Crash inside escodegen when minifying JavaScript class statement.

[kevincox]

// www/foo.js

export class Foo {
	foo = true;
}

// build.js
(async ()=>{
	let AssetGraph = require("assetgraph");

	let assetGraph = new AssetGraph({ root: "www/" });

	await assetGraph.loadAssets("*.js"); // Load all Html assets in the root dir

	for (let js of assetGraph.findAssets({type: "JavaScript"})) {
		js.minify();
	}

	await assetGraph.writeAssetsToDisc({ protocol: "file:" }, "out/");
})()

Result:

TypeError: this[type] is not a function
    at CodeGenerator.generateExpression (/home/kevincox/Downloads/node_modules/escodegen/escodegen.js:2516:28)
    at /home/kevincox/Downloads/node_modules/escodegen/escodegen.js:1133:38
    at withIndent (/home/kevincox/Downloads/node_modules/escodegen/escodegen.js:581:9)
    at CodeGenerator.ClassBody (/home/kevincox/Downloads/node_modules/escodegen/escodegen.js:1128:13)
    at CodeGenerator.generateStatement (/home/kevincox/Downloads/node_modules/escodegen/escodegen.js:2529:33)
    at CodeGenerator.ClassDeclaration (/home/kevincox/Downloads/node_modules/escodegen/escodegen.js:1159:30)
    at CodeGenerator.generateStatement (/home/kevincox/Downloads/node_modules/escodegen/escodegen.js:2529:33)
    at CodeGenerator.ExportNamedDeclaration (/home/kevincox/Downloads/node_modules/escodegen/escodegen.js:1237:42)
    at CodeGenerator.generateStatement (/home/kevincox/Downloads/node_modules/escodegen/escodegen.js:2529:33)
    at CodeGenerator.Program (/home/kevincox/Downloads/node_modules/escodegen/escodegen.js:1718:43)
    at CodeGenerator.generateStatement (/home/kevincox/Downloads/node_modules/escodegen/escodegen.js:2529:33)
    at generateInternal (/home/kevincox/Downloads/node_modules/escodegen/escodegen.js:2550:28)
    at Object.generate (/home/kevincox/Downloads/node_modules/escodegen/escodegen.js:2618:18)
    at get text [as text] (/home/kevincox/Downloads/node_modules/assetgraph/lib/assets/JavaScript.js:81:21)
    at get rawSrc [as rawSrc] (/home/kevincox/Downloads/node_modules/assetgraph/lib/assets/Text.js:82:30)
    at Promise.map.concurrency (/home/kevincox/Downloads/node_modules/assetgraph/lib/transforms/writeAssetsToDisc.js:60:19)
    at tryCatcher (/home/kevincox/Downloads/node_modules/bluebird/js/release/util.js:16:23)
    at MappingPromiseArray._promiseFulfilled (/home/kevincox/Downloads/node_modules/bluebird/js/release/map.js:68:38)
    at PromiseArray._iterate (/home/kevincox/Downloads/node_modules/bluebird/js/release/promise_array.js:115:31)
    at MappingPromiseArray.init (/home/kevincox/Downloads/node_modules/bluebird/js/release/promise_array.js:79:10)
    at MappingPromiseArray._asyncInit (/home/kevincox/Downloads/node_modules/bluebird/js/release/map.js:37:10)
    at _drainQueueStep (/home/kevincox/Downloads/node_modules/bluebird/js/release/async.js:97:12)

Versions

assetgraph: 7.12.0
node: 20.11.1

package-lock.json

[kevincox]

Inserting a print statement into escodegen I see that the unknown type is PropertyDefinition.

