Adds Publisher.prefix(while:behavior:).

[jasdev]

Figured we should add this to Ext after stumbling upon @jessegrosjean’s Swift Forums thread and @mayoff’s approach with composed operators.

[codecov]

Codecov Report

Merging #70 (9d7032e) into main (730d272) will increase coverage by 0.07%.
The diff coverage is 99.23%.

❗ Current head 9d7032e differs from pull request most recent head 05d483e. Consider uploading reports for the commit 05d483e to get more accurate results

@@            Coverage Diff             @@
##             main      #70      +/-   ##
==========================================
+ Coverage   97.12%   97.20%   +0.07%     
==========================================
  Files          62       64       +2     
  Lines        3336     3467     +131     
==========================================
+ Hits         3240     3370     +130     
- Misses         96       97       +1     

Impacted Files	Coverage Δ
Sources/Operators/PrefixWhileBehavior.swift	96.00% <96.00%> (ø)
Tests/PrefixWhileBehaviorTests.swift	100.00% <100.00%> (ø)

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 730d272...05d483e. Read the comment docs.

[mayoff]

The goal is an operator that passes through all of the upstream values, until and including the first value that fails the predicate.

In the linked Swift forums thread, I implemented the requested operator as follows:

• Turn each upstream value into a publisher that emits the value (in a wrapper), followed by an end-marker if the value fails the predicate. In my original version, I used Sequence.Publisher. In @jasdev's code, the Just ... append ... setFailureType expression produces these short publishers.

• Use flatMap to flatten those short publishers into one publisher that republishes each upstream value, with an end-marker after each upstream value that fails the predicate.

• Use prefix(while:) to terminate the stream at the first end-marker.

• Use compactMap to unwrap the values.

In my original code, the wrappers and the end-marker were cases of enum Cut. Here, @jasdev has renamed enum Cut to enum PrefixInclusiveEvent.

[jasdev]

(Cleaning up some ol’ PRs — @freak4pc any chance we could land this in the next release whenever you get a chance to review? 🙏🏽)

[freak4pc]

Sorry @jasdev & @mayoff,
Barely had any time lately and this totally slipped my mind. Thanks for the ping (and explanation), looks great.