if (!hasPlatformExport) {
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context.report({
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node,
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messageId: 'missingPlatformDeclaration',
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});
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}
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},
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};
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},
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};

‎lib/platform_support.ts‎

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*/
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export type Platform = 'browser' | 'node' | 'react_native' | '__universal__';
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export const __supportedPlatforms = ['__universal__'] as const;
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/**
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* Platform support declaration
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*

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