Include declaration files when resolving import specifiers

[webpro]

When a project has declaration files (.d.ts) added through e.g. the include: [] configuration in tsconfig.json, how to get ts.resolveModuleName() take them into account?

This PR includes a fixture that has assets.d.ts:

declare module '*.html?raw';

With a module importing another:

import b from './block.html?raw';

The result with Knip is an unresolved module, since I don't know how to properly include the declaration files in the TypeScript backend. Full repro:

$ git clone -b fix/include-dts [email protected]:webpro/knip.git
$ cd knip
$ npm install
$ cd fixtures/dts/
$ npx knip
Unused files (1)
src/assets.d.ts
Unresolved imports (1)
./block.html?raw  src/index.ts

The TypeScript backend is set up mainly in the constructor of the ProjectPrincipal class using a language service and compiler host in createHosts.ts with a custom resolveModuleNames function.

In this PR I have added some code and comments to indicate where the relevant bits are.

To rephrase my question: how to properly include declaration files not explicitly included through import statements?

(By the way, the current workaround in Knip is to let this slip through and eventually sanitize the import specifiers and ignore specifiers having an extension from this list.)

[webpro]

Asked in TS Discord:

• https://discord.com/channels/508357248330760243/640177429775777792/1142123565651607652
• https://discord.com/channels/508357248330760243/640177429775777792/1143792904825999443

[webpro]

Repro at https://github.com/webpro/knip-dts/blob/main/index.ts

[webpro]

🚀 This issue has been resolved in v2.29.0. See Release 2.29.0 for release notes.