fix(mock-api): provide an explainatory error message when the mocks A…

…PI hoisting doesn't work (#1098)

packages/vitest/src/node/plugins/mock.ts

@@ -33,6 +33,13 @@ export function hoistMocks(code: string) {
   return m
 }
 
+const API_NOT_FOUND_ERROR = `There are some problems in resolving the mocks API.
+You may encounter this issue when importing the mocks API from another module other than 'vitest'.
+
+To fix this issue you can either:
+- import the mocks API directly from 'vitest'
+- enable the 'globals' options`
+
 export const MocksPlugin = (): Plugin => {
   return {
     name: 'vitest:mock-plugin',
@@ -43,12 +50,22 @@ export const MocksPlugin = (): Plugin => {
       if (m) {
         // hoist vitest imports in case it was used inside vi.mock factory #425
         const vitestImports = code.matchAll(vitestRegexp)
+        let found = false
+
         for (const match of vitestImports) {
           const indexStart = match.index!
           const indexEnd = match[0].length + indexStart
           m.remove(indexStart, indexEnd)
           m.prepend(`${match[0]}\n`)
+          found = true
         }
+
+        // if no vitest import found, check if the mock API is reachable after the hoisting
+        if (!found) {
+          m.prepend('try { vi } catch (_) { try { vitest } catch (__)'
+           + `{ throw new Error(${JSON.stringify(API_NOT_FOUND_ERROR)}) } }\n`)
+        }
+
         return {
           code: m.toString(),
           map: m.generateMap({ hires: true }),

test/fails/fixtures/mock-import-proxy-module.test.ts

@@ -0,0 +1,8 @@
+import { expect, test, vi } from './proxy-module'
+
+// This can be used only when imported directly from vitest
+vi.mock('vite')
+
+test('hi', () => {
+  expect(1 + 1).toEqual(2)
+})

test/fails/fixtures/proxy-module.ts

@@ -0,0 +1 @@
+export * from 'vitest'

test/fails/test/__snapshots__/runner.test.ts.snap

@@ -6,6 +6,8 @@ exports[`should fails > expect.test.ts > expect.test.ts 1`] = `"AssertionError:
 
 exports[`should fails > hook-timeout.test.ts > hook-timeout.test.ts 1`] = `"Error: Hook timed out in 10ms."`;
 
+exports[`should fails > mock-import-alias.test.ts > mock-import-alias.test.ts 1`] = `"Error: There are some problems in resolving the mocks API."`;
+
 exports[`should fails > nested-suite.test.ts > nested-suite.test.ts 1`] = `"AssertionError: expected true to be false // Object.is equality"`;
 
 exports[`should fails > stall.test.ts > stall.test.ts 1`] = `"TypeError: failure"`;