Do not include the whole namespace when illegally mutating a namespace

[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:
#3633

Description

This will refine how we handle mutating namespace objects in that this no longer includes the whole namespace but only the mutated prop. Note that it will still (unnecessarily) include the whole namespace when mutating a missing prop but I found it too much effort to optimize for this rare condition that already displays two (!) warnings.

[rollup-bot]

Thank you for your contribution! ❤️

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

npm install rollup/rollup#refine-illegal-namespace-access-handling

or load it into the REPL:
https://rollupjs.org/repl/?circleci=11982

[codecov]

Codecov Report

Merging #3637 into master will not change coverage.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##           master    #3637   +/-   ##
=======================================
  Coverage   96.54%   96.54%           
=======================================
  Files         183      183           
  Lines        6244     6244           
  Branches     1830     1831    +1     
=======================================
  Hits         6028     6028           
  Misses        107      107           
  Partials      109      109           

Impacted Files	Coverage Δ
src/ast/nodes/MemberExpression.ts	98.30% <100.00%> (ø)

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[guybedford]

Thanks for fixing this up!