fix: allow relative baseUrl other than ./ (#2168)

packages/@vue/cli-service/__tests__/Service.spec.js

@@ -94,6 +94,26 @@ test('handle option baseUrl and outputDir correctly', () => {
   expect(service.projectOptions.outputDir).toBe('/public')
 })
 
+test('normalize baseUrl when relative', () => {
+  mockPkg({
+    vue: {
+      baseUrl: './foo/bar'
+    }
+  })
+  const service = createMockService()
+  expect(service.projectOptions.baseUrl).toBe('foo/bar/')
+})
+
+test('keep baseUrl when empty', () => {
+  mockPkg({
+    vue: {
+      baseUrl: ''
+    }
+  })
+  const service = createMockService()
+  expect(service.projectOptions.baseUrl).toBe('')
+})
+
 test('load project options from vue.config.js', () => {
   process.env.VUE_CLI_SERVICE_CONFIG_PATH = `/vue.config.js`
   fs.writeFileSync('/vue.config.js', `module.exports = { lintOnSave: false }`)

packages/@vue/cli-service/lib/Service.js

@@ -298,10 +298,10 @@ module.exports = class Service {
     }
 
     // normalize some options
+    ensureSlash(resolved, 'baseUrl')
     if (typeof resolved.baseUrl === 'string') {
       resolved.baseUrl = resolved.baseUrl.replace(/^\.\//, '')
     }
-    ensureSlash(resolved, 'baseUrl')
     removeSlash(resolved, 'outputDir')
 
     // deprecation warning