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fix(es/minifier): Fix detection of direct eval #6215

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merged 9 commits into from Oct 21, 2022

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kdy1
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@kdy1 kdy1 commented Oct 20, 2022

Description:

The existence of eval make the name mangler abort, but partial try logic causes minifier to generate an invalid code.

This is what I get if I disable eval detection.

image

With eval detection, I get

                     function r(r) {
                        var o = e[r];
                        if (void 0 !== o) return o.exports;
                        var n = e[r] = {
                            exports: {}
                        };
                        return t[r](n, n.exports, r), n.exports;
                    }

which is wrong

Related issue:


Investigation

image

Conclusion

eval breaks the name mangler.

@kdy1 kdy1 added this to the Planned milestone Oct 20, 2022
@kdy1 kdy1 self-assigned this Oct 20, 2022
@kdy1 kdy1 changed the title fix(es/minifier): Fix a bug fix(es/minifier): Fix detection of eval Oct 20, 2022
@kdy1 kdy1 changed the title fix(es/minifier): Fix detection of eval fix(es/minifier): Fix detection of direct eval Oct 20, 2022
@kdy1 kdy1 requested a review from jridgewell October 20, 2022 04:20
c();
var d = a.b;
d();
var e = eval;
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This is an indirect eval, so it cannot use c nor b

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swc-bump:

  • swc_ecma_transforms_base
  • swc_ecma_minifier

foo();
(0, foo.bar)();
(0, eval)("console.log(foo);");
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This is also an indirect eval, so we can mangle names

@kdy1 kdy1 marked this pull request as ready for review October 20, 2022 04:26
kodiakhq[bot]
kodiakhq bot previously approved these changes Oct 20, 2022
var i = e[r] = {
exports: {}
};
return t[r](i, i.exports, o), i.exports;
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This is the fix

@Smrtnyk
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Smrtnyk commented Oct 20, 2022

Does this also fix #5068?

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kdy1 commented Oct 20, 2022

No

@kdy1
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kdy1 commented Oct 20, 2022

Actually this is a workaround and we should fix #5068 ideally

Comment on lines +37 to +39
if let Callee::Expr(e) = c {
if let Expr::Ident(Ident {
sym: js_word!("eval"),
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Not sure how you represent optional chains, but eval?.() is not a direct eval either.

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image

Nice catch, thank you!

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Oh it was OptCall which does not contain Callee

function f1(a, eval, c, d, e) {
return a("c") + eval;
function f1(n, eval, c, r, t) {
return n("c") + eval;
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Nit: this eval can be renamed.

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I added code to explicitly prevent it because terser does so.

@kdy1 kdy1 enabled auto-merge (squash) October 21, 2022 02:51
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Automated review comment generated by auto-rebase script

@kdy1 kdy1 disabled auto-merge October 21, 2022 03:17
@kdy1 kdy1 merged commit 780b5de into swc-project:main Oct 21, 2022
@kdy1 kdy1 deleted the minifier-feedback branch October 21, 2022 03:18
@kdy1 kdy1 modified the milestones: Planned, v1.3.10 Oct 21, 2022
@swc-project swc-project locked as resolved and limited conversation to collaborators Nov 20, 2022
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4 participants