fix: typechecking with Vue 2.7+

Fixes #7213

Author: haoqunjiang

packages/@vue/cli-plugin-typescript/index.js

@@ -83,21 +83,24 @@ module.exports = (api, projectOptions) => {
     // this plugin does not play well with jest + cypress setup (tsPluginE2e.spec.js) somehow
     // so temporarily disabled for vue-cli tests
     if (!process.env.VUE_CLI_TEST) {
-      let compilerPath
+      let compilerPath; let useCompilerSFC = false
       try {
         // Vue 2.7+
         compilerPath = require.resolve('vue/compiler-sfc')
+        useCompilerSFC = true
       } catch (e) {
         if (isVue3) {
           // Vue 3.0.0-3.2.12
           compilerPath = require.resolve('@vue/compiler-sfc')
+          useCompilerSFC = true
         } else {
           // Vue <= 2.6
           compilerPath = require.resolve('vue-template-compiler')
         }
       }
 
-      if (isVue3) {
+      if (useCompilerSFC) {
+        // only v5 supports the compiler-sfc API
         config
           .plugin('fork-ts-checker')
           .use(require('fork-ts-checker-webpack-plugin-v5'), [{
@@ -116,6 +119,7 @@ module.exports = (api, projectOptions) => {
             }
           }])
       } else {
+        // fallback to v3, in order to not introduce breaking changes to legacy projects
         config
           .plugin('fork-ts-checker')
             .use(require('fork-ts-checker-webpack-plugin'), [{