Parcel: Property right of AssignmentExpression expected node to be of a type ["Expression"] but instead got null

[hakankaraduman]

🐛 bug report

I wanted to try out new tree shaking feature at 1.9.0 but the project don't build when I add that cli command.

🎛 Configuration (.babelrc, package.json, cli command)

{ "env": { "production": { "presets": ["env", "react", "flow"], "plugins": [ "emotion", [ "transform-runtime", { "polyfill": false, "regenerator": true } ], "transform-decorators-legacy", "transform-class-properties", ["import", { "libraryName": "antd", "libraryDirectory": "es", "style": "css"}] ] }, "development": { "presets": ["env", "react", "flow"], "plugins": [ "emotion", [ "transform-runtime", { "polyfill": false, "regenerator": true } ], "transform-decorators-legacy", "transform-class-properties", ["import", { "libraryName": "antd", "libraryDirectory": "es", "style": "css"}] ] }, "test": { "presets": ["env", "react", "flow"], "plugins": [ "emotion", [ "transform-runtime", { "polyfill": false, "regenerator": true } ], "transform-decorators-legacy", "transform-class-properties" ] } } }

🤔 Expected Behavior

It should build as when I use parcel build without this tree shaking command

😯 Current Behavior

It does not finish the build.

This is the error message:

Property right of AssignmentExpression expected node to be of a type ["Expression"] but instead got null

I also included the error log file

💁 Possible Solution

🔦 Context

I want to try out new features in Parcel.

💻 Code Sample

🌍 Your Environment

| Software | Version(s) |
| ---------------- | ---------- |
| Parcel | 1.9.0
| Node | 8.11.1
| npm/Yarn | 6.0.0
| Operating System | Windows 10 x64

yarn-error.log

[fathyb]

Could you show us the content of the file responsible for the error?

[hakankaraduman]

It gives the log below at the terminal. I don't understand which file it is from looking at this log. Can you help me spotting the file please

`C:\Users\HP\Desktop\HardwareWeb>yarn build
yarn run v1.5.1
$ npm run rm:build && cross-env NODE_ENV=production concurrently "npm run babel:build" "npm run parcel:build"

[email protected] rm:build C:\Users\HP\Desktop\HardwareWeb
rimraf build

[1]
[1] > [email protected] parcel:build C:\Users\HP\Desktop\HardwareWeb
[1] > parcel build src/index.html -d build/public --experimental-scope-hoisting
[1]
[0]
[0] > [email protected] babel:build C:\Users\HP\Desktop\HardwareWeb
[0] > babel src/server -d build
[0]
∞ Building index.html...
src\server\api_router.js -> build\api_router.js
[0] src\server\database\database.js -> build\database\database.js
[0] src\server\database\db_content.js -> build\database\db_content.js
[0] src\server\database\db_playlist.js -> build\database\db_playlist.js
[0] src\server\database\db_screen.js -> build\database\db_screen.js
∞ Building index.js...
src\server\database\models.js -> build\database\models.js
[0] src\server\express.js -> build\express.js
× Property right of AssignmentExpression expected node to be of a type ["Expression"] but instead got null
at Object.validate (C:\Users\HP\Desktop\HardwareWeb\node_modules\babel-types\lib\definitions\index.js:109:13)
[1] at Object.validate (C:\Users\HP\Desktop\HardwareWeb\node_modules\babel-types\lib\index.js:505:9)
[1] at NodePath._replaceWith (C:\Users\HP\Desktop\HardwareWeb\node_modules\babel-traverse\lib\path\replacement.js:176:7)
[1] at NodePath._remove (C:\Users\HP\Desktop\HardwareWeb\node_modules\babel-traverse\lib\path\removal.js:58:10)
[1] at NodePath.remove (C:\Users\HP\Desktop\HardwareWeb\node_modules\babel-traverse\lib\path\removal.js:30:8)
[1] at binding.referencePaths.concat.forEach.path (C:\Users\HP\Desktop\HardwareWeb\node_modules\parcel-bundler\src\scope-hoisting\shake.js:41:22)
[1] at Array.forEach ()
[1] at Object.keys.forEach.name (C:\Users\HP\Desktop\HardwareWeb\node_modules\parcel-bundler\src\scope-hoisting\shake.js:32:10)
[1] at Array.forEach ()
[1] at treeShake (C:\Users\HP\Desktop\HardwareWeb\node_modules\parcel-bundler\src\scope-hoisting\shake.js:20:33)
[1] npm ERR! code ELIFECYCLE
[1] npm ERR! errno 1
[1] npm ERR! [email protected] parcel:build: parcel build src/index.html -d build/public --experimental-scope-hoisting
[1] npm ERR! Exit status 1
[1] npm ERR!
npm ERR! Failed at the [email protected] parcel:build script.
[1] npm ERR! This is probably not a problem with npm. There is likely additional logging output above.
[1]
[1] npm ERR! A complete log of this run can be found in:
[1] npm ERR! C:\Users\HP\AppData\Roaming\npm-cache_logs\2018-06-15T09_49_40_650Z-debug.log
[1] npm run parcel:build exited with code 1
error An unexpected error occurred: "Command failed.
Exit code: 1
Command: C:\WINDOWS\system32\cmd.exe
Arguments: /d /s /c npm run rm:build && cross-env NODE_ENV=production concurrently \"npm run babel:build\" \"npm run parcel:build\"
Directory: C:\Users\HP\Desktop\HardwareWeb
Output:
".
info If you think this is a bug, please open a bug report with the information provided in "C:\Users\HP\Desktop\HardwareWeb\yarn-error.log".
info Visit https://yarnpkg.com/en/docs/cli/run for documentation about this command.
`

