angular-cli: ng build --prod: Cannot read property '_walk' of null

Bug Report or Feature Request (mark with an x)

- [x] bug report -> please search issues before submitting
- [ ] feature request

Command (mark with an x)

- [ ] new
- [x] build
- [ ] serve
- [ ] test
- [ ] e2e
- [ ] generate
- [ ] add
- [ ] update
- [ ] lint
- [ ] xi18n
- [ ] run
- [ ] config
- [ ] help
- [ ] version
- [ ] doc

Versions

Node: v8.11.1 NPM: 6.4.1

Angular CLI: 6.2.3 Node: 8.11.1 OS: win32 x64 Angular: 6.1.9 … animations, common, compiler, compiler-cli, core, forms … http, language-service, platform-browser … platform-browser-dynamic, router

Package Version

@angular-devkit/architect 0.8.3 @angular-devkit/build-angular 0.8.3 @angular-devkit/build-optimizer 0.8.3 @angular-devkit/build-webpack 0.8.3 @angular-devkit/core 0.8.3 @angular-devkit/schematics 0.8.3 @angular/cli 6.2.3 @ngtools/webpack 6.2.3 @schematics/angular 0.8.3 @schematics/update 0.8.3 rxjs 6.3.3 typescript 2.7.2 webpack 4.20.2

Windows 10

Repro steps

execute “ng build --prod” -> sorry, I can’t provide the repo.

This bug suddenly popped up on our build server two days ago. Before that, this problem never occurred. After cleaning node_moduls and npm install I can reproduce the error on my machine too.

The log given by the failure

`Date: 2018-09-28T18:28:46.879Z Hash: 2fa0d73885177ad3220b Time: 109957ms chunk {0} runtime.ec2944dd8b20ec099bf3.js (runtime) 1.44 kB [entry] [rendered] chunk {1} main.85d86102e68c1db8c7c4.js (main) 8.08 MB [initial] [rendered] chunk {2} polyfills.c2c353082061f41763b0.js (polyfills) 98.3 kB [initial] [rendered] chunk {3} styles.c5267d72f9cea9ab11f3.css (styles) 150 kB [initial] [rendered]

ERROR in main.85d86102e68c1db8c7c4.js from UglifyJs TypeError: Cannot read property ‘_walk’ of null at AST_Dot.eval (eval at <anonymous> (E:\jenkins\ProjectX\workspace\node_modules\uglifyjs-webpack-plugin\node_modules\uglify-es\tools\node.js:21:1), <anonymous>:1112:29) at TreeWalker._visit (eval at <anonymous> (E:\jenkins\ProjectX\workspace\node_modules\uglifyjs-webpack-plugin\node_modules\uglify-es\tools\node.js:21:1), <anonymous>:1513:21) at AST_Dot._walk (eval at <anonymous> (E:\jenkins\ProjectX\workspace\node_modules\uglifyjs-webpack-plugin\node_modules\uglify-es\tools\node.js:21:1), <anonymous>:1111:24) at AST_VarDef.eval (eval at <anonymous> (E:\jenkins\ProjectX\workspace\node_modules\uglifyjs-webpack-plugin\node_modules\uglify-es\tools\node.js:21:1), <anonymous>:1058:40) at TreeWalker._visit (eval at <anonymous> (E:\jenkins\ProjectX\workspace\node_modules\uglifyjs-webpack-plugin\node_modules\uglify-es\tools\node.js:21:1), <anonymous>:1513:21) at AST_VarDef._walk (eval at <anonymous> (E:\jenkins\ProjectX\workspace\node_modules\uglifyjs-webpack-plugin\node_modules\uglify-es\tools\node.js:21:1), <anonymous>:1056:24) at AST_Var.eval (eval at <anonymous> (E:\jenkins\ProjectX\workspace\node_modules\uglifyjs-webpack-plugin\node_modules\uglify-es\tools\node.js:21:1), <anonymous>:966:32) at TreeWalker._visit (eval at <anonymous> (E:\jenkins\ProjectX\workspace\node_modules\uglifyjs-webpack-plugin\node_modules\uglify-es\tools\node.js:21:1), <anonymous>:1513:21) at AST_Var._walk (eval at <anonymous> (E:\jenkins\ProjectX\workspace\node_modules\uglifyjs-webpack-plugin\node_modules\uglify-es\tools\node.js:21:1), <anonymous>:963:24) at walk_body (eval at <anonymous> (E:\jenkins\ProjectX\workspace\node_modules\uglifyjs-webpack-plugin\node_modules\uglify-es\tools\node.js:21:1), <anonymous>:513:17) at AST_Function.eval (eval at <anonymous> (E:\jenkins\ProjectX\workspace\node_modules\uglifyjs-webpack-plugin\node_modules\uglify-es\tools\node.js:21:1), <anonymous>:739:13) at TreeWalker._visit (eval at <anonymous> (E:\jenkins\ProjectX\workspace\node_modules\uglifyjs-webpack-plugin\node_modules\uglify-es\tools\node.js:21:1), <anonymous>:1513:21) at AST_Function._walk (eval at <anonymous> (E:\jenkins\ProjectX\workspace\node_modules\uglifyjs-webpack-plugin\node_modules\uglify-es\tools\node.js:21:1), <anonymous>:733:24) at AST_Function.walk (eval at <anonymous> (E:\jenkins\ProjectX\workspace\node_modules\uglifyjs-webpack-plugin\node_modules\uglify-es\tools\node.js:21:1), <anonymous>:467:21) at get_lvalues (eval at <anonymous> (E:\jenkins\ProjectX\workspace\node_modules\uglifyjs-webpack-plugin\node_modules\uglify-es\tools\node.js:21:1), <anonymous>:8804:34) at collapse (eval at <anonymous> (E:\jenkins\ProjectX\workspace\node_modules\uglifyjs-webpack-plugin\node_modules\uglify-es\tools\node.js:21:1), <anonymous>:8565:35) Build step ‘Execute Windows batch command’ marked build as failure [TASKS] Skipping publisher since build result is FAILURE Skipped archiving because build is not successful`

Desired functionality

Build optimization with uglifyjs works as before

Mention any other details that might be useful

Similar errors are filed for ember-cli: https://github.com/ember-cli/ember-cli/issues/8075