We'd like to be able to add custom functionality to *polymer build* and
*polymer
serve* by configuring custom babel plugins.
For example, since polymer-cli uses babel internally, we would add a
*babel.config.js* file to our workspace/project-root, e.g.:
module.exports = function (api) {
api.cache(true);
const presets = [ ];
const plugins = [
"@babel/plugin-proposal-optional-chaining"
];
return {
presets,
plugins
};
}
...and then we could serve or build our project with support for
optional-chaining, etc This would allow us to do all sorts of things by
writing additional babel plugins to handle stuff like minification inside
template HTML strings...
Unfortunately, this doesn't currently work. *polymer-build* seems to load
the configuration (due to its use of babel/core?), but *polymer-analyze*
doesn't. An error is generated in the build-optimization step performed by
polymer-analyze as soon as it encounters optional-chaining syntax in our
source:
error: Error: Unable to get document file:///.../somefile.js: This
> experimental syntax requires enabling the parser plugin: 'optionalChaining'
> (423:6)
> at BuildAnalyzer.<anonymous>
> (/usr/local/share/.config/yarn/global/node_modules/polymer-build/lib/analyzer.js:342:23)
> at Generator.next (<anonymous>)
> at fulfilled
> (/usr/local/share/.config/yarn/global/node_modules/polymer-build/lib/analyzer.js:17:58)
> at process._tickCallback (internal/process/next_tick.js:68:7)
polymer serve also generates an error:
Error { SyntaxError: This experimental syntax requires enabling the parser
> plugin: 'optionalChaining' (423:6)
> at Parser.raise
> (/usr/local/share/.config/yarn/global/node_modules/babylon/lib/index.js:776:15)
> at Parser.expectPlugin
> (/usr/local/share/.config/yarn/global/node_modules/babylon/lib/index.js:2084:18)
> at Parser.parseSubscript
> (/usr/local/share/.config/yarn/global/node_modules/babylon/lib/index.js:2792:12)
> at Parser.parseSubscripts
> (/usr/local/share/.config/yarn/global/node_modules/babylon/lib/index.js:2777:19)
> at Parser.parseExprSubscripts
> (/usr/local/share/.config/yarn/global/node_modules/babylon/lib/index.js:2767:17)
> at Parser.parseMaybeUnary
> (/usr/local/share/.config/yarn/global/node_modules/babylon/lib/index.js:2736:21)
> at Parser.parseExprOps
> (/usr/local/share/.config/yarn/global/node_modules/babylon/lib/index.js:2643:21)
> at Parser.parseMaybeConditional
> (/usr/local/share/.config/yarn/global/node_modules/babylon/lib/index.js:2615:21)
> at Parser.parseMaybeAssign
> (/usr/local/share/.config/yarn/global/node_modules/babylon/lib/index.js:2562:21)
> at Parser.parseExpression
> (/usr/local/share/.config/yarn/global/node_modules/babylon/lib/index.js:2515:21)
> pos: 13056,
> loc: Position { line: 423, column: 6 },
> missingPlugin: [ 'optionalChaining' ] }
In both cases, I've confirmed that the *babel.config.js* file is being
loaded. But babel is used in several different packages used by
*polymer-cli*, so my suspicion is that in some components aren't using the
part of babel that loads the configuration.
I had a look at polymer-cli, but I'm fairly new to TypeScript and NodeJS.
If there's any interest in this, I'd be willing to work on it if I can get
some initial help from someone involved with the project. Specifically,
confirmation that the approach is correct and identification of any other
known limitations that may become issues?
Cheers.
Follow Polymer on Google+: plus.google.com/107187849809354688692
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