[kevincox]

% rg -w PropertyDefinition node_modules
node_modules/acorn/dist/acorn.d.mts
375:  body: Array<MethodDefinition | PropertyDefinition | StaticBlock>
479:export interface PropertyDefinition extends Node {
480:  type: "PropertyDefinition"
565:export type AnyNode = Statement | Expression | Declaration | ModuleDeclaration | Literal | Program | SwitchCase | CatchClause | Property | Super | SpreadElement | TemplateElement | AssignmentProperty | ObjectPattern | ArrayPattern | RestElement | AssignmentPattern | ClassBody | MethodDefinition | MetaProperty | ImportSpecifier | ImportDefaultSpecifier | ImportNamespaceSpecifier | ExportSpecifier | AnonymousFunctionDeclaration | AnonymousClassDeclaration | PropertyDefinition | PrivateIdentifier | StaticBlock

node_modules/acorn/dist/acorn.d.ts
375:  body: Array<MethodDefinition | PropertyDefinition | StaticBlock>
479:export interface PropertyDefinition extends Node {
480:  type: "PropertyDefinition"
565:export type AnyNode = Statement | Expression | Declaration | ModuleDeclaration | Literal | Program | SwitchCase | CatchClause | Property | Super | SpreadElement | TemplateElement | AssignmentProperty | ObjectPattern | ArrayPattern | RestElement | AssignmentPattern | ClassBody | MethodDefinition | MetaProperty | ImportSpecifier | ImportDefaultSpecifier | ImportNamespaceSpecifier | ExportSpecifier | AnonymousFunctionDeclaration | AnonymousClassDeclaration | PropertyDefinition | PrivateIdentifier | StaticBlock

node_modules/acorn/dist/acorn.js
1565:    return this.finishNode(field, "PropertyDefinition")

node_modules/acorn/dist/acorn.mjs
1559:  return this.finishNode(field, "PropertyDefinition")

node_modules/terser/lib/mozilla-ast.js
434:        PropertyDefinition: function(M) {
448:                    throw new Error("Non-Identifier key in PropertyDefinition");
720:                        : p.type == "PropertyDefinition" || p.type === "FieldDefinition" ? (p.key === M && p.computed || p.value === M ? AST_SymbolRef : AST_SymbolClassProperty)
1606:                type: "PropertyDefinition",
1618:                type: "PropertyDefinition",

node_modules/terser/dist/bundle.min.js
7410:        PropertyDefinition: function(M) {
7424:                    throw new Error("Non-Identifier key in PropertyDefinition");
7696:                        : p.type == "PropertyDefinition" || p.type === "FieldDefinition" ? (p.key === M && p.computed || p.value === M ? AST_SymbolRef : AST_SymbolClassProperty)
8582:                type: "PropertyDefinition",
8594:                type: "PropertyDefinition",

node_modules/uglify-js/lib/mozilla-ast.js
176:        PropertyDefinition: function(M) {
741:            type: "PropertyDefinition",

node_modules/estraverse/estraverse.js
130:        PropertyDefinition: 'PropertyDefinition',
208:        PropertyDefinition: ['key', 'value'],

[kevincox]

It seems like the latest escodegen doesn't support this.

I see estools/escodegen#438. However it creates a handler for FieldDefinition not PropertyDefinition.

I see estools/escodegen#443 which creates PropertyDefinition however talks about state class fields. So unless the field is being promoted to static by Terser I'm not sure which is right without more research.

[kevincox]

This same issue appears to exist on master assetgraph/assetgraph#40f98a051c4e5ba4ff0b892af0641688a884c03f.

[papandreou]

@kevincox, would you be up for contributing a fix to escodegen?

[kevincox]

Unlikely to happen soon. But maybe at some point.

[papandreou]

In any case, that's where it has to be implemented.

A good starting point would be to look at the estree spec for PropertyDefinition and working up a test case for escodegen.

[papandreou]

I guess we could also try to replace escodegen with another module, such as astring. That's just a bit more complicated, as we've exposed some of escodegen's flags in different places.

[kevincox]

I ended up implementing it: estools/escodegen#465

[papandreou]

Excellent! 💪