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💀 Resolution failed

Import failed to resolve to type declarations or JavaScript files.

Explanation

This problem indicates that TypeScript can’t find any file with a supported file extension (.js, .mjs, .cjs, .jsx, .json, .ts, .mts, .cts, .tsx) by following its own resolution algorithm, or a modified version of its resolution algorithm that ignores type declaration (.d.ts, .d.mts, .d.cts, .d.*.ts) files (which allows it to find JS files it would otherwise ignore).

Consequences

  • Consumers will see TypeScript errors on imports/requires.
  • If the diagnosis is accurate, a runtime/bundle-time error will occur.

Common causes

False positive: unsupported file extension

TypeScript doesn’t record non-JS/TS files as resolution results, and its API can’t be used to distinguish between a result with an unsupported file extension and a non-existent file. If a package.json subpath exposes a non-JS asset like a .css file, designed to be processed by a bundler or runtime extension, this will show up as a failed resolution, when it might be more accurately described as an untyped resolution of an unknown file type.

If the asset is intended to be imported as a side-effect import (import "pkg/styles.css"), this problem can safely be ignored.

True positive: Node 10 doesn’t support package.json "exports"

When this problem occurs for the node10 resolution option but not any others, it usually means that the package uses package.json "exports" to map a subpath into a dist folder:

{
  "name": "pkg",
  "main": "./dist/index.js",
  "exports": {
    ".": "./dist/index.js",
    "./subpath": "./dist/subpath.js"
  }
}

In this example, an import of "pkg/subpath" can be used in Node 12+ and modern bundlers, but would fail to resolve in Node 10. Accordingly, TypeScript’s --moduleResolution node10 (also confusingly known as node, because history) does not resolve "exports" either.

While few libraries care about supporting a long-past EOL version of Node, maintainers of very popular libraries should be aware that many TypeScript users are still using --moduleResolution node. If they aren’t literally using Node 10, they really should move away from it, but sometimes migrating can be difficult because it introduces new errors caused by incorrect dependency typings—the problem this tool was made to diagnose. Popular libraries often choose to adopt a strategy that allows --moduleResolution node10 to work even without "exports" support. https://github.com/andrewbranch/example-subpath-exports-ts-compat demonstrates several such strategies.