Ensure import is removed when other tooling uses the same module.

In the default configuration of ember-cli-babel both `babel-plugin-debug-macros`
and `babel-plugin-ember-modules-api-polyfill` handle specific specifiers out of
`@ember/debug`. Prior to this change this package would not properly remove the
import declaration (even though it had no specifiers left after both plugins had
ran), because the `isImportRemovable` flag is eagerly cached.

After this change, the import is removed if the only remaining specifiers are
the ones that debug-macros is removing.

Author: Robert Jackson

fixtures/shared-debug-module/expectation.js

@@ -0,0 +1,5 @@
+var inspect = Ember.inspect;
+
+
+inspect('string thing');
+(true && !(false) && Ember.assert(false, 'This is an assertion 2'));

fixtures/shared-debug-module/sample.js

@@ -0,0 +1,4 @@
+import { assert, inspect } from '@ember/debug-tools';
+
+inspect('string thing');
+assert(false, 'This is an assertion 2');

src/lib/utils/macros.js

@@ -7,7 +7,6 @@ const SUPPORTED_MACROS = ['assert', 'deprecate', 'warn', 'log'];
 export default class Macros {
   constructor(t, options) {
     this.localDebugBindings = [];
-    this.isImportRemovable = false;
     this.envFlagBindings = [];
     this.hasEnvFlags = false;
     this.envFlagsSource = options.envFlags.envFlagsImport;
@@ -122,9 +121,6 @@ export default class Macros {
   collectDebugToolsSpecifiers(specifiers) {
     this.importedDebugTools = true;
     this._collectImportBindings(specifiers, this.localDebugBindings);
-    if (specifiers.length === this.localDebugBindings.length) {
-      this.isImportRemovable = true;
-    }
   }
 
   collectEnvFlagSpecifiers(specifiers) {
@@ -197,7 +193,11 @@ export default class Macros {
 
     if (!debugHelpers.module) {
       if (this.localDebugBindings.length > 0) {
-        if (this.isImportRemovable) {
+        this.localDebugBindings[0].parentPath.parentPath
+        let importPath = this.localDebugBindings[0].findParent(p => p.isImportDeclaration());
+        let specifiers = importPath.get('specifiers');
+
+        if (specifiers.length === this.localDebugBindings.length) {
           this.localDebugBindings[0].parentPath.parentPath.remove();
         } else {
           this.localDebugBindings.forEach((binding) => binding.parentPath.remove());

src/tests/debug-tools-test.js

@@ -77,6 +77,64 @@ let cases = {
     ]
   },
 
+  'foreign debug imports': {
+    transformOptions: {
+      presets,
+      plugins: [
+        [DebugToolsPlugin, {
+          externalizeHelpers: {
+            global: 'Ember'
+          },
+          debugTools: {
+            source: '@ember/debug-tools',
+            assertPredicateIndex: 0
+          },
+          envFlags: {
+            source: '@ember/env-flags',
+            flags: {
+              DEBUG: true
+            }
+          }
+        }],
+
+        [function(babel) {
+          let t = babel.types;
+
+          return {
+            name: 'import-remover',
+            visitor: {
+              ImportSpecifier(path) {
+                let importedName = path.node.imported.name;
+                if (importedName === 'inspect') {
+                  let importDeclarationPath = path.findParent(p => p.isImportDeclaration());
+                  let binding = path.scope.getBinding(importedName);
+                  let references = binding.referencePaths;
+
+                  let replacements = [];
+                  for (let reference of references) {
+                    replacements.push(t.variableDeclaration('var', [
+                      t.variableDeclarator(
+                        t.identifier(path.node.local.name),
+                        t.memberExpression(t.identifier('Ember'), t.identifier(importedName))
+                      ),
+                    ]));
+                  }
+
+                  path.remove();
+                  importDeclarationPath.insertAfter(replacements);
+                }
+              }
+            }
+          }
+        }]
+      ]
+    },
+    fixtures: [
+      'shared-debug-module',
+    ],
+    errors: [ ]
+  },
+
   'Global External Test Helpers': {
     transformOptions: {
       presets,