fix: generate valid js code for aliased enum values

[alexander-fenster]

Having an aliased default value in an enum now breaks the generated JS static code:

SyntaxError: Multiple default clauses
    at Espree.raise (/Users/fenster/repos/nodejs-appengine-admin/node_modules/protobufjs-cli/node_modules/espree/dist/espree.cjs:675:25)
    at Espree.raiseRecoverable (/Users/fenster/repos/nodejs-appengine-admin/node_modules/protobufjs-cli/node_modules/espree/dist/espree.cjs:691:18)
    at Espree.pp$8.parseSwitchStatement (/Users/fenster/repos/nodejs-appengine-admin/node_modules/protobufjs-cli/node_modules/acorn/dist/acorn.js:1107:34)
    at Espree.pp$8.parseStatement (/Users/fenster/repos/nodejs-appengine-admin/node_modules/protobufjs-cli/node_modules/acorn/dist/acorn.js:909:39)
    at Espree.pp$8.parseBlock (/Users/fenster/repos/nodejs-appengine-admin/node_modules/protobufjs-cli/node_modules/acorn/dist/acorn.js:1236:23)
    at Espree.pp$5.parseFunctionBody (/Users/fenster/repos/nodejs-appengine-admin/node_modules/protobufjs-cli/node_modules/acorn/dist/acorn.js:3285:24)
    at Espree.pp$8.parseFunction (/Users/fenster/repos/nodejs-appengine-admin/node_modules/protobufjs-cli/node_modules/acorn/dist/acorn.js:1358:10)
    at Espree.pp$8.parseFunctionStatement (/Users/fenster/repos/nodejs-appengine-admin/node_modules/protobufjs-cli/node_modules/acorn/dist/acorn.js:1058:17)
    at Espree.pp$8.parseStatement (/Users/fenster/repos/nodejs-appengine-admin/node_modules/protobufjs-cli/node_modules/acorn/dist/acorn.js:903:19)
    at Espree.pp$8.parseTopLevel (/Users/fenster/repos/nodejs-appengine-admin/node_modules/protobufjs-cli/node_modules/acorn/dist/acorn.js:817:23) {
  index: 1011,
  lineNumber: 54,
  column: 3
}

Fixing that by making sure that the default: clause is emitted only once. Updating the tests accordingly.

[bcoe]

I would usually use let, but it looks like var is internally consistent.

[alexander-fenster]

Yes, it's the remains of Node 4 support. We probably want a global refactor to make the code more modern.

[acode-x]

Hello @bcoe and @alexander-fenster,

Firstly, Thanks for developing and maintaining this amazing library.

Second, I use protobuf.js massively in IoT embedded devices without experiencing any issues.
Due to small memory footprint I use embedded Javascript engine - Duktape (ES5/5.1 complaint + some more features from ES6/7).

If it is planned to use modern syntax for feature/bug fixes, I am concerned about Duktape compatibility issues with the new code. In addition, I don't believe there are better protobuf alternatives in Javascript.

In the future, I see 2 options:


1. I maintain a forked ES5/5.1 version equivalent to protobuf.js releases (which could be a nightmare)
2. You’d also be maintaining another branch for ES5/5.1 syntax.

Requesting your thoughts and guidance on the same.

Thanks!