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

[rolphes]

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 (E:\jenkins\ProjectX\workspace\node_modules\uglifyjs-webpack-plugin\node_modules\uglify-es\tools\node.js:21:1), :1112:29)
at TreeWalker._visit (eval at (E:\jenkins\ProjectX\workspace\node_modules\uglifyjs-webpack-plugin\node_modules\uglify-es\tools\node.js:21:1), :1513:21)
at AST_Dot._walk (eval at (E:\jenkins\ProjectX\workspace\node_modules\uglifyjs-webpack-plugin\node_modules\uglify-es\tools\node.js:21:1), :1111:24)
at AST_VarDef.eval (eval at (E:\jenkins\ProjectX\workspace\node_modules\uglifyjs-webpack-plugin\node_modules\uglify-es\tools\node.js:21:1), :1058:40)
at TreeWalker._visit (eval at (E:\jenkins\ProjectX\workspace\node_modules\uglifyjs-webpack-plugin\node_modules\uglify-es\tools\node.js:21:1), :1513:21)
at AST_VarDef._walk (eval at (E:\jenkins\ProjectX\workspace\node_modules\uglifyjs-webpack-plugin\node_modules\uglify-es\tools\node.js:21:1), :1056:24)
at AST_Var.eval (eval at (E:\jenkins\ProjectX\workspace\node_modules\uglifyjs-webpack-plugin\node_modules\uglify-es\tools\node.js:21:1), :966:32)
at TreeWalker._visit (eval at (E:\jenkins\ProjectX\workspace\node_modules\uglifyjs-webpack-plugin\node_modules\uglify-es\tools\node.js:21:1), :1513:21)
at AST_Var._walk (eval at (E:\jenkins\ProjectX\workspace\node_modules\uglifyjs-webpack-plugin\node_modules\uglify-es\tools\node.js:21:1), :963:24)
at walk_body (eval at (E:\jenkins\ProjectX\workspace\node_modules\uglifyjs-webpack-plugin\node_modules\uglify-es\tools\node.js:21:1), :513:17)
at AST_Function.eval (eval at (E:\jenkins\ProjectX\workspace\node_modules\uglifyjs-webpack-plugin\node_modules\uglify-es\tools\node.js:21:1), :739:13)
at TreeWalker._visit (eval at (E:\jenkins\ProjectX\workspace\node_modules\uglifyjs-webpack-plugin\node_modules\uglify-es\tools\node.js:21:1), :1513:21)
at AST_Function._walk (eval at (E:\jenkins\ProjectX\workspace\node_modules\uglifyjs-webpack-plugin\node_modules\uglify-es\tools\node.js:21:1), :733:24)
at AST_Function.walk (eval at (E:\jenkins\ProjectX\workspace\node_modules\uglifyjs-webpack-plugin\node_modules\uglify-es\tools\node.js:21:1), :467:21)
at get_lvalues (eval at (E:\jenkins\ProjectX\workspace\node_modules\uglifyjs-webpack-plugin\node_modules\uglify-es\tools\node.js:21:1), :8804:34)
at collapse (eval at (E:\jenkins\ProjectX\workspace\node_modules\uglifyjs-webpack-plugin\node_modules\uglify-es\tools\node.js:21:1), :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: ember-cli/ember-cli#8075

[rolphes]

The error comes from the uglify-js package. With uglifyjs 3.3.4 it works as expected. The error "Cannot read property '_walk' of null" occours starting from version 3.3.5.

[tomjwilliamson]

+1 same issue

[seanzhu0925]

were you guys able to resolve the issue? what was the fix?

[seanzhu0925]

uglify-js is part of cli transitive dependency, when you do npm install, it will grab uglify-js 3.39 in my case. how can i override the dependency in package.json? or downgrade the version?

[clydin]

if using yarn, using the resolutions field within package.json would allow you to do that.

Also, CLI 7.0 (currently in release candidate stage) uses a new variant of uglify-es named terser which should alleviate the issues being faced here.

[seanzhu0925]

fixed the issue by changing the ES lib version in tsconfig.json file. it was es2017, changed to es2015 { "compileOnSave": false, "compilerOptions": { "outDir": "./dist/out-tsc", "sourceMap": true, "declaration": false, "moduleResolution": "node", "emitDecoratorMetadata": true, "experimentalDecorators": true, "target": "es5", "typeRoots": [ "node_modules/@types" ], "lib": [ "es2015", "dom" ] } }

[DingWeizhe]

If your project have a dependency tether, Try downgrade the version to 1.4.3.

shipshapecode/tether#291

[Ravell7]

Thank you @DingWeizhe ! I'm on that bug since yesterday !

[filipesilva]

Heya just wanted to mention we are aware of this issue, and waiting for a resolution in terser/terser#120. Then we'll update the version we use of terser (the uglifier in our pipeline).

[tomjwilliamson]

I fixed the issue the same as @DingWeizhe - downgraded tether. Just went through all my dependencies and checked which had the latest release, and tried the last version

[seanzhu0925]

also did npm update, @angular/compiler-cli version was updated, and it fixed the issue permanently.

[inpicksys]

@seanzhu0925 I updating everything, I can't fix this issue with @angular/compiler-cli.
Could someone describe in details how to avoid this issue during ng build --prod? (not locally but on CI server)?
This is blocking issue for me. I can't deploy application.

[filipesilva]

This issue is now fixed in terser@3.10.7. Angular CLI does not depend on terser directly, but you can force it to update by following these steps:

• check the current installed version of terser: npm ls terser
• install and uninstall terser to update your lockfile npm install terser@3.10.7 npm uninstall terser
• you should now see the latest terser in npm ls terser

[paustint]

@seanzhu0925 I updating everything, I can't fix this issue with @angular/compiler-cli.
Could someone describe in details how to avoid this issue during ng build --prod? (not locally but on CI server)?
This is blocking issue for me. I can't deploy application.

@inpicksys - my issue was that @angular-devkit/build-angular was not updated with ng update and I missed this, so I was still not using terser.

[Sijoma]

We are using Angular4 and this issue also effects our production build. How do I install terser so that Angular uses it instead of uglifyJS?

The weird thing is that we have not updated our dependencies.

[filipesilva]

@Sijoma you'll need to be using at least Angular CLI 7 for the build system to be using Terser.

[Sijoma]

@Sijoma you'll need to be using at least Angular CLI 7 for the build system to be using Terser.

Okay, we currently have stick with Angular 4, do you have any suggestions on how to fix the issue there?

[filipesilva]

You can try using Angular 4 with Angular CLI 7. It's not something we test for but might work. Other than that.. maybe we you can using Yarn to always resolve the uglify-js package to a version that doesn't exhibit this bug.

Hard to say at this point, it looks like the packages you are using are somewhat outdated. I really do encourage you to use a lockfile though, either through npm or yarn. Without it, your dependencies can change even if you don't update anything.

[Sijoma]

Thanks filipesilva, I found an older lockfile and managed to use that. Just FYI Building with the CLI Version 7 did not work.

I immediately removed the lockfile from the gitignore and committed it 😅.

[kzc]

https://github.com/terser-js/terser#replacing-uglify-es-with-terser-in-a-project-using-yarn

[JohnGalt1717]

This is back.

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