[hakankaraduman]

I executed only the parcel command for an isolated log. Here it is below

C:\Users\HP\Desktop\HardwareWeb>yarn parcel:build yarn run v1.5.1 $ parcel build src/index.html -d build/public --experimental-scope-hoisting × Property right of AssignmentExpression expected node to be of a type ["Expression"] but instead got null at Object.validate (C:\Users\HP\Desktop\HardwareWeb\node_modules\babel-types\lib\definitions\index.js:109:13) at Object.validate (C:\Users\HP\Desktop\HardwareWeb\node_modules\babel-types\lib\index.js:505:9) at NodePath._replaceWith (C:\Users\HP\Desktop\HardwareWeb\node_modules\babel-traverse\lib\path\replacement.js:176:7) at NodePath._remove (C:\Users\HP\Desktop\HardwareWeb\node_modules\babel-traverse\lib\path\removal.js:58:10) at NodePath.remove (C:\Users\HP\Desktop\HardwareWeb\node_modules\babel-traverse\lib\path\removal.js:30:8) at binding.referencePaths.concat.forEach.path (C:\Users\HP\Desktop\HardwareWeb\node_modules\parcel-bundler\src\scope-hoisting\shake.js:41:22) at Array.forEach (<anonymous>) at Object.keys.forEach.name (C:\Users\HP\Desktop\HardwareWeb\node_modules\parcel-bundler\src\scope-hoisting\shake.js:32:10) at Array.forEach (<anonymous>) at treeShake (C:\Users\HP\Desktop\HardwareWeb\node_modules\parcel-bundler\src\scope-hoisting\shake.js:20:33) error An unexpected error occurred: "Command failed. Exit code: 1 Command: C:\\WINDOWS\\system32\\cmd.exe Arguments: /d /s /c parcel build src/index.html -d build/public --experimental-scope-hoisting Directory: C:\\Users\\HP\\Desktop\\HardwareWeb Output: ". info If you think this is a bug, please open a bug report with the information provided in "C:\\Users\\HP\\Desktop\\HardwareWeb\\yarn-error.log". info Visit https://yarnpkg.com/en/docs/cli/run for documentation about this command.

[sujith97]

@fathyb
I can build but browser complains of undefined variable which looks like the bundled output here: https://medium.com/@devongovett/parcel-v1-9-0-tree-shaking-2x-faster-watcher-and-more-87f2e1a70f79

Command:

parcel build --experimental-scope-hoisting client/scripts/index.js --public-url /

Builds fine. Start the server and navigate to home page:

Uncaught ReferenceError: $37$exports is not defined

I opened dev tools and searched for $37$exports in the bundled file and there is just one usage without a declaration.

[TimNZ]

[Production builds]

I get the same AssignmentExpression error.
Added a console.log to shake.js to output the 'path' which was triggering the error in parent.remove() call.

Please output a summary of the node/file with the error.

In my case this declaration was tripping up babel (?)

var isInDisabledFieldset = function isInDisabledFieldset(inst) {
  var node;

  try {
    node = (0, _reactDom.findDOMNode)(inst);
  } catch (err) {
    /* ignore */
  }

  return !!node && (0, _matches.default)(node, 'fieldset[disabled] *');
};

I changed to below which fixed it.

var isInDisabledFieldset = function(inst) {
  var node;

  try {
    node = (0, _reactDom.findDOMNode)(inst);
  } catch (err) {
    /* ignore */
  }

  return !!node && (0, _matches.default)(node, 'fieldset[disabled] *');
};

Then I got a different error in a different stage of tree shaking saying an ES6 file didn't have a 'default' node - that file definitely has an 'export default ABC'

I then removed the scope hoisting flag and found my index.html wasn't get overwritten even though the primary './src/index.js' reference was changing in builds.

At that stage I reverted to 1.8.1

[fathyb]

Thanks @sujith97 and @TimNZ for reporting, could you open a dedicated issue for your bugs? It's very hard to keep track of tree-shaking issues otherwise. It's the most experimental feature of Parcel but it can get stable very quick if we get triage right.

Ah and @TimNZ if you're having issues unrelated the --experimental-scope-hoisting flag (index.html doesn't get overwritten) please also open an issue for it so we can fix this ASAP.

[sujith97]

@fathyb Thanks for the response. Here is the ticket: Issue 1552

[hakankaraduman]

@fathyb Hi, was my logs good enough for you? Do you need me to do anything?

[TimNZ]

@fathyb thanks.

I'll wait till at least 1.9.1.

I've got a large React code base and there's a few issues that will be a mix of Parcel and Babel, and need someone a lot more capable than me sorting them.
Includes isolated cases of array destructuring and anon functions slipping through into production builds when I am targeting stage 0, dynamic imports breaking nested require, and others.

[fathyb]

Thanks all, @hakankaraduman I pushed #1575 to fix it.

[devongovett]

Released in v1.9.3.