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# Legacy API
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Deprecated functions provided for backward compatibility with versions ≤14.2.0. These functions are maintained for existing projects but should not be used in new projects.
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## Capabilities
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### createConfig Function (Deprecated)
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Legacy configuration function that creates ESLint configs with simplified options.
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```typescript { .api }
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import type { FlatConfig } from '@typescript-eslint/utils/ts-eslint';
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/**
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 * @deprecated Use `defineConfigWithVueTs` + `vueTsConfigs` instead
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 * Creates ESLint configuration with legacy options format
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 * @param options - Configuration options with extends and script language support
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 * @returns ESLint flat configuration array
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 */
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export default function createConfig(options?: ConfigOptions): FlatConfig.ConfigArray;
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type ConfigOptions = ProjectOptions & {
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  /** Array of config names to extend from typescript-eslint. Defaults to `['recommended']` */
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  extends?: ExtendableConfigName[];
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  /** 
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   * @deprecated Use ProjectOptions.scriptLangs instead
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   * Record of script languages with boolean flags
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   */
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  supportedScriptLangs?: Record<ScriptLang, boolean>;
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};
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interface ProjectOptions {
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  tsSyntaxInTemplates?: boolean;
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  scriptLangs?: ScriptLang[];
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  allowComponentTypeUnsafety?: boolean;
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  rootDir?: string;
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}
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type ScriptLang = "ts" | "tsx" | "js" | "jsx";
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type ExtendableConfigName = 
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  | "all" | "base" | "disableTypeChecked" | "eslintRecommended"
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  | "recommended" | "recommendedTypeChecked" | "recommendedTypeCheckedOnly"
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  | "strict" | "strictTypeChecked" | "strictTypeCheckedOnly"
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  | "stylistic" | "stylisticTypeChecked" | "stylisticTypeCheckedOnly";
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```
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**Usage Examples (Legacy):**
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```typescript
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// Legacy import style
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import createConfig from "@vue/eslint-config-typescript";
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// Basic configuration
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export default createConfig();
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// Configuration with extends
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export default createConfig({
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  extends: ["recommended", "stylistic"],
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});
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// Configuration with script language support
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export default createConfig({
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  extends: ["strictTypeChecked"],
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  supportedScriptLangs: {
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    ts: true,
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    tsx: false,
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    js: false,
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    jsx: false,
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  },
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  rootDir: process.cwd(),
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});
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```
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**Migration to Modern API:**
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```typescript
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// OLD (deprecated)
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import createConfig from "@vue/eslint-config-typescript";
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export default createConfig({
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  extends: ["recommended", "stylistic"],
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  supportedScriptLangs: { ts: true, js: false, tsx: false, jsx: false },
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});
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// NEW (recommended)
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import { 
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  defineConfigWithVueTs, 
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  vueTsConfigs, 
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  configureVueProject 
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} from "@vue/eslint-config-typescript";
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configureVueProject({
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  scriptLangs: ["ts"],
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});
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export default defineConfigWithVueTs(
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  vueTsConfigs.recommended,
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  vueTsConfigs.stylistic,
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);
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```
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### defineConfig Function (Deprecated)
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Deprecated alias for `defineConfigWithVueTs` function.
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```typescript { .api }
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/**
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 * @deprecated `defineConfig` is renamed to `defineConfigWithVueTs` in 14.3.0
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 * Alias for defineConfigWithVueTs function
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 */
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export const defineConfig: typeof defineConfigWithVueTs;
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```
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**Usage Examples (Legacy):**
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```typescript
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// OLD (deprecated)
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import { defineConfig, vueTsConfigs } from "@vue/eslint-config-typescript";
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export default defineConfig(vueTsConfigs.recommended);
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// NEW (recommended)
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import { defineConfigWithVueTs, vueTsConfigs } from "@vue/eslint-config-typescript";
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export default defineConfigWithVueTs(vueTsConfigs.recommended);
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```
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### Legacy Configuration Behavior
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#### Automatic Migration
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The `createConfig` function automatically:
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1. Converts `supportedScriptLangs` object to `scriptLangs` array
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2. Calls `configureVueProject` internally with converted options
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3. Maps `extends` array to corresponding `vueTsConfigs` entries
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4. Returns result from `defineConfigWithVueTs`
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#### Error Handling
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Provides enhanced error messages for common migration issues:
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```typescript
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// Invalid config name detection
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createConfig({ extends: ["recommended-type-checked"] });
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// Error: The config name "recommended-type-checked" is not supported in "extends". 
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// Please use "recommendedTypeChecked" instead.
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// Unknown config detection  
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createConfig({ extends: ["unknown-config"] });
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// Error: Unknown config name in "extends": unknown-config.
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```
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#### Default Values
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```typescript
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// Default configuration when no options provided
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const defaultOptions = {
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  extends: ["recommended"],
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  supportedScriptLangs: { 
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    ts: true, 
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    tsx: false, 
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    js: false, 
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    jsx: false 
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  },
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  rootDir: process.cwd(),
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};
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```
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### Migration Guide
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#### Step 1: Update Imports
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```typescript
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// Before
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import createConfig from "@vue/eslint-config-typescript";
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import { defineConfig } from "@vue/eslint-config-typescript";
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// After  
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import {
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  defineConfigWithVueTs,
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  vueTsConfigs,
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  configureVueProject,
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} from "@vue/eslint-config-typescript";
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```
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#### Step 2: Replace Function Calls
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```typescript
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// Before - createConfig
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export default createConfig({
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  extends: ["strict"],
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  supportedScriptLangs: { ts: true, js: true, tsx: false, jsx: false },
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});
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// After - modern API
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configureVueProject({
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  scriptLangs: ["ts", "js"],
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});
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export default defineConfigWithVueTs(vueTsConfigs.strict);
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```
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#### Step 3: Handle Complex Configurations
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```typescript
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// Before - mixed legacy/modern patterns
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export default createConfig({
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  extends: ["recommendedTypeChecked"],
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  // Custom rules were difficult to add
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});
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// After - full flexibility
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configureVueProject({
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  scriptLangs: ["ts"],
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  tsSyntaxInTemplates: true,
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});
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export default defineConfigWithVueTs(
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  vueTsConfigs.recommendedTypeChecked,
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  {
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    name: "custom-overrides",
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    files: ["**/*.vue"],
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    rules: {
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      // Easy to add custom rules
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      "vue/multi-word-component-names": "off",
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    },
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  },
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);
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```
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### Deprecation Timeline
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- **14.2.0 and earlier**: `createConfig` was the primary API
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- **14.3.0**: `defineConfig` renamed to `defineConfigWithVueTs`, `defineConfig` marked deprecated
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- **15.0.0**: `createConfig` will be removed, `defineConfig` alias will be removed
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**Recommendation**: Migrate to the modern API (`defineConfigWithVueTs` + `vueTsConfigs` + `configureVueProject`) for better flexibility and future compatibility.