Performance: Re-use TS Program

As the number of React components in my project grew, I noticed a performance issue similar to what is discussed in https://github.com/styleguidist/react-docgen-typescript/issues/112: Creating a new Typescript program (ts.createProgram) when transforming each file is expensive.

I loosely adapted https://github.com/strothj/babel-plugin-react-docgen-typescript/blob/0b72d214444bf7a48ec22637654c5bee0eaad26f/src/index.ts to re-use the TypeScript program, and got big perf gains.

It might be possible to adapt this babel plugin. Hope this info could be helpful.

./docgen.js

```js const rdt = require('react-docgen-typescript'); const template = require('@babel/template'); const ts = require('typescript'); const glob = require('glob'); const util = require('util'); const files = glob.sync('src/**/*.{ts,tsx}', { absolute: true }); const program = ts.createProgram(files, {}); module.exports = function() { return { pre() { this.fileProcessed = false; }, visitor: { Program(path, state) { if (this.fileProcessed) { return; } this.fileProcessed = true; const { filename } = state.file.opts; if (files.indexOf(filename) === -1) { files.push(file); program = ts.createProgram(files, {}); } const docs = rdt .withCompilerOptions({}, { shouldExtractLiteralValuesFromEnum: true }) .parseWithProgramProvider(filename, () => program); docs.forEach((doc) => { path.node.body.push( template.default.ast(` try { ${doc.displayName}.__docgenInfo = ${util.inspect( doc, null, 10, )}; } catch (e) {} `), ); }); }, }, }; }; ```

babel.config.js

```js const useESM = process.env.ESM === '1'; module.exports = function(api) { api.cache(true); return { presets: [ '@babel/preset-typescript', ['@babel/preset-env', { modules: useESM ? false : 'commonjs' }], ], plugins: [ '@babel/plugin-transform-react-jsx', './docgen', '@babel/plugin-transform-runtime', ], }; }; ```

$ time npm run build:esm

> ESM=1 babel src --source-maps --out-dir dist/esm --extensions .ts,.tsx

Successfully compiled 38 files with Babel.

real    0m5.006s
user    0m7.779s
sys 0m0.538s

Before, it was about 40 seconds. Nearly a full order of magnitude improved.

strothj / babel-plugin-react-docgen-typescript

Performance: Re-use TS Program #17