Syntactically incorrect JS output with `declare const` globals -- due to Rollup treeshaking / side-effects

What happens and why it is wrong

I ran into a werid result, as you can see the

const T = COMMENT_OPTIONS,
  V = PAGE_INFO_I18N;
VALINE_I18N;

is absolutly wrong, and will return an error Uncaught SyntaxError: Unexpected token ':' after VALINE_I18N replace by an object.

The project is working good for the past week, when it suddenly ran into this issue.

At a glance, I regard this as a temp error, but this issue still happens after I:

• delete node_modules/.temp

• delete the whole node_modules/

I am not sure if it is a bug (it probably not), but is there other temp or cache I missed?

---

Sorry for not providing the config, but I think for this question it’s not needed. And won’t help.

[Mister-Hope]

Edited, I looked into my repo commit, I did not import a.

// define.ts
declare const CONST_A: xxx;
declare const CONST_B: xxx;
declare const CONST_C: xxx;

export const a = CONST_A;
export const b = CONST_B;
export const c = CONST_C;

// module.ts
import { b, c } from './define';

// real reference with b and c
// ...

It seems that rollup mark CONST_A with side effect because it does not know what’s it’s value and preserve it, but the declared a is removed because it’s unused, so that rollup proudly gives:

CONST_A;
const b = CONST_B,
  c = CONST_C;

Any way, it should not be a problem with this repo. I was new with rollup at that time.

[Mister-Hope]

It’s been a long time. I can tell that the original one is that:

// define.ts
declare const CONST_A: xxx;
declare const CONST_B: xxx;
declare const CONST_C: xxx;

export const a = CONST_A;
export const b = CONST_B;
export const c = CONST_C;

// module.ts
import { a, b, c } from './define';

// a treeshakable thing. e.g: function
const func = ()=> a;

// real reference with b and c
// ...

I am not sure about the real content in module.ts, but at that time it’s not a cache error, intead, it produce the weird result with:

CONST_A;
const b = CONST_B,
  c = CONST_C;

After investigating for sometime, I realize that rollup seems doing the correct thing, but it actually can produce an error if the content is replaced by an object, so rollup should better produce:

(CONST_A);
const b = CONST_B,
  c = CONST_C;

So I decide to close this in this repo. Also I mananged to find a workaround (instead of fixing it at that time).

I am not sure if the issue is still reproductable now, and I think that I was too lazy to raise another issue to rollup at that time, because it’s hard to say rollup was wrong.