Add module toStringTag to entries and interop namespaces

[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 #3760

Description

When using the output.namespaceToStringTag option, the "Module" tag will now be added to namespaces in the following situations:

• internal inlined namespaces (this was working before)
• entry chunks with exports that use named exports mode
• namespaces imported via dynamic imports
• external namespaces that were not ES modules but have been processed by an interop helper

Please have a look at the new tests for more details.

Moreover, this will now add the __esModule marker to exports of IIFE bundles as well (unless output.esModule is set to false).

[lukastaegert]

@guybedford Would be nice if you could have a look at this.

[rollup-bot]

Thank you for your contribution! ❤️

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

npm install rollup/rollup#extend-module-tostringtag

or load it into the REPL:
https://rollupjs.org/repl/?circleci=13222

[codecov]

Codecov Report

Merging #3822 into master will increase coverage by 0.01%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master    #3822      +/-   ##
==========================================
+ Coverage   97.05%   97.06%   +0.01%     
==========================================
  Files         185      184       -1     
  Lines        6477     6500      +23     
  Branches     1873     1881       +8     
==========================================
+ Hits         6286     6309      +23     
  Misses        101      101              
  Partials       90       90              

Impacted Files	Coverage Δ
src/Chunk.ts	100.00% <ø> (ø)
src/finalisers/index.ts	100.00% <ø> (ø)
src/finalisers/shared/getInteropBlock.ts	100.00% <ø> (ø)
src/finalisers/amd.ts	100.00% <100.00%> (ø)
src/finalisers/cjs.ts	100.00% <100.00%> (ø)
src/finalisers/iife.ts	100.00% <100.00%> (ø)
src/finalisers/shared/getExportBlock.ts	100.00% <100.00%> (ø)
src/finalisers/umd.ts	100.00% <100.00%> (ø)
src/utils/interopHelpers.ts	100.00% <100.00%> (ø)

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[guybedford]

Looks great, thanks for this fix.