Ability for checker to resolve modules by node similar to program when providing custom host

[dsherret]

🔍 Search Terms

module resolution location

✅ Viability Checklist

• 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 isn't a request to add a new utility type: https://github.com/microsoft/TypeScript/wiki/No-New-Utility-Types
• This feature would agree with the rest of our Design Goals: https://github.com/Microsoft/TypeScript/wiki/TypeScript-Design-Goals

⭐ Suggestion

The program provides the ability to resolve modules based on the specific string literal node, but the checker only resolves based on specifier text and node resolution mode. This means that if module specifiers with the same text and resolution mode resolve to different modules, the checker will always resolve to the same module based on whatever was last inserted into the program's ModeAwareCache.

TypeScript/src/compiler/program.ts

Lines 1973 to 1975 in 47ca599

	function getResolvedModule(file: SourceFile, moduleName: string, mode: ResolutionMode) {
	return resolvedModules?.get(file.path)?.get(moduleName, mode);
	}

📃 Motivating Example

import text from "./data.txt" with { type: "text" };
import bytes from "./data.txt" with { type: "bytes" };
const { default: textDynamic }   = await import("./data.txt", { with: { type: "text" }});
const { default: bytesDynamic } = await import("./data.txt", { with: { type: "bytes" }});

let invalid: number;
invalid = text;
invalid = textDynamic;
invalid = bytes;
invalid = bytesDynamic;

let validText: string;
validText = text;
validText = textDynamic;

let validBytes: Uint8Array<ArrayBuffer>;
validBytes = bytes;
validBytes = bytesDynamic;

Currently outputs:

[ERROR]: Type 'Uint8Array<ArrayBuffer>' is not assignable to type 'number'.
invalid = text;
~~~~~~~
    at file:///V:/scratch/main.ts:7:1

TS2322 [ERROR]: Type 'Uint8Array<ArrayBuffer>' is not assignable to type 'number'.
invalid = textDynamic;
~~~~~~~
    at file:///V:/scratch/main.ts:8:1

TS2322 [ERROR]: Type 'Uint8Array<ArrayBuffer>' is not assignable to type 'number'.
invalid = bytes;
~~~~~~~
    at file:///V:/scratch/main.ts:9:1

TS2322 [ERROR]: Type 'Uint8Array<ArrayBuffer>' is not assignable to type 'number'.
invalid = bytesDynamic;
~~~~~~~
    at file:///V:/scratch/main.ts:10:1

TS2322 [ERROR]: Type 'Uint8Array<ArrayBuffer>' is not assignable to type 'string'.
validText = text;
~~~~~~~~~
    at file:///V:/scratch/main.ts:13:1

TS2322 [ERROR]: Type 'Uint8Array<ArrayBuffer>' is not assignable to type 'string'.
validText = textDynamic;
~~~~~~~~~
    at file:///V:/scratch/main.ts:14:1

Found 6 errors.

If I swap the last two dynamic imports then it will error on validBytes instead of validText.

💻 Use Cases

1. Implementing bytes and text imports in Deno (which will be unstable and is currently non-standard: Import with type text, bytes, and URL whatwg/html#9444)