fix: do not use #private

[alexander-fenster]

Adding a # private method is technically a breaking change. Our packing tests across all client libraries are now failing with

node_modules/google-auth-library/build/src/auth/googleauth.d.ts:67:5 - error TS18028: Private identifiers are only available when targeting ECMAScript 2015 and higher.

67     #private;
       ~~~~~~~~

(in CI, this looks like a pack-n-play TypeScript test failure as a part of system tests)

Let's not be that modern and use the regular private method instead.

[ruyadorno]

Oh that's interesting, private class fields have been on Node.js since v12. I believe this is more of a matter of reconfiguring our TypeScript compiler to a little more modern level of ECMAScript support rather than being an unsupported feature.

That said, there's maybe an argument to be made on what is the more JS-idiommatic way of expressing the intent of a private method/property vs TS-idiommatic and I'm not sure where the collective consensus within the larger JavaScript ecosystem sits on that.

Anyways just wanted to highlight that it might be possible to support #private notations and that it might be more familiar to a lot of JS devs and hear your thoughts on it @alexander-fenster (I might be missing more context here, feel free to correct me if I'm making any wrong assumption) 😊

[danielbankhead]

@ruyadorno no problem, we just need to update gts & TypeScript in https://github.com/google/pack-n-play (the repo needs some love).

[DesAWSume]

a year after, this issue bothers me.
`node_modules/google-auth-library/build/src/util.d.ts:134:5 - error TS18028: Private identifiers are only available when targeting ECMAScript 2015 and higher.

134 #private;
~~~~~~~~

Found 1 error.`

[danielbankhead]

@DesAWSume the error message explains what to do; simply target es2015+ in TypeScript:

• https://www.typescriptlang.org/tsconfig#target

[DesAWSume]

Oh~. 2nd look. I have a tsconfig under src folder, which my yarn build command will target to it.
My bad. It fixed for me~