Add experimental logging for side effects

[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:

Description

This will add a new option experimentalLogSideEffects: boolean that will log the first side effect to that console that it finds in every input file. This can be very helpful for debugging. The output will contain a code-frame that roughly looks like this:

First side effect in main.js is at (3:0)
1: import './dep-mapped';
2: import './dep-long-line';
3: console.log('main effect');
   ^
4: console.log('other effect');

In case a transformation with source maps changed the location, the log will be extended to contain that information as well:

First side effect in dep-mapped.js is at (2:26)
1: const removed = true;
2: const alsoRemoved = true; console.log('mapped effect');
                             ^
Original location is at (1:0)
1: console.log('mapped effect');
   ^

This is just an experimental feature as "logging to the console" is probably not what we want in the long run. Once we have a proper logging mechanism that works similar to how warnings are handled at the moment, we can turn this into a proper feature.

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[github-actions]

Thank you for your contribution! ❤️

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

npm install rollup/rollup#fix-min-chunk-size-with-logging

or load it into the REPL:
https://deploy-preview-4871--rollupjs.netlify.app/repl/?pr=4871

[rollup-bot]

This PR has been released as part of rollup@3.17.3-0. Note that this is a pre-release, so to test it, you need to install Rollup via npm install rollup@3.17.3-0 or npm install rollup@beta. It will likely become part of a regular release later.

[codecov]

Codecov Report

Merging #4871 (7aed784) into master (1ab9833) will increase coverage by 0.00%.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##           master    #4871   +/-   ##
=======================================
  Coverage   98.98%   98.98%           
=======================================
  Files         219      219           
  Lines        7948     7967   +19     
  Branches     2189     2193    +4     
=======================================
+ Hits         7867     7886   +19     
  Misses         26       26           
  Partials       55       55           

Impacted Files	Coverage Δ
src/ast/nodes/shared/Node.ts	100.00% <ø> (ø)
src/utils/options/mergeOptions.ts	100.00% <ø> (ø)
src/ast/nodes/Program.ts	100.00% <100.00%> (ø)
src/utils/getCodeFrame.ts	100.00% <100.00%> (ø)
src/utils/options/normalizeInputOptions.ts	99.04% <100.00%> (+<0.01%)	⬆️

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[rollup-bot]

This PR has been released as part of rollup@3.17.3-1. Note that this is a pre-release, so to test it, you need to install Rollup via npm install rollup@3.17.3-1 or npm install rollup@beta. It will likely become part of a regular release later.

[rollup-bot]

This PR has been released as part of rollup@3.18.0-0. Note that this is a pre-release, so to test it, you need to install Rollup via npm install rollup@3.18.0-0 or npm install rollup@beta. It will likely become part of a regular release later.

[rollup-bot]

This PR has been released as part of rollup@3.18.0. You can test it via npm install rollup.