fix: Ensure correct scope references after traversal (#192)

* test: Add tests illustrating scope issue
* fix: Re-crawl scope after traversal to fix references

Author: leebyron

fixtures/with-changed-scope.js

@@ -0,0 +1,2 @@
+import { noop } from 'lodash'
+noop(noop() ? noop : noop)

package-lock.json

@@ -18,6 +18,7 @@
     "@babel/core": "^7.2.2",
     "@babel/preset-env": "^7.2.3",
     "@babel/register": "^7.0.0",
+    "babel-plugin-lodash": "^3.3.4",
     "chai": "^4.2.0",
     "coveralls": "^3.0.2",
     "cross-env": "^5.2.0",

package.json

@@ -70,6 +70,9 @@ function makeVisitor ({ types: t }) {
             inputSourceMap
           })
           this.__dv__.enter(path)
+          // Istanbul visitor may replace Identifiers and require re-crawling
+          // scope before continuing with other babel plugins.
+          path.scope.crawl()
         },
         exit (path) {
           if (!this.__dv__) {

src/index.js

@@ -171,4 +171,55 @@ describe('babel-plugin-istanbul', function () {
       resultAfter.code.should.match(/statementMap/)
     })
   })
+
+  describe('should leave scope with correct references', function () {
+    it('leaves scope references as Identifiers', function () {
+      // This is a unit test which inspects the root cause of the problem:
+      // scope references that are replaced to no longer be Identifiers
+      babel.transformFileSync('./fixtures/with-changed-scope.js', {
+        babelrc: false,
+        configFile: false,
+        plugins: [
+          [makeVisitor({ types: babel.types }), {
+            include: ['fixtures/with-changed-scope.js']
+          }],
+          function testScope (t) {
+            return {
+              visitor: {
+                ImportSpecifier (path) {
+                  const fileScope = path.hub.file.scope
+                  const localBinding = fileScope.getBinding(path.node.local.name)
+                  for (const localReference of localBinding.referencePaths) {
+                    localReference.type.should.equal('Identifier')
+                  }
+                }
+              }
+            }
+          }
+        ]
+      })
+    })
+
+    it('creates valid syntax with other transforming plugins', function () {
+      // This is a minimal end-to-end test which illustrates how scope
+      // reference alteration impacts the assumptions of other plugins
+      const result = babel.transformFileSync(
+        './fixtures/with-changed-scope.js', {
+          babelrc: false,
+          configFile: false,
+          plugins: [
+            [makeVisitor({ types: babel.types }), {
+              include: ['fixtures/with-changed-scope.js']
+            }],
+            'babel-plugin-lodash'
+          ]
+        })
+
+      function testSyntaxError () {
+        babel.parse(result.code)
+      }
+
+      testSyntaxError.should.not.throw()
+    })
+  })
 })