Start language service integration.

[strothj]

Hello,

Please don't merge this. This is a work in progress. I just want to see if this would be something you'd be likely to merge in and to get some initial feedback.

What I'd like to do is integrate the TypeScript language service into this package. This solves #112.

I was encountering poor performance on projects that hit large numbers of components (80+). I've reused the code from ts-loader (https://github.com/TypeStrong/ts-loader/blob/master/src/servicesHost.ts) to create a reusable instance of ts.Program. On one especially large project, I saw a drop from multiple minutes to about 30 seconds.

Issues needing resolving:

• Determine how we want to detect the user's project root. This is one of the following in ts-loader: webpack's context setting, location of tsconfig.json, current working directory.
• Possibily add a setting to explicitly enable this behavior
• Changes to files in the project are not detected. We will need to fill in the watcher setting in the language service setup. This was previously done by wiring it into the Webpack system. Currently, things compile as expecedt but changes are not reflected in watch mode.
• Bring over relevant unit tests

We can select which behavior to use (file by file or language service) by requesting a service host instance or creating a ts.Program.
parser.ts:

      const { instance } = getTypeScriptInstance(
        process.cwd(),
        compilerOptions
      );

      const filePaths = Array.isArray(filePathOrPaths)
        ? filePathOrPaths
        : [filePathOrPaths];

      const program = instance.languageService!.getProgram()!;
      // const program = ts.createProgram(filePaths, compilerOptions);

[tutman96]

Nice work! I just cloned your branch and copy-pasted your version into my application and it works great! Nice and fast. The watching did work for me however... so I don't know what your issue was.

[strothj]

I think the issue I had with watching was from testing in Storybook. This package is used by another as a Webpack loader.

I think I will need to hook into the file changed event from the watcher. I’d then need to supply an async version of this package’s export so that the loader can postpone the update until the watcher has finished processing.

[strothj]

I found it easier to test by using the utility called yalc. You type yalc publish in this package directory and then type yalc link react-docgen-typescript in your project.

[tutman96]

Gotcha.... I needed to get it to the rest of my team though, so I just pasted it into our repo :D

Thanks again for this awesome work! The team really loves the improvements

[strothj]

I've decided to take a slightly different approach to this problem. Submitting another pull request with a more digestible change.