Preserve rendered class names

[lukastaegert]

This PR contains:

• bugfix
• feature
• refactor
• documentation
• other

Are tests included?

• yes (bugfixes and features will not be merged without tests)
• no

Breaking Changes?

• yes (breaking changes will not be merged unless absolutely necessary)
• no

List any relevant issue numbers:

• Resolves Class names are mangled, breaking runtime behavior that relies on them. #4637

Description

This PR preserves the name property of classes even if the class needs to be renamed due to conflicts. The solution is to rewrite both class foo {} and let foo = class {} to e.g. let foo$1 = class foo {} if foo needs to be renamed.

[github-actions]

Thank you for your contribution! ❤️

You can try out this pull request locally by installing Rollup via

npm install rollup/rollup#gh-4637-preserve-class-name

or load it into the REPL:
https://rollupjs.org/repl/?pr=4674

[codecov]

Codecov Report

Merging #4674 (d6665ee) into master (11d425b) will increase coverage by 0.00%.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##           master    #4674   +/-   ##
=======================================
  Coverage   99.02%   99.02%           
=======================================
  Files         215      215           
  Lines        7552     7567   +15     
  Branches     2092     2096    +4     
=======================================
+ Hits         7478     7493   +15     
  Misses         24       24           
  Partials       50       50           

Impacted Files	Coverage Δ
src/ast/nodes/ClassDeclaration.ts	100.00% <100.00%> (ø)
src/ast/nodes/VariableDeclarator.ts	100.00% <100.00%> (ø)
src/ast/scopes/Scope.ts	84.61% <0.00%> (+1.28%)	⬆️

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[rollup-bot]

This PR has been released as part of rollup@3.2.1. You can test it via npm install rollup.

[hyf0]

Just happen to dig into here.

I notice that function.name seems doesn't apply the strategy. Are there any traps?

I guess

function foo() {
  console.log(foo)
}

is the same as

var foo$1 = function foo() {
  console.log(foo$1)
}

[lukastaegert]

No it is not.

foo("Hello"); // logs "Hello" 
function foo() {
  console.log(foo)
}

foo$1("Hello"); // throws because we cannot call "undefined" 
var foo$1 = function foo() {
  console.log(foo)
}

function has a hoisting magic that can not be replicated by other means.

[hyf0]

I take a look at esbuild's approach. It solves the problem in a non-intuitive(IMO) way.

Anyway, thanks for the detail explaining.