Correctly visit param decorators to prevent their imports being removed in typescript transform (#8738)

* Remove types on program exit in typescript transform

* Revert changes to typescript transform

* Correctly add visitors for param decorators

* Fix plugin for node 6

packages/babel-plugin-transform-typescript/test/fixtures/imports/parameter-decorators/input.mjs

@@ -0,0 +1,6 @@
+import { NgModule, Optional, SkipSelf } from '@angular/core';
+
+@NgModule({})
+export class CoreModule {
+  constructor(@Optional() @SkipSelf() parentModule) { }
+}

packages/babel-plugin-transform-typescript/test/fixtures/imports/parameter-decorators/options.json

@@ -0,0 +1,12 @@
+{
+  "plugins": [
+    "transform-typescript",
+    [
+      "proposal-decorators",
+      {
+        "legacy": true
+      }
+    ],
+    "./plugin"
+  ]
+}

packages/babel-plugin-transform-typescript/test/fixtures/imports/parameter-decorators/output.mjs

@@ -0,0 +1,9 @@
+var _dec, _class;
+
+import { NgModule, Optional, SkipSelf } from '@angular/core';
+export let CoreModule = (_dec = NgModule({}), _dec(_class = class CoreModule {
+  constructor(_parentModule) {
+    var _parentModule2 = Optional()(SkipSelf()(_parentModule));
+  }
+
+}) || _class);

packages/babel-plugin-transform-typescript/test/fixtures/imports/parameter-decorators/plugin.js

@@ -0,0 +1,54 @@
+"use strict";
+// https://github.com/benderTheCrime/babel-plugin-transform-function-parameter-decorators/
+
+Object.defineProperty(exports, "__esModule", {
+  value: true,
+});
+
+exports.default = function(_ref) {
+  var types = _ref.types;
+
+  return {
+    visitor: {
+      Function: function parseFunctionPath(path) {
+        (path.get("params") || [])
+          .slice()
+          .reverse()
+          .forEach(function(param) {
+            var name = param.node.name;
+            var paramUidName = path.scope.generateUidIdentifier(name).name;
+            var resultantDecorator = void 0;
+
+            (param.node.decorators || [])
+              .slice()
+              .reverse()
+              .forEach(function(decorator) {
+                resultantDecorator = types.callExpression(
+                  decorator.expression,
+                  [resultantDecorator || types.Identifier(paramUidName)]
+                );
+              });
+
+            if (resultantDecorator) {
+              var decoratedParamUidName = path.scope.generateUidIdentifier(name)
+                .name;
+
+              path.scope.rename(name, decoratedParamUidName);
+              param.parentPath
+                .get("body")
+                .unshiftContainer(
+                  "body",
+                  types.variableDeclaration("var", [
+                    types.variableDeclarator(
+                      types.Identifier(decoratedParamUidName),
+                      resultantDecorator
+                    ),
+                  ])
+                );
+              param.replaceWith(types.Identifier(paramUidName));
+            }
+          });
+      },
+    },
+  };
+};

packages/babel-types/src/definitions/core.js

@@ -388,7 +388,7 @@ export const patternLikeCommon = {
 
 defineType("Identifier", {
   builder: ["name"],
-  visitor: ["typeAnnotation"],
+  visitor: ["typeAnnotation", "decorators" /* for legacy param decorators */],
   aliases: ["Expression", "PatternLike", "LVal", "TSEntityName"],
   fields: {
     ...patternLikeCommon,

packages/babel-types/src/definitions/es2015.js

@@ -13,7 +13,7 @@ import {
 } from "./core";
 
 defineType("AssignmentPattern", {
-  visitor: ["left", "right"],
+  visitor: ["left", "right", "decorators" /* for legacy param decorators */],
   builder: ["left", "right"],
   aliases: ["Pattern", "PatternLike", "LVal"],
   fields: {
@@ -472,7 +472,11 @@ defineType("ClassMethod", {
 });
 
 defineType("ObjectPattern", {
-  visitor: ["properties", "typeAnnotation"],
+  visitor: [
+    "properties",
+    "typeAnnotation",
+    "decorators" /* for legacy param decorators */,
+  ],
   builder: ["properties"],
   aliases: ["Pattern", "PatternLike", "LVal"],
   fields: {