[Compiler API] Reuse default compiler host when customizing module resolution

Suggestion

A very similar question already has been asked here four years ago by @vivin:
Implementing custom module-resolution logic using Compiler API - StackOverflow

I need the same right now, and it is a pity that apparently, you still need to rewrite the entire compiler host configuration just in order to customize one aspect. What I would prefer to do would be something like:

const host = ts.createCompilerHost(options);
host.resolveModuleNames = myResolver;
const program = ts.createProgram(sourceFiles, options, host);

But this still seems to be impossible right now?

🔍 Search Terms

customize module resolution, configure compiler host, resolveModuleNames

✅ Viability Checklist

My suggestion meets these guidelines:

• This wouldn't be a breaking change in existing TypeScript/JavaScript code
• This wouldn't change the runtime behavior of existing JavaScript code
• This could be implemented without emitting different JS based on the types of the expressions
• This isn't a runtime feature (e.g. library functionality, non-ECMAScript syntax with JavaScript output, new syntax sugar for JS, etc.)
• This feature would agree with the rest of TypeScript's Design Goals.

💻 Use Cases

• customize compiler more easily without reinventing the wheel
• if you need to reinvent the wheel, the code will get harder to maintain against future changes to the default compiler host

Start by tracing the Compiler API entry points named in the issue: ts.createCompilerHost, resolveModuleNames, and ts.createProgram. Determine how the default compiler host handles module resolution and how a custom resolver could be layered onto it; done means the requested customization works without recreating the entire host configuration.