typecheck plugin performance in watch mode

[sidvishnoi]

Thank you for this helpful plugin. To make it better, I wanted to report a performance issue.

There's a significant difference in how long it takes to typecheck with the plugin vs raw --tsc --noEmit --watch

Configuration:

      typecheckPlugin({
        buildMode: 'readonly',
        watch: true,
        configFile: path.join(__dirname, '..', 'tsconfig.json'),
      }),

In screenshot: top = typecheck plugin can be seen taking around 3s, bottom = tsc --noEmit --watch can be seen taking less than a second.

Comparing result on second run (after initial type-checking in both), and incremental compilation is not enabled in tsconfig.
The project has around 900 files (tsc --listFiles, including node_modules .d.ts files)

[jgoz]

Hi, thanks for the report. I suspect the TypeScript compiler uses an in-memory cache of some kind when --noEmit and --watch are enabled. It might be possible to support this in the typecheck plugin, but I don't have time to work on it in the foreseeable future.