pezkuwi-dev/packages/dev-ts/src/loader.ts

// Copyright 2017-2025 @pezkuwi/dev-ts authors & contributors
// SPDX-License-Identifier: Apache-2.0

import crypto from 'node:crypto';
import fs from 'node:fs';
import path from 'node:path';
import { fileURLToPath } from 'node:url';
import ts from 'typescript';

import { EXT_TS_REGEX, loaderOptions } from './common.js';

interface Loaded {
  format: 'commonjs' | 'module';
  shortCircuit?: boolean;
  source: string;
}

type NexLoad = (url: string, context: Record<string, unknown>) => Promise<Loaded>;

/**
 * Load all TypeScript files, compile via tsc on-the-fly
 **/
export async function load (url: string, context: Record<string, unknown>, nextLoad: NexLoad): Promise<Loaded> {
  if (EXT_TS_REGEX.test(url)) {
    // used the chained loaders to retrieve
    const { source } = await nextLoad(url, {
      ...context,
      format: 'module'
    });

    // we use a hash of the source to determine caching
    const sourceHash = `//# sourceHash=${crypto.createHash('sha256').update(source).digest('hex')}`;
    const compiledFile = url.includes('/src/')
      ? fileURLToPath(
        url
          .replace(/\.tsx?$/, '.js')
          .replace('/src/', '/build-loader/')
      )
      : null;

    if (loaderOptions.isCached && compiledFile && fs.existsSync(compiledFile)) {
      const compiled = fs.readFileSync(compiledFile, 'utf-8');

      if (compiled.includes(sourceHash)) {
        return {
          format: 'module',
          source: compiled
        };
      }
    }

    // compile via typescript
    const { outputText } = ts.transpileModule(source.toString(), {
      compilerOptions: {
        ...(
          url.endsWith('.tsx')
            ? { jsx: ts.JsxEmit.ReactJSX }
            : {}
        ),
        esModuleInterop: true,
        importHelpers: true,
        inlineSourceMap: true,
        module: ts.ModuleKind.ESNext,
        moduleResolution: ts.ModuleResolutionKind.NodeNext,
        skipLibCheck: true,
        // Aligns with packages/dev/scripts/pezkuwi-dev-build-ts & packages/dev/config/tsconfig
        target: ts.ScriptTarget.ES2022
      },
      fileName: fileURLToPath(url)
    });

    if (loaderOptions.isCached && compiledFile) {
      const compiledDir = path.dirname(compiledFile);

      if (!fs.existsSync(compiledDir)) {
        fs.mkdirSync(compiledDir, { recursive: true });
      }

      fs.writeFileSync(compiledFile, `${outputText}\n${sourceHash}`, 'utf-8');
    }

    return {
      format: 'module',
      source: outputText
    };
  }

  return nextLoad(url, context);
}