feat: add TypeScript type definition generation for csv-loader

- Add emitTypes option (default true) to generate .d.ts files
- Add typesOutputDir option for custom output directory
- Generate interface based on CSV schema definitions
- Export RowType for explicit type imports

Co-authored-by: Qwen-Coder <qwen-coder@alibabacloud.com>

src/csv-loader/loader.ts

@@ -1,6 +1,8 @@
 import type { LoaderContext } from '@rspack/core';
 import { parse } from 'csv-parse/sync';
 import { parseSchema, createValidator, parseValue } from '../index.js';
+import type { Schema } from '../types.js';
+import * as path from 'path';
 
 export interface CsvLoaderOptions {
   delimiter?: string;
@@ -9,6 +11,10 @@ export interface CsvLoaderOptions {
   bom?: boolean;
   comment?: string | false;
   trim?: boolean;
+  /** Generate TypeScript declaration file (.d.ts) */
+  emitTypes?: boolean;
+  /** Output directory for generated type files (relative to output path) */
+  typesOutputDir?: string;
 }
 
 interface PropertyConfig {
@@ -18,6 +24,57 @@ interface PropertyConfig {
   parser: (valueString: string) => unknown;
 }
 
+/**
+ * Convert a schema to TypeScript type string
+ */
+function schemaToTypeString(schema: Schema): string {
+  switch (schema.type) {
+    case 'string':
+      return 'string';
+    case 'number':
+      return 'number';
+    case 'boolean':
+      return 'boolean';
+    case 'array':
+      if (schema.element.type === 'tuple') {
+        const tupleElements = schema.element.elements.map(schemaToTypeString);
+        return `[${tupleElements.join(', ')}]`;
+      }
+      return `${schemaToTypeString(schema.element)}[]`;
+    case 'tuple':
+      const tupleElements = schema.elements.map(schemaToTypeString);
+      return `[${tupleElements.join(', ')}]`;
+    default:
+      return 'unknown';
+  }
+}
+
+/**
+ * Generate TypeScript interface for the CSV data
+ */
+function generateTypeDefinition(
+  resourceName: string,
+  propertyConfigs: PropertyConfig[]
+): string {
+  const interfaceName = path.basename(resourceName, path.extname(resourceName))
+    .replace(/[^a-zA-Z0-9_$]/g, '_')
+    .replace(/^(\d)/, '_$1');
+  
+  const properties = propertyConfigs
+    .map((config) => `  ${config.name}: ${schemaToTypeString(config.schema)};`)
+    .join('\n');
+  
+  return `export interface ${interfaceName} {
+${properties}
+}
+
+export type RowType = ${interfaceName};
+
+declare const data: ${interfaceName}[];
+export default data;
+`;
+}
+
 export default function csvLoader(
   this: LoaderContext<CsvLoaderOptions>,
   content: string
@@ -29,6 +86,8 @@ export default function csvLoader(
   const bom = options?.bom ?? true;
   const comment = options?.comment === false ? undefined : (options?.comment ?? '#');
   const trim = options?.trim ?? true;
+  const emitTypes = options?.emitTypes ?? true;
+  const typesOutputDir = options?.typesOutputDir ?? '';
 
   const records = parse(content, {
     delimiter,
@@ -90,5 +149,16 @@ export default function csvLoader(
   });
 
   const json = JSON.stringify(objects, null, 2);
+  
+  // Emit type definition file if enabled
+  if (emitTypes) {
+    const dtsContent = generateTypeDefinition(this.resourcePath, propertyConfigs);
+    const relativePath = this.resourcePath.replace(this.context, '');
+    const dtsFileName = relativePath.replace(/\.csv$/, '.d.ts');
+    const outputPath = path.join(typesOutputDir, dtsFileName);
+    
+    this.emitFile?.(outputPath, dtsContent);
+  }
+  
   return `export default ${json};`;
 }