Exporting decorated class error

[Awk34]

Input Code

@Decorator()
export class MyClass {}

Babel Configuration (.bablerc, package.json, cli command)

{
    "plugins": [
        "syntax-decorators"
    ]
}

Expected Behavior

@Decorator()
export class MyClass {}

Current Behavior

export @Decorator()
class MyClass {}

Possible Solution

What I'm currently doing to circumvent this:

export let MyClass = @Decorator()
class MyClass {}

¯\_(ツ)_/¯

Context

I've got a project where I'm trying to parse ES6 code with Flow types, and just take the types out. This minimal case reproduces the same issue, though.

Your Environment

software	version
Babel	babel-cli@6.14.0
node	6.5.0
npm	3.10.3
Operating System	Win 10 x64

[Awk34]

This might be an issue for Babylon instead

[hzoo]

Is there a reason why you aren't using the transform? You can use https://github.com/loganfsmyth/babel-plugin-transform-decorators-legacy to transform decorators and https://babeljs.io/docs/plugins/transform-flow-strip-types/ to remove flow types

[loganfsmyth]

This should be a pretty self-contained code generator fix. We'll need the export declaration step to test what kind of declaration it has to potentially render decorators, and the opposite logic to skip them when rendering the class declaration itself.

[Awk34]

@hzoo it goes alongside #4388 that I reported. I have a Yeoman generator that I have parse JS files, and then strip flow types, but leave the remainder of the code mostly unchanged.

[Awk34]

Can you point me to where this might be fixed in the code?

[hzoo]

Yeah babel-generator. each node type has a function that prints it out.

Example with decorator:

babel/packages/babel-generator/src/generators/expressions.js

Lines 79 to 83 in 39c9216

	export function Decorator(node: Object) {
	this.token("@");
	this.print(node.expression, node);
	this.newline();
	}

Probably need to fix something in babel/modules.js like at

babel/packages/babel-generator/src/generators/modules.js

Lines 70 to 118 in 39c9216

	function ExportDeclaration(node: Object) {
	if (node.declaration) {
	let declar = node.declaration;
	this.print(declar, node);
	if (!t.isStatement(declar)) this.semicolon();
	} else {
	if (node.exportKind === "type") {
	this.word("type");
	this.space();
	}
	let specifiers = node.specifiers.slice(0);
	// print "special" specifiers first
	let hasSpecial = false;
	while (true) {
	let first = specifiers[0];
	if (t.isExportDefaultSpecifier(first) || t.isExportNamespaceSpecifier(first)) {
	hasSpecial = true;
	this.print(specifiers.shift(), node);
	if (specifiers.length) {
	this.token(",");
	this.space();
	}
	} else {
	break;
	}
	}
	if (specifiers.length || (!specifiers.length && !hasSpecial)) {
	this.token("{");
	if (specifiers.length) {
	this.space();
	this.printList(specifiers, node);
	this.space();
	}
	this.token("}");
	}
	if (node.source) {
	this.space();
	this.word("from");
	this.space();
	this.print(node.source, node);
	}
	this.semicolon();
	}
	}

Can use http://astexplorer.net/#/pzoRIHiZyd to view the AST

[devongovett]

Fixed by #5020.

[hzoo]

This isn't allowed in Stage 2 decorators anymore so closing

https://github.com/babel/babylon/pull/587/files#diff-cd89c8d2f00940bd0d50120e23c326edR1

3.4. export keyword in between of class body and decorators