ts-hover-text

Get TypeScript hover text (QuickInfo) for a symbol in a code string. Use this to test TypeScript type inference in your tests.

Installation

pnpm add -D ts-hover-text
# or
npm i -D ts-hover-text

Quick Start

import { tsHoverText } from 'ts-hover-text'

const getHoverText = tsHoverText({ sourceRoot: 'src' })

test('my type test', () => {
  const hover = getHoverText('const x: number = 1', 'x')
  expect(hover).toEqual(['const x: number'])
})

API

tsHoverText(options?)

Create a configured getHoverText function. Call this once per test file.

Options:

• sourceRoot - Directory for resolving imports, relative to your project root (default: 'src')
• tsConfigPath - Path to tsconfig.json (default: 'tsconfig.json')
• trimmedLines - Return array of trimmed lines (default: true), or raw string (false)
• compilerOptions - Override TypeScript settings

getHoverText(code, symbolName)

Get hover text for a symbol in your code string.

Parameters:

• code - TypeScript code to analyze
• symbolName - Identifier to get hover info for

Returns:

• string[] - Trimmed lines (default)
• string - Raw hover text (when trimmedLines: false)

Imports

Imports in your code resolve relative to sourceRoot, which is relative to your project root (where package.json is). For example:

// With sourceRoot: 'src'
getHoverText('import { Foo } from "./Foo"\nconst x = Foo', 'x')
// Resolves ./Foo to <project>/src/Foo.ts

Performance

The first call parses TypeScript lib and source directory files and takes around a second. Subsequent calls are usually around 50ms.

Examples

Test type inference:

/* eslint-disable @stylistic/indent */
test('object type inference', () => {
  const hover = getHoverText('const obj: { a: string; b: number }', 'obj')
  expect(hover).toEqual([
    'const obj: {',
      'a: string;',
      'b: number;',
    '}',
  ])
})

Test with imports:

// test/fixture.ts: export const foo = 'hello'
const getHoverText = tsHoverText({ sourceRoot: 'test' })

test('resolves imports', () => {
  const hover = getHoverText(
    'import { foo } from "./fixture"\nconst x = foo',
    'x'
  )
  expect(hover).toEqual(['const x: "hello"'])
})