feat: added jest expect support (#66)

Co-authored-by: Anthony Fu <[email protected]>

src/index.ts

@@ -1,3 +1,4 @@
+import type { MatchersObject } from './integrations/chai/types'
 import type { UserOptions } from './types'
 
 export * from './types'
@@ -16,6 +17,10 @@ declare module 'vite' {
 
 declare global {
   namespace Chai {
+    interface ExpectStatic {
+      extend(expects: MatchersObject): void
+    }
+
     interface Assertion {
       // Snapshot
       toMatchSnapshot(message?: string): Assertion

src/integrations/chai/jest-extend.ts

@@ -0,0 +1,83 @@
+import chai, { util } from 'chai'
+
+import * as matcherUtils from './jest-matcher-utils'
+
+import {
+  iterableEquality,
+  subsetEquality,
+  equals,
+} from './jest-utils'
+import type {
+  ChaiPlugin,
+  MatcherState,
+  MatchersObject,
+  SyncExpectationResult,
+} from './types'
+
+const isAsyncFunction = (fn: unknown) =>
+  typeof fn === 'function' && (fn as any)[Symbol.toStringTag] === 'AsyncFunction'
+
+const getMatcherState = (assertion: Chai.AssertionStatic & Chai.Assertion) => {
+  const actual = assertion._obj
+  const isNot = util.flag(assertion, 'negate') as boolean
+  const jestUtils = {
+    ...matcherUtils,
+    iterableEquality,
+    subsetEquality,
+  }
+
+  const matcherState: MatcherState = {
+    isNot,
+    utils: jestUtils,
+    // global assertionCalls? needed for built-in jest function, but we don't use it
+    assertionCalls: 0,
+    promise: '',
+    equals,
+    // needed for built-in jest-snapshots, but we don't use it
+    suppressedErrors: [],
+  }
+
+  return {
+    state: matcherState,
+    isNot,
+    actual,
+  }
+}
+
+function JestExtendPlugin(expects: MatchersObject): ChaiPlugin {
+  return (c, utils) => {
+    Object.entries(expects).forEach(([expectAssertionName, expectAssertion]) => {
+      function expectSyncWrapper(this: Chai.AssertionStatic & Chai.Assertion, ...args: any[]) {
+        const { state, isNot, actual } = getMatcherState(this)
+
+        // @ts-expect-error args wanting tuple
+        const { pass, message } = expectAssertion.call(state, actual, ...args) as SyncExpectationResult
+
+        if ((pass && isNot) || (!pass && !isNot))
+          c.expect.fail(message())
+      }
+
+      async function expectAsyncWrapper(this: Chai.AssertionStatic & Chai.Assertion, ...args: any[]) {
+        const { state, isNot, actual } = getMatcherState(this)
+
+        // @ts-expect-error args wanting tuple
+        const { pass, message } = await expectAssertion.call(state, actual, ...args) as SyncExpectationResult
+
+        if ((pass && isNot) || (!pass && !isNot))
+          c.expect.fail(message())
+      }
+
+      const expectAssertionWrapper = isAsyncFunction(expectAssertion) ? expectAsyncWrapper : expectSyncWrapper
+
+      utils.addMethod(chai.Assertion.prototype, expectAssertionName, expectAssertionWrapper)
+    })
+  }
+}
+
+export function JestExtend(): ChaiPlugin {
+  return (chai, utils) => {
+    utils.addMethod(chai.expect, 'extend', (expects: MatchersObject) => {
+      chai.use(JestExtendPlugin(expects))
+    })
+  }
+}